Rafters for a sharp roof. Strong roof: roof truss system and its types

In previous articles that described the roof structure, we already said that the hanging rafters rest on the Mauerlat with their lower end, and the upper ends of adjacent rafters abut (either directly or through a ridge board) against each other. In the very simplified version this is shown in Fig.1:

Picture 1

I think it is obvious to everyone that with such an arrangement, there are bursting loads on the walls. To reduce them, puffs are added to the truss truss. But let's talk about everything in order.

As an example, let's take a house with a semi-attic in the Volgograd region. The sum of snow and wind loads is 155 kg/m 2 . The dimensions of the house box are 8x10 meters. The thickness of the walls is 50 cm. The angle of inclination of the slopes is 40 ° (see Fig. 2):

Figure 2

STEP 1: We install . In this design, in addition to the usual loads, bursting forces will act on it, tending to move it off the wall. For more reliable fastening, you can add more metal mounting plates to the anchor bolts (or studs) (see Fig. 3). The plates can be fixed to the wall, for example, with frame anchors, and to the Mauerlat, you can use nails, self-tapping screws, and capercaillie.

Figure 3

STEP 2: We define required section rafters. We make the calculation in the "Arch" tab (see Fig. 4):

Figure 4

The cross section of the rafters is taken 50x200 mm in increments of 60 cm.

A question may immediately arise here. Where do we get the distance from the ridge to the puff (crossbar). We have it equal to 2 meters. Earlier on the site, we already said that before proceeding with the construction of the roof, we need to make a drawing of it on paper, be sure to scale (in all proportions). If you know how, you can draw on the computer. Further, according to this drawing, we determine all the dimensions and angles of interest to us.

Puffs are installed between hanging rafters to reduce bursting loads on the walls. The lower the puff, the more useful it is. Those. the less bursting load falls on the walls. But since in our example, puffs still play the role ceiling beams attic floor, then we determine the height of their location based on the height of the ceilings we need. I took this height of 2.5 meters (see Fig. 5):

Figure 5

STEP 3: We make a template for the lower rafter cut. To do this, we take a piece of board of the section we need about a meter long, apply it to the Mauerlat at our angle of inclination of the slopes of 40 ° (orient yourself along the pediment) and make the markup, as shown in Figure 6:

Figure 6

The vertical and horizontal lines we need (shown in blue) are drawn using a level. Depth washed down 5 cm.

So let's make a template.

STEP 4: We install a ridge board, through which all the rafters will be interconnected. First you need to outline the place of its installation.

We take the template made earlier and apply it to the Mauerlat. We are interested in the size shown in Figure 7 (here it is 18 cm):

Figure 7

Let's call the lower point on the Mauerlat point "A".

We transfer the resulting size to the top of the pediment, make markings in accordance with Figure 8:

Figure 8

Let's designate the lower right corner as point "B". Now we can measure the distance from the attic floor to point B (the length of the temporary posts).

We install strictly vertically temporary racks from a 50x200 board and put a ridge board of the same section on them. Under the racks for their fixation, you can put a board fixed with simple dowel nails to the floor slabs (see Fig. 9). It is not necessary to fasten strongly, then we will remove it. The distance between the racks is not more than 3 meters.

Figure 9

We fasten the ridge board to the gables with metal brackets. The stability of the racks is provided by jibs.

Perhaps you could see somewhere how hanging rafters are installed without a ridge board (see picture on the left). This method is very familiar to me, we used to do this too.

But when we tried the option with a ridge board, we settled on it. Despite the fact that it takes some time to install the racks and the ridge board, the subsequent installation of the rafters is much more convenient and faster. In the end, you win in time. In addition, the design is more stable and more geometrically even.

STEP 5: We manufacture and install rafters.

We do the rafter like this: we take a board of the desired length, apply a template to one end, mark it out and make the bottom washed down. Then we measure the distance between points "A" and "B" with a tape measure (see Fig. 7-8). We transfer this size to our workpiece and make the top washed down. The angle we need for the top notch is on our template (see Fig. 10). We have it equal to 90 ° + 40 ° = 130 °

Figure 10

Thus, we put all the rafters (see Fig. 11)

Figure 11

The connection of the rafters with the Mauerlat here does not look the same as it was, for example, I think you have already understood that this is due to the presence of bursting loads, which were not in that version. However, in future articles you will see that this option is just one of the possible, and not the only correct one. We will use more familiar to us washed down. The main thing is to securely fasten the rafters to the Mauerlat.

At the top, the rafters will protrude beyond the ridge board. You can drive small bars between them, or you can leave it as is. This, in principle, does not play any role (see Fig. 12):

Figure 12

We fasten the rafters to the ridge with nails or self-tapping screws. It is not necessary to install any additional fasteners here. In general, in this design, thanks to the lower gash, the rafters are obtained, as it were, sandwiched between the Mauerlat and the ridge board.

STEP 6: Installing braces.

