Step of clamps in the foundation. How to properly reinforce a strip foundation: diagrams, calculation of materials, installation methods

Reinforcing the foundation is a complex procedure, and it can be difficult to correctly take into account all the nuances. But if you follow all the reinforcement instructions strip foundation, watch a video on the topic, it’s still possible to deal with it yourself. One of the important stages of construction is the calculation of the foundation.

The strip base is a concrete strip that runs along the entire perimeter of the future building. It is most often used in country construction, as it allows you to quickly build a foundation on any type of soil. This type of foundation is universal.

The strip base can be used:

• for buildings made of concrete, brick and stone;
• for buildings with heavy floors (prefabricated reinforced concrete or monolithic, metal);
• if the site consists of different types of soil (for example, one part is sand, and the other is heaving loam);
• if planned in the building ground floor or basement.

Strip foundations are popular among private house builders due to their technological simplicity of execution.

Strip foundations are divided into: prefabricated, monolithic, rubble.

At the planning stage, it is necessary to correctly select the necessary elements for reinforcement and their quantity. That's why it is recommended to draw up a detailed drawing of the future foundation with the selected scheme. If you make a mistake at the design stage (saving building material, incorrectly designing the structure, or making an inaccurate drawing), this can subsequently lead to negative consequences.

Most often they encounter the following problems arising from incorrectly executed drawings:

• skew;
• insufficient amount of material;
• deformations of various kinds;
• uneven precipitation;
• appearance of cracks, etc.

Calculating the number of elements, correctly executed drawing and following it at all stages will allow you to build a strong and durable structure. In order to calculate the amount of reinforcement for a strip foundation, the easiest way is to use online calculator or a special program.

Laying depth

In order for such a foundation to function for a long time, it must be laid at the correct depth. To do this, you need to study the type of soil and the distance over which it freezes.

There are shallow and recessed types of foundation. The first type is used for construction on heaving and slightly heaving soils. This is the most common option used in summer cottage construction. The costs of its construction are only 15-18% of total cost the buildings.

In turn, the buried foundation is stable and durable. It is also suitable for two-story buildings. Accordingly, this is a more expensive option. The depth of the buried foundation is calculated using the formula freezing depth plus 10-20 cm. Of course, the more floors, the deeper the foundation needs to be made. It also depends on the type of soil. If the soil is good, the depth can be reduced. For easy one-story house Shallow foundations are often used. The foundation depth for a two-level house made of foam blocks reaches 50 cm.

A foundation laid above the freezing depth of the soil will be pushed out of the ground in winter, which can lead to its destruction.

Strip foundation reinforcement scheme

Reinforcement of a strip foundation is a critical stage on which the service life of the building depends. The reinforcement of shallow and buried foundations differs slightly. In the first case, strengthening the base is much easier. In addition, you can plan a small basement. It is suitable for building the base for most wooden buildings: cottages, bathhouses, agricultural buildings.

A recessed type of foundation is laid under houses made of stone with uniform concrete floors or in buildings in which several floors and basements are planned. Of course, in this case, large financial investments will be required.

Because the foundation experiences significant loads during operation, it is necessary to reinforce both the upper and lower parts. And if its height exceeds 150 mm, it is necessary to install more steel rods in the transverse and vertical directions. It is necessary to strengthen the foundation with hot-rolled reinforcement, the diameter of which is from 6 to 8 mm.

Working fittings should have a diameter of 10 to 20 mm, and auxiliary fittings - from 6 to 10 mm. The reinforcement bars are overlapped in order to prevent layering. The transverse rods are connected to longitudinal special clamps. Longitudinal reinforcement should be located inside the precast frame. After installing the rods, they need to be tied. This is done to ensure that cracks and chips do not form on the foundation in the future.

The distribution of reinforcement is carried out in accordance with building codes SNiP 52-01-2003. This provision indicates that the distance between vertically located rods is calculated based on the concrete filler and the method of laying it. The rule regulated in SNiP 52-01-2003 indicates the norms for laying longitudinal rods: the distance between them should not be more than 40 cm.

Methods for fastening reinforcement parts

There are two ways to connect rods: welding and knitting. IN individual construction Wire knitting is most often used, and welding is used in mass production. It is preferable to use knitting also because the places where the reinforcement is attached by welding are subject to corrosion, losing strength and reliability of adhesion. Welding of reinforcement is permissible if the rod is marked with the letter “C”.

