Elements for fastening parts of the mansard roof truss system. Calculation, fastening and installation of the mansard roof truss system

There are several options for roofs under which you can place a comfortable living space. In order to ensure the maximum amount of under-roofing attic space, it is necessary to choose the optimal angle of inclination of the slopes and do not forget about the snow and wind load on the roof. We will consider the most popular designs of the attic truss system in the middle lane.

Mansard roof truss system design

The mansard roof makes it possible to obtain additional usable space with a relatively small financial investment, so this architectural solution has gained great popularity. So what is an attic?

Attic (from French mansarde) - an exploited attic space (both residential and non-residential premises), formed on the top floor of the house, or the last floor of a part of the house, with a mansard roof.

Wikipedia
https://ru.wikipedia.org/wiki/Attic

The attic is located within the bearing walls of the building and rests on them through the Mauerlat, horizontal beams (puffs) and rafters. The larger the attic space, the greater its useful volume, which is achieved by increasing the angle of inclination of the slopes and is formed by a more complex truss system. The location of the mansard roof rafters depends on the design, which can be different types, namely:

Hipped or pyramidal design with a minimum amount of under-roof space.
The slopes of the tent structure rest on the side rafters and the central post, so the amount of under-roof space is minimal here.
Hip or semi-hip roof, in which the main living space is located under the trapezoidal slopes.
Hip roof rafters form two triangular and two trapezoidal slopes
Gabled construction, which is a symmetrical gable roof with gables cut at right angles, which provides a significant amount of attic space.
A multi-gable roof allows you to equip a full-fledged attic floor
gable symmetrical roof with an attic - a classic option, characterized by ease of installation and resistance to wind influences due to its rigid structure.
A gable roof requires the least amount of working time and a small consumption of building materials
The rafter system of the mansard sloping roof, providing the maximum amount of living space at a relatively low cost.
A sloping roof is the best solution in terms of the ratio of the cost of construction to the volume of useful attic space

The rafter system must withstand constant loads, which consist of the weight of structural elements, insulation and roofing. In addition, there are variable loads that depend on the strength of the wind and the weight of snow on the roof. The choice of the section of the bearing elements and the method of their connection should be aimed at creating the most durable and rigid structure that evenly distributes the load on the walls of the building.

Depending on the width of the building, different types of attic truss systems are used, which are divided into hanging, layered and combined.

Hanging rafters are called, which rest on the walls of the building through the Mauerlat and puff, and form a ridge in the upper part. With this method of connection, there is no intermediate support, and the bursting pressure on the walls of the house is reduced with the help of crossbars, racks and struts. The hanging rafter system is usually used with a building width of no more than 6 m.
To compensate for bursting forces in hanging truss structures with a span of up to 6 m, puffs and crossbars are used
Rafters are called rafters with an intermediate support on the inner wall of the house. They are used when the width of the building is from 6 to 16 m. The larger it is, the more elements are used to evenly distribute the load.
Rafter rafters have one or more supports inside the house
The combined type of truss system is used in mansard roofs with a variable angle of inclination of the slopes. The most characteristic example is a broken mansard roof, where the lower rafter legs are layered, supported by a rack and mauerlat, and the upper ones are mounted as hanging rafters, supported by a puff and headstock. When building mansard roofs, all types of truss systems are used, and their choice depends on the design in which they are used.
In the construction of a sloping roof, the upper rafters are hanging, and the lower ones are layered.

Scheme of the truss system of the mansard roof

To build a roof, you must have a project that indicates the list and size of structural elements, as well as the method of their connection. To understand the principle and sequence of installation, you need to know the purpose of the elements of the truss group and the way the roof fits to the walls of the building. The mansard roof consists of the following elements:

the connecting element between the wall of the building and the rafter group is the mauerlat, which is attached to the walls of the house with studs, brackets or anchors;
puffs are attached to the Mauerlat parallel to the short wall of the building, and beds are installed along the long side;
vertical racks are mounted on the central bed;
the ridge run rests on the racks;
the upper part of the rafters rests on the ridge run, and bottom connected with a puff, forming a cornice overhang;
rafter legs in the upper part are connected by crossbars;
on hip roofs, diagonal rafters and shortened sprigs are used;
Sprengels serve as an additional support for the diagonal rafters;
racks and struts are used for intermediate fastening of rafters;
if necessary, the rafters are lengthened with fillies.

The main load-bearing elements of the mansard roof are rafter logs, beds and puffs, as well as vertical racks and a ridge run.

The diagram indicates the dimensions of the elements of the truss system, their location, angles of inclination and methods of tie-in at the connection nodes. Be sure to also provide information about the location of the double rafters, the presence of additional supports, the dimensions of the eaves and gable overhangs.

The scheme is the main document for assembling the rafter system, it reflects all the necessary parameters. However, before cutting the material, it is necessary to check the calculations again and create templates for the main parts. In the absence of a project, you need to carry out calculations and create a scheme yourself.

Mansard roof rafter step

Before starting work, you need to choose the pitch of the mansard roof rafters. The distance between the rafters and the joists (in the case of a hip roof) depends on several factors:

building size;
type of truss system;
constant and variable load on the roof;
sections of rafters, racks and slopes;
type of roofing;
type and step of the crate;
heater dimensions.

For rafters, battens and counter battens, softwood material is selected in accordance with SNiP II-25, and the load on the rafters is calculated according to SNiP 2.01.07 and ST SEV 4868. Based on the above building codes and the rules, we can say that for rafters less than 9 m long, a beam section from 50X150 to 100X250 mm is applicable at a step of 60 to 100 cm. The size of the building affects the design of the farm and the presence of racks, struts and crossbars, the use of which increases the strength of the rafter legs and allows you to increase the step between the rafters up to 120 cm or more. Usually, reference tables are used to select a step, which contain recommendations, taking into account the length of the rafters and the cross section of the timber.

Table: dependence of the step between the rafters on the cross section of the beam and the length of the rafters

The type of roofing used also affects the choice of rafter spacing, because different materials have different weights:

tile, depending on the type, weighs from 16 to 65 kg / m 2, slate - 13 kg / m 2. Such heavy coatings imply a decrease in the pitch of the rafter legs to 60–80 cm;
the weight of metal coatings and ondulin does not exceed 5 kg / m 2, so the pitch of the rafters can be increased to 80–120 cm.

On hip roofs, in any case, the spacing of the sprigs is chosen to be 50–80 cm to make the slope more rigid.

In addition, the installation step of the rafters depends on:

The length of the rafters and lathing of the mansard roof

With independent calculations, the dimensions of some structural elements of the roof have to be calculated according to the existing dimensions of the building and the angle of inclination of the slopes. The length of the rafters sometimes has to be adjusted for different types of mansard roof, choosing optimal dimensions the entire structure as a whole.

Suppose that the main dimensions of the building are known and it is necessary to calculate the length of the rafter logs for several proposed options for the angle of inclination and the type of roof. Let half the width of the building L be 3 m, the size of the cornice slope be 50 cm.

Additional calculations show that an increase in the angle of inclination of the lower slope from 60 to 70 ° will increase the width of the attic by 10%.

The length of the sheathing connecting the rafter legs is determined taking into account the gable overhangs that protect the walls of the facade from precipitation. The length of the gable overhang depends on the height of the building and is selected in the range from 40 to 60 cm. Therefore, the total length of the slope will be equal to the length of the house, increased by twice the length of the overhang.

Suppose that the length of the house is 10 m, and the gable overhang is 0.6 m. Then the dimensions of the crate must be calculated taking into account the length of the slope, equal to 10 + 0.6 ∙ 2 = 11.2 m.

The parameters of the lathing should be calculated taking into account the length of the gable and eaves overhangs

Any adjustment of the project requires a careful recalculation of the parameters of the truss system, taking into account the changes that have occurred.

Video: mansard roof calculation

The nodes of the truss system of the mansard roof

The nodes of the roof truss system are the junction individual elements into a single structure, which allows you to evenly distribute the load on the walls of the building. The connection is made with nails, self-tapping screws or bolts using overhead wooden elements or metal squares and plates, as well as by connecting into a groove. For the construction of two pitched roof use the following main nodes:

A ridge knot that connects the rafter legs to each other and to the ridge run.
Places where the crossbar connects the rafters to give greater strength and rigidity to the truss trusses.
Attachment points for struts and struts that give additional support to the rafters.
A cornice assembly in which rafters are attached to a puff or mauerlat, forming a cornice overhang.

The nodal connections of the truss system must be carried out in such a way as to ensure the most rigid fastening of the elements to each other.

For a gable sloping roof, the node is characteristic, where the upper and lower rafter logs, a vertical post, a crossbar and a run are connected. Such a complex connection requires the use of tie-ins, bolts, steel plates and building brackets.

In the most complex node of a broken mansard roof, five truss elements are connected

The most complex node of the hip mansard roof is the junction of the lateral or diagonal rafter legs with the Mauerlat. The side rafter in the lower part rests on the corner beam of the Mauerlat and on the embedded beam; in another embodiment, a vertical stand or truss is placed between the embedded beam and the rafter leg. Top part hip rafters fastened to the ridge run with bolts or nails.

