Reinforcement of a strip foundation 40 wide step by step. Technological scheme of reinforcement and calculation of reinforcement for a strip foundation

home » Cards Reinforcement of a strip foundation 40 wide step by step. Technological scheme of reinforcement and calculation of reinforcement for a strip foundation

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 foundation, in fact, is a reinforced concrete strip passing along the outer part of the building and under the load-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 subjected to 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
Rebar diameter, mm	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 by regulatory 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 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:

Reinforcement is a building process that is used to increase the strength of a structure and increase its lifespan. It is the formation of a prefabricated skeleton, acting as a protective component that resists the impact of the soil on the walls of the structure.

To achieve maximum results, you should clearly calculate how much reinforcement is needed, as well as accurately reinforce the foundation of the building.

Proper reinforcement of the strip foundation with your own hands

At the base of the foundation, the primary component is a concrete mixture formed from cement, sifted sand and clean water. Since this solution does not have sufficient physical characteristics to provide a guarantee for the absence of various types of deformations in the foundation of the structure, metal is additionally used.

It allows you to increase the degree of resistance to base shifts, sudden changes in temperature and other negative influencing factors. The metal itself is plastic, but it is able to provide a decent fixation, so reinforcement is an important and necessary process in the entire construction complex.

Reinforcement should be carried out only in places where there is a high degree of vulnerability to tension. Most often it is found on the surface, so it should be in without fail reinforce the upper level of the base. In order to avoid corrosion of the material, it should be protected with a layer of concrete mortar.

The allowable indicator of the distance of the reinforcing belt from the surface should be about 5 cm.

Zones of possible deformation:

the lower part, when there is a downward deflection of its middle;
the upper part is the arching of the frame up.

For the middle level of the base, reinforcement is not necessary, since there is practically no tension in this zone.

Considering the possible deformation options, it is imperative to reinforce the bottom and top, using reinforcement with a ribbed surface and a diameter within 10–12 mm. In this embodiment, the closest contact with the concrete solution is observed. Other elements of the skeleton may be of small diameter and have a smooth surface.

If the foundation is reinforced with a width of up to 40 cm, 4 reinforcement rods with a diameter of 10–16 mm are used, which are connected into a frame with a diameter of 8 mm.

The tape type of the base of great length has a relatively small width, due to which only longitudinal tensions without transverse ones can be present in it. Therefore, in this situation, it is best to use smooth and thin rods to form the frame, and not to take heavy loads on the base.

Most attention should be paid to the reinforcement of corners, since in many cases deformations occur in this part of the structure. The reinforcement of the corners of the structure must be carried out so that one of the ends of the bent metal goes into one wall, and the other into another. Since not every reinforcement material can be welded, it is better to fasten the elements together using wire.

Rules for the correct reinforcement of the tape type foundation:

Work begins with the installation of formwork lined with parchment on the inside. This procedure further allows you to quickly disassemble the created structure.
Then you should drive the reinforcing bars into the ground trenches at a distance of 5 cm from the formwork and in increments of 40–60 cm. The length of the rods should be equal to the depth of the foundation.
A stand measuring 8–10 cm is laid at the bottom of the trench, and on top of it 2 or 3 threads of a row of reinforcement are formed. As a stand, you can use an ordinary brick laid on the edge.
Upper and lower reinforcement belt with cross connections is attached to vertical rods.
Where elements intersect, it is necessary to carry out fastening by wire or welding.

Be sure to keep the distance to the future surface of the foundation, for this you can use bricks.

Having installed fittings, ventilation holes should be made and concrete poured.

The presence of ventilation holes and holes increases depreciation performance and prevents the occurrence of rot.

The ideal option is to use a scheme for a strip foundation, consisting of primitive geometric shapes, such as a square or a rectangle, then it is easier to mount the frame correctly, and the foundation as a result is more reliable and strong.

The main errors of reinforcing the strip foundation

The most famous and often made mistakes:

It is forbidden to close the vents for the winter, as this leads to a lack of ventilation and rotting of the structure.

Why do you need reinforcement in a strip foundation?

Over time, any house has a subsidence, since the soil under the sole of the base gives in to pressure from above and compacts. The more pressure is applied to it, the stronger and faster it condenses. If the resulting pressure is distributed evenly over the entire area of \u200b\u200bthe strip foundation, then this is not a particular problem.

As a rule, in real conditions, the pressure on the base is not symmetrical, which is why the building settles unevenly. To avoid such a problem, tapes of various widths are used in the foundation, but even this technique does not always help to eliminate and equalize the pressure on the foundation.

Uneven settlement of the foundation contributes to:

Various inclusions of ground soil.
Uneven and unstable humidity.
Various additions and additions.
Leakage of water-bearing communications.
The absence of a blind area on either side, etc.

Under the influence of these causes of settlement, the soil surface under the foundation becomes curved relative to the vertical direction of the building. The corners of the structure and places with large load differences are most affected.

In such a situation, internal stress occurs in the foundation strip, which contributes to the occurrence of bending moments and cracks. To eliminate unwanted pressure on the foundation, to reduce the number of cracks and bends, reinforcement is added inside the foundation.

What reinforcement is needed for the foundation?

There are two options used in the construction of reinforcement:

Steel, which is subdivided into:
- rod;
- wire.
Composite reinforcement. It is used relatively rarely because of its characteristic disadvantages.

To reinforce a tape-type foundation, rod reinforcement is used as the main (working) material and smooth as an additional one.

The main property for working reinforcement is the ability to quickly and well adhere to concrete. This type of reinforcement is produced with a periodic profile, subdividing it into classes according to strength indicators.

According to GOST, which existed during the USSR, for a private type of construction, class A-ΙΙΙ fittings or an analogue of A400 (according to modern GOST) are used. For transverse reinforcement, a smooth rod of class A-Ι or A240 (modern GOST) is used.

There is a difference between the reinforcement of the old and the modern sample in the form of a modified crescent-shaped profile, in other aspects there are no differences.

To choose the right reinforcement for the foundation in the store, you just need to pay attention to the designations:

Index C indicates that the rebar is weldable;
Index K indicates that the reinforcement is resistant to corrosion cracking processes that occur due to pressure on the foundation.

