Reinforcement consumption must be determined at the foundation design stage in order to subsequently know exactly the amount of material purchased. Consider how to calculate reinforcement for strip foundation on the example of a shallow base 70 cm high and 40 cm thick.

1.2 Reinforcement of the strip foundation (video)

2 Work performance technology

After the amount of reinforcement is determined, a strip foundation reinforcement scheme must be selected, according to which the reinforcement cage will be assembled. The straight sections of the structure are made of solid rods, while at the corner places additional reinforcement is needed with reinforcement curved into a P or L-shape. The use of perpendicular overlap of individual reinforcement bars at corners and junctions is not allowed.

The correct reinforcement of the corners of the strip foundation is shown in the diagram:

Scheme of reinforcement of the strip foundation at the junctions:

Do-it-yourself reinforcement of the strip foundation involves assembling the frame in a convenient place and its subsequent placement inside the formwork. The technology requires bending reinforcement into rectangular clamps, which is easy to do at home with a homemade fixture.

On the 20th channel, grooves must be cut with a grinder, into which reinforcement is subsequently inserted, and a piece of steel pipe is put on the bar, which is used as a lever. Finished rings must be fastened by welding or tied with wire. For bars with a diameter of 10-15 mm, wire 1.2-1.5 mm is used.

The foundation is the most vulnerable part of the structure. Due to the fact that the upper part of the building is subjected to compressive stress, and the lower part is subjected to tension, the correct laying of the foundation plays a big role. To perform the correct reinforcement of the strip foundation with your own hands, you must perform the calculation according to the scheme.

Such a base, in fact, is a reinforced concrete strip passing along the outer part of the building and under bearing walls inside.

In compression, concrete structures can withstand 50 times more than in tension.. Both the upper and lower parts of the structure are overloaded, so it is necessary to reinforce both parts. There is almost no load on the middle part. Metal fittings help solve these problems.

To ensure the strength, reliability, durability of the building, any base must be reinforced. After all, the foundation is exposed various loads. This is the weight of the whole house, and various soil movements. The strip foundation reinforcement scheme resembles a structure skeleton, which is assembled from steel bars. In order to choose the necessary scheme for it, you need to understand what it is.

Reinforcement of the strip foundation can be easily done with your own hands, without involving specialists. It is important, first of all, to choose the right diameter of the reinforcement

reinforcing material

The choice of material is quite an important step. Do-it-yourself steel rods of different sections are used to reinforce the strip foundation or fiberglass reinforcement. But most often they use metal.

The main horizontal reinforcement has a section of rods from 12 to 24 mm. The rods that will be located vertically, which are auxiliary. That's why usually the cross section of vertical rods is from 4 to 12 mm. Such a large difference is due to the spread in the loads on the base and is directly dependent on the type of soil and the weight of the structure.

Auxiliary vertical rods are installed if the height of the foundation exceeds 15 cm. In this case, reinforcement with a cross section of 6-8 mm of class A1 is used. The frame is assembled from rods and clamps, cleaning them from rust. If necessary, the rods are straightened and cut. As a connection of rods, a knitting wire and a hook are used. Welding work can be performed if the rods are marked "C".

The choice of diameter is influenced by the number of horizontal levels and the reinforcement scheme of the strip foundation.

Calculation of the reinforcement of the strip foundation

The number of reinforcing elements must be calculated based on the dimensions of the base. For foundations whose width is 40 cm, 4 longitudinal rods are sufficient - two at the top and two at the bottom. To install a frame row in a strip base measuring 6x6 m, you will need, on average, 24 m of reinforcement. If you lay 4 bars, you will need 96 m of longitudinal rods.

For transverse and vertical reinforcement of a foundation with a width of 0.3 m and a height of 1.9 m for each fastening with a distance of 5 cm from the surface, according to the concrete calculator, (30-5-5)x2 + (190-5-5)x2 = 400 cm or 4 m smooth reinforcing elements.

If the mounting step of the clamps is 0.5 m, the number of connections will be: 24 / 0.5 + 1 = 49 pcs. So, based on the calculations, you will need 4x49 = 196 m of transverse and vertical rods.