We make them from boards of the same section as the rafters. There is no need to make any cuts and cuts here. We make puffs superimposed on the rafters. We fasten them with several nails and tighten them with a threaded stud with a diameter of 12-14 mm (see Fig. 13):

Figure 13

Thus, we install all the puffs and remove our temporary racks on which the ridge board was placed:

Figure 14

Now you can guess the purpose of the small windows in the upper part of the pediment. Through them, ventilation of the insulation will be carried out, which will lie on the ceiling of the half-attic floor (between puffs).

STEP 7: We attach filly to the lower ends of the rafters eaves overhang(see fig.15). We make them from boards with a section of 50x100 mm. We make the length of the filly such that we get a cornice overhang of the width we need (40-50 cm), and that it overlaps the rafter by at least 50 cm. We fasten the filly with several nails and tighten it with 2 threaded studs. In the middle part, for additional emphasis on the wall, you can fasten a small bar to the filly with nails or self-tapping screws.

Figure 15

Please note that at the junction of the filly of the overhang with the Mauerlat, we do not drink on it, because. this will reduce it and without that not a large cross section. Here we first make a small cut in the Mauerlat itself (see Fig. 16):

Figure 16

To make the cornice even, use a lace. First put the extreme fillies, then pull the lace between them and put all the rest. In Figure 17 the shoelace is shown in blue.

Figure 17

Step 8: The following steps are already known to us from previous articles. We put the fillies on the pediment and fasten the wind boards (see Fig. 18):

Figure 18

STEP 9: Now we can leave the cornices in the form in which they are.

Let's see another version of the eaves overhangs (see Fig. 19):

Figure 19

Such "earrings" are made from inch boards 10-15 cm wide. We fasten them with self-tapping screws.

Thus, now it remains for us to hem the siding belts to the bottom of the cornices; fastened to the rafters protective film, make a counter-lattice and crate; cover the roof with roofing material. We have covered these steps in previous articles. I think it makes no sense to repeat here and when considering other roof structures in the future.

Properly designed and assembled according to technology, the roof serves as a barrier that prevents cold air and moisture from entering the house. Outside, with the naked eye, we see only a small part of the structure - the roofing. But the roof frame, which is the most important component, performs the main supporting functions and absorbs the effects of wind and snow loads.

So that it does not deform as a result of operation, it is necessary to correctly calculate the cross-sectional value of its elements and determine the distance between them, taking into account the weight of the roofing material, slope and climatic conditions. In this article we will tell you what the gable roof truss system of a house is, what it consists of, how it is designed and assembled by hand.

The truss system for a gable roof of a house is a system of interconnected supporting elements, which together form the frame of the structure.

It is made of wood or metal in accordance with the calculation of the loads that will affect them during operation. The roof truss frame performs the following functions:

Gives roof slopes the necessary slope. Traditional equilateral rectangle shape gable roof gives exactly the rafter frame, which forms a slope between the base of the roof and its ridge. The angled surface allows snow and water to slide freely off the slope.
Distributes the load from the weight roofing cake . The weight of the roofing pie, taking into account the snow load, can reach up to 500 kg / m2, so the gable roof is subjected to intense load, especially in winter period. The rafters of a gable roof evenly distribute the weight that falls on them, and then transfer the load to bearing walls and the foundation of the house.
Serves as a basis for fixing thermal insulation and roofing material. The rafter frame of the roof serves as a kind of skeleton of the structure around which its “body” is built. Between rafter legs thermal insulation must be installed, and a roofing covering is fixed on the crate, which protects against moisture penetration.

Please note that the design of the gable roof truss system is quite complicated to design and assemble, especially if the master does not have enough experience. Indeed, in order for it to be able to withstand heavy loads, it is necessary to correctly calculate the cross-section of the rafters and the pitch of the rafters, taking into account the slope and length of the slopes, the roofing material used, and also draw up a drawing according to which the assembly will be performed.

Types of truss systems

Rafter systems differ in many factors, their composition depends on the layout of the wooden or brick house, the total weight of the roofing cake, the material from which the frame is made, as well as the type roofing.

An important characteristic of the design is their bearing capacity, which determines how much weight they can withstand without deformation. According to the characteristic features, the following types are distinguished truss systems:

Layered

A rafter frame of a layered type is a frame whose rafters have 2 points of support. The upper end of the leg rests on a ridge run, mounted on vertical posts fixed to the inner wall. And with the lower end it is installed on the Mauerlat.

The assembly of a rafter system of a layered type on a gable roof is possible only if there is at least 1 load-bearing partition or capital column inside the house. Such a construction is often called non-thrust, because the second fulcrum of the rafters compensates for the bursting load on the walls of the house, which is assumed by the hanging frame installation scheme.

Rafter legs of a layered type experience only a bending load, which can be eliminated by various struts. The layered truss system allows you to cover houses up to 14 meters wide.

hanging

The hanging truss system is distinguished by the fact that its rafters rest only with their lower end on a Mauerlat beam mounted on external load-bearing walls. The upper end of the rafter legs of this design does not rest on anything, but, as it were, hangs in the air, which causes 2 types of load: bending and bursting.