The corner rafters of the hip roof carry the greatest load, so the knot of their connection with the Mauerlat must be thought out most carefully

The nodes described are most often used in the installation of truss systems of various designs and allow the installation of load-bearing elements on their own. For efficient and high-quality assembly, drawings and the manufacture of templates with verified angles of joints and tie-ins are necessary.

Video: nodes of the truss system

Calculation of the truss system of the mansard roof

The truss system is the basis of the roof, so it is important to choose the design that best suits the climatic conditions of the region and the existing requirements for the size of a residential attic. After choosing the design, the angle of inclination of the slopes and the height of the ridge are calculated for the required dimensions of the attic room. Calculations are made taking into account the size of the cornice according to the following formulas:

The meaning of trigonometric functions can be found in the reference tables.

Table: values of trigonometric functions for various slope angles

The hardest part of designing mansard roofs is counting the lumber. Calculating the number of rafters needed and linking them to a standard length of 6 m can sometimes be quite difficult. Let's say that we have chosen the hip roof, the most difficult in calculations, with a size of 10X13 m, taking into account the cornice overhangs 80 cm long and the angle of inclination of the slopes is 45 °. Then the side rafters will have a length of 5 / sin 45 o = 7.04 m. Therefore, the standard six-meter beam will have to be lengthened. Usually, for rafters a little more than 6 m long, a 100X200 mm beam or a 50X250 mm board is used.

If the building is large, then it requires rafters longer than the standard size of 6 m, so the timber has to be lengthened

As for the horizontal floor beam, since the width of the building is 10 m, the puffs should consist of two parts, which either rest on the inner wall of the building, or are joined together by reinforcing elements and rely on the run. For puffs and runs, a beam with a cross section of at least 50X200 mm is used. A mauerlat runs along the perimeter of the building, for which a beam of 150X150 mm or 200X200 mm is used. According to the scheme we have chosen, the perimeter of the building is 39.6 m, so seven six-meter bars will be required to install the Mauerlat. The dimensions of all other elements of the truss system will not exceed 6 m.

The weight of the lumber of the truss system is calculated by summing up the lengths of all elements with a certain section and converting their number into cubic meters. This is necessary to determine the mass of the entire roof, and is also necessary when purchasing and transporting material. The calculation is made according to the table, and then the obtained values \u200b\u200bare multiplied by the weight of 1 m 3 of lumber.

Table: calculation of the amount of lumber in 1 m 3 and the volume of one unit of material

Pine lumber weighs 505 kg/m 3 at 12% humidity, and 540 kg/m 3 at 25% transport humidity. Here are some examples of calculations:

If 1 m 3 of material with a section of 50X200 mm contains 16.6 boards, then the weight of one board will be 540/16.6 = 32.5 kg.
If 25 m 3 of lumber is purchased, then it will weigh 25 ∙ 540 = 13,500 kg.
If 100 boards 25X200 are required, then you need to buy 100 / 33.3 = 3 m 3 of wood, which will weigh 3 * 540 = 1,620 kg.

It is important to note that it is advisable to purchase edged lumber with the lowest moisture content so that after installation it does not warp or crack, especially for large-section timber. For the construction of the truss system, the moisture content of the wood should not exceed 18%.

Installation of the attic truss system

Installation of a truss system with a residential under-roof space requires careful preparation. It is necessary to mount convenient scaffolding, decking and ladders, as well as provide workplaces with safety ropes. Workers must be provided with overalls, protective equipment and serviceable equipment. On the ground, you need to choose a flat place for pre-assembly of trusses, marking corners and making templates. All wooden elements must be treated with antiseptic and fire-fighting compounds.

After that, you can begin work, which takes place in the following sequence:

On walls with walled studs, a Mauerlat is mounted around the perimeter. If there is a load-bearing wall inside the building, we lay a bed or run of the same height with a Mauerlat on it.
If the house is being built from building blocks, then it is most convenient to lay the Mauerlat on threaded studs that are immured into the wall during its laying
Puffs with eaves extensions are attached to the Mauerlat parallel to the short wall.
On the puffs, vertical racks are set, limiting the attic room.
The racks are connected to the puff, which serves as the ceiling of the attic room. The trusses installed in this way are interconnected by horizontal runs.
Vertical racks, upper puffs and horizontal runs form the frame of the attic space
The lower and then the upper rafters are installed, which are attached to the ridge part.
To strengthen the lower and upper rafters, struts, grandmas and surfs are used.
The crate is installed and frontal board on the ledge.
After installing all the rafters, it remains to lay the crate and nail the frontal board

We examined the assembly of the truss system using the example of a broken mansard roof. The construction of other structures consists of similar operations and mainly consists in performing work according to the design installation diagram, which reflects the methods of connecting the elements of the truss system. In the presence of carefully calculated drawings, a team of four people able to mount a roof with a truss system of any complexity.

Video: installation of a mansard roof

We examined the truss group of the mansard roof, its design, calculation, as well as the diagram and description of the main components. They offered a variant of step-by-step installation of the supporting structures of the attic, attached illustrations and videos that explain the assembly procedure for the structural elements of the attic roof. Now its successful erection depends only on the thoroughness of fulfilling the requirements of instructions and technologies and the availability of certain skills for performing construction works. We wish you success.

A house with an attic is not only an additional living space, but also a respectable view of the entire building. Even if the room under the roof is made unheated and is used only in the summer, it still creates a powerful "air cushion" that helps to retain heat inside the entire capital building.

And about, then - read on our portal.

Attic project

When drawing up a scheme for building an attic, it is best to do this in different projections in order to see and understand the placement of all elements of the truss system. It is very important to correctly calculate the height of the roof ridge, since the size of the area under it will directly depend on it.

When drawing up a scheme-project for the construction of a mansard roof, you need to calculate the height of the ridge, the ceiling and the total area of \u200b\u200bthe room.

The minimum height from the floor to the ridge should be 2.5-2.7 m, if this distance is less, then the room is not an attic, it can only be called an attic. This parameter is set by the norms of SNIP.

In order for all elements to be drawn accurately and have the desired location in the overall system, it is necessary to start from a figure with right angles, that is, a rectangle or square - a section of the created attic room. Based on the sides (height and width of the future room), it will be almost impossible to make a mistake with the angles at which roof slopes are located, with the location of the ridge, rafters and all retaining elements. Determining these parameters, they must immediately be entered into the drawing.

First you need to find the middle of the width of the front wall. Starting from this point, the parameters of the height of the ridge, the future attic ceiling, the location of the rack-walls and the size are determined. eaves overhang.

Due to the fact that each of the structures has a certain number connecting nodes, which have different configurations, it would be nice to draw each of these ligaments separately in order to understand their features of pairing together all the elements that connect at this point.

Any truss system consists of basic elements and additional ones, which may not be in every design. The main components of the mansard roof are.

Floor beams, which are the basis for the rest of the elements of the truss system. They are laid on the main walls of the building.
Rafter leg, straight in a gable roof system or consisting of two sections - in a broken pattern. In this case, the upper rafter is called the ridge rafter, as it forms the highest point of the roof - and the rafters that form the walls of the attic are called side rafters.
A ridge board or beam is an indispensable element for a gable roof, but is not always used when constructing a broken roof model.
Mauerlat - a powerful bar, fixed to the main side walls of the building. Rafter legs are installed on this element.
Racks are supporting elements necessary to strengthen the gable and broken structure. In the latter case, a ridge and side rafters are attached to it, and in the first case, the stand is a reliable support for a long rafter. In addition, the racks serve as a frame for insulation and sheathing of the attic walls.
Diagonal braces or bevels additionally hold the posts or stringers and rafters together, making the structure more durable.
beams attic floor are used in all variants of the attic - they connect the racks, and they are also the frame for the ceiling device.
Interrafter runs are installed in a broken form of the roof for structural rigidity.

To be sure that the prepared project is developed correctly, you need to show it to a specialist. Only he can determine whether the attic parameters are correctly selected for the width and length of the walls of the building.

Video: professional mansard roof calculation using special software

Parameters of materials for the construction of a mansard roof

If the graphic project is ready, then, starting from the dimensions marked on it, you can calculate the amount of materials needed to build a mansard roof. Materials must be selected according to their characteristics, which must meet the requirements of fire and environmental safety. For wood, it is necessary to provide special treatment with fire retardants, which will reduce the combustibility of the material. So, for the construction you will need:

Boards for rafter legs. Their cross section is selected according to the results of special calculations - this will be discussed in more detail below.
A beam having a cross section of 100 × 150 or 150 × 200 mm - for floor beams, depending on the chosen truss system and the width between the bearing walls, as well as for purlins, diagonal legs or valleys - if they are provided for by the design.
Beam with a section of 100 × 150 mm or 150 × 150 mm for laying Mauerlat.
For racks, a beam of 100 × 100 or 150 × 150 mm is usually used.
Unedged board for subflooring and some fasteners.
Annealed steel wire with a diameter of 3-4 mm - for fastening together some parts.
Nails, bolts, staples of various sizes, corners of various configurations and other fasteners.
Metal sheet with a thickness of at least 1 mm - for cutting overlays.
Lumber for battens and counter battens for roofing material - depending on the type of roofing chosen.
- for thermal insulation of the roof.
Waterproofing and vapor barrier membranes.
Roofing material and fasteners for it.