The total cross-sectional area of ​​​​the reinforcement and its weight, based on the diameter of the rods, can also be calculated from the table:

Rebar diameter, mm	Estimated area of ​​the transverse rod, mm 2, with the number of rods									Theoretical weight of 1 m of reinforcement length, kg
	1	2	3	4	5	6	7	8	9
6	28,3	57	85	113	141	170	198	226	254	0,222
8	50,3	101	151	201	251	302	352	402	453	0,395
10	78,5	157	236	314	393	471	550	628	707	0,617
12	113,1	226	339	452	565	679	792	905	1018	0,888
14	153,9	308	462	616	769	923	1077	1231	1385	1,208

The minimum area of ​​foundation reinforcement is regulated normative documents, and the strength of the foundation depends on this

Which scheme is better to choose

There are two main reinforcement schemes that are most often used to reinforce the foundation for low-rise buildings:

• four rods;
• six rods.

In accordance with SNiP 52-101-2003, adjacent reinforcement bars must be located at a distance of 40 cm (400 mm) in one row. The extreme longitudinal reinforcement should be at a distance of 5-7 cm (50-70 mm) from the side walls of the base. That's why, if the width of the base is more than 50 cm, then it is better to use a six-rod reinforcement scheme.

Depending on this, the diameter of the steel rods is chosen.

Usually, for a strip base, the laying of rods “in a box” is used. In this case, all rods are attached at an angle of 90 °. For longitudinal arrangement, reinforcing materials of class A3 are used, which have a round shape.

How to reinforce corners

The corners are heavily loaded. Therefore, when reinforcing, it is necessary to take care of their strengthening.

Atthe following rules must be taken into account:

• the rod must be bent so that one of its sides is deepened into one wall of the foundation, and the second into the other wall;
• if the rod is not long enough to make a bend, then L-shaped profiles can be used to fasten the rods at the corner.

Most often, class A3 reinforcement is used for this.

How to make reinforcement with your own hands

To do this, you should take a square or rectangle as a basis.

Before installing the frame, a sand cushion 1 m deep must be laid out at the bottom of the trench.

The frame is set up like this:

• bricks are laid at the bottom of the trench, the height of which is 5 cm (in order to create a gap between the bottom of the base and the frame);
• to install the rack rods, it is necessary to make a sample in advance, according to which the rods will be cut;
• rods of a longitudinal shape are laid on the bricks;
• horizontal jumpers with a length slightly less than the thickness of the base (approximately 5 cm on each side) are tied to the longitudinal rods with a step of 50 cm using a knitting wire;
• to the corners of the cells formed, rods are attached vertically with a length of 10 cm less than the height of the base;
• upper longitudinal bars are mounted to the vertical reinforcement;
• the upper transverse rods are tied to the obtained angles.

When reinforcing a strip foundation, it is necessary to adhere to the requirements of SNiP 52-01-2003

Basic provisions of SNiP 52-01-2003

The main provisions of SNiP 52-01-2003 relate to the distance between the horizontal ribs of the steel frame and the diameter of the reinforcement. So, between the longitudinal rods should not be less than 25 cm and more than 40 cm.

The cross section of the rods is chosen according to the number of longitudinal rods. For a strip foundation, it should be at least 0.1% of the area of ​​​​the working section of the base. For example, if the height of the foundation is 1 m and the width is 0.5 m, the cross-sectional area should be approximately 500 mm2.

More clearly about the minimum diameter of the reinforcement can be seen in the table of examples:

Conditions for the use of fittings	Minimum rebar diameter	Regulatory document
Longitudinal working reinforcement along the side 3 meters or less	10 mm
Longitudinal working reinforcement along the side of more than 3 meters	12 mm	Reinforcement of elements of monolithic reinforced concrete buildings
Structural reinforcement	The cross section is equal to 0.1% of the cross-sectional area along the height of the distance between the layers of reinforcement and half the width of the tape
Transverse reinforcement (clamps) of compressed elements	Not less than ¼ of the largest diameter of the longitudinal reinforcement and not less than 6 mm
Transverse reinforcement (clamps) of knitted flexible frames	not less than 6 mm	SP 52-101-2003 Concrete and reinforced concrete structures without prestressing reinforcement.
Transverse reinforcement (clamps) of knitted frames with a section height of 80 cm or less	6 mm	Design Guide for Concrete and Reinforced Concrete Structures from Heavy Concrete
Clamps of knitted frames with a section height of more than 80 cm	8 mm	Design Guide for Concrete and Reinforced Concrete Structures from Heavy Concrete

Reinforcement of the strip foundation is easy to do with your own hands, it is enough to follow the technology and correctly perform the calculation. If it is difficult to do it yourself, it is better to resort to the help of professionals. After all, a reliable and solid foundation is the price and guarantee of the stability of the entire building.