If these indices are not on the package, it is better not to buy such a similar material.

Structural requirements for strip foundations and their reinforcement

Due to the inability to carry out an accurate calculation of the diameter for the strip foundation, special design requirements for its reinforcement were developed:

How much reinforcement is needed for a strip foundation?

For the foundation, reinforcement with a small diameter is used, for example, for low-rise construction, reinforcement with a diameter of 10-12 mm is used, somewhat less often - 14 mm.

Regardless of the height of the base for reinforcement, you will need to make two belts of class A3 ribbed reinforcement at a distance of 5 cm from the bottom and top of the foundation. Transverse and vertical bars can be made of smooth type A1 class reinforcement.

For a foundation width of about 40 cm, it is enough to use 4 longitudinal reinforcement bars, of which two are at the bottom and two at the top. If the width of the foundation is more than 40 cm or the construction is carried out on moving soils, more rods should be used, approximately 3 - 4 for the upper and the same for the lower belt.

To calculate the amount of reinforcement required, there are two methods:

self counting

Example. The length of the foundation for a building 6 by 10 m with two walls will be 48 meters (6+10+6+10+6+10=48m).

If the width of the base is 60 cm, and the reinforcement consists of 6 longitudinal rods, then their length will be 288 meters (6 * 48 = 248m).

The step between the transverse and vertical rods is observed at 0.5 m, the width of the foundation is 60 cm, the height is 1.9 m, the indentation of the rods from the frame is 5 cm.

In this case, the length of smooth reinforcement with a diameter of 6 mm for each connection is 640 cm or 6.4 m. ((60-5-5)*2+(190-5-5)*3=640 cm), and the connections will be 97 pieces (48 / 0.5 + 1 = 97 pieces), they will require 620.8 meters of reinforcement (97 * 6.4 = 620.8 m).

For each connection, 6 crossings are required for tying reinforcement and approximately 12 pieces of tie wire. One bundle requires 30 cm of wire. Based on these data, total consumption wire will be 349.2 m (0.3 * 12 * 97 \u003d 349.2 m).

Using the reinforcement factor

For buildings with a small number of storeys, there is an indicator of the amount of reinforcement already derived by the builders, which is 80 kg / m 3.

Example. If the foundation requires 20 m3 of concrete mortar, then the reinforcement will need 20 * 80 = 1600 kg. Calculating concrete is easy, you just need to know the perimeter of the house, the length of the inner walls, set the height of the tape to 30 cm and multiply it by the width.

To make the calculation more economical, it is best to make a more accurate calculation of the required amount of reinforcement by drawing a reinforcement scheme. And then, having calculated the moldings for longitudinal and transverse reinforcement, and also adding to this approximately 10% that will be spent on trimming, multiply the result obtained by the weight of a linear meter for each of the reinforcement diameters used.

Reinforcing the strip foundation - knit or cook?

Metal rods can be interconnected into a frame by knitting or welding. Each option has its own positive and negative qualities.

The main disadvantage of welding is the inability to make a high-quality cross connection using a hand electrode. In factories, frames and meshes are connected using contact, rather than arc, type of welding.

In this regard, insufficiently strong connections (lack of penetration) or weakening of the longitudinal rod (undercut) are very often observed. Also, a big disadvantage of welding is that not all materials can be welded, for example, class A3 fittings are made of 35GS steel, which is not weldable.

Also, if we take into account that the apparatus itself is needed for welding, the availability of knowledge, the ability to use it, as well as the consumption of electricity, then more advantages in construction are given to knitting.

Knitting is carried out using a wire with a diameter of 0.8–3 mm, and a special crochet hook acts as a tool. The only drawback of this connection option is the high complexity.

What materials are used for reinforcement?

The following materials are required for reinforcement:

Steel or composite reinforcement, the rods of which are made of fiberglass or metal.
Clamping tool(knitting hook).
steel wire(coupling collars) for knitting. For metal with index C, welding can be used. In this case, a welding machine is needed.
Hacksaw for metal etc.

Proper reinforcement of the strip foundation for many years will strengthen the building, reduce the number of cracks in the base and on the walls, and also protect the structure from settlement.

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

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 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

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, mm2, with the number of rods									Theoretical weight of 1 m of reinforcement length, kg
Rebar diameter, mm
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 by regulatory 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.

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

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

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

Related books:

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Shallow foundations. Rational designs and device technologies - Vitaly Krutov - 728 rubles - link to book review
Calculation of foundations on subsidence soils - Vladimir Krutov - 250 rubles - link to book review

Reinforcement of the strip foundation significantly increases its strength characteristics, allows you to create stable structures while reducing weight.

Strip foundation reinforcement

Reinforcement calculations and reinforcement schemes are carried out in accordance with the provisions of the current SNiPa 52-01-2003. The document has detailed requirements for calculations, provides footnotes to regulatory documents and codes of practice.

SP 63.13330.2012 Concrete and reinforced concrete structures. Basic provisions. Updated edition of SNiP 52-01-2003. Download file

SNiP 52-01-2003

The strip foundation must meet the requirements for durability, reliability, resistance to various climatic factors and mechanical loads.

concrete requirements

The main characteristics of the strength of concrete structures is the resistance to axial compression (Rb,n), tension (Rbt,n) and transverse fracture. Depending on the normative standard indicators of concrete, its specific brand and class is selected. Depending on the responsibility of the design, safety correction factors can be used, which range from 1.0 to 1.5.

Plot of bending moments

Reinforcement requirements

During the reinforcement of strip foundations, the type and controlled values of the reinforcement quality are established. The standards allow for the use of hot-rolled building reinforcement of a periodic profile, heat-treated reinforcement or mechanically hardened reinforcement.

Construction fittings

The reinforcement class is selected taking into account the guaranteed value of the yield strength at maximum loads. In addition to tensile characteristics, plasticity, corrosion resistance, weldability, resistance to negative temperatures, relaxation resistance and allowable elongation before the onset of destructive processes are standardized.