Basic principles of foundation reinforcement

First, small-diameter rods are driven in in increments of 50-80 cm. Their height should be no more than the height of the formwork. A brick is laid at the bottom of the trench, which will serve as a support for the lower tier of reinforcement. Then a metal rod is fixed at a certain height from the soil.

It is necessary that the frame is at a distance of 5 cm from each side of the trench. It is in this case that the reinforcement will be completely immersed in concrete. To make the supports even stronger, install a sand cushion.

A protective layer of concrete for reinforcement is intended to protect it from corrosion

The technological sequence is as follows:

• sand at least 10-20 cm high is poured onto the bottom of the pit;
• compacted thoroughly;
• watered with water.

When the sand dries, which usually takes 2-3 days, geotextiles are laid on the cushion.

Depending on the type of soil and the height of the future building, the size of the sand cushion may increase. In some cases, the size of the sand cushion reaches up to 80 cm.

Basic rules for reinforcing a monolithic foundation

For reinforcement monolithic foundation You will need from 2 to 4 rods in the lower belt and upper belt. They are folded into a structure resembling steps and reinforced with a special rod mesh.

Reinforcing rods should have a diameter of 10-12 mm. This subsequently determines how they will be fastened together - by welding or knitting. To give the structure a monolithic structure, the rods are laid in two directions and placed below the load-bearing floors or columns.

The reinforcing elements are installed after the formwork is completed and connected to each other with wire. Then a mesh is placed on top of them. It is necessary to take into account that the structure together with the mesh must be located at least 7 cm from the ground.

Reinforcement of the base of the strip foundation is carried out using a mesh that is placed below the cushion. The dimensions of the frame cells should be 20...30 cm. Moreover, it is better to use whole rods that do not have any connections.

Features of fiberglass reinforcement

Strip foundation reinforcement fiberglass reinforcement not much different from metal. The main difference is that in this case it is easier to reinforce the corners. The service life of this reinforcement is much longer than steel. In addition, there are no problems with corrosion. The weight of the rods is also much less, so all work can be completed faster.

Features of the formwork device

During the process of assembling the formwork, it is necessary to ensure that the reinforcing bars do not touch the ground, because this will accelerate the onset of corrosion. The layer of concrete mortar that protects the reinforcement must be at least 5-8 cm.

One of the important stages is reinforcing the corners of the foundation, because... she will be under the most pressure. If the reinforcing work is not performed correctly, the entire building will lose stability, and the reinforcement rods will not be able to cope with the pressure.

There are many options for constructing formwork, but for private owners the easiest way is boxes made of wooden panels

The corners are made from A3 class rods. One side should overlap the other by approximately 50-70 cm. The reinforcing bars that are inside the corners must be in contact with the outside of the reinforcement.

The reinforcement of the decorative parts of the base (bay window) and T-shaped elements of the abutment of the elements is also carried out. These vulnerable spots are strengthened with additional U-shaped or L-shaped fasteners.

For more information on how to reinforce a strip foundation with your own hands, watch the video:

Throughout its existence, humanity has accumulated vast experience in construction. The basis, the base of any building is a strong and reliable foundation. Today, the most common type of foundation is a strip foundation, because it is this design that allows you to evenly distribute the weight of buildings on the ground, which in turn affects the process of shrinkage of the house. And reinforcing a strip foundation is a way to make the foundation of a structure stronger and more reliable.

Steel and concrete are the main load-bearing materials Construction Materials. The properties of materials vary. comparison table properties of some materials:

As you can see, steel is much stronger and more reliable than concrete, but at the same time, concrete is 80 times cheaper than steel. Therefore, the composite material reinforced concrete appeared. Since concrete works well under compression, the location of steel in reinforced concrete structures is in places subject to tension and bending.

Many people believe that the foundation only works to compress and reinforce the strip foundation - money wasted. This is correct if the foundation is placed on rocky soils. But in most cases, the soil is not a solid monolith. There are many factors that cause the base to bend:

• Soil heterogeneity. Different densities of layers lead to uneven shrinkage.
• Soil erosion by precipitation or groundwater.
• Mobility of surface soil layers.
• Frost heaving. Close location groundwater and negative temperatures cause clay soils to increase in size by 10-15% (swell). In this case, the base begins to push the foundation upward.

