Reinforcement of the pile foundation grillage drawing dwg. Diagrams and tips for reinforcing the pile foundation grillage

Reinforcement of the grillage

Despite the fact that pile-grillage foundations are popular among developers, this is a specific base design. It is very difficult to calculate such a foundation on your own, for this you need to involve specialists who have experience in this area, and also know how to create a competent drawing of the foundation with clear data on the type of grillage, size and material of piles, as well as the distance between structural elements.

There are several popular types of foundations with a grillage: tape, slab and pile. All of them differ in design, load-bearing characteristics and strength, they are used on various types of soils, therefore, the scheme of their installation is significantly different. But the only element that ensures the maximum bearing load on

a base of this type is the correct reinforcement. And it must be indicated in the drawing, and the calculation of the reinforcement, its length and thickness, as well as the method of connecting the rods, must be performed. Accordingly, the entire process of reinforcement must be carried out strictly according to the drawing, all calculations must be observed, so that later the foundation does not collapse through non-compliance with the technology.

Reinforcement of slab and monolithic grillage

If you need to reinforce a monolithic grillage, then the horizontal belts are laid in two separate rows with a distance of 20-30 cm. Between the belts, it is necessary to provide longitudinal communication lines from the wire or reinforcement, connect the joints with bolt clamps, it is not recommended to use welding through deformation of the steel.

When calculating reinforcement, the number of horizontal belts is taken into account, as well as the presence of vertical connecting groups.

As a rule, verticals are installed in 20 cm increments, but this rule is sometimes circumvented by using a more powerful wire.

In the scheme of reinforcing a monolithic grillage, such belts are always provided. The frame is made spatial, vertical beams of cut reinforcement are used here, but the length is selected only so that the rods do not protrude beyond the grillage.

As a rule, the vertical rods are also connected to the horizontal belt by flexible wire. The reinforcement will be completed when all the bars have been laid and connected to each other and the bottom layer has been carefully protected. If all the rules and recommendations are followed correctly, then you can start filling the grillage with concrete.

Reinforcement of the tape grillage

The scheme of reinforcement of a tape grillage practically does not differ from a monolithic one, because such bases are similar to each other. The only difference is that the monolithic one has a single reinforced slab under the perimeter of the whole building. And the tape is built along the perimeter of only the bearing walls and is reinforced there. Accordingly, when calculating the reinforcement of a strip foundation, a smaller amount of reinforcement is taken into account, as well as the used concrete solution. The only difference is the way the formwork is installed, because it is a double-sided protective plane, which significantly limits the access to the reinforcement. Reinforcement of the tape grillage is also done only by connecting with a knitting wire, welding is unacceptable.

When developing a drawing for the reinforcement of a tape grillage, the complete absence of sagging of the rods, as well as vertical reinforcing beams, are immediately taken into account. Moreover, during the pouring of concrete, all the rods should stand exactly in those places where it is indicated in the diagram. Any misalignment is not allowed, so the connection must be rigid.

The only difference between tape and monolithic grillage is the method of reinforcement. In a monolithic structure, all the heads are connected, and in a strip structure - only adjacent structures, therefore, the calculation of the strip base is cheaper.

Features of the work

The key problem that arises in the calculation and construction of the foundation is the wrong choice of the section of the grillage itself. It is always necessary to take into account the presence of an air cushion under the plane of the grillage; it is strictly forbidden to do the option as in the figure.

Also, some designers, especially those without experience, can combine elements of a slab and tape structure in the scheme. If the soil swells in winter, then the foundation tape will rise, and the slabs will not allow it to be done. As a result, there will be a rupture of the piles and a rapid destruction of the base.

If you need to calculate the cross-section of the grillage and the size of the piles, then you must first develop a house project with the specifications of the load-bearing walls and floors. Due to these data, the calculation of the permissible loads for the future foundation is carried out, the type of factory pile elements is selected and only then the thickness of the grillage slab is selected.

If the choice is stopped on the tape type of base, then the thickness of the grillage corresponds to the thickness of the bearing walls or may be slightly larger due to insulation and decorative design. If such a foundation is built on a site with a natural slope, then piles of various lengths are immediately selected.

In some cases, the slope of the site is too steep. In such cases, it is not recommended to use piles of very long length, because horizontal breaks may occur even in the middle of the pile. In such cases, a stepped foundation is built. In such a design, the deepening of the support rods to a depth of 25 cm is provided, and the support is introduced by 5-7 cm. When choosing steps, they are also determined immediately with the thickness of the wall masonry, as well as the location of the supports. Here it must be remembered that the edges of the steps should not rest on the supports. Therefore, the piles are installed completely in a free order. The reinforcement is installed on the same plane with the building, its location should also be in the steps themselves, and the connection is flexible without welding elements.

Reinforcement of slab foundation

When calculating the required amount of reinforcement, you need to use the type and shape of the future foundation. These characteristics of a reinforced concrete base can be obtained by determining from the future load on the foundation and the bearing characteristics of the soil. Here, ribbed rods are often used in horizontal and vertical belts; these are A3 class reinforcement with a thickness of 10 mm. But when arranging reinforcing belts, you can use rods of greater thickness. After all, the thicker they are, the stronger the foundation will turn out. Also, when calculating, the designer must take into account the characteristics of the soil, the type of the future building, its height and perimeter. If the soil is dense, then the degree of deformation of the base will be less. If the soil is loose, then reinforcement with a diameter of 14-66 mm, or even larger, should be used in the piles and in the grillage. And the grid spacing for all types of reinforcement is 20 cm.

Quite often, a house under construction is erected on a pile type of foundation, in this case, the reinforcement of a grillage of a pile type of foundation becomes relevant.

The type of pile foundation is simply necessary in the case when construction work is carried out on weak and heaving soils, there are large differences in soil height at the construction site or there is groundwater.

In addition, a pile foundation is the only solution if the construction of a house is planned in permafrost regions, as well as in many other cases.

In general, for these purposes, piles are used, which differ from each other both in the method of immersion in the ground and in the material used for their manufacture.

What unites them is that it is the grillage that connects them into a single solid and durable structure.

In turn, to give strength to the grillage itself, it is imperative to reinforce it, having previously made a drawing and calculating all the expected loads during the subsequent operation of a private house.

The main features of the grillage

Immediately before proceeding to the arrangement of the grillage itself, and, accordingly, to its reinforcement, it is necessary to determine the type of pile foundation and the number of piles themselves.

Their minimum number can be from four pieces on the basis that each corner will have its own pile.

It is on such a foundation of the pile type that the grillage itself will subsequently be laid. It can be in the form of a single solid plate or tape type.

In general, the main purpose of the foundation grillage is to interconnect all parts of the pile-type foundation into a single whole for even distribution of the load.

In the case when concrete beams are used as a grillage, it resembles a tape-type foundation, however, the difference is that the grillage tape is never buried in the ground.

This is due primarily to the fact that in severe frosts the soil tends to bulge, and this, in turn, can lead to a violation of the integrity of the grillage itself, both of a tape type and a solid slab.

The device for the foundation grillage can be different.

So, it can be made of durable concrete and have a reinforcing cage, it can also be prefabricated from various elements manufactured at the factory, and combined.

It is possible to connect piles with various elements of the grillage itself using ordinary welding, as well as monolithic sections.

When equipping the foundation for a pile-type house, a variety of materials can be used for the grillage.

If a tape-type foundation is assumed, then the grillage can be made of metal channels or I-beams.