What section are required rafters

Rafters are roofing elements that will perceive the main external loads, therefore, the requirements for their cross section are very special.

The size of the required lumber will depend on many parameters - on the step between the rafter legs, on the length of these legs between the support points, on the snow and wind load that falls on them.

The geometric parameters of the design of the truss system are easy to determine in the drawing. But with the rest of the parameters - you will have to refer to the reference material and carry out some calculations.

Snow load is not the same for different regions of our country. The figure below shows a map on which the entire territory of Russia is divided into zones according to the intensity of the snow load.

There are eight such zones in total (the last, eighth, is more likely to be extreme, and it can not be considered for the construction of a mansard roof).

Now you can accurately determine the snow load, which will depend on the angle of the roof slope. For this, there is the following formula:

S = Sg × μ

Sg- tabular value - see the map and the table attached to it

μ — correction factor depending on the steepness of the roof slope.

If the slope angle is less 25° then μ=1.0
With a steepness from 25 to 60 ° - μ=0.7
If the roof is steeper than 60 °, then it is considered that the snow does not linger on it, and the snow load is not taken into account at all.

It is characteristic that if the mansard roof has broken structure, then for different parts of it, the load can have different values.

The angle of the roof slope can always be determined either by a protractor - according to the drawing, or by a simple ratio of the height and base of the triangle (usually - half the width of the span):

The wind load also mainly depends on the region of construction of the building and on the characteristics of its environment and roof height.

And again, for the calculation, the initial data on the map and the table attached to it are first determined:

The calculation for a particular building will be carried out according to the formula:

Wp = W × k × c

W- tabular value, depending on the region

k- coefficient taking into account the height of the building and its location (see table)

The following zones are indicated in the table with letters:

zone A - open areas, steppes, forest-steppes, deserts, tundra or forest-tundra, open to the winds of the coast of the seas, large lakes and reservoirs.
zone B - urban areas, wooded areas, areas with frequent obstacles to the wind, relief or artificial, at least 10 meters high.
zone V- dense urban development with an average height of buildings above 25 meters.

With- coefficient depending on the predominant wind direction (wind rose of the region) and on the angle of inclination of the roof slopes.

With this coefficient, the situation is somewhat more complicated, since the wind can have a double effect on the roof slopes. So, it has a direct, overturning effect directly on the roof slopes. But at small angles, the aerodynamic effect of the wind takes on special significance - it tries to raise the slope plane due to the emerging lifting forces.

In the drawings, diagrams and tables attached to them, the sections of the roof that are subject to maximum wind loads are indicated, and the corresponding coefficients for calculation are indicated.

It is characteristic that at slope angles up to 30 degrees (and this is quite possible on the site ridge rafters), the coefficients are indicated both with a plus sign and negative, that is, directed upwards. They somewhat extinguish the frontal wind load (this is taken into account in the calculations), and in order to level the effect of lifting forces, it will be necessary to carefully fix the truss system and roofing material in this area using additional connections, for example, using annealed steel wire.

After the wind and snow loads are calculated, they can be summed up, and, taking into account the design features of the system being created, determine the cross section of the boards for the rafters.

Please note that the data are given for the most commonly used coniferous material (pine, spruce, cedar or larch). The table shows maximum length rafters between support points, the section of the board depending on the grade of the material, and on the step between the rafters.

The value of the total load is indicated in kPa (Kilopascals). It is not difficult to bring this value into more familiar kilograms per square meter. With quite acceptable rounding, you can accept: 1 kPa ≈ 100 kg/m².

The dimensions of the board along its section are rounded up to the standard sizes of sawn timber.

	rafter section (mm)	Distance between adjacent rafters (mm)
		300	600	900	300	600	900
		1.0 kPa			1.5 kPa
higher	40×89	3.22	2.92	2.55	2.81	2.55	2.23
	40×140	5.06	4.60	4.02	4.42	4.02	3.54
	50×184	6.65	6.05	5.28	5.81	5.28	4.61
	50×235	8.50	7.72	6.74	7.42	6.74	5.89
	50×286	10.34	9.40	8.21	9.03	8.21	7.17
1 or 2	40×89	3.11	2.83	2.47	2.72	2.47	2.16
	40×140	4.90	4.45	3.89	4.28	3.89	3.40
	50×184	6.44	5.85	5.11	5.62	5.11	4.41
	50×235	8.22	7.47	6.50	7.18	6.52	5.39
	50×286	10.00	9.06	7.40	8.74	7.66	6.25
3	40×89	3.06	2.78	2.31	2.67	2.39	1.95
	40×140	4.67	4.04	3.30	3.95	3.42	2.79
	50×184	5.68	4.92	4.02	4.80	4.16	3.40
	50×235	6.95	6.02	4.91	5.87	5.08	4.15
	50×286	8.06	6.98	6.70	6.81	5.90	4.82
total snow and wind load		2.0 kPa			2.5 kPa
higher	40×89	4.02	3.65	3.19	3.73	3.39	2.96
	40×140	5.28	4.80	4.19	4.90	4.45	3.89
	50×184	6.74	6.13	5.35	6.26	5.69	4.97
	50×235	8.21	7.46	6.52	7.62	6.92	5.90
	50×286	2.47	2.24	1.96	2.29	2.08	1.82
1 or 2	40×89	3.89	3.53	3.08	3.61	3.28	2.86
	40×140	5.11	4.64	3.89	4.74	4.31	3.52
	50×184	6.52	5.82	4.75	6.06	5.27	4.30
	50×235	7.80	6.76	5.52	7.06	6.11	4.99
	50×286	2.43	2.11	1.72	2.21	1.91	1.56
3	40×89	3.48	3.01	2.46	3.15	2.73	2.23
	40×140	4.23	3.67	2.99	3.83	3.32	2.71
	50×184	5.18	4.48	3.66	4.68	4.06	3.31
	50×235	6.01	5.20	4.25	5.43	4.71	3.84
	50×286	6.52	5.82	4.75	6.06	5.27	4.30

Tools

Naturally, during work, one cannot do without tools, the list of which includes:

Electric drill, screwdriver.
Building level and plumb line, tape measure, square.
Axe, chisel, chisel, hammer
Circular saw, jigsaw, hacksaw.
Carpentry knife.

Installation will be accelerated if the tools for work are of high quality, and the work is carried out with competent mentors, with assistants, carefully and in stages.

Installation steps

It is necessary to strictly observe the sequence of work - only under this condition the design will turn out to be reliable and durable.

Mauerlat mount

The installation of any truss system begins with fixing a powerful supporting structure at the end of the side walls of the structure. timber - Mauerlat on which it will be convenient to install rafter legs. Mauerlat is made from a high-quality bar with a cross section of at least 100 × 150 mm. It must be laid on the roofing material waterproofing laid along the upper end of the wall (regardless of the material).

Due to the Mauerlat, the load will be evenly distributed along the walls and transferred to the foundation of the building.

The Mauerlat is fixed to the wall with metal studs, which are pre-embedded in a concrete belt or crown running along the upper edge of the wall, or with anchor bolts with a diameter of 12 mm. They must go deep into the wall by at least 150 — 170 mm. If the Mauerlat is installed on a wooden wall, then the bars are attached to it with the help of wooden dowels.

Installation of the truss structure

Installation of the truss system begins with the installation of floor beams. They can be mounted on the Mauerlat from above if the beams are planned to be taken out of the perimeter of the building and thereby increase the attic area. In this design, the rafter legs are fixed to the floor beams.

Floor beams fixed on top of the Mauerlat (Fig. A)

Otherwise, they may fit into waterproofed walls and fastened with corners or staples to the inner edge of the Mauerlat. This option is used when the rafter legs are planned to be fixed directly to the Mauerlat.

Another option - only rafter legs are attached to the Mauerlat

Next, you need to find the middle of the floor beam, since this mark will become a guideline for determining the location of the support posts and the ridge.
Racks should be located at the same distance from the marked middle of the floor beam. In the future, they will begin to determine the location of the walls of the attic room, that is, its width.
Bars for racks should have a cross section equal to the size of the floor beams. Construction sites are attached to the beams with the help of special corners and wooden linings. However, to begin with, they are first baited with nails, then carefully leveled with building level and a plumb line, and only then they fix it thoroughly, with the expectation of future loads.

When the first pair of racks is installed, they are fastened together from above with a bar, which is called a puff. This puff is also connected to the racks using special metal corners.

After fixing the puff, you get a U-shaped design. Layered rafters are installed on it on the sides, which are attached to the floor beam with their second end or are laid on the Mauerlat.
A special notch (groove) is cut out on the installed supports for the timber or in the rafters. With its use the rafters are tightly installed on the mauerlat beam, and fastened with metal brackets.

For structural rigidity, struts can be additionally installed from the base of the rack to the middle of the installed side rafter. If this seems not enough, and saving material is not in the foreground, then you can strengthen the overall design with additional racks and contractions (they are indicated in the drawing in Fig. A by translucent lines).
Further, the middle is calculated on the puff - a headstock will be attached to this place, supporting the ridge connection of the upper hanging subsystem of the rafters.
The next step is to install ridge rafters, which can be fastened together with different connections - this can be a metal lining or powerful bolts with metal plates or washers.