Table of reinforcement classes and steel grades

Smooth profile	A1 (A240)	6-40	St3kp, St3ps, St3sp
Periodic Profile	A2 (A300)	10-40, 40-80	St5sp, St5ps, 18G2S
Periodic Profile	A3 (A400)	6-40, 6-22	35GS, 35G2S, 32G2Rps
Periodic Profile	A4 (A600)	10-18 (6-8), 10-32 (36-40)	80S, 20HG2C
Periodic Profile	A5 (A800)	10-32 (6-8), (36-40)	23X2G2T
Periodic Profile	A6 (A1000)	10-22	22X2G2AYU, 22X2G2R

The calculation of the strip foundation is carried out in accordance with the recommendations of GOST 27751, the indicators of the limit loaded states by groups are calculated.

The first group includes conditions that lead to the complete unsuitability of the foundation, the second group includes conditions that lead to a partial loss of stability, hindering the normal and safe operation of buildings. According to the maximum permissible states of the second group, the following are produced:

calculations for the appearance of primary cracks on the surface of the strip foundation;
calculations for the time period of the increase in the formed cracks in concrete structures;
calculations for linear deformations of strip foundations.

The main indicators for resistance to deformation and strength of building reinforcement include the maximum tensile or compressive strength, determined in laboratory conditions on special test benches. Technology and test methods are prescribed in state standards. In some cases, the manufacturer may use the regulatory and technical documentation developed by the enterprise. At the same time, the regulatory and technical documentation must be approved by the regulatory authorities without fail.

For concrete structures, these values may be limited by the maximum change in concrete linearity. As generalized indicators, the actual diagrams of the state of the reinforcement are taken for a short-term one-sided impact of the calculated standard loads. The nature of the state diagrams of building reinforcement is established taking into account its specific type and brand. During the engineering calculation of the reinforced foundation, the state diagram is determined after replacing the normative indicators with the actual ones.

reinforcement requirements

Reinforcing cage - photo

Requirements for the dimensions of reinforced concrete structures. The geometric dimensions of the foundation should not interfere with the correct spatial placement of the reinforcement.
The protective layer must provide joint resistance to the loads of reinforcement and concrete, protect against the effects of the external environment and ensure the stability of the structure.
The minimum distance between the individual reinforcement bars must guarantee its joint work with concrete, allow it to be joined correctly and ensure the correct technological pouring of concrete.

Scheme of a strip reinforced foundation

For reinforcement, only high-quality reinforcement can be used; mesh knitting is carried out taking into account the calculated design indicators. Deviations from the values cannot go beyond the tolerance fields regulated by SNiP 3.03.01. Special construction measures must ensure reliable fixation of the reinforcing mesh in accordance with existing rules.

Reinforcing cage for strip foundation

SNiP 3.03.01-87. Bearing and enclosing structures. Building regulations. Download file

SNiP 3.03.01

During the bending of the reinforcement, special devices must be used, the minimum bending radius depends on the diameter and specific physical characteristics of the building reinforcement.

Video - Manual rebar bending machine, video instruction

Video - How to bend reinforcement. Work on a homemade machine

The reinforcement is inserted into the formwork, the formwork should be made in accordance with the requirements of GOST 25781 and GOST 23478.

STEEL FORMS FOR MANUFACTURING OF REINFORCED CONCRETE PRODUCTS. Specifications. Download file

Formwork for the construction of monolithic concrete and reinforced concrete structures. Classification and general technical requirements

Calculation of the number and diameter of reinforcement

For the strip foundation of baths, building reinforcement with a periodic profile Ø 6 ÷ 12 mm is used.

Reinforcement of a periodic profile Ø 10 mm

Current state regulations regulate the minimum number of bars in concrete to give it maximum strength characteristics. The minimum total cross section of the longitudinal bars of the reinforcement cannot be ≤ 0.1% of the sectional area of the foundation strip. For example, if the strip foundation has a cross section of 12,000 × 500 mm (the cross-sectional area is 600,000 mm2), then the total area of all longitudinal bars must be at least 600,000 × 0.01% = 600 mm2. In practice, developers rarely maintain this indicator; the weight of the bath, the nature of the soil and the specific brand of concrete are also taken into account. This calculated value can be considered indicative; deviations from the recommended values should not exceed ≈20% downwards.

The amount of reinforcement is calculated mathematically

To calculate the amount of reinforcement, you need to know the cross-sectional area of the foundation tape and the cross-sectional area of \u200b\u200bthe reinforcing bar. To facilitate the calculations, we bring to your attention a ready-made table.

Diameter, mm	1	2	3	4	5	6	7	8	9
6	28,3	57	85	113	141	170	198	226	254
8	50,3	101	151	201	251	302	352	402	453
10	76,5	157	236	314	393	471	550	628	707
12	113	226	339	452	565	679	792	905	1018
14	154	308	462	616	769	923	1077	11231	1385
16	201	402	603	804	1005	1206	1407	1608	1810
18	254,5	509	763	1018	1272	1527	1781	2036	2290
20	314,2	628	942	1256	1571	1885	2199	2513	2828

Now the calculations are much easier. For example, to reinforce a strip foundation, you use eight rows of reinforcement with a diameter of 10 mm. According to the table, the total area of the rods is 628 mm. Such a frame can work with a concrete tape 120 cm deep and 50 cm wide. A few extra square millimeters can be ignored, they will be additional insurance in case of a violation of the knitting technology or the manufacture of low-quality concrete.

In addition to these indicators, you need to determine the diameters of the rods for the foundations. These indicators depend on many components; for simplified calculations, you can use the proposed table.

Permissible rebar diameters

Using this table, you can easily select the recommended reinforcement diameter for strip foundations.

Strip foundation reinforcement rules

There are several schemes for knitting reinforcement, each developer can use the most convenient for himself. The choice of scheme must be carried out taking into account the dimensions of the foundation and its bearing characteristics.

Reinforcement knitting schemes

The reinforcement can be knitted separately, and then the finished structural elements can be lowered into the foundation trench and connected to each other, or you can immediately knit in the trench. Both methods are almost equivalent, but there is a slight difference. On the ground, all the main straight-line elements can be done independently; when working in a trench, an assistant is required. For knitting, you need to make a special hook, the connection is made with a soft wire with a diameter of ≈0.5 mm.