However, even despite the fact that the calculation of such a strip type of foundation shows its high reliability, in economic terms it is not profitable and will be quite expensive.

In this case, the most preferable will be the grillage, arranged in the form of a monolithic concrete structure, in which the corresponding reinforcement is made.

Calculation of the foundation with a grillage

In order to make the correct calculation of a foundation of this type, first of all, it is necessary to determine as accurately as possible the composition of the soil at the construction site, especially at the depth at which it is planned to equip the foundation itself.

This is necessary primarily in order to calculate the length of the piles, plan their structure, as well as the distance between the piles separately.

The calculation of the bearing capacity of the future pile is also carried out.

When calculating a pile foundation with a grillage, it is also necessary to determine the expected loads that the house will exert directly on the piles themselves, as well as on the ground.

In order to obtain a calculation of the total weight of the future structure, it is necessary to add together not only its weight, but also the weight of the roof and floors.

Natural loads are also taken into account, such as, for example, snow, the mass of people in the house, various equipment and furniture.

All subsequent calculations are made taking into account the total area of ​​the entire house.

In most cases, a foundation with a grillage is equipped for those buildings whose area will be at least three hundred square meters.

As a rule, the necessary calculation is carried out by specialists, since there are many different subtleties and nuances.

After the necessary calculation of the foundation of the house has been made, on the basis of which the number of piles, the distance between them and the depth of their installation is determined, an appropriate diagram and drawing should be drawn up.

It should be noted that screw piles are more profitable in economic terms and they can be equipped without the involvement of special equipment.

When carrying out work on the construction of the foundation for a house with a grillage, reinforcement of the structure must be performed, both for the tape type and for a solid monolithic slab.

Reinforcement of the grillage

In any case, the pile-type foundation must be reinforced without fail. The piles themselves are reinforced primarily in order to give them the appropriate strength.

In turn, the grillage is reinforced to maximize its bearing capacity.

The part of the reinforcement that will protrude from the pile structure will be used as a connecting element between the pile itself and the grillage.

The fastening itself, as a rule, is carried out by welding.

To carry out the reinforcement, it is necessary to use a previously drawn up drawing, in addition, the reinforcement diagram should be in front of your eyes and directly.

It should be remembered that those elements of the grillage, on which the appropriate reinforcement will not be made, simply will not withstand the loads during the construction of walls and floors of the house.

In the case when tape grillages are mounted, the reinforcing cage itself should be made of two separate belts.

They must be rigidly connected to each other using vertical metal rods with a cross-sectional diameter of up to eight millimeters.

This diameter is chosen in view of the fact that these metal rods are practically not subject to stress, but are mainly intended to give the frame an appropriate shape.

A prerequisite is that each belt must consist of at least two rods.

The belts are tied together with rods located in a horizontal position and tied with an ordinary knitting wire.

In the production of reinforcing cages for foundations with a grillage at industrial enterprises, welding machines are used for fastening transverse joints.

However, directly transverse circles or squares with longitudinal rods are connected exclusively by knitting.

If the warping device is supposed to be in the form of a solid monolithic slab, then the reinforcement scheme remains exactly the same as in strip-type foundations.

In this case, the upper frame of the frame is made in the form of a mesh of reinforcement with a cross-sectional diameter of 10 to 14 millimeters, and reinforcement with a smaller diameter is used for arranging vertical rods.

The cost of the foundation itself is mainly influenced by the amount of concrete and reinforcement used for its arrangement.

In addition, the price includes lumber, which is necessary for the construction of the formwork. Depending on their design, grillages can be high or low.

However, regardless of the type of structure chosen, the principle of grillage reinforcement remains unchanged.

In the event that a base of a ruined type is assumed, its lower part should be flush with the ground.

In some cases, it may drop a few centimeters lower.

It is necessary to arrange trenches between the piles, in which appropriate pillows are made from carefully compacted sand and rubble.

This reinforcing cage should be rigidly connected to the pile heads and not reach the walls of the installed formwork by about five centimeters.

Only after this is the foundation itself poured with concrete. It should be noted that such a grillage is possible only if the house is being built on non-porous soil.

In all other cases, it is necessary to equip high grillages, while special attention should also be paid to the reinforcement of the entire structure.

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Before building a house and deciding which foundation to create - or a pile foundation, novice builders are faced with such a concept as a grillage. Below we will consider what this is a grillage and its need for building foundations of a building.

Video: device grillage for a wooden house

Metal belt for foundation

The metal lathing is made of channel, I-beam or square profile and has high strength and rigidity. As a rule, this design is used when constructing pile-screw bases for. The channel is installed on the heads of the supports, and fixed by means of a welding joint.

A metal belt is used mainly in a hanging version. However, in recent years, such structures have been used very rarely, since, due to the severity of the material, the involvement of lifting special equipment is required, which is economically unprofitable. In addition, the metal is subject to the risk of corrosive processes.

Types and purpose of grillages

Grillage structures differ in type and purpose. Many factors are taken into account when choosing the required design.

Strip foundations with grillages

For buildings, pile foundations with a tape grillage are quite strong and reliable support, for the construction of which two technologies are used. One of them is used when arranging foundations above ground level, and the second is used at the stage of creating a lattice structure, which takes on part of the load.

A strip foundation is the best option for arranging a foundation on slopes and areas with difficult terrain, since it does not require complex preparatory work for planning the site with the involvement of special equipment. This design is perfect for the construction of structures made of lightweight materials.

Using a strip foundation during the construction of a house is imperative:

• Sand cushion, thickness of which is 200-300 mm. It is created under the concrete frame and piles to protect them from the destructive effects of soil moisture.
• Waterproofing of the lattice and supports, for which they use polyethylene film, roofing material or asbestos-cement pipes.

When arranging the foundation, it is necessary to carefully in the tape grillage, as well as its thickness and other parameters.

For the fence

The device of a grillage for fences is necessary for full protection of the structure, which the plane of the fence cannot provide. The creation of the belt is due not only to the provision from external factors, but also so that, for example, pets cannot get out of the site. The reasons can be any, but the performance must always be of high quality, to ensure the strength and durability of the structure.

In principle, the grillage under the fence practically does not differ from the belt used in the arrangement of the foundations of houses. It uses the same construction, building materials and performs similar functions.

For pile foundations

The need for a columnar foundation with a grillage is directly determined by the specific structure of the building, its weight and the rigidity of the structure's frame. In order to prevent the supporting columns from collapsing, they are obliged with a monolithic reinforced concrete, metal or even wooden belt.

In construction, several schemes of the pile foundation of buildings are used:

• Columns with a hinged belt are buried in the ground. This scheme is used in 90% of all pile foundations;
• The pillars rest on a crushed stone embankment without deepening into the ground. With this scheme, the high rigidity of the base of the house is ensured, which makes it possible to minimize the likelihood of subsidence of the structure as much as possible;
• Without grillage. This option is used for the construction of small houses.

On a note! Supports for a columnar base of a building can be combined, for example, brickwork is combined with concrete grouting or a base of construction rubble. In principle, the properties of the foundation do not change from this, but the process of arrangement is greatly simplified and the cost is reduced.

Pile-grillage foundations

Grillage technology with bored piles

Arrangement of foundations with a grillage on bored piles is mandatory when erecting buildings on uneven terrain, slopes and unstable soils. These structures are the best option for the construction of both small houses and medium-sized capital structures. Bored foundations with a grillage have a bearing capacity higher than that of monolithic and tape bases, and they are cheaper.