As a result, tension arises in concrete structures, destroying the material. Cracks and shrinkage of the foundation lead to the formation of cracks in the walls of the house, which spoils appearance structure or its collapse. In other words, saving on foundation reinforcement is more expensive for yourself, because repairing and restoring a house requires significant financial costs.

Reinforcement technology is the process of creating a spatial reinforcement frame. It consists of the following elements:

• longitudinal reinforcement;
• transverse;
• vertical;
• reinforcing clamps;
• knitting wire.

Longitudinal reinforcement is laid along the long side of the foundation, and the length of the rod usually reaches 6 or 12 m. It is this that resists tension. Longitudinal reinforcement is performed along the upper and lower edges of the reinforced concrete structure.

The laying scheme depends on the calculation of the required cross-sectional area of ​​the reinforcement. Such a calculation requires careful consideration of all loads on the foundation, including climatic loads from snow and wind, as well as the foundation’s own weight. Taken into account load bearing capacity soil according to geological research (geological section). In GOST 5781-82, Table 1 contains the cross-sectional area for each rod diameter; it remains to decide how many rods to place on the upper and lower sides of the foundation.

However, for those who decide to build a house with their own hands, you can do without calculations, using the recommendations of paragraph 10 and section 5 of the Manual “On the design of concrete and reinforced concrete structures made of heavy concrete without prestressing reinforcement.” They indicate that the minimum cross-sectional area of ​​the reinforcement is equal to Аs=µ*b*ho, where:

Аs is the cross-sectional area of ​​the reinforcement;

µ= 0.1% - percentage for bendable structures;

b – cross-sectional width of the strip foundation;

ho – height working area section (equal to half the height of the foundation section).

The diameter of the upper rods can be equal to the diameter of the lower ones or taken smaller. The maximum distance between the axes of the longitudinal rods (step) is recommended to be no more than 1.5h or no more than 400 mm in beams and slabs, where h > 150 mm is the height of the cross section of the foundation (clause 10.3.8 SP and clause 5.13 of the Manual). Only in this case is the effective operation of concrete and reinforcement ensured, limiting the width of the opening of cracks between the longitudinal rods.

The minimum pitch of the rods (the distance between the axes) is limited for reasons of ease of laying and compaction concrete mixture and equals:

• d + 25 mm – for the lower reinforcement row;
• d + 30 mm – for the top.

Let's look at an example:

It is necessary to reinforce a strip foundation 400 mm wide and 600 mm high. You need to calculate how many rods are needed and select the diameter. Minimum area reinforcement cross-section is equal to: As=40x30x0.1%=1.2 cm². The distance between the rods is 1.5x600 = 900 mm, therefore, we will take no more than 400 mm. That is, 2 rods are installed along the width of the section. We select the diameter of the reinforcement according to GOST 5781-82 Table 1: two rods Ø 8 mm have an area As = 2x0.503 = 1.006 cm², which is less than the required 1.2 cm². Consider the following diameter Ø 10 mm. As=2x0.785=1.57 cm². As a result, the layout of the rods looks like this: take the upper and lower reinforcement equal to Ø 10 mm and lay them in two rows.

Many builders today use following rules: the diameter must be at least 10 mm if the side of the foundation is less than or equal to 3 m, and 12 mm for the side more than 3 m (see the manual “Reinforcement of elements of monolithic reinforced concrete buildings” Appendix 1). However, the rules of the manual are developed for the design of monolithic reinforced concrete structures multi-storey buildings taking into account emergency loads and progressive collapse. Of course, a safety margin will not hurt, but we are no longer talking about reasonable consumption of reinforcement.

When installing reinforcement, one should not forget about the protective concrete layer - the distance between the side surface of the strip foundation and the reinforcement rod. A protective layer is necessary for several reasons: it protects the steel from the aggressive effects of air and groundwater. In addition, for reinforced concrete to function properly, the reinforcement must be located inside the concrete. The minimum layer size depends on the operating conditions of the structure and for structures located in soils, foundations with a concrete preparation device is equal to 40 mm and not less than the diameter of the working reinforcement (Table 10.1 SP and Table 5.1 of the Manual).

Read more about the calculation of reinforcement.

Transverse structural reinforcement

Structural transverse reinforcement means horizontal and vertical rods that:

• Maintain longitudinal reinforcement in the designed operating position.
• Prevents the development of cracks.
• They absorb unaccounted loads, for example, lateral buckling of the foundation.