Crochet armature

In some articles you can find tips to use a hand-held electric drill during knitting - do not pay attention to them. So can write those who have no idea about the work.

Drill with hook

Firstly, the hand will get tired much more and faster from a drill than from a light hook. Secondly, cables will always get tangled underfoot, cling to the ends of reinforcement, etc. Thirdly, not all construction sites have electrical energy. And, fourthly, your wire knots will always be either underdrawn or torn.

For knitting reinforcement, thin soft wire is used, and it has low strength. Pull the wire well, strong binding should occur in two to three turns of the hook. Otherwise, labor productivity is greatly reduced and fatigue increases. There are still options for welding reinforcement, we will talk about them in the next section of the article.

How to knit reinforcing mesh yourself

We have already said above that in this way you can knit reinforcement on the ground. Only straight sections of the grid are made, the corners are tied after they are lowered into the trench.

Step 1. Prepare pieces of rebar. The standard length of the bars is six meters; if possible, you do not need to touch them. If you are afraid that such a dyne will be difficult to work with, cut them in half.

Rebar cutting

We advise you to start knitting reinforcement for the shortest section of the strip foundation, this will give you the opportunity to gain a little experience and more confidently deal with long bars. Cutting them is not recommended, this increases the consumption of metal and reduces the strength of the foundation. Consider the dimensions of the blanks using the example of a strip foundation 120 cm high and 40 cm wide.

The reinforcement must be poured from all sides with concrete with a thickness of at least 5 centimeters. These are the initial conditions. Taking into account such indicators, the net dimensions of the reinforcing cage should be no more than 110 cm in height (minus 5 cm on each side) and 30 cm in width (minus 5 cm on each side). For knitting, you need to add two centimeters on each side to overlap. This means that the blanks for horizontal jumpers should be 34 cm long, the blanks for vertical jumpers should be 144 cm long. But you shouldn’t make the frame so high, it’s enough to have a height of 80 cm.

How to knit armature

Step 2 Choose a flat area, put two long rods, trim their ends.

Step 3 At a distance of ≈ 20 cm from the ends, tie horizontal spacers on both extreme sides. For knitting, you need a wire about 20 centimeters long. Fold it in half, slide it under the binding point and tighten the wire with the usual scrolling of the crochet hook. Do not overdo it with force, the wire may not hold. The magnitude of the twisting forces is determined empirically.

Step 3 At a distance of approximately 50 centimeters, tie in turn all the remaining horizontal braces. Everything is ready - set the structure aside in the free space and in the same way make another frame element. You have the top and bottom part, now you need to fasten them together.

Step 4 Next, you should adapt the stops for the two parts of the grid, you can rest them against any object. The main thing is that the connected elements should occupy a stable lateral position, the distance between them should be equal to the height of the knitted reinforcement.

Armoframe knitting

Step 5 At the ends, tie two vertical spacers, you already know the dimensions. When the frame began to more or less resemble the finished product, tie all the other pieces. Don't rush, check all sizes. Even though your blanks are the same length, it doesn't hurt to check the dimensions.

Step 6 According to the same algorithm, you need to connect all the straight sections of the frame on the ground.

Step 7 Lay linings at least five centimeters high at the bottom of the foundation trench, on which the lower bars of the grid will lie. Put the side supports, set the grid in the correct position.

Reinforcement (the frame is installed in the formwork)

Step 8 Remove the dimensions of untied corners and joints, prepare pieces of reinforcement to connect the frame into a single structure. Keep in mind that the overlap of the ends of the reinforcement must be at least fifty bar diameters.

Step 9 Tie the bottom turn, then the vertical posts and the top one to them. Check the reinforcement spacing to all formwork surfaces.

Knitting reinforcement in the corners

The reinforcement is ready, you can start pouring the foundation with concrete.

Knitting reinforcement with a special device

To make a fixture, you will need several boards about 20 mm thick, the quality of lumber can be arbitrary. It is not difficult to make a template, and it will greatly simplify the work.

Step 1. Cut four boards along the length of the reinforcement, connect them two at a time at the distance of the vertical posts. You should get two identical templates. Make sure that the distance markings between the rails are the same, otherwise there will be no vertical position of the connecting elements.

Step 2 Make two vertical supports, the height of the supports should correspond to the height of the reinforcing mesh. Supports must have lateral corner stops that do not allow them to tip over. All knitting work must be carried out on a flat area. Check the stability of the assembled device, exclude the possibility of it tipping over during the work.

Step 3 Place the legs of the supports on the two knocked down boards, place the two upper boards on the upper shelf of the stops. Fix their position in any way.

Scheme of knitting reinforcement with clamps

You have a layout of the reinforcing mesh, now the work can be done quickly and without outside help. Install the prepared vertical reinforcement struts on the marked places, first temporarily fix their position with nails. Place a rebar on each horizontal metal jumper. This operation should be repeated on all sides of the frame. Check their position again. That's right - take the wire and hook and start knitting. Adaptation is advisable to do if you have many identical sections of the reinforcement mesh.

Video - How to knit reinforcement with a fixture

How to knit reinforced mesh in a trench

Working in a trench is much more difficult because of the cramped conditions. It is necessary to think carefully about the knitting pattern of individual elements so that you do not have to crawl between the reinforcement bars later. In addition, it will not work to link the grid on your own, you need to work with an assistant.

Step 1. Place stones or bricks at least five centimeters high at the bottom of the trench, they will lift the metal from the ground and allow the concrete to close the reinforcement on all sides. The distance between the stones should be equal to the width of the grid.

In the photo - a retainer for the armoframe

Step 2 On the stones you need to put longitudinal bars. Horizontal and vertical rods should already be cut to size, as we have already described how to measure them.

Step 3. Start forming the frame skeleton on one side of the foundation. If you previously tie horizontal struts to the lying bars, it will be easier to work. The assistant should hold the ends of the bars until they are locked in position.

Reinforcement works

Step 4 In turn, continue to knit reinforcement, the distance between the spacers should be approximately fifty centimeters.

Step 5 Using the same algorithm, tie the reinforcement on all straight sections of the foundation tape.