You can see more about reinforcing the strip foundation with your own hands in the video:

Despite the fact that the depth of the strip foundation is not the only indicator of reliability and durability, it plays a huge role in the integrity of the entire house during its operation. Reinforced concrete tape of any size and brand of concrete may burst over time if it is incorrectly placed in the ground, not taking into account its features.

In order not to get confused in all types of foundations and soils, let's try to understand everything in order. First, we will analyze the types of monolithic tapes, and then, specifically for each type of strip foundation, we will determine the depth of the foundation.

Factors affecting the depth of strip foundations

It is probably worth starting with the fact that the strip foundations themselves are divided into three main types:

1. Unburied
2. Shallow
3. Buried

Each of these types is laid to a certain depth, which depends on several main factors:

• Soil freezing depth
• Soil type
• Level ground water

It is worth noting that strip foundation depth- this is the distance from the soil surface to the base of the foundation, and not the depth to which the trench is dug. In the trench, in addition to the foundation, there may be a pillow.

Now let's see how these factors affect each type of strip foundation separately.

Unburied strip foundation

An unburied strip foundation is extremely rarely used in the construction of private houses, because it is a very weak support for the future structure. As a rule, it is all located on top of the ground, and inside there is only a sand or sand and gravel cushion.

I won’t write much about the non-buried strip foundation, especially since a whole article was already devoted to it earlier. And in general, the very concept of the depth of laying in such a foundation is absent.

Calculation of the depth of laying strip shallow foundations

This is the most capricious, in terms of the depth of the foundation. Firstly, it is not as reliable as buried, and secondly, in order for such a strip foundation to withstand the load of the structure, and also to restrain all the heaving forces transmitted from the ground, its calculation must be approached with special responsibility.

How to fill in, I have already described in detail in one of the previous articles. Therefore, we will not go into details.

Such a strip foundation is laid to a depth that is much higher than the depth of freezing of the soil, which is why it is called shallow. It, in contrast to the buried one, can be largely affected by the forces of heaving of the soil.

Also, an important difference shallow foundations is that it must be made monolithic not only below the ground level, but immediately, having set up the formwork, pour the above-ground part of the foundation - the basement. This will greatly strengthen the entire strip foundation.

The depth of laying a shallow foundation directly depends on all three factors described above. In order not to get confused, let's look at the table.

Table No. 1: Depth of laying a strip shallow foundation (minimum), depending on the type and depth of soil freezing

Depth of soil freezing, m		Depth foundation, m
The soil is slightly heaving	The soil is not porous, hard rocks
over 2.5	-	1,5
1,5 - 2,5	3.0 or more	1,0
1,0 - 1,5	2,0 - 3,0	0,8
less than 1.0	less than 2.0	0,5
Note:In order to find out what the depth of soil freezing is in your region, look at table No. 2 below, where the values ​​\u200b\u200bare given for some cities, taking into account the type of soil. Click on the table to enlarge.

Table No. 2: Depth of soil freezing in some regions

Note: In addition to the fact that the depth of freezing and the type of soil affect the depth of the strip foundation, one more very important factor should not be discarded - the level of groundwater, which we will talk about later.

The dependence of the depth of laying the strip foundation on the groundwater level (GWL)

There are two options for the location of groundwater - when they are located below the freezing depth of the soil, and when - above.

The groundwater level is below the freezing depth of the soil

This can be considered a good indicator, and in this case, groundwater in most types of soils does not have a particular effect on the depth of the installation of a monolithic reinforced concrete tape.

The only limitation, in this case, is that in such soils as loams, clays and the like, the tape must be laid at least half the freezing depth of such soil. In other, “good” soils, this factor does not affect the laying of the foundation.

In other words, if the freezing depth in your region is, for example, 1.5 meters, then the tape shallow foundation must be arranged at least 0.75 meters.

The groundwater level is above the depth of soil freezing

If groundwater is high, then the depth of digging a trench for strip foundation does not depend on their level only on rocky soils, sandy coarse-grained, gravel and the like.

On any other types of soils with a high GWL, the monolithic tape will have to be buried below the freezing depth by 10-20 cm (table No. 2). In this case, it will become a deep foundation.