The diameter of the transverse reinforcement in knitted bendable frames is taken to be at least 6 mm. In Appendix 1 of the Manual “Reinforcement of elements of monolithic reinforced concrete buildings”, transverse reinforcement is recommended to be performed in the form of a closed clamp with a rod diameter of at least 8 mm.

A device for bending reinforcement clamps.

The distance between the rods (pitch) is taken to be no more than twice the cross-sectional width and no less than 600 mm. Regarding the protective layer, the minimum distance between the rod and the concrete edge is 5 mm less than minimum size layer for longitudinal working reinforcement, that is, equal to 35 mm.

Materials used

Materials for reinforcement are accepted in accordance with GOST 5781-82. The fittings are made of low-alloy and carbon steel in accordance with GOST 380-2015. The surface of the rods can be smooth or have a periodic profile. Depending on the properties, the material is divided into the following classes:

• A 240 (A-I);
• A 300 (A-II);
• A 400 (A-III);
• A 600 (A-IV);
• A 800 (A-V);
• A 1000 (A-VI).

The foundation requires reinforcement with a crescent profile.

The numerical code reflects the yield strength, for example 240 corresponds to 235 N/mm². Among them, only A 240 (A-I) is made with a smooth profile. The product range is limited to diameters from 6 to 40 mm.

Frames can be welded or bonded. For binding and reinforcement, round low-carbon steel wire GOST 6727-80 is used ( grade B-I) or ribbed (grade BP-I), with a diameter of 3.0; 4.0.

Advice: The optimal solution for the foundation would be A400 (AIII) grade reinforcement; the use of higher grades is not justified, because Without prestressing, its strength potential will not be used at 100%.

I would like to note that in last years Fiberglass composite reinforcement has appeared in the construction industry. The material is durable and lightweight. The material has many advantages: easy installation technology, has high anti-corrosion properties.

Photo of composite reinforcement.

However, the material also has disadvantages. It has self-extinguishing characteristics when burning, but at a temperature of 200 ° C it loses its properties. In addition, it bends poorly, which makes it difficult to use bent elements. Many professional builders refused to work with this material due to lack of practical experience ( Foreign experience was not taken into account) and calculation recommendations.

But since July 2015, Appendix L appeared in SP 63.13330.2012 with rules for the design and calculation of structures.

Rules for reinforcement of corners and junctions

Often on construction site reinforcement has to be made from leftovers, so the rods are overlapped, welded, or special butt joints are used. When joining with an overlap, the ends of smooth profile reinforcement are bent in the form of tabs, hooks and loops, while the ends with a periodic profile do not need to be bent. The distance between the joined bars can be from zero to 4 reinforcement diameters. The length of the joint is calculated according to the design manual, but cannot be less than 15 rod diameters or 200 mm.

Butt welded joints are made using staples, and mechanical joints use threaded and crimp couplings.

Important! The rules prohibit reinforcing corners with a simple overlap, since in this case the corner will not be integral and motionless.

Corner and T-shaped junctions of frames are made in three ways: with claws, additional curved clamps of L and U shapes.

Photo of how to properly reinforce a corner.

Learn more about corner reinforcement.

Knitting reinforcement

It would seem that using welded frames is faster and more convenient. However, builders prefer to knit spatial frames. And there are reasons for this:

• Welding reduces the quality of the metal.
• Soil settlement during the production of foundations provokes additional stresses at the joints. Welding joints do not always cope with loads and are destroyed. The connected parts do not change their position in space, but have a certain mobility.

Foundation reinforcement is a process necessary to strengthen the structure and increase the service life of the building. In other words, this is an assembly of a “skeleton” that plays the role of a protective component that restrains soil pressure on the walls of the base. But in order to this function has been implemented to the maximum extent, it is necessary not only to correctly calculate the reinforcement for a strip foundation, but also to know how to organize the progress of construction work.

The basis of a strip foundation is a concrete solution consisting of cement, sand and water. Unfortunately, the physical characteristics of the building material do not guarantee the absence of deformation of the base of the building. To increase the ability to withstand foundation shifts, temperature changes and other negative factors, the presence of metal in the structure is necessary.
This material is plastic, but provides reliable fixation, so reinforcement is an important stage in the complex of works.

Reinforcement for strip foundation - steel bar with stiffeners

Foundation reinforcement is required in areas where tension zones may occur. It is noted that the greatest tension appears on the surface of the base, which creates the prerequisites for reinforcement close to the upper level. On the other hand, in order to avoid corrosion of the frame, it must be protected from external influences by a layer of concrete.