Step 6 Check the dimensions and spatial position of the frame, if necessary, correct the position and exclude metal parts from touching the formwork.

Foundation reinforcement

Step 7 Now it's time to tackle the corners of the foundation. The picture shows a rather complicated version of knitting in the corners, you can come up with an easier one for yourself. The main thing is that the length of the overlaps is observed. And one more note. In the corners, the foundation works not only for bending, but also for vertical rupture. These efforts hold the vertical bars of building reinforcement, do not forget to install them. As a guarantee, fittings with a larger diameter can be used for these purposes.

Rebar welding for reinforcement

You need to know that any welding degrades the physical characteristics of the strength of the reinforcement, this method should be used only in extreme cases.

Rebar welding for reinforcement

If you still have to use welding, then do everything possible to apply the minimum number of seams in one place, move the step of fixing the horizontal and vertical stops a few centimeters. During welding, accurately maintain the optimal current strength and electrode diameter. The metal in the places where the seam is applied should not overheat.

Rebar welding - photo

And most importantly, only special fittings are suitable for welding, the brands of such fittings are indicated by the letter "C". By the way, this armature is much more expensive than ordinary.

Strip foundation reinforcement scheme

There are several ways in which you can speed up and facilitate the knitting process, while improving the quality of construction and reducing material consumption.

For spacers, bend the reinforcement in the form of the letter "P". To do this, you can make an elementary machine in a couple of hours, but it will come in handy not only for bending bars. First you need to bend one sample, check its dimensions, and only then, using the sample as a template, prepare all the connections. Such spacers are much easier to knit, they immediately hold the desired size of the structure. Another plus is that the consumption of expensive material is reduced. At first glance, the savings seem insignificant, a maximum of ten centimeters per connection. But if you multiply ten centimeters by the number of pieces and by the price of reinforcement, you get a very “nice” amount.

Homemade rebar bending machine

Bent reinforcing mesh

For spacers, you can use smaller diameter reinforcement and optionally expensive building periodic profile. Even metal rods or wire rod of the appropriate diameter will do.

If you do not have any experience in performing such work, then it is better not to do it yourself. Having an assistant makes the process much easier and safer.

At a price, a reinforced foundation is much more expensive than an ordinary one; use this method of strengthening architectural structures in extreme cases. There are many cheaper ways to increase the load-bearing characteristics of a strip foundation. True, they cannot always be used, it all depends on the features of the bath project, the characteristics of the soil and the landscape.

A few words can be said about preloaded reinforcement. This is a complex method that allows you to significantly improve all the indicators of the strip foundation without increasing the amount of reinforcement. The essence of the method consists in preloading the bars with forces opposite to those that will act on the structure during the operation of the foundation. For example, if the bar will work in tension, then it is pre-compressed, etc.

Video - Reinforcement of shallow monolithic strip foundations

Video - Do-it-yourself foundation reinforcement

The strip foundation is most common in the construction of private, low-rise buildings. It is simple in execution, it does not require the involvement of special equipment, complex equipment. 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. What this is, how it affects the life of the building, we will consider below in more detail.

The strip foundation is the foundation of the building. The service life, the need for repair or additional strengthening depends on its strength. In order not to detect distortions in the walls in a year or two or five, not to watch how cracks “grow” under the windows, reinforcement should not be neglected. How to do it right, what requirements must be met, this article will tell.

What is reinforcement

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

The base has two components:

concrete. Resistant to compressive loads. But with an increase in the bending or tensile moment, the strip foundation is destroyed;
reinforcing frame. Reduces the load on the concrete mass under the influence of a bending or tensile force. 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 a shallow depth up to 1 meter, 2 are enough;
if the height exceeds 120 cm, an intermediate reinforcement belt is added.

Expert opinion

Sergey Yurievich

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The width of the base is not taken into account. You can't look at her.

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

Expert opinion

Sergey Yurievich

Construction of houses, outbuildings, terraces and verandas.

Ask an expert

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

Reinforcing cage configuration

When calculating reinforcement, the requirements of SNiP 2.03.01-84 "Manual for the design of foundations for buildings and structures" are necessarily taken into account:

elements of the longitudinal frame of the tape base are located at a distance of 10 cm or less;
between the tiers of the frame - 50 cm or less;
transverse vertical jumpers are located at a distance of 30 cm or less;
from jumpers, the frame contour to the formwork - at least 5 cm. Otherwise, the destruction of the concrete belt and the reinforcement to the surface of the strip foundation are possible;
the lower belt should not lie on the ground. If sand and gravel are not previously filled, a single brick or special plastic supports are placed under the tier, depending on the state of the soil, its uniformity.

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, not to look for where to urgently buy a few bars or a coil of wire. In the above calculation, a conditional strip foundation is taken as a basis with the following parameters: height 70 cm, width 40 cm. The perimeter of the building is 50 meters.

Expert opinion

Sergey Yurievich

Construction of houses, outbuildings, terraces and verandas.

Ask an expert

For a base with a height of 70 cm, two reinforcing belts are sufficient.

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

Quantity calculations:

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

In total: 200.4 meters of reinforcement will have to be purchased for vertical type lintels, 100.2 meters for horizontal ones. 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, provide a margin in case of marriage and reinforcing corners. Consider also parameters such as the length and width of the facade, the number of meters in one rod. If possible, purchase pre-cut rods to the correct size to reduce waste.

How reinforcement is 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 fittings must be bent with the letter "P" or "G".

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

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

The bars prepared for reinforcement are laid in the trench in accordance with the requirements described above after the formwork has been installed. Tiers - 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 brand of concrete is M200. After exposure in accordance with the norms of building regulations, the strip foundation will gain strength and will be ready for further use. Concrete for 28 days should be covered with an opaque film, protected from direct sunlight and periodically moistened with water.

Expert opinion

Sergey Yurievich

Construction of houses, outbuildings, terraces and verandas.

Ask an expert

To avoid problems associated with heaving of the soil, layers of sand and gravel at least 10 cm each are poured into the bottom of the trench before reinforcement. Otherwise, the strip foundation will not withstand numerous freeze / thaw cycles.

Video about the reinforcement of the strip foundation

To achieve maximum results, you should clearly calculate how much reinforcement is needed, as well as accurately reinforce the foundation of the building.