Buried strip foundation

A recessed strip foundation is considered the most reliable of all tapes. It is laid below the freezing depth of the soil by 10-20 cm. Another condition for its construction is that the soil under its sole must be more or less solid.

In the case of swampy soils, peat bogs and the like, the strip foundation is laid to a depth that is below these layers. In some cases, it is enough to dig a trench to hard ground, and then arrange a sand or sand and gravel cushion to a level that is slightly below the freezing depth of the soil in your area.

When the soil at the construction site is very bad for laying a strip foundation, or its installation is very expensive, you can try to calculate another type of foundation, for example, slab. Perhaps it will be both cheaper and more reliable.

How to reduce the depth of the strip foundation

After carrying out all the calculations on the depth of laying the strip foundation, it often happens that, taking into account the soil and the region, it must be laid very deep. This raises the question of how to cut costs and reduce depth.

There are several ways to reduce the depth of strip foundations, all of which are based on reducing the importance of the main factors affecting the foundation.

Reducing the depth of soil freezing

Of course, we will not be able to change the climate in the region, but we will be able to change the depth of freezing, specifically under the base of the foundation, by insulating the foundation itself and the soil adjacent to it from the outside.

In this way, we can reduce the depth of the foundation, as well as reduce the cost of it.

Groundwater drainage from the strip foundation

Another effective way to reduce the depth of the strip foundation is to drain water from it.

This is done with the help of a good drainage system, which will divert a significant part of the water from the foundation and prevent it from adversely affecting it.

Sand or sand and gravel cushion under the foundation

In the case when heaving layers of soil lie deep enough on the site, strip foundation will also have to be laid to a greater depth. You can reduce it by replacing the heaving soil with a sandy or sandy-gravel cushion.

In other words, it is necessary to dig a deep trench to hard ground rocks, and then arrange a massive sand and gravel cushion there, which will distribute the load from the foundation and the house to the ground evenly and prevent heaving forces from adversely affecting the foundation.

It is advisable to make a pillow not only under the sole of the foundation, but also next to it, as shown in the diagram.

It should be noted that the most reliable method for reducing the depth of the strip foundation is the combined method, i.e. and a pillow device, and insulation, as well as a drainage device, if necessary.

The foundation is an important supporting structure of the building, the quality of which determines its durability and safety of operation. Depending on the features of the house and the characteristics of the base under it, they choose from several types of structures, each of which requires calculation and competent design. The strip foundation is one of the most commonly used for private construction. When it is constructed, different technologies are used, one of which is reinforcement.

Strip foundation reinforcement is used for both prefabricated and monolithic structures. If, when using factory-produced foundation blocks, it is not possible to adjust the percentage of reinforcement and the diameters of the rods, then in monolithic structures the process of selection of reinforcement and its placement in the thickness of the tape plays an important role. Why is reinforcement needed and how is it carried out?

Why and when is it necessary to reinforce strip foundations

A feature of concretes, which are used in the production of many types of foundations, is that they do not respond equally to different types of loads. Compressive, tensile, twisting, bending forces act on each building element of a building to a different extent. Concrete reacts differently to them. For example, if it can withstand a compressive load of a certain value without problems, then the same tensile force can lead to cracking and destruction of the material.

Reinforcement is used to solve the problem. It consists in the fact that steel rods are installed in tension zones, which are connected to concrete in one structure and perceive tensile loads. When calculating, it must be borne in mind that stretching is possible in different parts of the foundation, depending on the acting forces. There are also conditions that in one zone there are first compressive, and then (during heaving or subsidence) tensile forces.

To reinforce a monolithic strip foundation, rolled steel rods are used. The fittings are divided into classes, depending on the features (A-I, A-II, A-III). Directly in the thickness of concrete apply:

• separate rods;
• reinforcing meshes;
• reinforcing frames.

Grid - a flat structure of longitudinal and transverse rods interconnected. Frame - a three-dimensional element, which is the same longitudinal and transverse rods connected into a three-dimensional structure. The choice of the type of reinforcement scheme for the strip foundation is justified during the design, depending on the value of the loads and the features of the foundation.

Necessary materials

For reinforcement, rods made of rolled steel of several classes are used. For strip foundations, the following are most often used:

• A-III with a diameter of 10-16 mm as a working one, which perceives tensile loads;
• Vr-1 with a diameter of 4-5 mm for transverse reinforcement (smooth wire).