After their installation, a headstock is attached to the ridge and the middle of the puff.
Having completed work on one part of the truss system, you need to make all the rest according to the same principle. The distance between adjacent rafters in such a system should be no more than 900 — 950 mm, but the interval of 600 mm will probably still be optimal - this will give both the necessary rigidity and stability of the structure, and will be convenient for insulation using standard mineral wool mats. True, this makes the structure heavier and will require more materials.

First, the side parts of the complete system are installed, and then the intermediate ones. Between themselves, they are connected by runs, which are installed between the upper ends of the racks and act as spacers. Thus, a rigid structure of the attic rafters will be obtained, in which the frame for wall cladding will already be ready.

Prices for various types of fasteners for rafters

Fasteners for rafters

Mansard roof waterproofing

When the truss system is built, you can proceed to finishing it and their accompanying materials.

The first coating to be fixed immediately on top of the rafters will be waterproofing and windproof film. it is attached to the rafters with staples and a stapler, starting from the eaves. Cloths are overlapped by 150 — 200 mm, and then the joints are glued with waterproof tape.
On top of the waterproofing, a counter-lattice is stuffed onto the rafters, which will more reliably fix the film on the surface and create the necessary ventilation distance between the windproof and roofing material. The counter-lattice is usually made of boards with a width of 100 — 150 mm and 50 thick — 70 mm.

A crate is fixed perpendicular to the counter-lattice, on which the roofing material will then be laid. The step between the rails must be calculated depending on the type and size of the sheet roofing material, taking into account the overlap required for it.
If chosen soft roof, then plywood sheets are most often fixed to the counter-lattice.

Roofing installation

Roofing material is fixed on the prepared crate or plywood. Its installation usually starts from the roof eaves and runs in order, from one of the edges - depending on the type of roof. Roofing sheets are mounted with an overlap. If a metal profile or metal tile is used for coating, then such material is fixed with special self-tapping screws with elastic gaskets. Fasteners are usually matched in color to the roofing material.

The most difficult thing in covering a mansard sloping roof is the transition from layered side rafters to hanging ridge rafters. There may be certain difficulties in the event that ledges are provided on the roof for roofing over balconies or windows.

In addition, if a chimney pipe goes to the roof, it requires a separate opening of the hole inside the rafter system and insulating layer, and on the roof - a device around the pipe of reliable waterproofing.

How and what is better to cover the roof, you can find out in detail on our portal, there is a whole section in which you can find answers to many questions, including recommendations for reliable insulation of the attic room.

Prices for popular types of corrugated board

Decking

Video: a detailed video tutorial on building a mansard roof

It should be noted that the work on the construction of any roof, and even more so complex as an attic, is not only responsible, but also quite dangerous, it requires special, increased security measures. If there is no experience in carrying out such construction processes, then it is better to entrust their implementation to professionals or to perform all actions under the supervision of an experienced craftsman, and with the utmost care and accuracy.

The attic, which allows you to effectively use the floor area of a private house, is a rather complicated design. As a rule, homeowners entrust its construction to experienced craftsmen - roofers. But if you are a carpenter and are not afraid of difficulties, then you can certainly cope with the task yourself. The first step is to gain theoretical knowledge about how a mansard roof is calculated and built with your own hands according to individual drawings. You will find this information presented in the form of a step-by-step guide in this article.

The choice of roof design

For the device of the attic floor, instead of the usual attic, the following types of roofs are suitable (shown in the diagram below):

ordinary gable with a slope of 45 ° or more (steep);
broken roof;
four-slope semi-hip.

Note. As can be seen from the diagram, various half-hip coverings are complicated gable roofs, so it makes no sense to consider them separately. In terms of design, the multi-gable design shown in the photo is of interest, but decent experience is needed to build it.

A gable mansard roof is the simplest in execution and economical in terms of material consumption. But you will have to pay for this with a smaller usable area and sloping walls. attached floor, not allowing to place high furniture. This will not be a problem if it is planned to equip a bedroom in the attic - the beds will calmly stand near the longitudinal walls. Another way to resolve the issue is to raise the truss system to the required height, as shown in the drawing below.

Roofing with broken shapes is the most popular option, since it allows you to make full-fledged living rooms upstairs. If protruding windows are not provided on its slopes, then according to the installation technology, such a roof is not much more complicated than a gable roof, although the consumption of building materials will increase. To simplify your choice, we propose to consider and compare the 3 most common options for an attic superstructure for a private house in standard sizes of 6 x 6 m:

Steep roof with two pitches inclined at an angle of 45°.
A broken structure, where the lower rafters are inclined at an angle of 60 °, and the upper - 30 °.
Same as option 1, only the trusses are raised to a height of 60 cm, and the rafter legs are at an angle of 37.5 °.

For convenience, we have depicted all three structures in one drawing, which can be taken as a basis for future construction.

Note. A board was taken as the main building material for the manufacture of rafters and other frame elements. cross section 50 x 150 mm.

To choose the best of the three options, we propose to study the comparative table, which presents the parameters of the attic space based on 1 linear meter of the length of the building.

Knowing the length of the roof slopes indicated in the plate, you can roughly estimate the consumption of building materials for the frame, coating and insulation. The following table makes it possible to estimate the total area of the rooms on the second floor when implementing all 3 solutions in private houses with different sizes.

Calculation of the truss system

Do-it-yourself attic rafters must withstand the following loads during the entire period of operation:

own weight;
mass of roofing and insulation;
maximum wind gusts for the area;
snow cover pressure.

Reference. With a roof slope of more than 45 °, snow practically does not linger on it, and at 60 ° it is not taken into account at all in the calculations. But the wind pressure increases due to the height of the structure and its position close to vertical.

The result of the calculations should be 2 parameters - the cross section of the rafters with beams (otherwise - puffs) and the step of their installation. It is a mistake to think that the dimensions of the wooden beams of the roof grow along with the loads on it. The maximum rigidity of the structure is achieved through the use of roof trusses made of logs with a diameter of 120-200 mm or lumber with a thickness of 40 to 200 mm, installed in increments of 50-120 cm. If you are not a civil engineer, you will not be able to determine these values more precisely, since the technique pretty complicated.

Online calculators posted on the Internet do not solve the issue, because their calculations still need to be checked. The way out is this: use ready-made data that has been calculated for a long time. To do this, you will need table No. 1, which shows the sections of the rafter legs for various lengths and loads:

Let us explain the calculation method with an example. Suppose that the snow load on a flat surface (projection of a pitched roof) in your area is 100 kg / m², the slope is 60 °, the span is 4.5 m (to the strut), the rafter spacing is 120 cm. The roofing is slate. We believe:

The actual weight of the snow cover: 100 x 0.32 = 32 kg / m². The slope factor of 0.32 is taken from Table 2 below.
The specific weight of a slate coating with a conventional profile is 25 kg / m².
General specific gravity- 32 + 25 = 60 kg / m².
We calculate the specific gravity per 1 linear meter of rafters by multiplying 60 kg / m² by an installation step of 1.2 m. We get 72 kg.
We return to table No. 1 and select the cross section of the beam along the length of the span. We accept a load of 100 kg per 1 meter of rafters (with a margin). A log with a diameter of 140 mm, a board of 40 x 200 mm and other materials whose dimensions are in the same horizontal line are suitable.

Reference. When installing a broken mansard roof, 2 types of rafters are used - layered and hanging. On a gable roof, only hanging ones are used, what is the difference between them, is shown in the diagram.

The last table No. 3 will help you correctly determine the installation interval for truss trusses:

The proposed method is suitable for small rectangular houses with dimensions of 6 x 6 m. To build a mansard roof on a large cottage, it is strongly recommended to contact specialists - designers for calculations.

Frame manufacturing

The simplified method presented below involves the installation of a mansard sloping roof in 2 stages: assembly of roof trusses on the ground and subsequent installation on finished walls timber or log house. The structural material is boards with a section of 15 x 5 and 10 x 5 cm with a standard length of 6 m.

The beginning of the assembly - the formation of the upper belt of the truss system

Step by step technology looks like this:

Prepare the beams of the lower chord of the truss, taking into account the roof overhangs 25-27 cm on each side. If the length of the beam is not enough, it must be increased using a lining of the same section, nailed.
Lay the beam on the ground and attach the vertical posts to it with corners that form the walls of the attic room. Install ceiling beam and a support for the ridge (headstock), then attach two boards of hanging rafters for marking to it and the corners of the frame, as is done in the photo.
Cut the elements in place and secure them. From the remaining parts of the boards, make layered (lower) rafter legs in the same way and nail them to the frame. The farm is ready.
Make the rest of the trusses in the same way.

Advice. As a rule, windows or doors to the balcony are provided on the front gables. It is also convenient to make racks and belts for their installation on the ground, as well as sheathe openings with clapboard.

How to quickly and accurately assemble the rafters for the attic is described in the video:

Finished frames rise to the walls and are alternately fixed in place, starting from the first pediment. To prevent it from falling, install spacers and nail them to the walls of the log house. The second and subsequent farms are placed in the design position and connected to each other by boards.

After placing the rafters, they must be fixed to the walls in the following ways:

staples to the second crown of logs or beams from above;
on steel corners and galvanized screws, as shown in the photo.