Proper reinforcement of the strip foundation with your own hands

Reinforcement should be carried out only in places where there is a high degree of vulnerability to tension. Most often it is found on the surface, so it is imperative to reinforce the upper level of the base. In order to avoid corrosion of the material, it should be protected with a layer of concrete mortar.

The allowable indicator of the distance of the reinforcing belt from the surface should be about 5 cm.

Zones of possible deformation:

the lower part, when there is a downward deflection of its middle;
the upper part is the arching of the frame up.

For the middle level of the base, reinforcement is not necessary, since there is practically no tension in this zone.

If the foundation is reinforced with a width of up to 40 cm, 4 reinforcement rods with a diameter of 10–16 mm are used, which are connected into a frame with a diameter of 8 mm.

Rules for the correct reinforcement of the tape type foundation:

Work begins with the installation of formwork lined with parchment on the inside. This procedure further allows you to quickly disassemble the created structure.
Then you should drive the reinforcing bars into the ground trenches at a distance of 5 cm from the formwork and in increments of 40–60 cm. The length of the rods should be equal to the depth of the foundation.
A stand measuring 8–10 cm is laid at the bottom of the trench, and on top of it 2 or 3 threads of a row of reinforcement are formed. As a stand, you can use an ordinary brick laid on the edge.
Upper and lower reinforcement belt with cross connections is attached to vertical rods.
Where elements intersect, it is necessary to carry out fastening by wire or welding.

Be sure to keep the distance to the future surface of the foundation, for this you can use bricks.

Having installed fittings, ventilation holes should be made and concrete poured.

The presence of ventilation holes and holes increases depreciation performance and prevents the occurrence of rot.

The main errors of reinforcing the strip foundation

The most famous and often made mistakes:

Angles. The main problem and mistake is to lay the corner rods crosswise. Because of this laying in the foundation, cracks very often occur.
waterproofing material. Very often, when creating formwork, they forget about the use of waterproofing, as a result of which water washes out the cement and makes the concrete less stable and durable. It also contributes to the formation of shrinkage cracks. The waterproofing layer must be very well and carefully attached to the formwork in order to eliminate the formation of unwanted folds and depressions in the foundation.
Pouring concrete. Filling the strip foundation with a concrete mixture in height very often does not reach the edges, and topping up is carried out only after a couple of days. This type of technology is no longer a monolith structure, it looks like two ordinary beams with single-layer reinforcement, which are combined by the bonding of layers of concrete mix and transverse reinforcement. The pouring of concrete during the creation of the foundation should be continuous, and the maximum allowable interval for a break should be no more than two hours.
Ventilation. A huge mistake is made when installing and during the operation of the products necessary for the ventilation of a cold underground. They are made of pipes with a diameter of 10 cm. The smallest area required for ventilation should be about 0.05 m2 (approximately 20x25 cm).

It is forbidden to close the vents for the winter, as this leads to a lack of ventilation and rotting of the structure.

Why do you need reinforcement in a strip foundation?

Uneven settlement of the foundation contributes to:

Various inclusions of ground soil.
Uneven and unstable humidity.
Various additions and additions.
Leakage of water-bearing communications.
The absence of a blind area on either side, etc.

What reinforcement is needed for the foundation?

There are two options used in the construction of reinforcement:

Steel, which is subdivided into:
- rod;
- wire.
Composite reinforcement. It is used relatively rarely because of its characteristic disadvantages.

To reinforce a tape-type foundation, rod reinforcement is used as the main (working) material and smooth as an additional one.

There is a difference between the reinforcement of the old and the modern sample in the form of a modified crescent-shaped profile, in other aspects there are no differences.

To choose the right reinforcement for the foundation in the store, you just need to pay attention to the designations:

Index C indicates that the rebar is weldable;
Index K indicates that the reinforcement is resistant to corrosion cracking processes that occur due to pressure on the foundation.

If these indices are not on the package, it is better not to buy such a similar material.

Structural requirements for strip foundations and their reinforcement

Due to the inability to carry out an accurate calculation of the diameter for the strip foundation, special design requirements for its reinforcement were developed:

At the working rods must be at least 12 mm in diameter.
Number of longitudinal bars should be at least 4, and preferably 6.
Longitudinal rods are interconnected into a spatial frame by knitting wire or welding.
Step for transverse reinforcement should be 20-60 cm, and the diameter of the reinforcement 6-8 mm.
Places with the highest possible rainfall, as well as T-shaped intersections, require reinforced reinforcement using reinforcing tabs or haunches with a diameter equal to that used for longitudinal rods.
Thickness of tape type base is usually about 30 cm.

How much reinforcement is needed for a strip foundation?

For the foundation, reinforcement with a small diameter is used, for example, for low-rise construction, reinforcement with a diameter of 10-12 mm is used, somewhat less often - 14 mm.

To calculate the amount of reinforcement required, there are two methods:

self counting

Example. The length of the foundation for a building 6 by 10 m with two walls will be 48 meters (6+10+6+10+6+10=48m).

If the width of the base is 60 cm, and the reinforcement consists of 6 longitudinal rods, then their length will be 288 meters (6 * 48 = 248m).

The step between the transverse and vertical rods is observed at 0.5 m, the width of the foundation is 60 cm, the height is 1.9 m, the indentation of the rods from the frame is 5 cm.

For each connection, 6 crossings are required for tying reinforcement and approximately 12 pieces of tie wire. One bundle requires 30 cm of wire. Based on these data, the total wire consumption will be 349.2 m (0.3*12*97=349.2 m).

Using the reinforcement factor

For buildings with a small number of storeys, there is an indicator of the amount of reinforcement already derived by the builders, which is 80 kg / m3.

Reinforcement of the strip foundation - knit or cook?

Metal rods can be interconnected into a frame by knitting or welding. Each option has its own positive and negative qualities.

Concrete can withstand bending effects well, but cannot cope with bending on its own. To ensure the bearing capacity, do-it-yourself reinforcement of the foundation is performed. To a greater extent, this applies to tape and slab structures. In piles and poles, metal is laid more out of design considerations than real necessity.