Bored piles, able to withstand a load of about 1500 kg. To erect a medium-sized structure, you will need several dozen columns, the diameter of which can reach 150 cm, and the length up to 40 m.

To equip the base of the building, no major earthworks are required. Each pile is waterproofed with two layers of roofing felts or roofing felt and fixed in a frost-free soil layer. Waterproofing protects concrete from destruction and reduces soil pressure on the supports.

Advantages of the foundation on bored supports:

The tops of the installed pillars are cut off at the same level, after which they are united by a common belt. A grillage on bored piles allows for an even distribution of the load exerted by the weight of the structure throughout the entire base of the building. The device of the pile-grillage foundation can be seen in the video below:

The downside of this design is the fact that due to the presence of free space between the floor and the ground, the bored foundation with a grillage needs to be insulated. This leads to additional labor and material costs.

Grillage on screw piles

The advantage of foundations on screw piles is that they do not require excavation to be installed, and they are usually used on clay and heaving soils. After the supports are installed, their heads are cut into one level and the lattice belt is installed.

Monolithic reinforced concrete and concrete structures for screw piles are extremely rare, since this type of support is used for the construction of light structures. Most often, the pile-screw grillage is made from a metal corner or channel.

Before installing the grillage on the heads, metal platforms are welded to them, the size of which should allow the axial displacement of the supports to be corrected. Further, all piles are strapped with a channel or a corner, as a result of which a strong and reliable structure is created.

Important! Before installing the foundation and grillage on screw piles, it is necessary to carry out anti-corrosion treatment of all metal structural elements. This will significantly increase the service life of the structure under construction.

Main dimensions and dimensions

To create a strong and durable foundation, it is necessary to make the correct calculations. The shape and dimensions of the grillage used are determined by the structural features of the building being erected, loads on the foundation, the number and location of piles.

The grillage is created, as well as the construction of the strip foundation. The height of the grillages for pile foundations directly depends on the level to which the structure should be raised from the ground, as well as on its weight. You can independently perform the calculation of a structure based on the ground or slightly deepened. In the case of a hanging belt device, it is better to entrust the calculations to specialists, since they are very difficult for a layman.

• B - the minimum permissible height for the belt support;
• M - the weight of the structure of the structure excluding the used supports;
• L - belt length;
• R - the strength of the soil at the surface of the earth.

Reinforcement cages for belts on a pile foundation are created in the same way as for structures on a strip foundation. In the structure, it is necessary to carry out longitudinal (working), horizontal and vertical transverse reinforcement. The total section of the longitudinal reinforcement must be at least 0.1% of the section of the belt. To select the cross-section of each rod and their even number, an assortment of reinforcement is used.

Main manufacturers and standard series of pile grillages

For private or small buildings, you can make lattice belts yourself directly at the construction site, but when erecting industrial buildings, multi-storey buildings, etc. use factory-made designs. Among the main manufacturers of reinforced concrete grillage from 35 tons, the following companies can be distinguished:

• JSC APSK "Gulkevichsky" ;
• CJSC "OBD" ;
• JSC "T-Beton" ;
• LLC LSR. Construction-Ural " ;
• LLC "ZKPD Tomsk House-Building Company" ;
• JSC "PZSP" .

Series	Description
Monolithic reinforced concrete grillages Series 1.411.1-1 / 89	For the construction of bases for prefabricated reinforced concrete columns of one- and multi-storey industrial buildings of the II 20-1 / 70, II 20-2 / 70, II 20-3 / 70 series.	Supports of structures of the II 20-1 / 70, II 20-2 / 70, II 20-3 / 70 series have a section of 400 * 400 and 400 * 600 mm. and must be embedded in the foundation by 600 mm.
Series 1.011-6	Made of heavy concrete, class B 12.5	Square piles 300 * 300 and 350 * 350 mm.
Series for metal grillage: 3.407.9-1581	For the operation of the structure at a temperature: ● up to - 40˚C, the grillage is made of carbon steel grade ВСт 3, corresponding to GOST 380-71; ● below - 40˚C for the grillage, low-alloy steel of 09G2S grade is used, which corresponds to GOST 19281-73 and 19282-73.

The name, which designates typical grillages for pile foundations, includes the mandatory letter indices RS and RB and serial numbers. PC1 - PC5 markings are used on square supports, and RB markings are used for rectangular piles.

Important! If it is necessary to order grillages from 50 tons, the manufacturer of concrete products must be chosen very carefully in order to guarantee the strength and durability of the entire structure.

Basic provisions for the design and calculation of the pile grillage

When constructing a pile-grillage foundation, it is necessary to know the basic requirements for a grillage and to carry out competent calculations of the entire structure. It is also necessary to have an executive scheme for grillages, on which all the main structural elements are indicated. An important point in the design of the foundation of a building is the exact calculation of the required number of supports for each specific type of structure. The calculation is based on the total weight of the structure and the bearing capacity of the soil. The mass of the house must be divided by the bearing capacity of the soil and, we get the value of the area of ​​the projected base. To determine the safety factor, the foundation area should be increased by 30%. To calculate the required number of support columns, the base area must be divided by the volume of each pile, while the following conditions must be met:

• supports must be installed in all corners of the structure being erected;
• piles are mounted at the intersection points of the walls of the building;
• according to SNIP, the distance between the piles in the grillage is 2-2.5 m.

The connection of the pile to the belt can be rigid or free. In the case of a free connection, the heads of the supports enter the grillage to a depth of 50-100 mm. This type of fastening is suitable for centrally loaded support columns.

With a rigid connection, the pile head breaks, and the reinforcement is exposed, after which it is monolithic into a concrete or reinforced concrete grillage. This type of attachment is performed in cases when:

• the installation of pile foundations with grillages is performed on unstable soils;
• horizontal loads are placed on the supports;
• combined or inclined supports are installed at the base;
• the supporting columns work with pulling loads.

Calculation example

Consider an example of calculating a pile foundation with grillages for a one-story brick house with a hip roof made of metal tiles. The building has two reinforced concrete floors with a thickness of 220 mm. The dimensions of the house in the plan are 6 * 9 m, the thickness of the load-bearing walls is 380 mm. The total floor height is 3.15 m, from floor to ceiling - 2.8 m, and the total length of partitions inside the building is 10 m (there are no internal walls in the premises). On the site there is a refractory mixture with a porosity of 0.5 and a depth of 3.1 m.

We pre-set the width of the grillage to 400 mm. and a height of 500 mm. The length of the support is 3 m, and the cross-section is 50 cm.We are guided by the step of the support piles - 1.5 m.To determine the total number of piles, it is necessary to divide the length of the grillage by the step of the supports and add 1 (if necessary, the resulting value is rounded down to a whole numbers - 30 / 1.5 + 1≈21).

• Support area, m 2 3,14*0,52/4 = 0,196
• Perimeter, m - 2*3,14*0,5 = 3,14
• Grillage weight, kg- 0.4 m. * 0.5 m. * 30 m. * 2500kg / m 3 = 19500
• Support weight, kg- 21 * 3 m. * 0.196 m 2 * 2500 kg / m 3 * 1.3 = 40131
• Building weight, t- Weight of supports + weight of grillage + total from the table ≈ 224

To calculate the volume of the grillage and other parameters, it is necessary to determine the mass of the structure without foundation supports. As a result, we get M = 204 t.The width of the salting is equal to M / (L * R) = 204 / (30 * 75) = 0.09 m. Such a belt cannot be used for construction, in this case, since the overhangs of brick walls should not be more than 40 mm. Therefore, we assign the width - 400 mm, and the height remains - 500 mm.