Important! The optimal distance of reinforcement for the foundation is 5 cm from the surface.

Since the progression of deformation cannot be predicted, stretch zones can appear both in the lower part (when the middle bends down) and in the upper part (when the frame bends upward). Based on this, reinforcement should pass from below and above with reinforcement with a diameter of 10-12 mm, and this reinforcement for a strip foundation should have a ribbed surface.

This ensures perfect contact with the concrete.

Strip foundation stretch zones

The remaining parts of the skeleton (horizontal and vertical transverse rods) may have a smooth surface and a smaller diameter.
When reinforcing a monolithic strip foundation, the width of which usually does not exceed 40 cm, it is allowed to use 4 reinforcement rods (10-16 m), connected into a frame with a diameter of 8 mm.

Important! The distance between the horizontal rods (with a width of 40 cm) is 30 cm.

The strip foundation, although long, has a small width, so longitudinal tensions will appear in it, while there will be no transverse ones at all. It follows from this that transverse vertical and horizontal rods, which will be smooth and thin, are needed only to create a frame, and not to bear loads.

Particular attention must be paid to corner reinforcement

Special attention it is necessary to pay attention to the reinforcement of the corners: there are often cases when the deformation occurs not in the middle, but in the corner parts. The corners should be reinforced so that one end of the bent reinforcement element goes into one wall, and the other into the other.
Experts advise connecting rods using wire. After all, not every type of reinforcement is made from steel that can be welded. But even if welding is permissible, problems often arise that can be avoided by using wire, for example, overheating of the steel, leading to a change in properties, thinning of the rod at the welding site, insufficient strength of the weld, etc.

Reinforcement structure construction diagram

Reinforcement begins with the installation of formwork, the inner surface of which is lined with parchment, making it easier to remove the structure in the future. The frame is created according to the following scheme:
1. Reinforcing bars with a length equal to the depth of the foundation are driven into the trench soil. A distance from the formwork of 50 mm and a pitch of 400-600 mm should be maintained.
2. Stands (80-100 mm) are installed at the bottom, on which 2-3 threads of the bottom row of reinforcement need to be laid. Bricks placed on edge will work well as stands.

3. The upper and lower rows of reinforcement are secured together with the transverse jumpers to the vertical pins.
4. At intersections, fastening is carried out using wire tying or welding.

The video will introduce you to in a convenient way tying reinforcement using a template:

Important! The distance to the outer surfaces of the future foundation should be strictly observed. It is better to do this with the help of bricks. This is one of the most important conditions, because metal constructions should not be based directly on the bottom. They must be raised above ground level by at least 8 cm.

After installing the reinforcement, all that remains is to make ventilation holes and pour concrete mortar.

You need to know this!
Ventilation holes not only help improve the depreciation characteristics of the foundation, but also prevent the occurrence of putrefactive processes.

Calculation of material consumption

To calculate a strip foundation, you need to know some parameters in advance. Let's look at an example. Let's assume that our foundation has a rectangular shape and the following dimensions: width - 3.5 meters, length - 10 meters, casting height - 0.2 meters, belt width - 0.18.
First of all, you need to calculate the total volume of the casting, for which you need to find out the dimensions of the base as if it had the shape of a parallelepiped. To do this, we will perform several simple manipulations: find out the perimeter of the base, and then multiply the perimeter by the width and height of the casting.
P = AB + BC + CD + AD = 3.5 + 10 = 3.5 + 10 = 27
V = 27 x 0.2 x 0.18 = 0.972

But the calculation of a monolithic foundation does not end there. We learned that the base itself, or rather the casting, occupies a volume approximately equal to 0.97 m3. Now you need to find out the volume of the internal part of the foundation, i.e. what is inside our feed.

We get the volume of the “filling”: multiply the width and length of the base by the height of the casting and find out the total volume:
10 x 3.5 x 0.2 = 7 (cubic meters)
Subtract the volume of the casting:
7 – 0.97 = 6.03 m3

Result: casting volume - 0.97 m3, internal filler volume - 6.03 m3.

Now you need to calculate the amount of reinforcement. Let's say the diameter will be 12 mm, the casting will have 2 horizontal threads, i.e. 2 rods, and vertically, for example, the rods will be located every half a meter. The perimeter is known - 27 meters. This means we multiply 27 by 2 (horizontal rods) and get 54 meters.