Note. Installation on brick and other main walls is carried out by means of a mauerlat - a wooden beam laid on load-bearing structures around the entire perimeter of the building. In turn, the mauerlat is mounted on studs or anchor bolts, and a waterproofing layer of roofing material is arranged between it and the stone wall. The assembly looks like this:

The next step is to lay a diffusion membrane over the truss system - a film that protects against wind and precipitation, but allows water vapor from the insulation to pass out. Roll out the first sheet in the lower part of the roof and fasten it to the boards with a stapler, lay the next one with an overlap of 10-15 cm. When you cover the entire roof, nail the boards of the crate. More installation is shown in the video:

Roofing is laid on top of the crate - slate, metal tiles, and so on. The technology of laying and fastening depends on the chosen material.

Attic insulation

Since the attic space is planned as residential, it should be well insulated. Of the heat-insulating materials, mineral wool is the best “friends” with wood, because it allows moisture to pass through and allows it to “breathe”. The layer thickness is at least 150 mm, and in the northern regions - up to 300 mm. Warming is done in the following order:

Cut mineral wool slabs and insert them between the rafters.
To isolate the gables, nail additional racks and lay insulation between them in the same way.
If the width of the rafter legs is not enough to create thermal insulation of the required thickness, after laying the first layer, pin horizontal bars of the counter-lattice to them. Insert plates of the second layer between them.
Cover the insulation from the inside with a vapor barrier film, laying it with an overlap of 15 cm and gluing the joints with aluminum tape.
Nail the battens on top for cladding with drywall or other finishing material.

An important point. When laying the insulation, make sure that between it and the windproof membrane there is a ventilation air of 3-5 cm. The moisture formed in the mineral wool due to the dew point will be removed through it.

The process of thermal insulation of the attic is clearly shown in the next video:

Conclusion

Building a mansard roof is a laborious task and you cannot overcome it alone. Most of the work needs to be done with an assistant, and 3 people will be required to lift the trusses. Also, the success of your event largely depends on the correctness of the initial calculations. If the calculation method confuses you, and there are no smart engineers nearby, consult with experienced craftsmen– roofers, in whose competence there is no doubt. They will prompt the right decision and, perhaps, tell about the details of the installation of such systems.

Structural engineer with over 8 years experience in construction.
Graduated from East Ukrainian National University. Vladimir Dal with a degree in Electronic Industry Equipment in 2011.

During the operation of a private house, country cottage or country house, often the question arises of increasing living space. It is usually solved by means of an extension or add-on.

Building a house is a tricky business. In addition, the residential extension has one significant drawback - it “steals” the usable area of the site.

Therefore, a popular way to expand living space of an individual house is the device of the second floor or attic, i.e. attic roof. The design of the mansard roof allows you to use the resulting space as a living space.

What is better attic or second floor

The following facts speak in favor of the attic: lower construction costs, better insulation of living space, less load on the foundation. In general, the attic is the highlight of the house, giving it a certain flavor.

If in essence, then a full-fledged 2nd floor is more practical and easier in terms of implementation than an attic one. It all depends on the situation, if the house is being designed, then it is better to immediately provide for the second floor, because. arranging an attic is a more troublesome task. And if the house is residential and has a roof attic type, then it would be wise to equip in it living room instead of an attic "for the right things."

Types of mansard roof

The optimum angle of inclination is 40°. The slope should be located on the leeward side. Allows you to equip a small attic above the attic. Due to only one acute angle, the usable area of \u200b\u200bthe room increases.

Double pitched mansard roof

A simple gable (pitch or gable) consists of two slopes connected at a certain angle. The advantage of a gable roof is the ease of manufacturing the rafter part and finishing. The disadvantage is the appearance of a "deaf" area (at the junction of the roof to the wall), which is usually not used. Often attics with a gable roof are erected along with the walls. A 45° pitched roof is ideal for houses up to 6m wide.

Asymmetrical gable roof. A private house with such a roof will be original and functional at the same time.

The complexity of building a roof with asymmetrical slopes is to carry out calculations.

Broken mansard roof. Its difference is that each slope has two components. The sloping roof device allows you to get a higher attic space. And also reduce the unused area. Such roofs are most common, due to the possibility of attaching a garage or summer kitchen under one roof.

Four-pitched mansard roof

Hip mansard roof. In this design, the roof slopes play the role of walls.

One of the varieties of hip mansard roof is the Danish hip roof. Its construction is distinguished by the presence of gables, which allow you to mount ordinary windows (dormer windows) rather than roof windows.

Semi-hip mansard roof (two-slope, four-slope). A complex design, low slopes protect the gables of the house from precipitation.

Pitched roofs can be single or multi-level.

Non-standard solutions are also quite possible for a mansard roof. Their device requires careful calculation of loads, stability, etc. Without special education, installation is difficult, so the cost of work is higher compared to classical designs.

Some examples of the original mansard roof are in the photo.

We have decided on the types, the question remains how to make a mansard roof with your own hands.

Brief instructions contain the main stages of work and draw your attention to some of the nuances of their implementation.

Stage 1 - Design and calculation

The choice of the appearance of the mansard roof, and the calculation of its parameters is made taking into account such factors as:

slope angle;

finishing material;

A reliable assistant in the calculations will be SNiP 2.01.07-85 "Loads and Impacts".

Nuance. The greater the angle of inclination, the lower will be the height of the attic room (the minimum ceiling height of the room on the attic floor is 2.2 m). Accordingly, the smaller the angle of inclination of the mansard roof, the larger the area of \u200b\u200bthe room will be. If the slope is insufficient, then precipitation can collect on the roof, which will lead to additional loads on it.

Closer attention is paid to the calculations if a non-standard mansard roof is being built. For example, an asymmetrical gable mansard roof has a displaced center of gravity. This affects the uniformity of the load transfer on bearing walls and foundation.

At this stage, such an issue as a way to access the attic floor is also solved. The choice of the location of the stairs to the attic is an important decision. The internal location allows you to use it at any time of the year. External allows you to save the usable area of the lower floor.

Advice. Ceiling folding ladder for the attic floor is the most economical option, but the least practical.

Mansard roof truss system

The choice of truss system is influenced by:

attic dimensions;
span parameters;
roof shape;
construction of the first floor;
location of load-bearing walls and additional supports;
roofing weight.

Mansard roof truss system design

There are two types of roof rafter system with an attic:

hanging rafters. The walls of the house serve as the basis for the rafter legs. During the construction of hanging trusses, a mauerlat is not always installed (depending on the wall material);

layered rafters. In this case, it is necessary to build an additional support. Which is used as a ridge run or an attic wall reinforced with reinforced concrete. The device of a layered truss system is allowed with a distance between the bearing walls of up to 7 meters.

The structural difference between the device of the roof with hanging and layered rafters is shown in the diagram.

When building a mansard roof, a combined type is more often used - hanging rafters on top of the system, and layered on the sides.

At the same time, drawings are necessarily made indicating the location of individual elements and the distance between them. An example is shown in the figure.

The material was prepared for the site www.site

Calculation of the rafter leg for the mansard roof

The choice of wood species and the rationale for its optimal thickness.

The amount of material required for the truss system depends on its type and all the factors listed above.

Nuance. The gap between the rafter legs depends on the lumber used.

The step of the rafter legs under the mansard roof will be 60-90 cm.

As a material, glued timber (80x80, 100x100 mm), a board (for slate and metal tiles section 50x150, for ondulin 50-200) can be used.

Nuance. The length of the spans increases the diameter (section) of the rafters or reduces the gap between them.

As for the breed, it is recommended to use pine. Its wood is characterized by high strength, flexibility, ease of processing, and the absence of knots. Commercial wood must be at least grade 2. Solid beams can be replaced with glued timber, it has higher quality characteristics.

The thickness of the board for the manufacture of rafters (section of the rafter leg) must be at least 50 mm. The width of the board for the rafter leg is from 150 mm (if the length of the rafters is up to 6 meters, if more, then 180-200 mm). On the one hand, this requirement is due to the fact that it has a load, on the other hand, a heater is placed between the rafter legs.

Council - any construction or restructuring must be legalized in the relevant authorities.

Stage 2 - Installing the Mauerlat

Mauerlat - additional wooden trim along the upper perimeter of the building.

The purpose of the Mauerlat is to create conditions for secure fastening of the lower part of the rafters. As well as the redistribution of the load, which is created from the pressure of the roof on the load-bearing walls and the foundation of the building.

Installation of a simple gable mansard roof requires the installation of a Mauerlat only on those walls on which the rafter legs will rest. A four-pitched roof requires its installation around the entire perimeter of the building.

Advice. In a wooden frame, the role of the Mauerlat is played by the upper crown. This can be done, but subject to the installation of rafter legs on sliding fasteners. Because due to the load on the rafter system (wind, snow), horizontal pressure is created and the upper logs can move outward. In addition, if the material for the truss system is not properly dried, then over time, with rigid fastening, the roof is deformed.

Nuance. A stone cottage and house requires the arrangement of a Mauerlat around the entire perimeter of the outer walls. In brick, you can install its links only under the rafters.

Mauerlat parameters for logs - diameter 150 mm, for timber - 100x100 mm.