The bursting load of such an arrangement of elements on the outer walls is so great that it has to be compensated with the help of numerous crossbars and ties, due to which the rafter pairs are tied together.

The device of a gable roof with hanging rafters consists of triangular trusses, the rigid form of which is not subjected to loads. It is believed that the complexity of the hanging circuit is much higher.

Do-it-yourself do-it-yourself rafter system of a gable roof is mounted without difficulty, if you correctly calculate the pitch of the rafters, that is, the distance between the rafters and the size of their cross section.

Combined

Combining the best of both systems, it is recognized as the most reliable. It is used in cases where, indoors, not walls, but columns are used as a support inside the house. Then hanging and layered rafters can be alternated to strengthen the structure due to additional elements without increasing the consumption of building materials.

Important! A sliding rafter roof is another type of frame, which differs in that the rafter legs are installed on the Mauerlat not with a rigid mount, but using a movable support. The sliding mount allows the roof to change dimensions within the power reserve during the shrinkage of a wooden house.

Design

The device of the truss system of a gable roof of any of the listed types is a combination of auxiliary and supporting elements. They evenly distribute the weight of the roofing cake, and also compensate for the bursting and bending loads that occur between them.

The cross section, length and pitch of the rafters are determined using an engineering calculation that takes into account the weight of the roofing pie, the climatic conditions in the construction region, and the slope of the structure. Part roof frame gable roof usually includes the following elements:

Mauerlat. Mount the Mauerlat beam on the outer walls of the house, on which the roof slopes rest. It serves to relieve pressure on the supports and uniform distribution load from the weight of the roofing cake. It is made of a durable beam with a section of 150x150 mm or 200x200 mm and is attached to the upper belt of the walls using anchor bolts or long metal studs.
Sill. This is an analogue of the Mauerlat, only it is installed on internal load-bearing walls, and vertical stands must be placed on it for mounting a ridge run.
rafter legs. This term refers to the elements of the frame, which are made of boards with a cross section of 150-40 mm and are installed at an angle to the base of the roof, forming the angle of inclination of the slope. What to do the distance between the rafters, their length and thickness is determined by calculation, taking into account the total load to which they are subjected during operation.
puff. A puff is called beams that are placed horizontally and connect the legs of one rafter pair to each other in order to reduce the bursting load on the outer walls of the structure. A crossbar is a puff installed under the very ridge of the structure.
Racks. A stand is a vertical beam placed on a bench to support a ridge run. It is easy to determine what distance should be between the racks, because it repeats the step of the rafters.
Struts. Diagonally located supports that support the rafter legs in the middle or at the bottom, preventing their deflection, are called struts.

Please note that only the calculation of temporary and permanent loads to which they will be subjected during operation can determine how to properly position the elements of the truss system. Calculating the total weight of the roofing cake helps determine the correct distance between the rafters, calculate their length and the required thickness.

The calculation of the gable roof truss system is based on the fact that in the frontal dimension it has the shape of an equilateral triangle, the sides of which can be easily calculated using simple trigonometric formulas.

These simple calculations help determine the optimal distance between the rafters, their thickness and length. The design calculation is performed in the following sequence:

Determine the design and slope of the roof. Exists various ways choice of the type and slope of the roof structure. This parameter depends on the climatic conditions and performance characteristics of the selected roofing material.
Determine the total load on the structure. To do this, they sum up the constant loads (the weight of the roofing, their weight of the frame, thermal insulation and floors) with the temporary loads (snow load, wind load), multiply by a correction factor that takes into account the slope of the slopes, and then add 10-15% to this figure to the frame had some margin of safety.
Calculate the length of the rafter legs. To do this, use the Pythagorean theorem, because the truss truss is an equilateral triangle. It turns out that the square of the length of the rafter leg is equal to the sum of the squares of the height of the blood and half the length of the laying. Knowing how to calculate the length of the rafters, you can calculate the height of the ridge.
Determine the section of the elements. The optimal section of the elements is selected according to the tables in accordance with the length of the rafter legs and the distance between them. The higher these indicators, the thicker the rafter should be.

Remember that before you calculate the rafters on the roof, you need to decide on the basic design parameters. In particular, it is necessary to know exactly the height of the ridge and the slope of the roof, as well as the dimensions of the room to be covered. The result of the calculation of the roof elements should be a detailed diagram of the truss system, reflecting their dimensions and the angles between them.

We calculate the angle of inclination

The angle of inclination of the slopes is selected not depending on aesthetic preferences, but based on weather conditions, taking into account the roofing material. Steeper slopes of 40-45 degrees are built in areas with a large amount of snow cover, and more gentle slopes of 10-20 degrees in places with strong gusty winds.