Vertical rods: 54/2 + 2 = 110 rods (108 0.5 m intervals and two at the edges). We add one more rod per corner and we get 114 rods.
Let's say the height of the rod is 70 cm. It turns out: 114 x 0.7 = 79.8 meters.

The final touch is the formwork. Suppose we build it from boards 2.5 cm thick, 6 meters long and 20 cm wide.
We calculate the area of ​​the side surfaces: multiply the perimeter by the height of the casting, and then by 2 (with a margin, not taking into account the decrease in the internal perimeter versus the external): (27 x 0.2) x 2 = 10.8 m2
Board area: 6 x 0.2 = 1.2 m2; 10.8/1.2 = 9
We need 9 boards 6 meters long. Don't forget to add connection boards (optional).

Result: 1 m3 of concrete will be required; 6.5 m3 of aggregate; 134 meters of reinforcement and 27 linear meters of boards (20 cm wide), screws and bars. The values ​​given have been rounded.

The results of the painstaking calculation work

Now you know not only how to properly reinforce a strip foundation, but also how to calculate the necessary components. This means that the foundation you build will be reliable and strong, allowing the construction of monolithic structures of any configuration.

Shallow strip foundation that can be easily erected in as soon as possible with their own hands, most often used for the construction of low-level buildings or fences on summer cottage. To increase its stability and strength, reinforcement is performed.

Before starting any work, it is necessary to clear the area: remove vegetation and remove debris. It is necessary to dig trenches according to pre-made markings. This can be done manually or using special equipment. For that, To ensure that the walls are smooth, it is recommended to install formwork. The frame is usually installed together with the formwork. Then the solution is poured in layers and waterproofed using sheets of roofing material. If the process sequence is followed correctly The service life of a strip foundation is from 20 years. But it is recommended to carry out repair work every 10 years.

Why reinforce a strip foundation?

The question is often asked about how to properly reinforce a strip foundation with your own hands. Concrete is a fairly strong, but not sufficiently plastic material. He can cope well with compressive loads, but fail under tensile loads.

Concrete works extremely poorly in tension, and in order to “help” it, steel reinforcement is introduced for the tensile layers of concrete, which takes on the tensile forces

To increase the strength of the base and extend its service life, reinforcement of the strip foundation is used, which can be done with your own hands, without involving specialists. It is enough to follow the technological sequence and select good quality material.

After all, if the work is carried out in compliance with all requirements, then the strength of the foundation noticeably improves:

• reinforcement bars laid horizontally significantly increase tensile and bending strength;
• rods located vertically serve as reinforcing elements and provide shear strength.

To reinforce the strip foundation, rods of different diameters are used depending on the purpose.

How to calculate the amount of reinforcement and its diameter

Thanks to this calculation, you can find out how many reinforcement bars and what sizes are needed in order to give the strip foundation sufficient strength. In this case, fittings are used different types and thickness.

To construct a strip foundation for a residential building, ribbed rods with a diameter of 10-20 mm are used, and for transverse and vertical reinforcement, smooth round rods with a diameter of 6-12 mm are used.

The reinforcement scheme depends on the minimum content of longitudinal rods and their minimum diameter. Thus, according to SNiP standards, longitudinal rods must constitute at least 0.1% of the cross-sectional area of ​​the tape. For example, if the height of a strip foundation is 1200 mm and the width is 400 mm, then, based on calculations, the minimum with total area The cross-section of the rods is 480 mm2.

The figure obtained in the previous calculation must be divided by the cross-section of the selected reinforcement. This will be the approximate number of longitudinal rods for the frame.

But you can select the number of rods of a certain diameter according to the table:

Reinforcement, depending on the steel grade, has different tensile strength

In addition, the minimum permissible diameter of the reinforcement bars should be taken into account.

Depending on its use it will differ:

In order to calculate the materials for reinforcing the strip base, it is necessary to measure or calculate the length of its strip and multiply by the number of longitudinal rods at all levels.

In order to calculate the required number of transverse rods, the number of clamps that are planned to be installed is calculated (the length of the tape is divided by the distance between the clamps) and multiplied by the length of the reinforcement required to make one clamp. The calculation is made in the same way if not clamps are used, but pieces of reinforcement.

How to properly reinforce a strip foundation with your own hands

When the calculation has been completed, the required number and cross-sectional diameter of the longitudinal rods for reinforcing the strip foundation have been selected, it is necessary to select a knitting pattern for the frame.