The breed is pine, but larch is better.

The Mauerlat mount must be reliable, because this is the basis for the entire truss system.

There are several ways to fasten the Mauerlat: with anchor bolts, studs or reinforcement (fixed at the base of the load-bearing wall);

Advice. If the building is erected from foam concrete or other porous material, only long bolts or reinforcement can be used, the length of which is 3 times the width of the Mauerlat beam. This is due to the fact that any other fasteners are pulled out very easily from a porous material.

annealed wire (embedded in brickwork);

wooden dowel (used when installing a Mauerlat in a log house).

Nuance. To prevent the destruction of the Mauerlat, it is necessary to provide proper waterproofing, for example, put roofing material, and treat the beam itself with antiseptic solutions.

If the width of the attic matches the width of the house, the rafter legs rest on the base of the load-bearing wall. But, it’s better to install a Mauerlat anyway.

Stage 3 - Mansard roof construction

Mansard roof frame device

Cover beams. Installed on the Mauerlat. In the future, they will serve as the basis for the device floor in the attic.

Mansard roof truss system

For a simple roof, the manufacture of rafter legs consists in the formation of simple triangles. They can be assembled on the ground and installed in the form of ready-made triangles.

For a gable sloping roof, a U-shaped frame is first attached, and the rafter part is already fixed on it in a hanging (for the top) and inclined (for the sides) way. The diagrams below show this more clearly.

The lower ends of the rafter leg must be sawn down and attached to the Mauerlat with nails or metal staples (movable fastening).

Nuance. Wash down the legs must be very accurate to ensure a snug fit to the Mauerlat.

Rafter legs are installed at the same distance from each other. Otherwise, the load on the system will be unevenly distributed.

Installation starts from the extreme legs. Then between them you need to pull the rope. So the horizontal will be maintained when installing the intermediate legs.

After all the rafters are installed, they are interconnected. The step of the lathing depends on the chosen roofing material.

Advice. Places intended for the installation of roof windows are reinforced with a transverse beam. Thus, the window will be securely fixed.

With a significant width of the mansard roof, you need to install a ridge beam. It will serve as an additional support. And part of the load (from the weight of the roof and snow) is redistributed to it.

With a considerable length, the ridge beam is supplemented by a support.

Mansard roof waterproofing

A hydrobarrier film is attached to the crate. The peculiarity of its fastening is to make an overlap of 100 mm. Most manufacturers mark the overlap with a bright stripe.

The waterproofing film is fastened with a construction stapler. And in case of rain, it will reliably protect the structure even in the absence of roofing material.

Mansard roof insulation

The insulation is placed under the waterproofing. Professionals recommend using flexible heaters for these purposes - mineral and basalt wool. Their advantage is flexibility, the ability to fill any voids.

Laying the vapor barrier

The vapor barrier film protects the roof insulation from steam penetrating into it from the attic living quarters.

Advice. It is important to provide the necessary gaps between the roofing material and the insulation. Their presence and parameters are determined by the type of insulation, the class of films used and the roofing material.

Mansard roof construction - video

Stage 4 - Installation of skylights

The area of windows, for sufficient daylight penetration, should be at least 12.5%.

Due to the design features of the mansard-type roof, special roof windows are used for glazing. The installation technology provides for the installation of windows before finishing work. At the same time, windows must be opened to allow fresh air to enter. In bad weather, they, of course, should be closed.

Stage 5 - Mansard roof roof

Thanks to the construction of a mansard roof, it is possible to significantly increase the usable space of a low-rise private house. However, this is a very time-consuming process that requires a preliminary calculation, compliance with certain rules and techniques. A well-designed mansard roof truss system is the key to creating a comfortable, reliable, functional and durable residential building.

Before the construction of the attic is necessary good project. The appearance of the future roof should be in harmony with general view building. There are several types of construction roof frame, which depend on the type of roof, the pitch of the rafters and the variant of the mansard roof. Having opted for a specific configuration, you should know exactly what structural elements the truss system consists of. It is the supporting skeleton of the roof, and can withstand not only its weight, but also the impact of precipitation.

Proper installation of the truss system ensures its reliability, functionality and durability.

When creating a mansard roof project, you should:

perform the correct calculation of the load on the supporting load-bearing walls and foundation, not allowing it to be exceeded;
choose high-quality thermal insulation to avoid uneven heating of the room;
choose good sound insulation thanks to the right roofing material;
choose a good waterproofing;
choose light weight facing materials for finishing the attic.

Mansard roof schemes

The truss system can have an inclined or hanging structure. In hanging structures, the rafters are supported by a mauerlat and a ridge run. To distribute the load on the rafters, lower and upper puffs are installed. When the length of the slope is more than 4 m, to prevent sagging in the lower part of the structure, the rafter legs are supported with racks and struts. The main advantage of this design is that all its elements are placed in unused places in the attic, which creates more free space.

An inclined structure is used in houses where a load-bearing partition is located in the middle of the building, on which the building legs rest. A bed is laid on the internal supporting structure, which plays the role of a Mauerlat, and racks holding the ridge run are mounted on it. This system is used for large areas of the mansard roof of a private house, the device of which can be seen in the photo. Here you can use roofing materials with a lot of weight, such as slate or ceramic tiles.

There are projects for mansard roofs of private houses, where both options for roof systems are used. To free up free space, the frame elements can be shifted to one of the sides, where they will be used as the basis for wall decoration, and the crossbar is suitable for ceiling cladding. In some architectural styles, beams and studs can be used as decorative elements.

To equip a large eaves overhang, the mansard roof is carried out with an emphasis outside the load-bearing walls. Mauerlat is not installed here. The system is mounted using beams. Be sure to install a brace, special racks cut into the floor beams, and the rafters are fixed using a reliable anchor connection and wire twists.

Mansard roof construction elements

The rafter system under the mansard roof consists of the following structural elements:

Mauerlat;
rafter legs or racks from beams;
vertical racks;
runs;
ridge beam;
crates;
additional beams, regels and runs.

The basis of the entire roof structure is the Mauerlat, which consists of square-section wooden beams attached to the outer walls of the building. The remaining elements of the mansard roof frame are attached to these boards. The main purpose of the Mauerlat is the perception and uniform distribution the entire load from common system roofs on the load-bearing walls of the building.

Rafter legs or racks of beams form the frame of the roof structure. For these elements, boards should be selected that are able to withstand the load of the roofing pie together with the outer coating. To support racks from beams or rafter legs, runs installed at an angle are used. Vertical posts hold the central part of the rafters, preventing them from bending. They also provide support for the ridge bar.

To ensure the rigidity of the future roof structure, a ridge beam is mounted on long truss systems. The crate is an additional wooden structure, which is attached to the truss system, and is the basis for the future roof.

Types of mansard roofs

Today, there are several options for mansard-type roofs that have different design truss frame:

lean-to;
gable;
broken lines consist of two or more slopes with different angle inclination;
hips have two triangular slopes from the short sides of the roof and two trapezoidal slopes from the long ones;
half-hips have two short end hips above the frontal part of the roof;
domed are characterized by a round or polygonal shape;
vaulted have an arc shape in section.

Shed roof is the easiest option to perform. He is often approached when it is necessary to make an attic on a small country house. The most popular among other types of mansard roofs of private houses, the photo clearly confirms this, is a gable roof. Its design and construction with your own hands does not cause difficulties. Especially if we are talking about the gable roof.

When choosing a sloping roof, it is possible to get a large, functional and comfortable attic room without additional work associated with the construction of walls. Today, many prudent owners of private houses prefer the gable roof truss system for corrugated boarding, the construction of which does not require numerous technological and technical tricks and is unjustifiably high flow funds for building materials.

The most difficult to install are hip, domed and vaulted mansard roofs. Their device requires a professional approach. These mansard roofs, photos of private houses clearly display this, have an unusual and very aesthetic design. They are characterized by a large number of pitched fractures, for which the installation of valleys is performed. The scheme of the truss system clearly shows the peculiarity and uniqueness of this design. The unsatisfactory condition of each of the valleys (internal corners) can pose a potential danger to the integrity of the entire roof.

Single pitched mansard roof. Photos of successful projects

The simplest, most reliable and cheapest option is a shed mansard roof. The result is a custom-designed building. This type of roof is used for industrial and commercial buildings. Also, it is often used for one-story small private houses. All roofing materials can be used here.

The design involves the creation of a window in the high part of the mansard roof. There is no ridge in this design, which simplifies its installation. Mauerlat is fixed on walls with different levels, due to which a bevel is formed. Beams rest on it.

The slope angle should be within 35-45 degrees. The smaller the slope, the more snow will accumulate on the roof surface, which will require the creation of additional supports and strengthening of the supporting beams. In addition, it will significantly reduce the attic room. The design is able to withstand strong winds with the correct orientation of the roof slope, which is necessary to increase the stability of the structure.

Useful advice! If the distance between the opposite load-bearing walls is no more than 4.5 m, you can not mount the supporting elements, but simply lay long wooden beams on the walls. This further reduces the cost of building a roof.

This type of roof involves the use simple elements to create ventilation of under-roof spaces. It is enough to sew up two overhangs with a perforated soffit, or to mount a ventilation grill.