A knitting wire is also needed, with the help of which the rods are connected to each other into a single frame or mesh. Knitting occurs with the use of a special hook, which is made from a steel rod or purchased at hardware stores.

To increase the service life of the reinforcement and protect it from atmospheric action, it is necessary to provide a distance from the outer surface of the concrete to the edge of the rod. This distance is called the protective layer. For the foundations of private houses, it is at least 30 mm.

Various methods are used to provide a protective layer. Basically, this is the laying of supports made of different materials. To do this, use trimmings of reinforcement, pieces of steel, or purchase special coasters in hardware stores.

Reinforcement scheme for buried foundations

Reinforcement of a buried strip foundation is carried out with longitudinal reinforcement bars connected into a frame. Where are the working rods located? Since they perceive tensile forces, they are placed in zones of such loads. In a strip foundation, this is the upper and lower part of the structure. At the same time, tensile forces do not occur in these two parts of the foundation, but when designing it is not always possible to determine with a high probability that the load will occur only in the upper or only in the lower zone.

The foundation works like a beam, which is affected by the weight of the building and possible heaving forces. If the design is calculated and built correctly, then the house evenly presses on the entire tape. In this case, tensile forces may not arise. But if there is a drawdown, or heaving, then the loads increase unevenly. For this, reinforcement is carried out.

The frame is positioned in such a way that the working reinforcement is protected by a layer of concrete. For it, rods of brand A-III are used. The diameter is selected by calculation, but more often it is 12-14 mm. The transverse rods are made of wire Vr-1 4-5 mm in increments of 150-200 mm.

In the cross section, two working rods are more often placed in the lower and upper zones, but with a large width of the tape, three can also be used. This option is possible if the tape width is from 400 mm and above.

The corners of the foundation, as well as the joints of the walls, are reinforced with reinforcing diagonal rods, the edges of which are turned around and hooked to the frame or stack on each side.

Since fittings are often sold in lengths of 6 or 12 mm, it is important to calculate the dimensions before purchasing so that they are cut into the required lengths directly upon purchase.

Reinforcement scheme for shallow foundations

The difference between shallow foundations is that their sole is not located below the depth of seasonal freezing of the soil. The principles of reinforcement and work technology are the same as for buried ones. There are options and location of the tape directly on the upper surface of the soil. The lack of deepening leads to the fact that it is especially necessary to take into account the effect of heaving forces in the winter period.

Basically, the reinforcement of shallow strip foundations is carried out with grids. Their location depends on the degree of heaving of the soil. On non-rocky and weakly rocky soils, reinforcement is not always used. This makes the design cheaper.

Grids consist of longitudinal reinforcement bars of class A-III of different diameters. For small buildings, rods with a diameter of 10 mm are more often used. In the cross section of the tape, two rods are more often placed at the top and bottom of the foundation. For transverse reinforcement, wire Vr-1 with a diameter of 4 mm is used.

Reinforcement of the corners of a strip foundation of this type is carried out by the same methods as for a deep foundation - by the device of reinforcing rods of the corner joint. Also, the joints of the walls need to be strengthened.

Stages of work

Let us consider in more detail the stages of work for reinforcing the strip foundation with our own hands. Before starting work, it is important to correctly calculate the amount of reinforcement and choose a scheme. You can also use standard solutions, but there is always a possibility that the characteristics of the soil in your area require the use of special measures to strengthen the foundation and the proposed average frame parameters are not suitable for strength characteristics.

Another option is also possible, when the base is strong and does not require the use of such an amount of material as is proposed for use. There is an overspending and appreciation of the house. To avoid these troubles, it is recommended to carry out a professional calculation of the structure with the involvement of a civil engineer.

If the scheme is developed and materials are purchased, proceed with the installation. Work is carried out in the following order:

1. It is necessary to mark the dimensions of the foundation on the surface of the soil. It is important to observe the dimensions and angles exactly.
2. Mark out trenches. Their width should be such that it is convenient to assemble the formwork. More often, a margin of 15-20 cm on each side is enough for this.
3. Dig trenches for belts. The depth of the trench consists of the height of the foundation and the sand bed. The thickness of the sand cushion depends on the heaving of the soil. In low-heaving clay soils, 10 cm is enough, and in heavily-heavy clay soils, 60 cm of backfill is also arranged. It is better to choose the exact value of the layer thickness by calculation or according to tables in the regulatory literature. Buried foundations are located below the freezing depth of the soil in the region.
4. Install formwork. For it, wooden boards or sheet materials (OSB, steel) are used. Most often, softwood boards 25-40 mm thick are used. The height of the formwork should be 5-10 cm higher than the top of the tape itself. Before installation, the boards are knocked into shields of the desired width. The shields are successively installed in the trench and fixed.
5. Prepare fittings. If meshes are used, then vertical rods from reinforcement scraps are driven in for them in the prepared formwork. A distance of 50-100 mm is arranged between them. The distance from the pins to the formwork is chosen in such a way as to provide a protective layer of reinforcement (from 30 mm). The frames are knitted either directly in the formwork, or outside it, and then transferred.
6. The reinforcement bars are knitted together with a special wire using a hook.
7. The corners and intersections of the walls are reinforced with additional rods.
8. After creating the frames or fixing the grids in the formwork, their reliability is checked and the foundation is concreted.

The construction of walls can begin after reaching the required strength. This period depends on the quality concrete mix and ambient temperature. On average, the design strength of concrete is achieved in 28 days.

Reinforcement of the sole of the strip foundation, if any, is carried out with a reinforcing mesh, into which it is connected to the frame of the strip itself before concreting.

The strip foundation has a non-standard geometry: its length is tens of times greater than the depth and width. Due to this design, almost all loads are distributed along the belt. On its own, a concrete stone cannot compensate for these loads: its bending strength is not enough. To give the structure increased strength, not just concrete is used, but reinforced concrete - this is a concrete stone with steel elements located inside - steel reinforcement. The process of laying metal is called strip foundation reinforcement. It is not difficult to make it with your own hands, the calculation is elementary, the schemes are known.

The quantity, location, diameters and grade of reinforcement - all this should be spelled out in the project. These parameters depend on many factors: both on the geological situation on the site and on the mass of the building being erected. If you want to have a guaranteed strong foundation, a project is required. On the other hand, if you are building a small building, you can try to do everything yourself, based on general recommendations, including designing a reinforcement scheme.

Reinforcement scheme

The location of the reinforcement in the strip foundation in cross section is a rectangle. And there is a simple explanation for this: this scheme works best.

Reinforcement of the strip foundation with a strip height of not more than 60-70 cm

Two main forces act on the strip foundation: from below, in frost, heaving forces press, from above, the load from the house. At the same time, the middle of the tape is almost not loaded. To compensate for the action of these two forces, two belts of working reinforcement are usually made: top and bottom. For shallow and medium-depth foundations (up to 100 cm deep), this is enough. For deep belts, already 3 belts are required: too high a height requires reinforcement.

In order for the working reinforcement to be in the right place, it is fixed in a certain way. And they do it with the help of thinner steel rods. They do not participate in the work, they only hold the working reinforcement in a certain position - they create a structure, which is why this type of reinforcement is called structural.

As can be seen in the reinforcement scheme of the strip foundation, the longitudinal bars of the reinforcement (workers) are tied up with horizontal and vertical supports. Often they are made in the form of a closed loop - a collar. It is easier and faster to work with them, and the design is more reliable.

What fittings do you need

For the strip foundation, two types of bar are used. For longitudinal, which carry the main load, class AII or AIII is required. Moreover, the profile is necessarily ribbed: it adheres better to concrete and transfers the load normally. For structural lintels, cheaper fittings are taken: smooth first class AI, 6-8 mm thick.

Recently, fiberglass reinforcement has appeared on the market. According to manufacturers, it has better strength characteristics and is more durable. But many designers do not recommend using it in the foundations of residential buildings. According to the regulations, it should be reinforced concrete. The characteristics of this material have long been known and calculated, special reinforcement profiles have been developed that contribute to the fact that metal and concrete are combined into a single monolithic structure.

How concrete will behave paired with fiberglass, how firmly such reinforcement will adhere to concrete, how successfully this pair will resist loads - all this is unknown and has not been studied. If you want to experiment - please use fiberglass. No - take iron fittings.

Do-it-yourself calculation of the reinforcement of the strip foundation

Any construction work is standardized by GOSTs or SNiPs. Reinforcement is no exception. It is regulated by SNiP 52-01-2003 "Concrete and reinforced concrete structures". This document indicates the minimum amount of reinforcement required: it must be at least 0.1% of the cross-sectional area of ​​\u200b\u200bthe foundation.

