Monolithic slab foundations are installed on soils that have poor load-bearing characteristics, and are also suitable for areas with high groundwater levels. Reinforcement of the foundation slab is a mandatory stage of work, performed immediately before pouring the base with concrete. Reinforcement ensures the creation of a reliable support that can withstand multidirectional loads - if pure concrete can withstand compression well, then the reinforcement helps it cope with tensile and torsional forces. The required amount of material can be approximately determined using a reinforcement calculator for a monolithic slab, but final calculations must be made by specialists.

Pouring a reinforced slab foundation with concrete Source pikabu.ru

Why is reinforcement made?

The foundation is based on concrete, which can withstand compression, but has low bending and tensile strength. When constructing a building on a concrete foundation, the load on it will be distributed unevenly - this contributes to the occurrence of bending moments. This feature is very dangerous for concrete structures, so the installation of reinforcement or reinforcing mesh is designed to neutralize the negative impact of these forces. The combination of concrete, which takes on compressive loads, with reinforcement that takes bending, will ensure the reliability of the structure.

On a note! To strengthen the structure, you will need steel reinforcement, which must be combined into a rigid frame. Reinforcing a concrete wall in this way will increase the strength characteristics of the base and increase the operational life of the building.

Foundation construction technology

The reliability of a monolithic foundation depends on the quality of the concrete mixture and well-executed reinforcement. Reinforcement of a slab foundation is a very responsible and complex process that is performed immediately before pouring the foundation. All work on the production of a concrete base is carried out in the following stages:

The site is cleared and markings are made.

Dig a pit of the required size.

Form a drainage system.

The base is filled with sand and gravel and compacted.

Foundation cushion made of sand and crushed stone Source designwow.ru

Lay waterproofing.

Assemble and fix the formwork.

A reinforcement cage is installed and the base is reinforced.

The structure is filled with concrete.

Current standards regulate piping schemes for monolithic foundations, which are used for the construction of various buildings. A reinforced concrete base with steel rods is the key to the reliability of future construction. Laying reinforcement will improve the following characteristics of the foundation:

enhances the strength of the monolithic base, gives the ability to withstand increased loads;

prevents the risks of shrinkage of the building, which are associated with insufficient strength of the base;

does not allow deformation of the monolithic concrete foundation under the influence of negative factors of high groundwater levels.

Reinforcement scheme

When reinforcing a slab foundation is carried out, the layout of the reinforcement must be drawn up strictly according to the technology. In addition, reinforcement schemes for a monolithic foundation slab, if necessary, require an uneven order of placement of rods. Areas where it is planned to erect load-bearing partitions and columns are further reinforced. Such places are called squeeze zones. The reinforcement is laid in one layer with a reinforced concrete slab thickness of 15 cm or less. If the plan of a monolithic foundation assumes a layer size of more than 15 cm, it is recommended to reinforce it with frames. For a slab-pile foundation, calculations must be made separately - depending on the location and material of the piles. In any case, in order to correctly reinforce the foundation slab, the drawing must be drawn up based on careful preliminary calculations.

Source pingru.ru

foundation repair

Basic parameters of the plate

Let's look at the main components of the structure using an example. The diagram shows a grid with constant cell sizes. The distance between the rods must be the same. When calculating the loads, the steps of the rods are made every 20-40 cm. For brick buildings, 20 cm is suitable, and for light frame houses it is permissible to lay reinforcement less frequently. In any case, according to the building rules from the paragraph about “concrete and reinforced concrete structures” it is stated that the distance between the rods should not exceed the thickness of the base by 1.5 times.

A common laying method is in two rows. Their combined action will be ensured by the installation of vertical rods. The distances between such rods must be equal to the steps of the main steel structure, and twice the distance is allowed. According to the rules, the slab at the ends should be reinforced with U-shaped clamps, the length of which should be equal to two thicknesses of the base or more. The rod binding should cover the top and bottom rows. This technique ensures reliable perception of torques at the edge of the foundation and will make it possible to anchor the ends of the longitudinal rods.

Reinforcement at the edges and laying in two rows Source ufa.masterdel.ru

It is important! The entire reinforcement structure should be sunk into the concrete solution by about 2-3 cm on all sides - bottom, top, sides. Otherwise, an accelerated process of corrosion of the reinforcement occurs, which will subsequently lead to structural damage.