Article

In those regions where rains or flooding are frequent, when building a house, you need to erect a pile foundation with a grillage. This design makes it possible to raise the structure to a height of up to 2 m.

Figure 1. Diagram of the grillage device.

As you know, such a design presupposes the presence of driven or bored piles. The first type of columns is driven in using a special technique, and for the second type, a construction drill is used, they make funnels.

Grillage dimensions

The diameter of the funnel is 30 cm, and the length of the rod is 5 m.First, we will determine the number of columns, while taking into account that the house has dimensions of 5 X 8 m.And the distance between the posts should be 1.5 m - a coefficient that can be a maximum of 2 m (picture 1).

Knowing these values, we determine that 10 piles will be needed, the depth of which is 2 m, but at the same time they protrude 20-30 cm above the ground.

The height of the grillage is 0.25 m, and the width should not be less than the width of the basement. If the basement is not provided, then the width of the grillage should be equal to the width of the outer wall, but not less than 0.4 m. The tape is located at a distance of 10 to 15 cm from the ground.

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Calculation of the pile foundation

Scheme of reinforcement of the strip grillage of the pile foundation.

An important point is the calculation of the number of support piles for a particular building. Experts take the bearing capacity of the soil and the total weight of the future building as the basis for calculations. The weight of the structure is divided by the value of the bearing capacity of the soil, and as a result we get the area of ​​the foundation. It is recommended to increase this area by 30% to create a safety factor. Further, to obtain the number of pillars, the foundation area is divided by the support volume of each pillar. Now on the plan you need to mark a place for each support pile. This is done taking into account the following rules:

1. Pillars should be in all corners of the building.
2. They are installed at all intersections of the walls.
3. The distance between the supports along the perimeter of the walls is on average 2-2.5 m. With a decrease in this value, the cost of material increases and it takes more time to complete work on the construction of the foundation. And with an increase in the distance to 3-3.5 m, there is a danger of cracks in the grillage and its fracture is possible, which leads to the destruction of the entire structure.

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Rules for calculating and arranging a tape grillage

The top of each pile should be embedded in the grillage by about 10 cm. For this, the reinforcing rods of the pillars are bent parallel to the ground and attached with a knitting wire to the grillage reinforcement. The column should be at least 30 cm high. Most often it is made of reinforced concrete. To fill it, a formwork is mounted, the bottom of which is made of a board with a thickness of at least 40 mm, otherwise it may break during the filling of the formwork with liquid concrete. In order to prevent the loss of cement laitance, the formwork is lined with plastic wrap from the inside.

Figure 2. Diagram of the foundation pile device.

The reinforcement cage is calculated in such a way that it is spaced from the walls of the formwork by the value of the threefold diameter of the reinforcement rods. It is advisable to fix the lower and upper chord so that the reinforcement cannot move during the pouring of concrete. This can be done using horizontal rods inserted into the holes in the side walls. In 25-30 minutes after pouring the formwork, they are removed.

For light loads on the pile foundation, it is permissible to use synthetic reinforcement. The poured concrete mass must be treated with a construction vibrator or pierced in several places with a rod of reinforcement. This is done to remove air from the concrete. From above, the poured grillage is covered with plastic wrap. During the next week, the film is removed, the concrete is moistened and covered again.

The grillage on heaving soils should be about 20 cm above the ground.

Its width is approximately equal to the width of the base or the thickness of the walls. In practice, it is made at least 40 cm wide, and its height is 30 cm or more. The grillage should not intersect with various pipelines and have seams and joints. The correctness and evenness of the upper plane is checked with a level.

As reinforcement rods with a diameter of 10 - 14 mm are used. It is desirable that their length matches the size of the wall. The number of rods that the top and bottom bands should contain (together) depends on their diameter. With a thickness of 10 mm, you will need up to 8 rods, with a diameter of 12 mm - up to 6, and if their section is 14 mm, then 4 to 5 pieces are used. A pile foundation with a grillage is not intended for multi-storey buildings, but it can be indispensable for low-rise construction of houses, offices, shops, baths on loose soils.

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How to calculate the correct reinforcement for the slab base?

To calculate the amount of reinforcement, they are guided by the shape and type of foundation, as well as the bearing capacity of the soil. Let's consider how to make it if the size of the future structure is 5 X 8 m, with two internal walls (Figure 2).

Figure 3. Diagram of the strip-pile foundation

During construction, we use rods with a ribbed surface, that is, reinforcement of class A3, with a cross section of 1 cm, such rods are suitable for panel and frame houses. But if the soil on which the structure is being erected has a weak bearing capacity, then reinforcement with a diameter of 1.4 to 1.6 cm is used, while the grid step of the frame will be 20 cm.

Let's start calculating:

• ((8 / 0.2) + 1) = 41 (reinforcing rods 8 m long);
• ((5 / 0.2) + 1) = 26 (reinforcing rods 5 m long);
• 41 + 26 = 67 (reinforcing rods).

In view of the fact that we are building a slab base, we use two reinforced belts, therefore we double the number of rods, and it turns out that we need 134 rods, while 82 of them are 8 m long, and 52 - 6 m:

• 82 * 8 = 656 m;
• 52 * 6 = 312 m;
• 656 + 312 = 968 m.

We connect the rods of the lower mesh to each other, at the intersection of the longitudinal and transverse rods. Let's calculate the number of connections:

• 41 * 26 = 1066 (connections).

If the plate used has a thickness of 20 cm, and the distance from its surface to the frame is 5 cm, then 20 - 5 - 5 = 10 cm, then:

• 1066 * 10 = 10660 cm or 106.6 m;
• 106.6 + 968 = 1074.6 m (the required number of rods for the slab base).

Let's calculate the amount of knitting wire:

• 41 * 26 * 2 = 2132 (connections).

Connections are made by folding the wire in two additions, so if the wire has a length of 15 cm, then it is multiplied by 2, you get 30. And in order to calculate the number of ties, you need to multiply the result by the number of connections, then we get:

• 2132 * 0.3 = 639.6 m.

In the field of individual construction, when using a pile foundation, a monolithic reinforced concrete grillage is the most popular option, since even with a significant size it can always be made on its own.

The materials used for this can be delivered to the construction site by conventional trucks or even light vehicles without the use of special platforms or cranes.

However, the installation of a monolithic grillage is more complicated than a prefabricated one, and the main difficulty lies in the correct reinforcement of the pile grillage.

You can often hear about the similarity of the grillage device and the usual strip foundation, but this statement is only partially true. Indeed, in its appearance and function, the grillage is very similar to a tape base, however, the operating conditions of these structures are significantly different:

• if for a strip foundation the occurrence of a bending moment in a vertical plane is more likely a phenomenon out of the ordinary, then for grillages, which are beams laid on piles, this is the norm. The span located between the supports takes the weight of the building parts and other loads, while being, as it were, suspended in the air, which causes the deflection;
• another difference is that the load on the strip foundation is less predictable. The underlying soil under various parts of the base may "float" or swell. This causes multidirectional deflections, in which both the upper and lower part of the cross section can be stretched. And the stretched zone that occurs during the deflection of a reinforced concrete element is, as you know, exactly the zone in which the reinforcement should be located. Thus, a conventional strip foundation has to be reinforced in the same way both at the top and at the bottom.

In the case of the grillage, the impact from the soil is completely excluded, therefore, the stresses arising in it are quite predictable: in the spans between the piles, the lower part of the cross section is always stretched, in the areas supported by the piles - the upper part.