Keep in mind that the steeper the slope, the higher the consumption of materials, the greater the total cost of the roof. Be sure to take into account the requirements of the material:

Tiles, slate require a slope of at least 22 degrees, otherwise, precipitation seeps through the joints between the elements.
The metal tile is laid at an angle of at least 14 degrees, as it suffers greatly from gusts of wind, it can deform or even fly off.
Soft roofing allows a slope angle of up to 5-10 degrees, making it possible to cover slopes of any geometry with it.
Ondulin is considered one of the most reliable materials and can even be used for roofs with a slope of less than 6 degrees.
Profiled sheets cannot be laid at an angle of less than 15 degrees, however, even slopes with an acceptable slope should be treated with a sealant for better waterproofing.

Assembly technology

Before mounting the roof frame, it is necessary to calculate the parameters of its elements, based on the calculation of the total load on the structure, and also create detailed drawing representing its results.

Having a frame diagram in front of you, it is much easier to qualitatively install the gable roof truss system. The assembly technology of the structure implies the following sequence:

First, a Mauerlat is laid on the upper belt of the outer walls, on which the slopes will rest, and a bed is mounted on the inner partitions, if the system is layered. These elements must be firmly fixed with anchor bolts or studs.
Then the rafters are fastened. They are fixed with nails to the Mauerlat, and are also interconnected using a metal lining. It is worth recalling that in the rafters they make a drink under the Mauerlat beam, and not vice versa. First, the installation of rafters located on the edge is carried out in order to set the level along which the rest of the pairs will be aligned.
After installing the rafters, auxiliary supporting elements that I will support them - struts, puffs, contractions. To more securely fix the crossbar, its end is made with a protrusion half the thickness of the beam and it is hemmed to the rafters, fixing it with nails in several places.
A crate is nailed over the rafter legs, on which the roofing material is fixed. The material and pitch of the lathing is selected in accordance with the characteristics of the roofing material and the slope of the roof.

Remember that a well-designed and high-quality assembled truss system is a guarantee of strength, reliability and durability of a gable roof. Therefore, do not neglect the help of professional roofers and designers when creating a roofing design for your home.

Video instruction

At the heart of each roof is a large number of beams, rafters, racks and girders, which are collectively called the truss system. Over the centuries-old history of types and methods of its organization, a lot has accumulated, and each has its own characteristics in the construction of knots and cuts. We will talk in more detail about what the gable roof truss system can be and how the rafters and other elements of the system should be attached in more detail.

The design of the gable roof truss system

In the context of a gable roof is a triangle. It consists of two rectangular inclined planes. These two planes are connected at the highest point into a single system with a ridge beam (run).

Now about the components of the system and their purpose:

Mauerlat - a beam that connects the roof and walls of the building, serves as a support for the rafter legs and other elements of the system.
Rafter legs - they form the inclined planes of the roof and are the support for the crate under the roofing material.
Skate run(bead or skate) - combines two roof planes.
A puff is a transverse part that connects opposite rafter legs. Serves to increase the rigidity of the structure and compensate for bursting loads.
Beds - bars located along the Mauerlat. Redistribute the load from the roof.
Side runs - support the rafter legs.
Racks - transfer the load from the runs to the beds.

Filly may still be present in the system. These are boards that extend the rafter legs to form an overhang. The fact is that in order to protect the walls and foundation of the house from precipitation, it is desirable that the roof ends as far as possible from the walls. To do this, you can take long rafter legs. But standard length lumber of 6 meters is often not enough for this. Ordering non-standard is very expensive. Therefore, the rafters are simply grown, and the boards with which this is done are called “fillies”.

There are quite a few designs of truss systems. First of all, they are divided into two groups - with layered and hanging rafters.

With hanging rafters

These are systems in which the rafter legs rest only on the outer walls without intermediate supports (bearing walls). For gable roofs, the maximum span is 9 meters. When installing a vertical support and a strut system, it can be increased up to 14 meters.

The hanging type of gable roof rafter system is good because in most cases there is no need to install a Mauerlat, and this makes the installation of rafter legs easier: no need to make cuts, just mow the boards. To connect the walls and rafters, a lining is used - a wide board, which is attached to studs, nails, bolts, crossbars. With such a structure, most of the bursting loads are compensated, the impact on the walls is directed vertically downwards.

Types of truss systems with hanging rafters for different spans between load-bearing walls

Gable roof truss system for small houses

Exists cheap option truss system when it is a triangle (photo below). Such a structure is possible if the distance between the outer walls is not more than 6 meters. For such a rafter system, it is possible not to calculate the angle of inclination: the ridge must be raised above the puff to a height of at least 1/6 of the span length.

But with this construction, the rafters experience significant bending loads. To compensate for them, they either take rafters of a larger section or cut the ridge part in such a way as to partially neutralize them. To give greater rigidity in the upper part, wooden or metal plates are nailed on both sides, which securely fasten the top of the triangle (also see not the picture).