Punching zones

In places where load-bearing vertical structures will rest on the foundation, the layout should be done by reducing the reinforcement steps. In the case when the reinforcement is laid every 20 cm along the main width of the slab, it means that under the partitions it is necessary to move to a distance of 10 cm. This method allows you to prevent the occurrence of punching and the formation of cracks.

If the interface zone coincides with a monolithic basement wall, the laying depth will be made in accordance with the height of the planned room. In this option, work is carried out with the base tied to the walls.

When reinforcing foundations, it is recommended to jointly tie the frames of monolithic walls and slabs. When pouring the foundation, you need to leave parts of the vertical rods that will serve as connecting links. These ends are inserted into the base, the edges are bent to approximately two parts of the height of the slab, and then they are tied to the main part of the frame.

After pouring and hardening of concrete, vertical rods are used to “tie” the walls to the base Source dvamolotka.ru

To make a competent calculation of building materials and reinforcement of a slab foundation, you will need a diagram and drawing. Data on the steps between the rows of reinforcement and its diameter must be entered.

On our website you can find contacts of construction companies that offer foundation design services. You can communicate directly with representatives by visiting the “Low-Rise Country” exhibition of houses.

Which fittings are best to choose?

Steel reinforcement is manufactured in accordance with GOST 5781-82, with various types of profiles. For reinforced concrete monolithic slabs, class A400 rods are used. The rods have visual distinctive features, namely:

A 240 – a product with a smooth surface;

A 300 - has a periodic profile with a ring pattern on the surface;

And 400 - there is a crescent-shaped pattern on the herringbone profile.

Important! It is not permissible to use fittings of low categories.

Method of manufacturing reinforcing mesh and frame

There are two options for connecting rods to each other - tying and welding. When using the binding method, wire with a diameter of 2-3 mm is used. Winding occurs manually or using special equipment that helps to wrap around the rods. This option is labor-intensive, but will ensure reliable connections.

Video description

How to manually knit a reinforcement cage, see the video:

Ready-made welded meshes are quicker and easier to install than using the tying method. The only negative is the difficulty that arises when selecting the required size.

Source bigbang.in.ua

The welding method is used in rare cases, since the main disadvantage of this option is the rigid and immovable connection. This has a bad effect on the quality of the monolithic foundation. When welding, metal elements melt, after which the strength of the reinforcing elements decreases.

Work on laying reinforcement

When laying the reinforcing structure into the formwork, everything should be calculated so that all the rods after pouring are covered with a protective concrete layer of 2-3 cm. To maintain the required distance, special plastic fixing elements, metal “frogs” or “chairs” are used.

In the case where the length of the rod is shorter than the entire width of the foundation, an overlap of at least 40 diameters of the working rods is made. For example, for a rod 1.2 cm, the recommended overlap is 48 cm.

Reinforcement of a monolithic foundation in a pre-prepared pit will reduce the duration of work and will help to carry out installation directly on site without any difficulties.

Source dostroyka.com

The disadvantage of this installation is the risk of damage to the installed compacted cushion and waterproofing material. It is best to lay the frame in this order:

The assembled lower belt is placed on supports.

Install cross bars.

The upper part of the structure is assembled, and the racks and the upper chord are connected using wire binding.

How to calculate the diameter of reinforcement

When reinforcing a slab foundation, even using the diagrams you can make approximate calculations of the material. The total cross-sectional area of the reinforcement for a monolithic foundation in one direction is taken to be no less than 0.3% of the total cross-sectional area of the foundation. If the side length of the slab is less than 3 m, a rod diameter of 1 cm is suitable, for a longer length - 1.2 cm. Vertical rods must be at least 6 cm. The maximum product dimensions are 4 cm; in practical applications, 1.2, 1.4, 1.6 cm are used.

Calculation example

The initial data indicates a reinforced concrete surface of 8x8 m. The recommended step size for private houses is 20 cm. This example does not consider strengthening the areas where load-bearing walls will be located. To determine the diameters, it should be taken into account that laying will be done in two rows. Because the thickness of the structure exceeds 15 cm.