There are several options. It is better to choose a simple and reliable one. Sometimes a scheme is chosen in which only the lower or only the upper part of the strip base is reinforced. But you shouldn't do this. After all, the foundation is influenced by the weight of the house itself on the one hand, and on the other by the force frost heaving soil may cause stress in the upper parts of the foundation. Hence, It is necessary to reinforce both the upper and lower parts of the base.

The middle part can just be ignored. But if the number of reinforcement bars is such that it cannot fit into two rows (top and bottom), then, of course, it’s worth thinking about installing an additional tier in the middle.

It is better to think over and apply a simple reinforcement scheme from a square or rectangle. Then, if you make the frame axes correct, then the base itself will be strong and stable.

Frame installation

It is necessary to take into account in advance the compatibility of the length of the foundation with the length of the supplied reinforcement. This will help reduce the number of joints and save material resources.

Specialists It is recommended to make a footing before installing the frame. This sand and gravel cushion is made as follows: the base of the foundation is filled with concrete mortar with a layer of 5-8 mm and wait for it to harden.

If it is decided to do without concrete footings, then stands are installed under the lower rows (tiers) of reinforcing bars. At the same time, make sure that there is a gap of at least 15 mm between such a cushion and the reinforcement so that the concrete solution can penetrate from below and thereby strengthen the reinforcement.

For installation of horizontal rows most often they use round ribbed reinforcement, the diameter of which is 10 -16 mm. Longitudinal rods can be connected with horizontal transverse reinforcement. The longitudinal reinforcement rods are fastened with overlapping reinforcement of at least 50 cm in length.

If the height of the strip foundation is more than 0.15 m, the upper and lower levels must also be fastened with vertical reinforcement bars. For this purpose, smooth reinforcement with a diameter of 6-8 mm is often used. It is recommended to use rod clamps as transverse and vertical reinforcement, which bend like a frame and are mounted according to the dimensions of the frame.

But, no matter what reinforcement scheme for the strip base is chosen, we must not forget that the distance between the reinforcement and the formwork, as well as the top layer of concrete pouring, should not be less than 15 mm.

The rods are connected to each other by soft steel binding wire. To facilitate the work, you can use special devices. For example, a crochet hook. You can buy it in a store, or you can make it yourself. To do this, you only need a piece of reinforcement and a wooden or plastic handle.

The hole inside the handle should be such that the core together with the hook can rotate freely when tying the wire. So, it is folded in half and placed under the joint of the reinforcement. Use the sharp part of the hook to hook the wire loop and make 2-3 turns, tying it to the other end. At the same time, do not tighten it too tightly so as not to tear it. Some use welding. But experts do not recommend using it, because... joints are often subject to corrosion.

When performing work, it is necessary to ensure that the diameter of the longitudinal rods for the strip base is the same and is placed evenly across the width of the entire foundation. If for some reason the diameter of the rods is different, then reinforcement with a larger diameter is placed in the lower part of the tape. It is necessary to strictly ensure that the reinforcement bars of the upper level of the frame are placed above the gaps between the bars of the lower level.

Craftsmen adapt a homemade crochet hook to a screwdriver and thereby dramatically speed up the process of knitting the frame

Reinforcement of a strip foundation can be done with your own hands, without purchasing expensive tools. It is enough to follow the technological sequence and use materials of the recommended sizes. In this case, the service life of the base will be long.

For more information on how to properly reinforce a foundation with your own hands, you can watch the video:

Strip foundations are most common in the construction of private, low-rise buildings. Easy to implement, no special equipment or complex equipment required. All work can be done independently. The most important and difficult thing is to correctly reinforce the strip foundation with a width of 40 cm. We will consider what this is and how it affects the service life of the building in more detail below.

The strip foundation is the basis of the building. Its durability determines its service life, the need for repairs or additional strengthening. In order not to discover distortions in the walls in a year, two or five, not to watch how cracks “grow” under the windows, you should not neglect the reinforcement. This article will tell you how to do it correctly, what requirements need to be met.

How is reinforcement performed?

Before starting construction, you must familiarize yourself with the requirements of SNiP 2.03.01-84. It contains a direct indication that a strip foundation for a residential building cannot be without reinforcement. The width and height of the base and building do not matter.