The photo also shows how to grow rafter legs to create a roof overhang. A notch is made, which should go beyond the line drawn from the inner wall upwards. This is necessary to move the incision site and reduce the likelihood of a rafter breaking.

Ridge knot and fastening of the rafter legs to the backing board when simple version systems

For mansard roofs

Option with the installation of a crossbar - used when. In this case, it is the basis for filing the ceiling of the room below. For reliable operation systems of this type, the notch of the crossbar must be hingeless (rigid). The best way- semi-pan (see the figure below). Otherwise, the roof will become unstable to loads.

Please note that in this scheme there is a Mauerlat, and the rafter legs should extend beyond the walls to increase the stability of the structure. To secure them and dock with the Mauerlat, a cut is made in the form of a triangle. In this case, with an uneven load on the slopes, the roof will be more stable.

With such a scheme, almost the entire load falls on the rafters, therefore they must be taken with a larger section. Sometimes the raised puff is reinforced with a suspension. This is necessary to prevent it from sagging if it serves as a support for ceiling sheathing materials. If the puff is short, it can be secured in the center on both sides with boards nailed to the nails. With a significant load and length, there may be several such insurances. In this case, boards and nails are also enough.

For big houses

With a significant distance between the two outer walls, a headstock and struts are installed. This design has high rigidity, since the loads are compensated.

With such a long span (up to 14 meters), it is difficult and expensive to make a one-piece puff, because it is made from two beams. It is connected by a straight or oblique cut (picture below).

For reliable docking, the junction is reinforced with a steel plate mounted on bolts. Its dimensions should be larger than the dimensions of the cut - the extreme bolts are screwed into solid wood at a distance of at least 5 cm from the edge of the cut.

In order for the circuit to work properly, it is necessary to correctly make the struts. They transmit and distribute part of the load from the rafter legs to the puff and provide structural rigidity. Metal strips are used to reinforce the connections.

When assembling a gable roof with hanging rafters, the cross-section of lumber is always larger than in systems with layered rafters: there are fewer load transfer points, therefore, each element has a greater load.

With rafters

In gable roofs with layered rafters, their ends rest on the walls, and the middle part rests on load-bearing walls or columns. Some schemes burst walls, some do not. In any case, the presence of a Mauerlat is mandatory.

Bezporny schemes and knots of cuts

Houses made of logs or timber do not respond well to spacer loads. For them, they are critical: the wall can fall apart. For wooden houses the truss system of a gable roof must be non-thrust. Let's talk about the types of such systems in more detail.

The simplest non-spacer scheme of the truss system is shown in the photo below. In it, the rafter leg rests on the Mauerlat. In this embodiment, it works on a bend, without bursting the wall.

Pay attention to the options for attaching the rafter legs to the Mauerlat. In the first, the support platform is usually beveled, while its length is no more than the cross section of the beam. The depth of the cut is no more than 0.25 of its height.

The top of the rafter legs is laid on the ridge beam without fastening it to the opposite rafter. Two are obtained by structure shed roofs, which in the upper part are adjacent (but not connected) to one another.

It is much easier to assemble the option with rafter legs fastened in the ridge part. They almost never give a thrust on the walls.

For this scheme to work, the rafter legs below are attached using a movable joint. To fix the rafter leg to the Mauerlat, one nail is hammered from above or a flexible steel plate is placed from below. See the photo for options for attaching rafter legs to a ridge run.

If the roofing material is planned to be heavy, it is necessary to increase bearing capacity. This is achieved by increasing the cross section of the elements of the truss system and strengthening the ridge assembly. It is shown in the photo below.

Strengthening the ridge assembly for heavy roofing material or with significant snow loads

All of the above gable roof schemes are stable in the presence of uniform loads. But in practice, this almost never happens. There are two ways to prevent the roof from sliding in the direction of greater load: by installing a brace at a height of about 2 meters or by struts.

Options for truss systems with contractions

The installation of contractions increases the reliability of the structure. In order for it to work normally, at the places where it intersects with drains, you need to attach nails to them. The cross section of the beam for the scrum is used the same as for the rafters.

They are attached to the rafter legs with bots or nails. Can be installed on one or both sides. The knot for attaching the bout to the rafters and the ridge run, see the figure below.

In order for the system to be rigid and not “crawl” even under emergency loads, it is enough in this embodiment to provide a rigid fastening of the ridge beam. In the absence of the possibility of its displacement in the horizontal, the roof will withstand even significant loads.

Rafter systems with braces

In these options, rafter legs, which are also called struts, are added for greater rigidity. They are installed at an angle of 45° with respect to the horizon. Their installation allows you to increase the span length (up to 14 meters) or reduce the cross section of beams (rafters).

The strut is simply substituted at the required angle to the beams and nailed from the sides and bottom. An important requirement: the brace must be cut accurately and fit snugly against the uprights and the rafter leg, excluding the possibility of its deflection.