Determination of reinforcement thickness

Since the strip foundation in the section has the shape of a rectangle, the cross-sectional area is found by multiplying the lengths of its sides. If the tape has a depth of 80 cm and a width of 30 cm, then the area will be 80 cm * 30 cm \u003d 2400 cm 2.

Now you need to find the total area of ​​\u200b\u200bthe reinforcement. According to SNiP, it should be at least 0.1%. For this example, this is 2.8 cm 2 . Now, using the selection method, we determine the diameter of the bars and their number.

Quotes from SNiP that relate to reinforcement (to enlarge the picture, click on it with the right mouse button)

For example, we plan to use rebar with a diameter of 12 mm. Its cross-sectional area is 1.13 cm 2 (calculated by the formula for the area of ​​a circle). It turns out that in order to provide recommendations (2.8 cm 2), we need three rods (or they also say “threads”), since two are clearly not enough: 1.13 * 3 \u003d 3.39 cm 2, which is more than 2.8 cm 2 recommended by SNiP. But three threads cannot be divided into two belts, and the load will be significant on both sides. Therefore, four are laid, laying a solid margin of safety.

In order not to bury extra money in the ground, you can try to reduce the diameter of the reinforcement: calculate under 10 mm. The area of ​​this rod is 0.79 cm 2 . If we multiply by 4 (the minimum number of bars of working reinforcement for a tape frame), we get 3.16 cm 2, which is also enough with a margin. So for this option strip foundation, you can use class II ribbed reinforcement with a diameter of 10 mm.

Reinforcement of the strip foundation for the cottage is carried out using bars with different types of profile

Installation step

For all these parameters, there are also methods and formulas. But for small buildings, it's easier. According to the recommendations of the standard, the distance between horizontal branches should not be more than 40 cm. They are guided by this parameter.

How to determine at what distance to lay reinforcement? In order for steel not to corrode, it must be embedded in concrete. The minimum distance from the edge is 5 cm. Based on this, the distance between the bars is calculated: both vertically and horizontally, it is 10 cm less than the dimensions of the tape. If the width of the foundation is 45 cm, it turns out that there will be a distance of 35 cm between the two threads (45 cm - 10 cm = 35 cm), which corresponds to the standard (less than 40 cm).

The reinforcement step of the strip foundation is the distance between two longitudinal bars

If we have a tape of 80 * 30 cm, then the longitudinal reinforcement is located one from the other at a distance of 20 cm (30 cm - 10 cm). Since two reinforcement belts are required for medium-level foundations (up to 80 cm high), one belt from the other is located at a height of 70 cm (80 cm - 10 cm).

Now about how often to put jumpers. This standard is also in SNiP: the installation step of vertical and horizontal dressings should be no more than 300 mm.

All. Do-it-yourself reinforcement of the strip foundation was calculated. But keep in mind that neither the mass of the house nor the geological conditions were taken into account. We were based on the fact that these parameters were based on .

Corner reinforcement

In the design of the strip foundation, the weakest point is the corners and the junction of the walls. In these places, loads from different walls are connected. In order for them to be successfully redistributed, it is necessary to correctly bandage the reinforcement. Just connect it incorrectly: this method will not ensure the transfer of the load. As a result, after some time, cracks will appear in the strip foundation.

The correct scheme for reinforcing corners: either drives are used - L-shaped clamps, or longitudinal threads are made 60-70 cm longer and bent around the corner

To avoid this situation, when reinforcing corners, special schemes are used: the bar is bent from one side to the other. This "overlap" should be at least 60-70 cm. If the length of the longitudinal bar for bending is not enough, use L-shaped clamps with sides also at least 60-70 cm. The diagrams of their location and fastening of the reinforcement are shown in the photo below.

By the same principle, the adjoining walls are reinforced. It is also advisable to take the reinforcement with a margin and bend it. It is also possible to use L-shaped clamps.

Reinforcement scheme for adjoining walls in a strip foundation (to enlarge the picture, click on it with the right mouse button)

Please note: in both cases, in the corners, the installation step of the transverse jumpers is halved. In these places, they are already becoming workers - they are participating in the redistribution of the load.

Reinforcement of the sole of the strip foundation

On soils with not very high bearing capacity, on heaving soils or under heavy houses, often strip foundations are made with a sole. It transfers the load over a large area, which gives greater stability to the foundation and reduces the amount of subsidence.