This also determines the scheme of reinforcement of the pile foundation grillage. The lower belt of the reinforcing cage in the areas between the piles is made more powerful, and at the points of support on the piles, the upper belt is strengthened.

Selection of materials for the reinforcement cage and determination of its parameters

The diameter of the reinforcement used and the parameters of the frame are selected on the basis of a calculation that takes into account permanent and temporary loads.

The calculation of the reinforcement of the pile foundation grillage should be performed by an experienced construction engineer who is well versed in the topic of reinforced concrete structures.

Typical solutions

In practice, in individual construction, the following rules are followed:

• in the stretched zones of the grillage, several longitudinal rods of class AIII reinforcement with a diameter of 20 mm or more are laid;
• reinforcement with a diameter of 8 - 15 mm is placed in the compressed belt. The step between the bars of the longitudinal reinforcement, also called working, is 80 - 100 mm.
• For the perception of transverse tensile forces, as well as for combining longitudinal reinforcement into a single frame, transverse bars are attached to it - smooth reinforcement of class AI with a diameter of 6 to 8 mm. The distance between them should not be less than 250 mm, but usually it is taken equal to 3/8 of the height of the grillage section.

If the height of the grillage exceeds 150 mm, vertical bars are installed in the reinforcement cage, the pitch of which corresponds to the pitch of the transverse reinforcement.

Most often, instead of separate longitudinal and transverse rods, clamps are used - parts made of reinforcement in the form of a closed rectangle or an inverted letter "P".

Reinforcement of the abutment zones of the grillage tapes

Where the grillage ribbons form an L-shaped or T-shaped intersection, it is not enough to simply fasten the intersecting bars of the working reinforcement together.

Here, rods bent at right angles are placed, each part of which fits into one of the adjoining tapes and goes into it at least 40 diameters.

Clamps in these areas are installed twice as often.

Manufacturing jobs

Reinforcement of the pile foundation grillage is performed immediately after the construction of the formwork. An obligatory element of the latter should be transverse jumpers in the upper part, to which, in the end, the reinforcing cage will be suspended.

Work on the installation of reinforcement in the future grillage can be divided into several operations.

The device of the lower belt of the reinforcing cage

At the bottom of the formwork, special plastic bosses are laid on top of the waterproofing, on which the lower belt of the reinforcing cage will then be located.

If the bosses are not available, they can be replaced with fragments of bricks or wooden blocks 40-50 mm high:

• the height of all shims must be the same so that the reinforcement rods take a strictly horizontal position;
• the spacing between the bosses or elements used as an alternative depends on the diameter of the working reinforcement: it must be such that the rods do not bend;
• on the lugs with an equal pitch, it is necessary to lay the working reinforcement of the lower chord. The distance from the outer rods to the side surfaces of the formwork should be 30 - 40 mm.

When constructing the frame, the contractor must be guided by the requirements of the documents describing the reinforcement of the grillage of the pile foundation: a design drawing with all the necessary instructions is given in the construction project.

If the grillage tape has a significant length, each thread of the working belt is recruited from several reinforcing bars connected with an overlap of 1 m.

Transverse reinforcement rods or clamps are attached to the lower chord, which combine transverse and vertical reinforcement.

Upper belt device

The working reinforcement of the upper chord is suspended from the lintels of the formwork, which were mentioned at the beginning of the section. The length of the suspensions should be such that after the grillage is poured over the reinforcement, a protective layer of concrete 30 to 40 mm thick is formed.

The rods of the upper chord are connected with transverse and vertical reinforcement or with clamps, if any.

Then both working chords should be tied to the reinforcement protruding from the piles. The reinforcing frame can be considered ready.

Reinforcement knitting methods

The most common fastening method is tying the reinforcement with a special wire. Electric welding is used very rarely and only for fittings marked with the letter "C".

It is not allowed to connect ordinary fittings by welding, since due to exposure to high temperatures it becomes weaker.

For knitting of reinforcement, only annealed round wire with a diameter of 1 mm is used. Unfired wire is less ductile, so it bends poorly and breaks easily.

The fastest way to knit fittings is using a special pistol equipped with a battery. But its acquisition is advisable only for large volumes of work, moreover, it is not very convenient when knitting reinforcement in hard-to-reach places.

Reinforcement of the pile - grillage foundation for a private house is mainly carried out using another tool - a special hook. Professionals prefer homemade crochet hooks, but purchased hooks are also suitable for one-time work.

On sale you can find both conventional and screw hooks, also called semi-automatic.

The latter make it possible to knit reinforcement a little faster, but due to their design, after tightening the knot, they leave too long free ends of the wire, which often protrude from the concrete and begin to rust.

The simplest and most common types of knots are the so-called "loop" and "two loops". The first is used for overlapping reinforcement, the second for butt joints. In practice, the loop is often used not only for overlap joints, but also for corner joints.

At the final stage of the installation of the reinforcing cage, remove the bosses on which the working reinforcement of the lower belt was installed. After that, the entire frame will be suspended on a wire twisted around the upper formwork lintels. Now you can start pouring concrete.

Video about the reinforcement of the pile foundation grillage

A pile foundation is a universal foundation for the construction of brick (about reinforcing brickwork - read separately), wooden, aerated concrete (about reinforcing aerated concrete - read separately) and foam concrete low-rise buildings in any soil conditions. Such bases are also used for other structures (for example, fences, columns). The strength and reliability of the pile foundation directly depends on the grillage, the reinforcement technology of which we will talk about in this article.

Reinforcement of the grillage

You will learn why it is necessary to reinforce the pile-grillage foundation, what materials are used for this and how the process itself is performed. Diagrams and drawings will be given, explaining all the nuances of the reinforcement of a monolithic grillage.

What functions does the grillage perform and why do you need its reinforcement?

The grillage is a strip structure (read separately about how a conventional strip foundation is reinforced), connecting the free-standing piles to each other. Due to the strapping of the supports, additional spatial rigidity and resistance to tipping loads are obtained. Also, the grillage acts as a supporting surface on which the walls of the building are erected.

See also: What is reinforcement anchoring and why is it necessary?

There are several types of strapping according to the material of manufacture - steel (from a channel or I-beam), wooden (from a bar) and reinforced concrete. It is in the case of the installation of a monolithic pile grillage, which is used when arranging houses from heavy materials, that it is necessary to reinforce the strapping.

The need to strengthen the monolithic grillage with reinforcement is due to the fact that concrete as a material has a high resistance to compressive loads, but at the same time it has a weak resistance to bending and tensile loads, which can cause its deformation.

Diagram of the pile-grillage foundation

The reinforced frame placed inside the monolithic grillage absorbs the above loads, preventing the risk of its destruction, which significantly increases the reliability and durability of the structure. Reinforcement is necessary not only when installing a pile-grillage foundation, but also in a columnar base, which has a similar configuration.

See also: what kind of mesh is the reinforcement of the floor screed?

Note that the foundations are subject to reinforcement, in which two types of piles are used - driven and bored. Driven piles are prefabricated structures that, upon completion of installation, are cut with a special hydraulic pile cutter using a pile driver.

After trimming, the reinforcement is exposed on the end part of the pile, which is subsequently connected to the frame of the monolithic grillage. When installing bored supports, their reinforcement cage is made so that reinforcement protrusions with a height of 30-40 cm are above the concrete body of the pile.
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What and how to reinforce?

Reinforcement of the tape grillage is carried out by means of a spatial reinforcement cage, consisting of two longitudinal reinforcement belts (upper and lower), interconnected by horizontal and vertical bridges.