Systems with rafter legs. Above is a spacer system, below is a non-spacer system. The nodes of the correct felling for each are located nearby. At the bottom - possible schemes strut mounts

But not in all houses, the average load-bearing wall is located in the middle. In this case, it is possible to install struts with an angle of inclination relative to the horizon of 45-53°.

Bracing systems are necessary if significant uneven shrinkage of the foundation or walls is possible. The walls can sit in different ways on wooden houses, and foundations - on layered or heaving soils. In all these cases, consider the installation of truss systems of this type.

System for houses with two internal load-bearing walls

If the house has two load-bearing walls, two rafters are installed, which are located above each of the walls. Beds are laid on the intermediate load-bearing walls, the load from the rafter beams is transferred to the beds through the racks.

In these systems, a ridge run is not installed: it gives expansion forces. The rafters in the upper part are connected to one another (cut and joined without gaps), the joints are reinforced with steel or wooden plates, which are nailed.

In the upper non-expansion system, the expanding force is neutralized by tightening. Please note that the puff is placed under the run. Then it works efficiently (the top diagram in the figure). Stability can be provided by racks, or jointing - beams installed obliquely. In the spacer system (in the picture it is below), the cross member is a crossbar. It is installed above the run.

There is a variant of the system with racks, but without rafters. Then a rack is nailed to each rafter leg, which rests on the intermediate load-bearing wall with the second end.

Fastening the rack and tightening in the rafter system without a rafter run

To fasten the racks, nails for 150 mm and bolts 12 mm are used. Dimensions and distances in the figure are in millimeters.

The gable roof, thanks to its simple, reliable and presentable design, has been popular for many years. Depending on the slope of the slopes, it is used in regions with different amounts of precipitation. The truss system of the gable roof provides natural rainfall.

Symmetrical - both slopes have the same length and are mounted at the same angle. Such a roof is an isosceles triangle with an obtuse or acute angle.
A sloping roof is created to accommodate an attic room, its truss system implies a complex, two-level structure.
Different slope angles are original design emphasizing the unusual architecture of the house.

Tilt angle value

The angle of inclination is selected after analyzing several indicators: the type of roofing, rainfall, wind load. For regions with heavy rainfall, a small slope angle is recommended, but not less than 5 degrees. Snow masses do not linger on a steep surface. sloping roofs with obtuse angle stingrays are suitable for windy climates.

The gable roof truss system must comply with accepted safety standards and be built according to standards.

Rafter systems

Bearing elements and rafters take on the load from external forces and redistribute it to the walls of the building. The strength of the entire roof depends on their reliability. When constructing a structure, two rafter systems are used:

Hanging - rafter legs have two points of support on the walls of the building. They are subjected to compressive and flexural loads. For span distances exceeding 8 meters, a headstock with struts is required. To reduce the impact of the rafters on the walls of the building, they are connected with a puff.
Layered - these bars are supported on inner wall or special design.

If it is impossible to use one of the systems in its pure form, they resort to a hybrid design that allows you to alternate between hanging and layered rafters.

The device of the gable roof truss system allows you to carry out calculations yourself, based on knowledge of geometry. To calculate the area of \u200b\u200bthe structure, you need to set the length of the slope. Quantity required material depends on the angle of inclination. An acute angle allows you to save money, but at the same time minimizes attic space.

We calculate the height of the ridge, the length of the rafters and the area of the roof using geometric formulas. Suitable for visualization scheme Houses. Example - let's take the slope angle of 45 degrees, the width of the house (the base of the isosceles triangle) is 6 m, the length is 10 m.

First, we divide the triangle in half with the height lowered from the top corner. It turns out two right triangle, and one of their legs is the desired roof height. The height divides the isosceles triangle in half, which means that one leg is 3 m. The second is calculated by the formula:

3 × tg 45 0 \u003d 3 m.

Knowing the legs, using the Pythagorean theorem, we calculate the hypotenuse, which is the rafter:

3 2 + 3 2 = X 2 .

The length of the rafter will equal the square root of 18, approximately 4.25

The number of rafters is calculated by dividing overall length per step (0.6 m):

10: 0.6 \u003d 16.6 - this value must be doubled.

We calculate the area by multiplying the length of the slope and the house and multiplying the value by 2:

4.25 × 10 × 2 \u003d 85 m 2.

The supporting base for the roof is a Mauerlat - a durable bar with a section of 150 × 150 mm made of treated coniferous wood. Its fastening is carried out on anchors walled up in the upper row of masonry. They should rise 2-3 cm above the timber to provide room for tightening the nut. A layer of roofing material is laid under the Mauerlat to protect it from moisture. A transverse beam is laid between the walls, fastening the Mauerlat and protecting it from longitudinal loads. To maintain the ridge, a special beam is laid along the slope - a bed, with a cross section equal to the Mauerlat. With a significant width of the building, the installation of runs is necessary.