Source slo.wikiwiex.ru

The required area of metal rods is calculated according to the following sequence:

calculation of the cross-sectional area of the foundation: 8 m * 0.2 m = 1.6 m 2;

calculations of the minimum area of all reinforcing material: 1.6 m2 * 0.3% = 0.0048 m2 (36cm2);

indicators of the minimum reinforcement area, one direction, one row: 48 cm 2 /2 = 24 cm 2.

the thickness of the concrete layer intended for protection is 2-3 cm on both sides;

permissible overlap;

vertical reinforcement;

number of rods for U-shaped clamps.

Video description

You can also calculate the foundation using an online calculator. You just need to take into account that it is unknown what tolerances and formulas are hidden behind the program interface. Therefore, the reinforcement calculator for a monolithic slab can only be used for approximate calculations.

Errors when installing reinforcing structures

Even minor defects can lead to the destruction of the foundation or complicate the concreting process. Common mistakes when creating a frame and how to avoid them:

rods connected end-to-end will lead to loss of strength of the frame structure;

When installing a reinforcing frame, the rods are located in close proximity to the ground or stuck into it. When the soil moves, the reinforcement will crash into the ground and with this interaction, metal corrosion will form, and this in turn will reduce the strength of the entire foundation;

Reinforcement clamp, which is installed between the meshes Source buildpj.ru

if the ends of the rods do not have a protective coating, corrosion of the products will form under the influence of moisture from the concrete mixture;

special attention should be paid to proper reinforcement in the corners of the building and in areas under the load-bearing wall;

the frame was installed on wooden blocks or other unsuitable elements - this is a gross mistake. Only special fasteners should be used. Otherwise, moisture will penetrate to the metal parts, which in turn will lead to a violation of the integrity of the concrete base.

Video description

For a clear overview of the production of formwork and reinforcement of a slab foundation, watch the video:

Conclusion

The strength and service life of the entire foundation of your house depends on the correct implementation of the reinforcement of the slab foundation. Therefore, all calculations, preparatory and installation work must be carried out by professionals who will not only do everything quickly and efficiently, but also give a guarantee for their work.

Reinforcement of a strip foundation is a mandatory procedure, without which it is impossible to guarantee the high-quality construction of a future building. The work of reinforcing the foundation is very important, but it is not very difficult to perform, and if you understand all the subtleties and nuances, then you can do it without any problems with your own hands.

Materials and tools

To reinforce a strip foundation, both steel rods and fiberglass reinforcement are used; we will focus on steel rods (read how to choose steel reinforcement here), because fiberglass is, firstly, an expensive pleasure, and secondly, it is very rarely used for country house construction in a number of reasons.

We will prepare the following tools:

A container for mixing concrete or a concrete mixer;
Construction mixer;
Bulgarian;
Shovel;
Pliers;
Gloves.

Preparatory work

First: It is necessary to calculate and purchase fittings and binding wire. There is nothing complicated in calculating the required amount of reinforcement. Horizontal guides, for which 12mm reinforcement is used, are usually laid in increments of 30 - 60 cm. Transverse and vertical sections are formed with 8mm reinforcement, in increments of 40 - 70cm. Knowing these data, it is very easy to estimate how many linear meters of reinforcement you need to buy specifically for your purposes, plus take a small reserve and purchase 10% more than you need.

Important: For a ribbon with a height of less than 90 cm, a two-row frame is usually used; for a height of more than 90 cm, a three or more tier frame is knitted.

As for the knitting wire, everything is even simpler; it takes about 25 - 30 cm for each connection.

Second: After the material is delivered to the construction site, it must be carefully inspected and cleaned of dirt and rust. Many people neglect this operation, but it must be remembered that extraneous “inclusions” can, although insignificantly, still worsen the performance characteristics of concrete.

Step-by-step instructions for reinforcing a strip foundation

Step 1: We form a concrete base. To do this, pour sand at the bottom of the trench, 20 -30 cm thick, tamp it down and fill it with concrete with a layer of 5 - 10 cm. This way we will protect the lower reinforcement from corrosion.

Advice: in order to save money, you can not “bother” with filling the “sole”, but waterproof the trench with ordinary dense polyethylene film.

Step 2: We install the formwork. We will not stop at this stage because we have an article on the topic “how to install formwork for a foundation,” where everything is described in detail.