Longitudinal belts are made of rods of A3 class reinforcement (hot-rolled corrugated profile), the diameter of which is 13-16 mm. It is possible to use fiberglass reinforcement, which is confirmed by reviews on the successful operation of such pile-grillage foundations on specialized forums.

Connecting vertical and horizontal bridges can be made in two versions - in the form of separate bars welded to the longitudinal belts of the reinforcement (the diagram shows the configuration). In this case, it is necessary to use rods of the same standard size as when arranging a longitudinal belt.

Drawing of the connection of belts with separate jumpers

Also, the frame can be connected with jumpers from the reinforcement curved into the clamps of the rectangular shape (the diagram below). With this approach, smooth rods of class A2 (diameter 8-10 mm) are used. Bent clamps are laborious to install, however, due to the smaller number of welded seams, they are more reliable and durable. Fiberglass reinforcement, which cannot be bent, is not used to create clamps.

Drawing of the connection of belts with clamps

According to the provisions SNiP No. 2.03.01 "Manual for the design and arrangement of pile-grillage foundations", when installing the reinforcement cage, the following step must be observed between the constituent elements:

• the number of rods in the longitudinal belts is at least 4, the distance between them is up to 10 cm;
• the step between the transverse crosspieces of the longitudinal belt is 20-30 cm;
• the step between the vertical connecting jumpers - up to 40 cm;
• a protective layer of concrete - at least 5 cm.

The protective layer is the distance between the outer contours of the reinforcement cage and the walls of the concrete body of the monolithic grillage. If the protective layer does not have the required thickness, two problems will arise - the frame will not be able to correctly redistribute the loads acting on the grillage and the reinforcement will be excessively susceptible to corrosion under the influence of moisture penetrating into the concrete micropores.

Plastic stand for fittings

To make a protective layer along the bottom edge of the grillage, special plastic mushroom stands are used, which raise the reinforcement above the formwork. The use of pieces of brick for these purposes is not allowed.
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As an example, we give the calculation of the amount of reinforcement for a monolithic grillage with a perimeter of 8 * 6 m.We use the conditional dimensions of the strapping 40 * 40 cm.The reinforcement frame for such a strapping will consist of two longitudinal belts of 3 rods A3 with a diameter of 14 mm each (the pitch between the rods is 10 cm , 5 cm on each side eats away the protective layer of concrete). The belts are connected by jumpers made of reinforcement A1 with a diameter of 11 mm, located with a step of 20 cm.

The calculation is performed according to the following algorithm:

1. Determine the total length of the rods in the upper longitudinal belt. To do this: a) determine the perimeter of the grillage: 8 + 8 + 6 + 6 = 30 m; b) we calculate the length of 3 rods: 3 * 30 = 90 m; c) we calculate the length of the A3 reinforcement for both belts: 90 * 2 = 180 m.
2. To connect the rods of the longitudinal belt, we need jumpers 30 cm long, which will be located with a step of 20 cm.Calculate their number for both grillage contours: 2 * (30 / 0.2) = 300 pcs, after which we calculate the total length of the transverse jumpers: 300 * 0.3 = 100 m.
3. It remains to calculate the length of the vertical bridges connecting the upper and lower contours of the frame to each other. But since in the example a rectangular grillage is calculated, their number and length will be identical to the transverse lintels. If a grillage of rectangular configuration is used, the calculation is performed according to the formula specified in paragraph No. 2.

As a result, the calculation showed us that the grillage reinforcement requires 180 m of A3 class reinforcement and 200 m (100 + 100) A2 rods with a diameter of 11 mm. It may also be necessary to calculate the tying wire if you do not plan to use a butt weld. It is carried out taking into account the fact that one connection takes about 40 cm of material: we determine the number of connections: 4 * (30 / 0.2) = 600 pcs; and calculate the material consumption - 600 * 0.4 = 240 m.
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Features of the grillage reinforcement (video)

Monolithic grillage reinforcement technology

The reinforcement of the grillage begins after all the previous stages of the arrangement of the pile foundation have been completed - the installation of piles, their trimming and the arrangement of the formwork. You must have a ready-made formwork, inside of which the reinforced frames of the piles protrude to a height equal to the cross-section of the strapping.

Formwork and piles before reinforcement

When assembling the frame, the reinforcement can be knitted with each other using a wire or the rods can be connected by welding. There is no significant difference in the method of joining - it is often argued that a welded frame, due to the lack of elasticity, resists deformations worse than a connected viscous structure, however, in industrial multi-storey construction, the frames of pile-grillage foundations are always welded, so these fears are groundless. In addition, welding is a more practical and quicker way to implement.

See also: how stairs are reinforced, and should it be done?

Reinforcement of the grillage - step by step instructions:

The assembly of the reinforcement cage on the straight sections of the grillage is quite simple to perform. Difficulties arise when reinforcing the corners, which must be additionally reinforced, since this part of the frame experiences maximum loads.

Scheme of the correct reinforcement of the corners and abutments of the grillage

The corners and places of abutment of the inner walls of the strapping to the outer cannot be reinforced with overlapping reinforcement... In these areas, it is necessary to lay solid rods bent in a L or U-shaped configuration. A diagram of the correct reinforcement of the corners of the pile grillage is shown in the image.

Related articles:

Reinforced concrete monolithic structures are one of the prerequisites for the strength, reliability and durability of an object. Reinforced concrete means that the concrete is reinforced with a special frame, tied or welded from reinforcing bars. You should learn how to properly knit reinforcement for the foundation before reinforcing concrete in your garden plot, building a house, garage or other durable objects.

Rebar knitting options

The basics of correct knitting of reinforcement

Basically, in individual construction, a reinforcing frame is used when laying a strip foundation. The strip base is a monolithic structure made of concrete and reinforced cage inside, in which the frame takes on tensile loads and lateral displacements of the soil. Due to the multidirectional loads on the reinforcement cage, it is important to correctly make its calculations, as well as to find out the parameters of a house or other building that uses reinforcement in the structure, the number of building materials and their characteristics.

In order to tie a reinforcing belt with your own hands for any type of foundation in which it can be used, you need to be able to tie the transverse and longitudinal joints of the rods in the correct way. Welding is very often not recommended for assembling the reinforcing cage due to a too rigid connection, which, under sufficiently strong loads, can burst and weaken the entire structure. Therefore, you should use a special factory or homemade hook, plus know the basic layouts of reinforcing bars in concrete.

Reinforcement parameters when calculating the frame for a strip foundation

The knitting steel wire must be soft or annealed, and in order to correctly crochet the reinforcement, it is necessary to study the requirements for the knitting wire, which are regulated in GOST 3282.

Professional builders categorically deny knitting of metal reinforcement with plastic clamps, which are allowed to knit fiberglass reinforcement, since the mass of concrete pouring into the formwork displaces the knitting points along with the mortar. Slab concrete foundations are a separate topic, and reinforcing frames are allowed to be welded in them. There are ready-made industrial mesh welded from rods. But such a frame is much more expensive than a home-made one, in addition, the end joints need to be additionally reinforced with U-shaped clamps in place, which makes the welded frame even more expensive. Therefore, for the foundation of a private or country house, it is easier to knit the reinforcement cage by hand using a coil of soft wire, a special crochet hook, and instructions for use.