However, don't choose shed roof for narrow buildings, where it is impractical to arrange the attic floor in this way.

Gable mansard roof: construction features

The gable roof is the most common and rational decision, which allows you to get a comfortable attic. Photos of houses with a mansard roof of this configuration confirm the demand for the design.

Do-it-yourself design and construction of a gable mansard roof does not cause any difficulties. It is formed due to two inclined planes (slopes) that intersect in the ridge area at a certain angle. Thanks to right choice the optimal angle, you can create a reliable protection of the building from heavy precipitation, strong gusts of wind, excessive snow pressure during heavy snowfalls.

There are varieties of the configuration of the truss system of gable mansard roofs:

gable symmetrical roof is a classic option, which makes it possible to evenly distribute the load on the load-bearing walls and roof support. The disadvantage of this design is the presence of sharp corners that take away the free space of the attic;
an asymmetric roof is a non-standard design, where the ridge can move to one side. If one of the corners is more than 45 degrees, you get a fairly spacious attic room. However, the calculations should take into account the uneven distribution of the load on the Mauerlat and load-bearing walls.
a broken mansard roof has a surface of slopes, bent in the middle, forming edges resembling two rectangles.

Roof truss system. Drawings of the classic version

When the question arises of how to make a mansard roof at home with your own hands, you should choose the most simple and practical option for further operation. Therefore, for private houses, preference is given to broken roofs.

This design allows not only to create a large attic space, but also, thanks to overhangs that fall quite low, to protect the upper part of the walls of the building and the foundation from precipitation. In addition, this is a good solution for creating the original exterior of a private house.

Related article:

How to choose the right material. How to avoid common mistakes at work. Do-it-yourself step-by-step work.

The angle of inclination of a sloping roof depends on the region, climatic conditions and the choice of roofing material. The classic broken mansard roof, the drawing of which clearly displays this, has a ratio of the slope of the upper slopes to the floor plane of 30 degrees, and the lower ones - 60 degrees. The angle of inclination of the side surfaces can vary from 45 to 80 degrees.

Useful advice! For regions where strong winds, it is better to arrange sloping roofs. Because the larger the ramp, the greater the windage it creates.

Based on these data, the parameters of the house, and the fact that the ceiling height in the attic should not be less than 2 m, you can calculate all the parameters. In the classic version, you can ignore the load on side surfaces from precipitation, as they will be held at the top of the roof.

Mansard roof calculation

On specialized sites you can find a do-it-yourself drawing of a broken mansard roof for a small house. It can be taken as a basis for future calculations, which include the calculation of the attic space, loads, roof structure elements and the amount of building materials.

To calculate the mansard roof, you can use the many years of experience of specialists who have repeatedly built a classic broken roof and can suggest what material to use. It is on this that many parameters of the truss frame depend. Payment required amount lumber to create a truss system comes down to determining the height and width of the spans, and, accordingly, the number of wooden bars, which is multiplied by their height.

The step between the rafters depends on the width of the insulation, which should be 3 cm less than the width thermal insulation material to reduce waste and simplify installation. Boards for rafter legs are also selected taking into account the thickness of the insulation material. In the case of using basalt wool, 200-250 mm thick and creating the required ventilation gap of 20-30 mm, the minimum width of the board is 230 mm. The thickness of the rafters must be more than 50 mm.

For beams and racks, you should choose a beam with parameters of 100 × 100 mm, which will create a solid and reliable structure even for areas in difficult weather conditions.

To calculate the amount of insulating and roofing materials, mathematical formulas are used to determine the areas of geometric shapes, from which a certain type of attic roof is formed.

Today, on the Internet, you can perform an online calculation of the mansard roof. To begin with, the type of the mansard roof, the scheme of the truss system, the insulation and roofing material are indicated and the requested geometric parameters are entered. To obtain a more accurate result, you should use the services of a specialist who will not only calculate all the loads and dimensions of building elements, but also tell you which material is better to choose.

Mansard roof windows

The attic differs from ordinary rooms in that its walls are a truss frame, which consists of certain roofing surfaces, which is clearly shown in the drawings of mansard roofs. This also affects the design of the window for a given room, which should transmit natural light well, and at the same time withstand the load in the form of strong gusts of wind or heavy precipitation. This is due to the fact that the influence of weather conditions on the sloping part of the roof is much stronger than on the massive load-bearing elements of the building.

Important! According to SNiP, the window area should be at least 10% of the total floor area.

The window in the mansard roof, the photos clearly show this, can be located in the plane of the roof, inclined or vertical, or be at the end of the attic. Vertical windows in the roof plane can be protruding above it (dormer), or recessed into the room.

The most popular and easiest to install is the sloped window in the roof plane. It can skip maximum amount natural daylight. After its installation, the roof surface does not change, but remains flat. However, this option requires the creation of proper waterproofing of the junction. Here you should use special models with reinforced glass and a reinforced metal-plastic frame.

The area of the window opening is selected in proportion to the angle of inclination of the roof. The width of the window should be selected in such a way that the element fits into the distance between the rafters without violating the integrity of the structure. If the window is much wider, then you will have to install a reinforced beam that will connect the cut rafters to install the window. In this case, if one narrow window is not enough, it is better to install two adjacent narrow elements, which will ensure the integrity of the truss frame.

To install a dormer window, a complication of the geometry of the roof is required, namely, the installation of side and upper valleys is required, followed by their thorough waterproofing. It also makes the installation of roofing more difficult.

It is advisable to arrange a vertical window recessed into the room only when access to the balcony is made through it. In other cases, these are unjustified significant financial costs (complication of the roof geometry) with a minimal effect (insufficient natural lighting).

The simplest, most practical and cheapest option is to install a window at the end of the roof. This is especially true for country houses with a mansard roof.

Mansard roof installation methods

The device of the truss system of the mansard roof can be carried out in two ways. The first option involves collecting the truss frame on the ground, followed by lifting it ready-made to the top of the house and solidly fixing it. The method is effective for small structures.

How to make a mansard roof with the collection of part of the truss system on the ground? Previously, at the top of the building, the extreme structures are vertically exposed and fixed, which will later be the pediments. You can temporarily fix them with long bars nailed to the wall. In the Mauerlat, recesses are created with a given step, where the assembled structure will be mounted. To ensure the correct geometry and create structural rigidity, its elements can be fixed with spacers. When the installation of the side beams is completed, and the entire system acquires the necessary rigidity, the spacers can be removed. The installation video of the gable roof truss system will clearly show all the features of this option.

The second option is more traditional. It involves the installation of a mansard roof on site in compliance with a strict sequence of actions. This method is the most convenient and effective in the construction of a large truss system. Because to lift the assembled structure up, you will need to attract specialized equipment.

How to build a mansard roof in the traditional way?

Some subtleties in the technology of erecting mansard roofs of private houses depend directly on its type. However, the sequence of actions is similar for all types of mansard roofs.

Before you make a mansard roof, it is necessary to lay a Mauerlat in the longitudinal direction on the load-bearing walls, and fix it on the masonry or armored belt with studs or wire rod. Mansard roof truss structure wooden house can be attached to the upper crown, which will play the role of a Mauerlat.

The construction of a mansard roof begins with the installation of floor beams. They are attached to the Mauerlat. Then the construction legs are attached to the beams. In the center of the beams, the mounting points for the supports and the ridge element should be noted.

With the same distance, you should mount the racks from the boards, fixing them with the help of corners. The first pair of racks is fastened with puffs from wooden bars. Rafters should be mounted on the formed U-shaped structure. They can be installed on a power plate or by cutting a groove on a floor beam.

Next, you should proceed to the installation of ridge rafters, which are connected using metal plates or bolts with washers. To create the necessary rigidity of the structure, struts must be attached to the central part of the side rafter and the rack, and beams should be mounted in the center of the puff. Similarly, the installation of other trusses with a distance of 60-100 cm is carried out. They are attached to each other with the help of runs.

With the help of brackets, all nodes of the attic structure are fixed, and final strength is given to it. After that, the crate should be mounted, which can be solid or sparse, depending on the roofing option.

If used flexible tile, asbestos cement flat slate or roll material, should be done solid crate. It is installed in two layers. The lower flooring consists of 20 cm thick bars laid in 30 cm increments.

For clay tiles, asbestos-cement slate, steel, metal coating sparse type is used. To do this, the installation of bars is carried out, with a section of 5 × 5 cm and a step of 20-30 cm, from the eaves upwards perpendicular to the rafters. On the overhang, it is necessary to install a flooring of wooden boards with a width of about 70 cm. Next, you should fix the bars along the ridge and ribs, which are joined end-to-end. This process can be clearly seen in the photo of the gable roof truss system under the metal tile.

Mansard roof insulation technology

Insulation of the mansard roof of a private house allows not only to insulate the attic, but also to create proper thermal insulation of the entire roofing system so that it lasts for many years.

As part of the mansard roof insulation scheme, there is a set of measures, which include the creation of heat, hydro and vapor barriers. Roofing material is laid on top of this roofing cake, which protects the entire structure from negative factors. environment. To protect the insulation from the negative effects of condensate, which reduces it thermal insulation properties, it is necessary to protect it from the roofing material. For this, one of the proposed sheet materials can be used:

waterproofing film, which is attached from the outside to the rafters. It should not touch the insulation material, therefore it is cut off from it by a crate or counter rails;
diffusion membrane ̶ is attached to the insulation and protects it from any moisture.