So that the sole does not fall apart from pressure, it also needs to be reinforced. The figure shows two options: one and two belts of longitudinal reinforcement. If the soils are complex, with a strong tendency to winter baking, then two belts can be laid. With normal and medium soils, one is enough.

Reinforcement bars laid in length are working. They, as for the tape, take the second or third class. They are located from each other at a distance of 200-300 mm. They are connected using short pieces of rod.

Two ways of reinforcing the sole of the strip foundation: on the left for bases with normal bearing capacity, on the right - for not very reliable soils

If the sole is not wide (rigid scheme), then the transverse segments are constructive, they do not participate in the distribution of the load. Then they are made with a diameter of 6-8 mm, bent at the ends so that they cover the extreme bars. Tied to everyone with a knitting wire.

If the sole is wide (flexible), the transverse reinforcement in the sole is also working. She resists the ground's attempts to "collapse" her. Therefore, in this version, the soles use ribbed reinforcement of the same diameter and class as the longitudinal one.

How much rod do you need

Having developed a strip foundation reinforcement scheme, you know how many longitudinal elements you need. They fit around the perimeter and under the walls. The length of the tape will be the length of one reinforcing bar. Multiplying it by the number of threads, get the required length of the working reinforcement. Then add 20% to the resulting figure - the margin for joints and "overlaps". That's how much in meters you will need working fittings.

Now you need to calculate the amount of structural reinforcement. Consider how many cross jumpers should be: divide the length of the tape by the installation step (300 mm or 0.3 m, if you follow the recommendations of SNiP). Then you calculate how much it takes to make one jumper (add the width of the reinforcing cage with the height and double it). Multiply the resulting figure by the number of jumpers. Add 20% to the result (for connections). This will be the amount of structural reinforcement for reinforcing the strip foundation.

By a similar principle, consider the amount that is needed to reinforce the sole. Putting it all together, you will find out how much reinforcement you need for the foundation.

Technologies for assembling reinforcement for a strip foundation

Do-it-yourself reinforcement of the strip foundation begins after installation. There are two options:

Both options are not ideal and everyone decides how it will be easier for him. When working directly in the trench, you need to know the procedure:

• The longitudinal bars of the lower armored belt are laid first. They need to be raised 5 cm from the edge of the concrete. It is better to use special legs for this, but pieces of bricks are popular with developers. Reinforcement is also spaced 5 cm from the formwork walls.
• Using transverse pieces of structural reinforcement or molded contours, they are fixed at the required distance using a tie wire and a hook or a tie gun.
• Next, there are two options:
  • If contours shaped in the form of rectangles were used, the upper belt is immediately tied to them at the top.
  • If during installation cut pieces are used for transverse jumpers and vertical racks, then the next step is to tie up the vertical racks. After they are all tied, the second belt of longitudinal reinforcement is tied.

There is another technology for reinforcing a strip foundation. The frame turns out to be rigid, but there is a large consumption of the bar for vertical racks: they are driven into the ground.

The second technology for reinforcing the strip foundation - first, vertical racks are driven in, longitudinal threads are tied to them, and then everything is connected by transverse ones.

• First, vertical posts are driven in at the corners of the tape and at the junctions of the horizontal bars. Racks should have a large diameter of 16-20 mm. They are set at a distance of at least 5 cm from the edge of the formwork, checking the horizontal and vertical, they are driven into the ground by 2 meters.
• Then vertical bars of the calculated diameter are hammered. We determined the installation step: 300 mm, in the corners and at the junction of the walls it is half as much - 150 mm.
• Longitudinal threads of the lower reinforcement belt are tied to the racks.
• At the intersection of racks and longitudinal reinforcements, horizontal jumpers are tied.
• The upper reinforcement belt is tied up, which is located 5-7 cm below the upper surface of the concrete.
• Attached horizontal jumpers.

It is most convenient and fastest to make a reinforcing belt using preformed contours. The rod is bent, forming a rectangle with the given parameters. The whole problem is that they must be made the same, with minimal deviations. And it takes a lot of them. But then the work in the trench moves faster.

As you can see, reinforcing a strip foundation is a lengthy and not the easiest process. But you can cope even alone, without helpers. It will take, however, a lot of time. It is more convenient to work together with two or three people: both to carry the bars and to expose them.