Reinforcement rules

Reinforcement of the strip foundation and any other is carried out taking into account the following rules:

for working reinforcement, rods of a class not lower than A400 are used;
it is not recommended to use welding to connect the rods, since it weakens the section;
without fail, it is necessary to tie a metal frame from reinforcement at the corners, welding is not allowed here;
even for clamps, smooth fittings are not recommended;
it is necessary to strictly observe the protective layer of concrete, equal to 4 cm, this will protect the metal from corrosion (rust);
in the manufacture of frames, the rods in the longitudinal direction are connected with an overlap, which is taken equal to at least 20 rod diameters and at least 25 cm;
with a frequent location of the metal, it is worth controlling the size of the aggregate in concrete: it should not get stuck between the rods.

An example of the placement of a reinforcing cage
in strip foundation

Properly prepared reinforcing cage is half the success. It is he who will save the foundation in case of uneven deformations that create bending loads. It is worth considering the issue in more detail using the example of a strip foundation with your own hands.

What reinforcement is needed for the structure

Reinforcement of the strip foundation assumes the presence of three groups of rods:

workers who fit along the tape;
transverse horizontal;
transverse vertical.

Transverse reinforcement under the strip foundation is also called clamps. Its main purpose is to connect the working rods into a single whole. Reinforcement of the strip foundation is carried out in strict accordance with regulatory documents. What reinforcement is needed for the foundation? To give an accurate answer, complex calculations are performed.

In order not to hire professionals, you can get by with a simplified version. The technology of reinforcing a strip foundation for a small house allows you to assign sections constructively. This is due to the fact that the tape perceives relatively small loads and works mainly in compression.

To make a reinforcing frame, use constructive, that is, the minimum allowable, cross-sectional dimensions:

For working reinforcement - 0.1% of the cross-sectional area of \u200b\u200bthe foundation for the house. However, if the side of the tape is 3 meters or less, the minimum allowable value is assumed to be 10 mm. If the side of the building has a length of more than 3 m, then the diameter of the working reinforcement cannot be less than 12 mm. rods with a cross section of more than 40 mm are not allowed.
Horizontal clamps cannot be less than one quarter of the workers in diameter. For design reasons, a size of 6 mm is prescribed.
The diameter of the vertical reinforcement depends on the height of the tape for the foundation of the house. For shallow ones, the dimensions of which are 80 cm or less, rods from 6 mm are suitable.

The rules for reinforcing a strip foundation of a recessed type provide for the use of rods of 8 mm or more.

Scheme of typical sections of reinforcement bars

If a brick building is being built, it is worth laying reinforcement with a small margin. This option will give confidence in the reliability of the design.

Rebar knitting

The reinforcement scheme of the strip foundation involves connecting the rods by tying. A bonded frame is more durable than a welded frame. This is due to the fact that the likelihood of burning through the metal increases. But this rule does not apply to factory-made elements. Outside the construction site, it is possible to connect parts without significant loss of strength.

Places for knitting reinforcement

It is allowed to reinforce the foundation in straight sections by welding to increase the speed of work. But reinforcing corners is possible only with the use of knitting wire. These sections of the structure are the most critical, so you should not rush.

Before knitting reinforcement for a strip foundation, you need to prepare materials and tools. There are two ways in which metal bonding is performed:

special hook;
knitting machine (gun).

The first option is available, but only suitable for small volumes. Laying reinforcement in a strip foundation in this case will take a lot of time. For connection, an annealed wire is used, the diameter of which is 0.8-1.4 mm. The use of other materials is not allowed.

Scheme of knitting reinforcement for a strip foundation

To build your house, you need to show patience and care. It is not worth saving time and money, as this can cause trouble during operation. With the connection of the rods along the length of the problems should not arise. In this case, the process is quite simple, it is only important to observe the minimum amount of overlap.

But how to knit reinforcement for a strip foundation in the corners? There are two types of corner joints: between two perpendicular structures and at the junction of one wall to another.

Both options have several technologies for performing work. For corner walls use the following:

Hard paw. To perform work, a “foot” is made at the end of each rod at a right angle. In this case, the rod resembles a poker. The length of the foot should be at least 35 diameters, it is better to prescribe more. The bent part of the rod is attached to the corresponding perpendicular section. Thus, it turns out that the outer rods of the frame of one wall are connected to the outer ones of the other wall, and the inner ones are welded to the outer ones.
With the use of L-shaped clamps. The principle of action is similar to the previous option. But in this case, the foot is not made, but an l-shaped element is taken, the side of which has a length of at least 50 diameters of the working reinforcement. One side is tied to the frame of one wall, and the second to the frame of a perpendicular one. In this case, the inner rods must be connected to the outer ones. The spacing of the clamps should be three-quarters of the height of the basement wall.
With the use of U-shaped clamps. At the corner you need two elements, the length of the sides of which will be 50 diameters of the reinforcement. Each of their clamps is welded to two parallel rods and to one perpendicular rod.

How to properly reinforce a strip foundation at obtuse corners. To do this, the outer rod is bent to the desired degree value and an additional one is attached to it as a reinforcement. The inner elements are bound to the outer.

Scheme of correct and incorrect reinforcement of obtuse corners

To lay the reinforcement at the junction of one wall to another, they use approximately the same methods as in the previous case:

overlap;
L-shaped clamps;
U-shaped clamps.

The value of overlaps and joints is taken equal to 50 diameters. When performing work, it is worth remembering the most common mistakes:

binding at right angles;
lack of communication between external and internal elements;
longitudinal rods are connected by viscous crosshairs.

Do not repeat these mistakes when building your own home.

Using a crochet hook

Before reinforcing the strip foundation, it is worth learning how to use the working tool. A special gun is rarely used for private housing construction; such equipment requires additional costs. It is profitable to invest in a tool only for the fulfillment of orders, and not for the construction of one house.

For this reason, the hook has become the most common knitting tool in private housing construction. It will be easier to use it if you prepare special templates in advance. Such a detail works like a workbench and greatly facilitates the work. Things will go faster. To make a template, wooden bars are required, the width of which is about 30-50 cm, and the length cannot be more than 3 m, since such a workbench is inconvenient to use.