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Step 3: We begin to knit the reinforcement. This work can be done both directly in the trench and next to it. It is more convenient, of course, to tie the individual sections close to the installation site, and then install them in the proper place. The general scheme will be as follows.

Important: It is highly not recommended to use welding to connect reinforcement to each other; with this method of fastening, the joints will begin to rust very quickly.

The assembly of the structure should begin with the lower transverse rods (8mm), they are laid out in increments of no more than 80cm from each other. Then we lay working reinforcement (12mm) longitudinally on them; the distance between the longitudinal rods should not exceed 40 cm, but if it is more than 40 cm, then we add another rod to the structure. The joints of the transverse and longitudinal rods are secured with knitting wire.

So, we previously formed the lower level of the frame, then we should fix the vertical jumpers (8mm). This is done like this - in the places where the longitudinal and transverse reinforcement rods come into contact, we install another rod vertically and connect it with wire to the main structure, thus installing all the necessary vertical elements.

Important: Be careful and when installing, make sure that the vertical reinforcement is fixed in relation to the longitudinal reinforcement exactly at 90 degrees.

The next stage of assembling the frame will be the installation of the upper transverse and longitudinal rods. All actions are the same, to the vertically fixed reinforcement using a knitting wire with an overlap at the edges of at least 20 cm, we first attach the transverse and then the longitudinal elements of the reinforcement.

Using the method described above, we assemble the required number of sections, install them in a trench if the assembly was not carried out in it, and using spacers we rigidly fix the frame in relation to the formwork, leaving a gap between them of 3-5 cm.

The main part of the work has been completed, but the most important stage remains, the reinforcement of the strip foundation in the corners.

Step 4: Fastening reinforcement in the corners. Here you need to be extremely careful and do the work as efficiently as possible, because the corners of the foundation take on the greatest concentrated stress. To reinforce the foundation at the corners, U- or L-shaped reinforcement techniques are used. See below for how to do this job correctly.

For right angles:

For angles greater than 160 degrees:

Well, the crosshairs are reinforced like this:

The work is all finished, good luck with your construction.

How to properly reinforce a strip foundation with your own hands?

When carrying out construction activities for the construction of residential buildings and industrial facilities, various types of foundations are used to ensure the stability of the structure being built. Foundations made along the perimeter of the building are widely used. To strengthen this structure, tape reinforcement is performed.

The need to reinforce a strip foundation is due to the properties of concrete, which maintains its integrity under the influence of compressive loads, but at the same time is prone to cracks under the influence of bending moments and tension. This serious drawback of the concrete monolith can be compensated for by the reinforcement of a monolithic strip foundation, which increases the stability and service life of the buildings being built.

The foundation of the building absorbs significant loads associated with the reaction of the soil, the mass of the structure and other factors. The reinforcement frame is exposed to increased stress concentrations, ensuring the integrity of the concrete mass. Errors in foundation reinforcement associated with the destruction of the zero level can cause fatal consequences.

The foundation is the basis of a building for any purpose; it is the most important part of any building.

That is why we will consider in detail how to properly reinforce a strip foundation, and dwell on the criteria for choosing reinforcement and the technology for reinforcing a strip foundation.

Settlement stage

At the design stage, it is important to skillfully calculate what kind of reinforcement is needed for a strip foundation. This will create a reliable foundation that will ensure the strength characteristics of the building under construction with a long service life. When performing calculations at the preparatory stage of work, many factors should be analyzed:

soil characteristics in the conditions of a specific construction site;
acting loads, which the reinforcement frame perceives;
the mass of the building due to the design features and materials used;
climatic conditions in the construction area;
soil reaction associated with the proximity of groundwater and soil freezing at negative temperatures.

The rules for reinforcing a strip foundation provide a special approach to the selection of base material

Based on the results of design work, the diameter of the reinforcement for the strip foundation is determined and a decision is made on the degree of penetration of the foundation into the ground:

To a depth limited to 0.5 m for hard soils that are not prone to heaving.
To an immersion depth increased below the soil freezing level for problem soils.

The options don't end there. After all, construction science does not stand still; new supporting structures with increased strength are being developed. A new base option has been introduced and tested in operation, when a monolithic reinforced slab is poured onto a pre-made reinforced strip frame. Which base design is better is determined at the design stage, taking into account the specific conditions of the actual terrain. Depending on the characteristics of the base chosen according to the project, designers decide whether to reinforce the tape or reinforce the foundation slab, as well as which reinforcement is best to use for the foundation.