Rebar Tying Hook

When knitting a frame for a foundation, operations are performed in the following order:

1. A piece of knitting wire 20-25 cm long is used for tying reinforcing rods Ø 8-16 mm. A segment of this length must be cut off from the bay;
2. The segment is bent in half in the center, is brought under the intersection of the rods along the diagonal;
3. The sharp end of the crochet hook needs to be threaded into the loop, which turned out when the piece of wire was folded;
4. The clamp, which turned out from a piece of wire, should be pulled tight;
5. the free end of the clamp is applied to the working end of the crochet hook;
6. now we knit two intersections together: when you rotate the hook 3-5 turns, you get a strong but flexible twist;
7. After removing the knitting hook from the loop, the remaining free ends of the wire clamp must be bent inside the reinforcement cage.

Important: If reinforcement with a diameter of 25 mm or more is used for the aromatic cage, the intersections of the rods must be welded and not tied. Connected joints can break during operation of the finished reinforced foundation under the weight of the concrete and the building.

Ready reinforcement cage

Common mistakes when knitting a reinforcing frame that do not need to be repeated:

1. Straight line segments of the rods at the corners of the frame are connected by the overlap method;
2. The reinforcing frame is installed not on pads, but on the vertical rods of the frame;
3. In the context of a concrete tape, the reinforcing binder and reinforcing material is less than 0.1% of the total volume of concrete;
4. There is no protective layer on the sides of the formwork, due to which the rods can come into contact with the formwork material.

Corner intersections of the frame rods in the strip foundation cannot be simply tied and left in the form of an overlap of the rods. The connection of the rods is done according to specially designed anchoring schemes for such cases, one of which is presented below:

Anchorage schemes for frame corners

Reinforcement of the concrete foundation must take into account some of the features of the strip structure:

1. Reinforcing frame for concrete tape can be tied both in the ground and in the finished formwork. For this, reinforcing bars, metal clamps and anchors are used;
2. A deep foundation is reinforced before installing the panel formwork - this option is preferable due to the fact that the heavy frame does not have to be lowered into the trench and deform it;
3. The reinforced frame must be reinforced with U-shaped or L-shaped anchors at the corners of the structure;
4. To ensure the protection of the frame from below with concrete, props 5-7 cm in size are used, which are called glasses;
5. Elongation of short longitudinal bars occurs with an overlap, the overlap must be ≥ 20 bar diameters, or ≤ 25 cm;
6. Reinforcement cage should not be placed on stones, bricks or pieces of reinforcing bars - only iron, plastic or concrete linings should be used;
7. The overlapping reinforcement joints must be spaced apart - in one section, more than half of the total section of the longitudinal rods should not be connected.

Important! Clamps in the reinforcement cage are used to create and hold the geometry of the structure. Therefore, the diameter of the long horizontal rods should be 6 for a length ≤ 0.8 m and 8 mm for a rod length ≥ 80 cm.

Reinforcement of a tape with L-shaped and U-shaped reinforcements

Reinforcement of a slab floating foundation should take into account some design features and not repeat common mistakes:

1. The rods at the corners of the upper and lower levels should be connected with U-shaped clamps;
2. You cannot use one reinforcing mesh instead of two frames - the lower frame takes on tensile loads from the weight of the house, and loads from heaving forces are applied to the upper layer of the frame. One reinforcement mesh is allowed if the thickness of the concrete slab is ≤ 15 cm;
3. Non-compliance with the provision of concrete protective layers for the frame from above and below. Concrete layers should be ≥ 5-7 cm thick;
4. The mesh size of the reinforcing mesh should be ≤ 40 cm, the optimal mesh size is taken at 20 cm.

To assemble the concrete slab reinforcing frame, the upper belt of the mesh is fixed using such bracket-bending devices as "tables", "conductors", "pawns", "frogs", "clubs", "spiders", and other supporting elements with extended rods, which rest against the design of the lower belt.

Brackets for reinforcing frames and meshes

Bending of reinforcing bars should not be carried out by gas welding. The rods are bent on special bending mills or clips, in which the required radius can be set.

Near the bearing walls, the foundation should be reinforced with additional rods, since the dimensions of the mesh cells near the walls are half the size of the others. If slabs with stiffeners are used for the base, then the reinforcement cage is used the same as for the strip foundation or grillage.

Bending machine

Reinforcement of the grillage

Due to the fact that the grillage is like a foundation strip, many craftsmen make mistakes in reinforcing it. Tensile loads from the weight of the house are applied to the concrete tape in the area of ​​the sole, and the upper part of the foundation is subjected to loads from seasonal heaving of the soil. The grillage never experiences loads from heaving forces, since it rises above the soil and has an air gap or a layer of expanded polystyrene, which crumples during deformations. Only vertical bending forces are applied to the grillage in the areas where the supports are pinched.

Important: In the grillage, the reinforcing frame is necessarily reinforced with longitudinal reinforcement connected with steel clamps. Strengthening is carried out for the upper columns, piles or pillars, as well as for the lower armored belt.

Reinforcement of grillage for piles

The section of the reinforcing frame is of different types:

1. If the formwork is tubular, then the frame can be tied round or square;
2. For a columnar foundation in the formwork from prefabricated panels, round or square clamps are used, which are used to knit vertical reinforcement rods;
3. One support must have at least four longitudinal bars.

Pile reinforcement

The bottom of the piles does not need to be reinforced. The pile head at a distance of 1 meter from the bottom must be reinforced and poured with concrete. Vertical rods of reinforcement are bent at an angle of 900 and then tied to the grillage.

Pile reinforcement

A homemade reinforcing frame is made only on twists of soft knitting wire. Ready-made reinforcing cages for floating, slab, pile and columnar foundations are fastened using electric welding. It is forbidden to use gas welding, as the reinforcement rods become soft in the heating places.

Using the above recommendations, you can tie the reinforcement cage or mesh yourself - on the ground or in the formwork. Each type of foundation has its own structural differences that affect the thickness of the protective concrete layer, and the most difficult operation during reinforcement is anchoring the corners of the base, strengthening the stretching and squeezing areas.

The arrangement of foundations for any building is a very responsible and important stage from which the main construction work begins. It is recommended to manufacture foundations in strict accordance with the design documentation.

For monolithic structures, a rather important part of the work is the reinforcement of the grillage. The strength of the entire structure largely depends on the quality of the connected reinforcement. You can make the reinforcement yourself, having previously familiarized yourself with the technology of this type of work.

What is a grillage

A grillage is a monolithic element of the base of a building that connects free-standing pillars or piles into a single system. It is manufactured in the form of a strip foundation, on which the supporting and external enclosing structures of the building are installed. The tape evenly distributes the loads over the entire base of the building, which in turn transfers them to the ground.

Grillage device diagram

The grillage can be made not only in the form of a monolithic strip foundation. It is also made from wood, metal and reinforced concrete products located between the columnar support structures. Such a device in the form of beams is used much less often than a monolithic one.

Distinguish between hanging and recessed structures

Depending on the height of the grillage foundation relative to the ground level, there are hanging and recessed versions of the device. When building a buried grillage, a monolithic version is chosen. If a hanging one is made, then the base of the grillage can be arranged from horizontal beams.

Monolithic grillage is based on concrete and reinforcement. Reinforcement takes the bulk of the time when constructing this type of foundation. When carrying out work on the reinforcement of the strip foundation, it is necessary to be guided by building codes and rules 52-01-2003.

The grillage must serve as a reliable support and protect the structure from moisture. The pile-grillage foundation is suitable for the construction of buildings with no more than three floors.

Monolithic grillage device

To make a monolithic grillage foundation, you will need to complete several stages of work.