The most common knitting method is crochet.

In a wooden fixture, you need to drill grooves and holes that will repeat the outlines of the rods in the frame. In such holes, pieces of knitting wire 20 cm long are laid out in advance, and then reinforcement rods are fixed.

In order to understand the knitting technology, you can consider examples. During construction, two options will be required: for crosshairs (when the elements are perpendicular to each other) and for overlap joints. In a strip foundation, the second technology is more often needed; when erecting a slab structure, the first one will be the most relevant.

To connect the laid frame into a single whole when overlapping, the hook should be used in this order:

connections are made in several places along the length of the joint, the location of the wire is appointed so that it is in the recessed part of the reinforcement profile;
the wire is folded in half and laid under the junction;
with the help of a hook, a loop is hooked;
the free end is brought to the instrument and placed on it with a slight bend;
begin to rotate the hook, twisting the wire;
carefully remove the instrument.

For one overlapping connection, the procedure is repeated 3-5 times. Connecting elements at once, as is done with cross-connection, is not enough. The knitting of the reinforcement under the strip foundation in this case will be unreliable, since fixing at one point does not prevent the elements from shifting.

Proper connection of the frame will ensure the reliability, strength and durability of the supporting part of the building.

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

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

Reinforcement for strip foundation - steel bar with stiffeners

Reinforcement of the foundation is required in places where tension zones can 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 it is impossible to predict the progress of deformation, tension zones can occur both in the lower part (when the middle bends down) and in the upper part (when the frame bends up). Based on this, reinforcement should pass from above and below with reinforcement with a diameter of 10-12 mm, and this reinforcement for strip foundations should have a ribbed surface.

This ensures perfect contact with the concrete.

Tensile zones of the strip foundation

The remaining parts of the skeleton (horizontal and vertical transverse bars) 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 bars (with a width of 40 cm) is 30 cm.

The strip foundation has, with a large length, 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 accept loads.

Reinforcement of corners must be given special attention

Particular attention should be paid 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 goes into one wall, and the other into another.
Experts advise connecting rods with a wire. After all, not every type of reinforcement is made from steel that can be welded. But even if welding is acceptable, 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.

Scheme of the construction of the reinforcing structure

Reinforcement begins with the installation of formwork, the inner surface of which is laid out with parchment, which makes it easier to remove the structure in the future. The frame is created according to the scheme:
1. Reinforcing bars are driven into the soil of the trench with a length equal to the depth of the base. A distance from the formwork of 50 mm and a step of 400-600 mm should be observed.
2. Stands (80-100 mm) are installed on the bottom, on which 2-3 threads of the lower row of reinforcement must be laid. As supports, bricks mounted on an edge are quite suitable.

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

The video will introduce convenient way reinforcement knitting using a template:

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

After installing the fittings, it remains to make ventilation holes and pour the concrete solution.

You need to know!
Ventilation holes not only contribute to the improvement of the depreciation characteristics of the foundation, but also prevent the appearance of putrefactive processes.

Calculation of material consumption

To calculate the strip foundation, you need to know some parameters in advance. Let's look at an example. Suppose 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 basis as if it had the shape of a parallelepiped. To do this, we will perform a few simple manipulations: find out the perimeter of the base, and then multiply the perimeter by the width and height of the casting.
P \u003d AB + BC + CD + AD \u003d 3.5 + 10 \u003d 3.5 + 10 \u003d 27
V \u003d 27 x 0.2 x 0.18 \u003d 0.972

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

We get the volume of the "filling": we 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)
We subtract the volume of the casting:
7 - 0.97 = 6.03 m3

The result: the volume of the casting is 0.97 m3, the internal volume of the filler is 6.03 m3.

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

Vertical rods: 54/2 + 2 = 110 rods (108 intervals of 0.5 m 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 will build it from boards 2.5 cm thick, 6 meters long and 20 cm wide.
We calculate the area of the side surfaces: we multiply the perimeter by the height of the casting, and then by 2 (with a margin, not taking into account the decrease in the inner perimeter against the outer one): (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 is required; 6.5 m3 aggregate; 134 meters of reinforcement and 27 linear meters of boards (20 cm wide), screws and bars. Values shown have been rounded off.

The results of painstaking settlement work

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

reinforcing material

Calculation of the reinforcement of the strip foundation

Which scheme is better to choose

How to reinforce corners

How to make reinforcement with your own hands

Basic provisions of SNiP 52-01-2003

Proper reinforcement of the strip foundation with your own hands

The main errors of reinforcing the strip foundation

Why do you need reinforcement in a strip foundation?

What reinforcement is needed for the foundation?

Structural requirements for strip foundations and their reinforcement

How much reinforcement is needed for a strip foundation?

self counting

Using the reinforcement factor

Reinforcing the strip foundation - knit or cook?

What materials are used for reinforcement?

reinforcing material

Calculation of the reinforcement of the strip foundation

Which scheme is better to choose

How to reinforce corners

How to make reinforcement with your own hands

Basic provisions of SNiP 52-01-2003

concrete requirements

Reinforcement requirements

reinforcement requirements

Calculation of the number and diameter of reinforcement

Strip foundation reinforcement rules

How to knit reinforcing mesh yourself

Knitting reinforcement with a special device

Video - How to knit reinforcement with a fixture

How to knit reinforced mesh in a trench

Rebar welding for reinforcement

What is reinforcement

The base has two components:

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

Reinforcing cage configuration

Calculation of reinforcement for reinforcing a strip foundation 40 cm wide

How reinforcement is performed

Video about the reinforcement of the strip foundation

Proper reinforcement of the strip foundation with your own hands

The main errors of reinforcing the strip foundation

Why do you need reinforcement in a strip foundation?

What reinforcement is needed for the foundation?

Structural requirements for strip foundations and their reinforcement

How much reinforcement is needed for a strip foundation?

self counting

Using the reinforcement factor

Reinforcement of the strip foundation - knit or cook?

Reinforcement rules

What reinforcement is needed for the structure

Rebar knitting

Scheme of knitting reinforcement for a strip foundation

Using a crochet hook

Scheme of the construction of the reinforcing structure

Calculation of material consumption

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