The cross section of the rafters is determined by the pitch and length of the rafter element, usually these are boards 50 × 150 mm. Rafter trusses are easier to assemble on the ground and ready to be fed to the roof. For the template, two boards are taken, equal in length to the rafters, and connected with a nail. The free ends are laid on supports, the resulting angle is fixed with a crossbar. The places and shape of the cuts are marked with a second template made of plywood. The beams are fastened at the right angle with bolts, cuts are made on them, and after the truss they are lifted up for installation.

The rafters on the gables are installed first. They are attached to the Mauerlat with the help of corners or brackets. The first farms are set strictly according to the level. A cord is stretched between them, which is a guide for installing the remaining elements.

To give sufficient rigidity to the entire structure, struts and crossbars are attached to the rafter leg. The ridge run is bolted to each roof truss. This connecting element must be made of durable timber.

With a significant width of the building, it is necessary to install runs, this is a horizontal beam measuring 50 × 150 mm supporting the rafters. For its installation, vertical racks are installed, based on a bed. These elements will form the basis of the frame for the attic space.

To avoid water flowing onto the walls, it is necessary to provide for an overhang; for this, the rafters are made hanging by 30 cm or additional “filly” boards are attached.

A crate is stuffed onto the finished rafters, the desired step is selected for each roofing material, for shingles continuous flooring is carried out. Roof insulation is an important part of construction. You can reduce heat loss to a minimum by correctly laying the insulation. For this, basalt wool is taken, the width of the material is equal to the step between the rafters, which allows you to quickly and reliably perform insulation. Provide reliable protection roofing from moisture will help laying waterproofing.

The symmetrical gable roof model is the easiest to build and most reliable option in operation. The load in the truss system is distributed evenly, which allows you to extend the life of the structure. Visual video lessons will help to master the intricacies of work.

Video

This video explains how to build a gable roof truss system:

In this video you can see the truss system using one gable roof as an example:

When designing any residential building, architects Special attention pay to the roof, as it performs not one, but several functions at once, depending on its design features. It must be said that not all future homeowners are satisfied with the usual gable roof, although it can be called the most reliable, since it has only two pitched planes and one joint between them. Many are attracted more complex structures, which add a special attraction and originality to the structure. Other, more practical homeowners prefer attic structures, which are simultaneously capable of performing the role of a roof and a second floor.

The basis of any roof is an individual truss system, which has its own design features. Making the choice of the desired roof frame will be much easier if you figure out in advance which ones types and schemes of truss systems used in building practice. After receiving such information, it will become more clear how complex such structures are in installation. This is especially important to know if the roof frame is supposed to be built independently.

The main functional tasks of truss systems

When arranging pitched structures roofs, the truss system is a frame for covering and for holding materials of the "roofing pie". With proper installation of the frame structure will be created the necessary conditions for correct and non-insulated types of roofs that protect the walls and interior of the house from various atmospheric influences.

Roof structure is also always final architectural element exterior design of the building, supporting its stylistic direction with its appearance. Nevertheless, the design features of the truss systems must first of all meet the requirements of strength and reliability that the roof must meet, and only then - aesthetic criteria.

The frame of the truss system forms the configuration and angle of inclination of the roof. These parameters largely depend on the natural factors characteristic of a particular region, as well as on the desire and capabilities of the homeowner:

The amount of precipitation in different periods of the year.
direction and average speed wind in the area where the building will be erected.
Plans for the use of space under the roof - arranging residential or non-residential premises in it, or using it only as air gap for thermal insulation of the rooms below.
Variety of planned roofing material.
Financial capacity of the homeowner.

Atmospheric precipitation and the strength of wind currents give a very sensitive load on the structure of the roof. For example, in regions with heavy snowfalls, you should not choose a truss system with a small angle of inclination of the slopes, as snow masses will linger on their surface, which can lead to deformation of the frame or roofing or leaks.

If the area where the construction will be carried out is famous for its winds, then it is better to choose a structure with a slight slope of the slope so that the sharp gusts that occur do not disrupt individual elements roofs and roofs.

The main elements of the roof structure

Details and nodes of truss systems

Depending on the chosen type of truss system, the structural elements used can vary significantly, however, there are details that are present in both simple and complex roof systems.

The main elements of the pitched roof truss system include:

Rafter legs forming roof slopes.
- wooden beam, fixed on the walls of the house and serving to fix the lower part of the rafter legs on it.

The ridge is the junction of the frames of two slopes. It is usually the highest horizontal roof line and serves as a support on which the rafters are fixed. The ridge can be formed by rafters fastened together at a certain angle or fixed on a ridge board (run).
Lathing - these are slats or beams mounted on rafters with a certain pitch and serving as the basis for the flooring of the selected roofing material.
Retaining elements, where you can take beds, girders, racks, struts, ties and other parts, serve to increase the rigidity of the rafter legs, support the ridge, bind individual parts into the overall design.

In addition to the structural details mentioned above, other elements can be included in it, the functions of which are aimed at strengthening the system and optimal distribution of roof loads on the walls of the building.