1. Formwork installation.
2. Reinforcement of the grillage.
3. Concreting.
4. Stripping.
5. Waterproofing tape.

Formwork installation

The formwork must be installed strictly at an angle of 90 degrees

The grillage foundation is made hanging or buried in the ground. The formwork design directly depends on its shape.

Regardless of the design, the side walls of the formwork must be assembled in a strictly vertical level, and the angles must correspond to 90 °, unless a different design is provided for by the project.

When making a tape in the ground, you can use soil instead of formwork, as a support for the future foundation. Above ground level, formwork is usually assembled from boards or plywood. It is knocked together or pulled together in such a way that the concrete does not squeeze out the boards and does not spread during the laying process. The part of the foundation that protrudes above the ground will be fenced with such a structure.

If the hanging version of the grillage device is chosen, then it is necessary to provide a high-quality base in the formwork. It needs to be calculated based on the load that it must withstand. The load is determined by the mass of concrete and reinforcement. It is also necessary to take into account the mechanical effects on the structure from vibration of concrete in the process of pouring it.

The side walls of the formwork must be firmly assembled. For this, transverse ties, spacers, tubes with pins and other materials can be used, which will ensure the reliability of the structure.

Poor-quality formwork can lead to disruption of the concrete placement process. This is unacceptable in construction, but often happens due to negligence in this part of the work.

Reinforcement of the grillage

Reinforcement of the structure

Reinforcement of the grillage of a pile or columnar foundation is one of the most critical stages of the foundation for a building.

Periodic metal reinforcement is used as the main material for the reinforcement of foundations. Recently, they began to replace it with composite fiberglass. It should be noted that fiberglass reinforcement is not suitable for hanging structures. It is good where there is support on the ground.

Reinforcement is welded into beams

The reinforcement is bonded or welded in some cases into frames, the so-called beams. There are several types of beams. The type of reinforcement, and hence the type of beams, is determined at the design stage.

In case of self-construction, when there is no project, and there is no way to contact specialists, there is an option to use the online reinforcement calculator. It is advisable to find several such online programs on the Internet and make calculations in each, so that, by comparing the data, determine the error in the calculations. Having calculated the reinforcement according to the entered parameters of the foundation, you can start work.

Reinforcement of a monolithic grillage in the most common form consists of straight longitudinal and transverse rods, which are interconnected by knitting wire or welding. To correctly make the connection of the structure, clamps and U-shaped products are made from reinforcement. They are the connecting elements at the nodes of the reinforcing cage.

To find out how to correctly manufacture reinforcing cages and their assemblies, you need to familiarize yourself with the guidelines for the design of concrete and reinforced concrete structures from heavy concrete (without prestressing).

Reinforcement of pile-grillage foundations is impossible without connecting the reinforcement of the piles to the grillage frame. When arranging a pile field at the stage of reinforcement, vertical rods are made with allowances in height. When installing the reinforcing cage of the strip foundation, the rods released from the piles are bent at the desired horizontal level and connected to the main frame. Thus, the integrity of the structure is achieved. For all the details on pouring the pile-grillage foundation, see this video:

Do not heat metal fittings in order to bend them. For bending, you must use special devices or a pipe bending machine.

Concreting the tape

It is necessary to pour concrete into the formwork without interruption in order to get a high-quality monolith

The grillage foundation is poured with concrete at a time without interruption in the work until their complete completion. It is strictly forbidden to make gaps along the length of the foundation. The only permitted action is to break the height of the grillage. After pouring a layer of 150-200 mm across the entire volume of the tape, a break is made in the work.

Before proceeding with construction work, you must wait until the concrete has reached the minimum permissible strength. Then it is required to clean off the top layer, the so-called concrete milk, and only then continue concreting the tape.

It is important to carry out work so that there are no pores in the concrete mass. The concrete is required to fill the entire space in the formwork. There should not be a single air pocket inside the grillage.

Stripping

It is important not to remove the formwork ahead of time.

You can neglect this process once and make it ahead of time in order to incur losses that will significantly affect the construction budget.

If the formwork is prematurely removed, the foundation can crack, which will leave almost no options other than dismantling it. In this case, a new foundation will be required, respectively, the construction costs will increase significantly.

Concrete gains strength depending on its grade and ambient temperature. The ideal temperature is considered to be 20 ° C, in such conditions concrete of the M200-300 grades will gain 100% strength in 28 days.

Data on concrete strength gain are presented in the table.

Concrete grade	Curing time, days	-3 ° C	0 ° C	+ 5 ° C	+ 10 ° C	+ 20 ° C	+ 30 ° C
	1	3	5	9	12	23	35
	2	6	12	19	25	40	55
M200-300 on Portland cement M-400 and M-500	3	8	18	27	37	50	65
	5	12	28	38	50	65	80
	7	15	35	48	58	75	90
	14	20	50	62	72	90	100
	28	25	65	77	85	100	-

The table shows that at low temperatures it is advisable to use concrete with additives for a quick set of strength. This slightly increases its cost, but also significantly speeds up the construction process.

It is allowed to make stripping when concrete gains strength of at least 50%.

Waterproofing tape

With a hanging grillage, you can use a coating waterproofing. In the recessed version, it is possible to lay the roll waterproofing in the ground before pouring the concrete and, after removing the formwork of the upper part, completely close the foundation with it. For more information on waterproofing grillage structures, see this video:

It is important to protect the substrate from moisture. If the foundation absorbs water, then in winter at subzero temperatures during the expansion of the freezing water, microcracks will form in it. This must be avoided.

Reinforcement errors and how to avoid them

It is not necessary to reinforce the corners by crossing the reinforcement

There are a number of mistakes related to reinforcement that inexperienced builders make in order to save money or simply because of ignorance of building codes and regulations. Below are the most frequently recurring ones.

1. A decrease in the diameter of the bored pile, according to some builders, should be accompanied by a decrease in the number of vertical reinforcement rods, to which the grillage frame should subsequently be attached. Reducing the allowance for vertical bars.
2. Reinforcement of corner sections by crossing straight reinforcement rods. Many do this so as not to complicate the knitting of the frame.
3. Failure to comply with the step of installing jumpers when reinforcing the grillage. Skipping required connections. This often happens in order to save money.
4. Deviation of the reinforcement cage from the central axis. This will lead to an uneven bearing capacity of the base, which often happens due to trivial negligence. All the subtleties of the reinforcement of the pile foundation, see this video:

The solutions to the above errors are given below.

1. The pile diameter should not be less than 300 mm, and the number of vertical rods should be less than 4, the reinforcement allowance for the grillage should be at least 0.5 m.
2. For the correct connection of the nodes of the beams, it is necessary to make bent U- and L-shaped parts with which it is required to connect the corner elements.
3. When constructing a reinforcing cage, a pitch of 200 to 400 mm between the jumpers must be observed. The exact step size is determined at the design stage.
4. It is required to make all measurements using building levels so that the frame is aligned relative to the central axis.

Reinforcement is a significant part of the construction process. Everything is important and the quality of materials, and the experience of builders, and the availability of working documentation.

Failure to comply with the rules of reinforcement can lead to the most serious consequences. This stage of construction is one of the most critical.

During construction work, any mistake leads to a decrease in the life of the building without the need for repair. This is at its best. At worst, even at the stage of construction of the building, it undergoes reconstruction.

To achieve the maximum service life, it is required to comply with building codes and regulations, avoiding deviations from the project. Construction combines a set of measures that must be followed to achieve the desired result. If possible, it is better to entrust such work to professionals.