Useful advice! Waterproofing material should be laid with a slight sag, excluding the possibility of pulling it.

The waterproofing layer must be laid out across the rafters. You should start from the bottom. The first row descends into the gutter. Each next one must be rolled out with an overlap of 10-12 cm. Thus, you should reach the ridge. There, the material along the upper edge is cut off and fixed on both sides. A strip should be rolled along the ridge, which descends from both sides of the roof to the gutter itself, which ensures uniform drainage of water.

The vapor barrier layer in the form of a membrane is reliable protection insulation from penetration into its thickness of steam from the room. The material is also overlapped and attached to the joists using stapler staples. All joints and junctions should be carefully glued using a special double-sided vapor-proof adhesive tape.

Useful advice! On the vapor barrier film a thick line is applied, from which it is necessary to start the next layer. Following it, the canvases are fastened with adhesive tape.

Important rules for insulating a mansard roof

When the question arises, which insulation is best for a mansard roof, there is no definite answer here. However, due to the fact that the attic roof is characterized by a large angle of inclination, you should not use soft materials, which will cake and slide off the surface.

Roll insulation must be laid from the bottom up. To do this, use a construction stapler and string. Rolling out the roll, the material is pressed against the slats. With the help of lace and staples, the letter Z is drawn. Each layer of insulation is attached using this technology.

It is better to give preference to plates with a density of 30-50 kg per cubic meter. m. In this case, the pitch of the rafters will have to be adjusted to the size of the insulation, which should be 10-15 mm less than the width of the insulation plate. This is required so that the material can become loose without the formation of cracks and be well held between the beams. If the width is smaller or larger, it will be necessary to cut the material. It is not always possible to create an even cut, and besides, a large number of residues remain. The plates should be positioned in such a way that the seams of the previous row overlap with the next.

The insulation is laid in such a way as to ensure a minimum number of cold bridges. Additionally, the remaining material can be placed on planks of the required width stuffed from the side of the room. A vapor barrier is laid on top of the insulation layer and a crate is made for future finishing. This option, where even the rafters overlap, almost completely eliminates the formation of cold bridges. Despite the fact that a little more insulation material is required, the attic will ultimately turn out to be warmer, which will make it possible to reduce the cost of heating the room.

Important! Cold bridges contribute to the formation of moisture in the roofing cake. This can lead to rotting of the rafters, swelling of the heat-insulating material, corrosion metal elements design, the occurrence of unpleasant odors indoors.

How to properly insulate a mansard roof: progress of work

There are two ways to insulate a roof: from the inside or from the outside. When using the first option, you can postpone the execution of interior decoration for a certain period. The second option assumes full complex works, which allows to achieve a quick completion of construction.

How to insulate a mansard roof from the outside? To do this, it is necessary to prepare the surface of the rafters by cleaning it from protruding elements that can damage the layer of hydro and vapor barrier. From the inside of the room across the rafters, it is necessary to fill the crate on which the insulation will be located. Instead of crates, you can attach galvanized wire or cord.

From the side of the roof, this crate is mounted thermal insulation layer subject to the above rules. The thickness of the mansard roof insulation must be more than 100 mm. A superdiffusion membrane is laid over the heat-insulating material. Next, you need to fill the crate on which the roofing will be laid.

Now from the inside of the room it is necessary to fix and glue the vapor barrier layer. Next, you can proceed to interior decoration. This option of roof insulation is considered the easiest to perform. Heat-insulating plates easily keep within on earlier created crate.

The technology of insulating the attic roof with your own hands from the inside is carried out in two stages. The first required step is as follows:

The waterproofing layer is rolled out and fixed on the rafters.
The crate is stuffed.
Roofing material is installed.

After completing the mandatory list of works, it is possible to postpone the insulation of the mansard roof indefinitely, which may be due to the lack of financial opportunities at the present time.

The second stage is less convenient in execution. Insulation of the mansard roof will be carried out from the inside. Here it is necessary to create a building envelope that will hold the insulation and prevent it from being pushed out more than possible. To do this, planks are stuffed between the lags in increments of 40-50 cm. They will not only hold the insulation, but also create the necessary ventilation gap.

Next, the installation of a heat-insulating layer is carried out in compliance with all the rules. A crate is stuffed on it. Next, you need to position and stick the vapor barrier membrane. After that, you can begin to perform finishing work. To do this, you can mount the crate, or you can do without it.

Varieties of insulation for a mansard roof. What is the best heater?

Today, there are several options for insulation for a mansard roof:

mineral wool;
expanded polystyrene;
polyurethane foam;
Styrofoam;
glass wool;
isovert;
ecowool.

The most popular material is mineral wool, namely basalt. This relatively inexpensive material is available in a convenient thickness and sufficient rigidity. It retains heat well, is not combustible and does not rot. However, she is afraid of moisture. Therefore, in order to ensure the preservation of all technical and operational properties, it must be carefully protected from all sides.

Polyfoam has good performance characteristics, which give it the ability to create good thermal insulation. The price of the material is relatively low. It is easily mounted between the rafters by surprise due to its elasticity and due to the fact that plates can be purchased required size. All joints should be sealed with mounting foam.

Useful advice! During combustion, it is able to release harmful substances, so it is better to give preference to self-extinguishing brands where special additives are used.

The material is not afraid of moisture. It does not conduct steam, which is the main disadvantage of foam. In this regard, it is necessary to create a good ventilation system in the attic, which will lead to additional financial costs.

Extruded polystyrene foam has the best characteristics, the thickness of which is two times less than that of mineral wool, and one and a half than that of polystyrene. The material is equipped with a locking system, which eliminates the formation of cracks. EPPS does not form fungus and mold; rodents and insects do not like it. However, it does not let steam through, which requires a good ventilation system. Another disadvantage is the high cost of the material.

Recently, a new type of insulation has appeared - expanded polystyrene foam. It is applied to the surface in liquid form, filling all the cracks. At the same time, having reacted with oxygen, it increases several times in size, forming a monolithic coating.

Useful advice! The use of expanded polystyrene foam will correct the situation in the absence of a waterproofing layer during the installation of the roofing.

Another insulating material of the new generation is ecowool, which has good characteristics. However, its use requires compliance with a special technology. The loosened cotton wool is fed under pressure into a closed cavity, filling all the voids and forming a strong integral layer of insulation. To organize a closed cavity, sheet material in the form of plywood, GVL or fiberboard is nailed to the rafters from below and from above.

A distinctive advantage of this material is its ability to conduct steam. Here the humidity is regulated natural way, which does not require the organization of a vapor barrier. However, a ventilation gap must be created between the insulation and the roof, where the movement of air masses occurs.

Today, among the possible projects of houses with a mansard roof, you can choose the most acceptable and attractive option, and bring it to life for your own private home. To make the house visually beautiful and aesthetic, it is necessary to take seriously the issue of choosing the type of mansard roof, which should be in harmony with the structure of the building. A well-arranged roof truss system is able to flawlessly perform all its operational and protective functions, which will create a warm, cozy and comfortable room.

Elements for fastening parts of the mansard roof truss system. Calculation, fastening and installation of the mansard roof truss system

Mansard roof truss system design

Scheme of the truss system of the mansard roof

Mansard roof rafter step

Table: dependence of the step between the rafters on the cross section of the beam and the length of the rafters

The length of the rafters and lathing of the mansard roof

Video: mansard roof calculation

The nodes of the truss system of the mansard roof

Video: nodes of the truss system

Calculation of the truss system of the mansard roof

Table: values ​​of trigonometric functions for various slope angles

Table: calculation of the amount of lumber in 1 m 3 and the volume of one unit of material

Installation of the attic truss system

Video: installation of a mansard roof

Attic project

Video: professional mansard roof calculation using special software

Parameters of materials for the construction of a mansard roof

What section are required rafters

Tools

Installation steps

Mauerlat mount

Installation of the truss structure

Prices for various types of fasteners for rafters

Mansard roof waterproofing

Roofing installation

Prices for popular types of corrugated board

Video: a detailed video tutorial on building a mansard roof

The choice of roof design

Calculation of the truss system

Frame manufacturing

Attic insulation

Conclusion

What is better attic or second floor

Types of mansard roof

Double pitched mansard roof

Four-pitched mansard roof

Mansard roof truss system

Mansard roof truss system design

Calculation of the rafter leg for the mansard roof

Mansard roof frame device

Mansard roof waterproofing

Mansard roof insulation

Laying the vapor barrier

Mansard roof construction - video

Mansard roof schemes

Mansard roof construction elements

Types of mansard roofs

Single pitched mansard roof. Photos of successful projects

Gable mansard roof: construction features

Roof truss system. Drawings of the classic version

Mansard roof calculation

Mansard roof windows

Mansard roof installation methods

How to build a mansard roof in the traditional way?

Mansard roof insulation technology

Important rules for insulating a mansard roof

How to properly insulate a mansard roof: progress of work

Varieties of insulation for a mansard roof. What is the best heater?

Creating a mansard roof with your own hands step by step. Video instructions

Table: values of trigonometric functions for various slope angles