The truss system is divided into several categories depending on different features of its design.

attic space

Before proceeding to consider different types roofs, it is worth figuring out what an attic space can be, as many owners successfully use it as utility and full-fledged living quarters.

The design of pitched roofs can be divided into non-attic and attic. The first option is called just that because the space under the roof has a small height and is used only as an air layer that insulates the building from above. Such systems usually include or have several slopes, but located at a very slight angle.

The attic structure, which has a sufficiently large ridge height, can be used in different ways, be insulated and not insulated. These options include attic or gable option. If a roof with a high ridge is chosen, then it is imperative to take into account wind loads in the region where the house is built.

Slope slope

To determine the optimal slope of the roof slopes of the future residential building, first of all, you need to look at the already built low-rise neighboring houses. If they have been standing for more than one year and steadfastly withstand wind loads, then their design can be safely taken as a basis. In the same case, when the owners set a goal to create an exclusive original project, unlike standing side by side buildings, it is necessary to familiarize yourself with the design and operational features of various truss systems and make the appropriate calculations.

It should be borne in mind that the change in the tangent and normal values of the wind force depends on how large the slope of the roof slopes is - the steeper the angle of inclination, the greater value have normal forces and smaller tangents. If the roof is sloping, then the structure is more affected by the tangential wind load, since the lifting force increases on the leeward side and decreases on the windward side.

Winter snow load should also be taken into account when designing the roof. Usually this factor is considered in combination with the wind load, since the snow load on the windward side will be much lower than on the leeward slope. In addition, there are places on the slopes where snow will definitely collect, giving a big load on this area, so it should be strengthened with additional rafters.

Roof slopes can vary from 10 to 60 degrees and must be selected not only with regard to the consolidated external load, but also depending on the roofing that is planned to be used. This factor is taken into account because roofing materials differ in their mass, their fixing requires a different number of elements of the truss system, which means that the load on the walls of the house will also vary, and how large it will be, also depends on the angle of the roof slope. Equally important are the features of each coating in terms of resistance to moisture penetration - in any case, many roofing materials need one or another slope to ensure the free flow of storm water or melting snow. In addition, when choosing a roof slope, you need to think in advance how the cleaning process will be carried out and repair work on the roof.

When planning this or that angle of the roof slopes, you need to know that the fewer joints between the sheets of the coating, and the tighter they are, the less you can make the slope of the slope, of course, if it is not supposed to arrange a residential or utility room in the attic space.

If a material consisting of small elements, for example, ceramic tiles, is used to cover the roof, then the slope of the slopes must be made steep enough so that water never lingers on the surface.

Given the weight of the roofing material, you need to know - the heavier the coating, the greater the angle of the slopes should be, since in this case the load will be correctly distributed to the rafter system and load-bearing walls.

Can be used to cover the roof the following materials: or profile sheet, galvanized steel, corrugated asbestos-concrete and bitumen-fiber sheets, cement and ceramic tiles, roofing material, soft roof and other roofing materials. The illustration below shows the permissible slope angles for slopes for various types roof coverings.

Basic structures of truss systems

First of all, it is worth considering the basic types of truss systems regarding the location of the walls of the house, which are used in all roof structures. The basic options are divided into layered, hanging, and also combined, that is, including elements of both the first and second types of systems in their design.

fasteners for rafters

Layered system

In buildings where internal load-bearing walls are provided, a layered truss system is often installed. Mounting it is much easier than hanging, as the internal load-bearing walls provide for its elements reliable support, and in addition, this design will require fewer materials.

For rafters in this system, the defining reference point is the ridge board, on which they are fixed. The non-thrust type of the layered system can be equipped in three versions:

In the first version, the upper side of the rafters is fixed on a ridge support, called a sliding one, and their lower side is fixed by cutting to the Mauerlat. Additionally, the rafters in the lower part are fixed to the wall with wire or staples.

In the second case, the rafters in the upper part are cut at a certain angle and interconnected using special metal plates.

The lower edge of the rafter legs is attached to the Mauerlat with movable fasteners.

In the third version, the rafters are rigidly fastened in the upper part with bars or processed boards located horizontally, parallel to each other on both sides of the rafters connected at an angle, and a ridge run is pinched between them.

In the lower part, sliding fasteners are used to fix the rafters, just as in the previous case.

It is necessary to explain why sliding fasteners are often used to fix the rafters on the Mauerlat. The fact is that they are able to save the load-bearing walls from excessive stress, since the rafters are not rigidly fixed, and when the structure shrinks, they have the ability to move without deforming general design roofing system.

This type of fastening is used only in layered systems, which also distinguishes them from the hanging version.

However, in some cases, a spacer system is used for layered rafters, in which the lower end of the rafters is rigidly fixed to the Mauerlat, and in order to remove the load from the walls, puffs and struts are built into the structure. This option is called complex, as it includes elements of a layered and hanging system.