Reinforcement selection criteria

Proper reinforcement of the strip foundation determines the strength characteristics of the supporting structure. When deciding whether to reinforce a slab located on a strip base, or to reinforce a standard base, be guided by the marking features of the reinforcing bars.

Reinforcement of a monolithic strip foundation requires compliance with certain rules

Reinforce the base with steel rods having the following characteristic features:

the presence of the index “C” in the designation of steel rods indicates the possibility of using electric welding equipment to combine elements with a common frame;
the presence of a capital letter “K” in the abbreviation confirms the resistance of the rods to corrosion that occurs when concrete is saturated with moisture;
product class designation A2 and A3, which allows the use of steel rods fixed in a common frame with wire, while maintaining the strength of each of the connected elements. The use of electric welding to fix such rods is not permitted.

Foundation reinforcement made from steel rods with a cross section of 10–12 mm has the required operational strength. The optimal diameter of the reinforcement for a strip foundation is determined according to calculations that take into account specific operating conditions, soil characteristics and the values of the operating loads.

About the need for strengthening

To what extent is it necessary to strengthen a concrete mass with steel wire? After all, concrete has fairly high strength characteristics. Indeed, concrete has increased resistance to compressive loads, but requires reinforcement against the destructive effects of tensile forces.

The greatest likelihood of stretching is on the surface of the base, this is where the reinforcement should be placed

Strip foundation reinforcement technology

The reinforcement of a strip foundation is a key factor in its reliability and durability (you can also read separately about the reinforcement of a pile-grillage foundation). According to the provisions of SNiP No. 2.03.01-84, unreinforced foundations are not approved for use in residential construction.

Strip foundation reinforcement

From this article you will learn how to properly reinforce a strip foundation. We will look at methods for calculating reinforcement and study reinforcement diagrams, as well as get acquainted with the technology of doing the work ourselves.

1 How to reinforce the foundation strip?

The foundation structure consists of two components - a concrete body and a reinforcement frame embedded inside it. Concrete, as a material, is highly resistant to deformation loads in compression, but it is weak in tension and bending, under the influence of which the tape can collapse. These loads are absorbed by the reinforcement frame, which resists deformations in the zone of increased external influence.

Reinforcement of a strip foundation is carried out using a spatial frame consisting of longitudinal reinforcement belts connected to each other by transverse and vertical jumpers. The number of longitudinal belts is selected based on the height of the tape:

shallow foundations are reinforced with a frame in two longitudinal belts - upper and lower;
recessed foundations, the height of which exceeds 120 cm, are reinforced with a frame with a middle reinforcement belt.

The longitudinal belt of the frame is made of corrugated rods fittings with a diameter of 12-16 mm, class A3 rods are used. Jumpers are made from sections of rods of similar diameter or from smooth profile reinforcement bent into rectangular clamps with a diameter of 8-10 mm.

Reinforced frame with two longitudinal belts

Assembly of the reinforced frame is carried out using tying wire or welding. The first method does not require the use of special equipment, however, it is quite labor-intensive to implement, while welding is a faster way to install the frame. For knitting, steel wire with a diameter of 1-2 mm is used.

The frame configuration is determined by the provisions of SNiP No. 2.03.01-84 “Manual for designing foundations for buildings and structures.” The following distances must be maintained:

the pitch between the constituent elements of the longitudinal belt is no more than 10 cm (determines the number of rods in the belt);
the step between the longitudinal belts in the vertical plane is no more than 50 cm;
the step between the transverse and vertical connecting jumpers is no more than 30 cm;

Transverse diagram of reinforced frame

When installing the frame, it is necessary to provide a protective layer of concrete - a distance of 5 centimeters between the contours of the frame and the walls of the concrete body. The size of the reinforcement skeleton is selected based on the dimensions of the foundation so that the above rule is observed. Laying of reinforcement on the bottom of the formwork is done using plastic mushroom stands, which raise the rods to the required height.
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1.1 Calculation of reinforcement for strip foundations

The consumption of reinforcement must be determined at the foundation design stage in order to subsequently know exactly the amount of material purchased. Let's look at how to calculate reinforcement for a strip foundation using the example of a shallow foundation 70 cm high and 40 cm thick.