There are two components at its core:

• concrete. Resistant to compression loads. But when the bending or tensile moment increases, the strip foundation is destroyed;
• reinforcement frame. Reduces the load on the concrete mass under the influence of bending or tensile forces. It consists of longitudinal tiers connected into a single structure by jumpers: transverse and vertical.

The number of tiers or belts directly depends on the height of the strip foundation:

• for shallow depths up to 1 meter high, 2 are enough;
• if the height exceeds 120 cm, an intermediate reinforcement belt is added.

For longitudinal belts and lintels, the optimal material is corrugated reinforcement with a diameter of 12-16 mm. Smooth, 8-10 mm in diameter, recommended only as lintels if a strip foundation is being installed

For dressing, a special knitting wire with a diameter of 1-2 mm is used. Welding is not recommended: the metal gets very hot, and “weak” spots appear at the joints, which need to be looked after especially carefully during the process of pouring concrete. If damaged, the reinforcement will not perform its function. At the same time, wire ligation is a complex and lengthy process that requires special skills. Welding is much faster.

Reinforcing frame configuration

When calculating reinforcement, the requirements of SNiP 2.03.01-84 “Manual for designing foundations for buildings and structures” must be taken into account:

• elements of the longitudinal frame of the strip base are located at a distance of 10 cm or less;
• between tiers of the frame - 50 cm or less;
• transverse vertical jumpers are located at a distance of 30 cm or less;
• from the lintels, frame contour to the formwork - at least 5 cm. Otherwise, the destruction of the concrete belt and the release of reinforcement to the surface of the strip foundation is possible;
• The lower belt should not lie on the ground. If a backfill of sand and crushed stone has not been made beforehand, a single brick or special plastic stands are placed under the tier, depending on the condition of the soil and its homogeneity.

Calculation of reinforcement for reinforcing a strip foundation 40 cm wide

It is better to calculate the required volumes before starting work, so as not to stop and look for where to urgently buy several rods or a coil of wire. In the above calculation, a conditional strip foundation with the following parameters is taken as a basis: height 70 cm, width 40 cm. The perimeter of the building is 50 meters.

Each tier has 3 rods. For connection, reinforcement with a diameter of 12 mm is used, the pitch is 30 cm.

Quantity calculations:

1. laying 3 rods in 2 tiers will require 300 meters;
2. 167 jumpers are planned for the entire house, placed in increments of 30 cm;
3. for a vertical jumper the length is 60 cm, for a transverse one - 30 cm. Each joint requires 2 vertical and 2 horizontal jumpers.

Total: for vertical lintels you will have to purchase 200.4 meters of reinforcement, for horizontal ones - 100.2 meters. In total, the building requires at least 600.6 meters of reinforcing bars with a diameter of 12 mm. This number is not final. When placing an order, please provide a reserve in case of defects and reinforcement of corners. Take into account such parameters as the length and width of the facade, the number of meters in one rod. If possible, purchase rods that are pre-cut to size to reduce waste.

How is reinforcement performed?

For straight sections, it is important to choose whole rods. The fewer joints and connections, the stronger the strip foundation. When forming corners, overlapping of elements located perpendicularly is not allowed. The reinforcement should be bent in a “P” or “G” shape.

The frame can be assembled both directly on site, in the pit, and outside it. The first may not be very convenient due to the small space. In the second case, it is important to accurately observe all the dimensions, so as not to subsequently have to rework the frame for the strip foundation.

It is difficult, but possible, to bend the reinforcement at the required angles at home. To do this, you will need a section of channel in which holes are cut with a grinder strictly on the same line. The reinforcement rod is placed in the grooves. A steel pipe is placed on the long end and used as a lever. Bending requires a lot of effort, but allows you to do without purchasing a sheet bender. The ligation of the rods is done with wire.

The rods prepared for reinforcement are laid in the trench in accordance with the requirements described above after the formwork is installed. The tiers are strictly horizontal to the ground. At the next stage, when all the belts are installed and tied, you can proceed to pouring concrete. It is important to ensure that the reinforcement remains in place and does not move. For a private low-rise building, the optimal grade of concrete is M200. After curing in accordance with building regulations, the strip foundation will gain strength and will be ready for further use. Concrete should be covered with an opaque film for 28 days, protected from direct sunlight and periodically moistened with water.

To avoid problems associated with soil heaving, before reinforcement, the bottom of the trench is filled with layers of sand and crushed stone of at least 10 cm each. Otherwise, the strip foundation will not withstand numerous freezing/thawing cycles.

Video about reinforcing strip foundations