Read also: how to reinforce a floor screed, and what kind of mesh is required for this?

First you need to determine the frame configuration. It will consist of an upper and lower chord, 3 reinforcement bars in each. The distance between the rods of 10 cm + 10 cm goes to the protective layer of concrete. The connection will be made by welding sections of reinforcement of similar sizes in increments of 30 cm. The diameter of the reinforcement for the strip foundation is 12 mm, class A3.

Reinforced frame of strip foundation

We determine the required amount of reinforcement:

To find out the consumption of rods for the longitudinal belt, you need to calculate the perimeter of the foundation. Let’s take a conventional building with a perimeter of 50 m. Considering that there are 6 reinforcement bars in two belts (3 in each), its consumption will be: 50 * 6 = 300 m.
Next, we calculate how many connections will need to be made to join the belts. To do this, we divide the perimeter by the step between the jumpers: 50/0.3 = 167 pcs.
Taking into account the required thickness of the protective layer (5 cm), the length of the vertical jumper will be 60 cm, and the transverse one - 30 cm. The number of each type of jumper for each connection is 2 pieces.
We determine the consumption of rods for vertical jumpers: 167 * 0.6 * 2 = 200.4 meters.
We calculate the material consumption for the cross lintels: 167*0.3*2 = 100.2 m.

In total, the calculation of the reinforcement for the strip foundation showed that the total consumption of A3 rods with a diameter of 12 mm will be 600.6 m. This quantity is not final, the material must be taken with a margin of 10-15%, since it will be necessary to use additional reinforcement to strengthen the corner parts of the foundation strip.
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1.2 Reinforcement of a strip foundation (video)

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2 Work technology

After the amount of reinforcement has been determined, a strip foundation reinforcement scheme must be selected, according to which the reinforced frame will be assembled. Straight sections of the structure are made of solid rods, while in corner areas additional reinforcement is required with reinforcement curved in a U or L-shape. The use of perpendicular overlap of individual reinforcement bars at corners and junctions is not permitted.

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

Reinforcement of foundation corners

Scheme of reinforcement of strip foundations at junctions:

Reinforcing a strip foundation with your own hands involves assembling the frame in a convenient place and then placing it inside the formwork. The technology requires bending reinforcement into rectangular clamps, which can be easily done at home using a homemade device.

On the 20th channel, you need to cut out grooves with a grinder, into which the reinforcement is subsequently inserted, and a section of steel pipe is placed on the rod, which is used as a lever. The finished rings must be fastened by welding or tied with wire. For rods with a diameter of 10-15 mm, 1.2-1.5 mm wire is used.

Read also: how to reinforce a column so that it stands for many years?

The length of the rods on the longitudinal belt should be equal to the length of the side of the house. The rods are threaded inside the ring and fixed with knitting wire at the corners of the clamp and in its central part. The step between the clamps is 30 cm. At the exit you should have 4 components of the frame - 2 equal to the length and 2 smaller ones equal to the width of the house. Next, the frames are laid in the trench and connected with reinforcement bars bent at an angle in accordance with the diagram presented above.

Bending of clamps from reinforcement

When installing the frame inside the trench, the following rules must be observed:

the frame must be raised 5 cm above the bottom of the trench using stands - SNiP requirements do not allow the use of brick fragments for this purpose;
installation must be carried out strictly at a horizontal level;
the frame must be fixed relative to the side walls of the trench using pins driven into its walls so that the reinforcement does not move during concreting.

Read also: how is brick and aerated concrete masonry reinforced, and is it necessary to do it?

The reinforcement of a strip foundation according to the execution technology is identical for shallow and recessed foundations. After installing the reinforced frame, the concreting stage begins - for pouring it is used concrete grade M200. You can determine the required amount of concrete based on the volume of the foundation - you need to multiply the length, width and perimeter of the tape.

Reinforced frame of the foundation tape

Note that the technology for constructing a strip foundation requires the obligatory arrangement at the bottom of the trench of a compacting cushion made of layers of sand and crushed stone of equal thickness (thickness from 10 to 20 cm each). The cushion is used to protect the foundation from vertical heaving loads, which is especially important when constructing a shallow foundation located in a layer of freezing soil.

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 instructions for reinforcing a strip foundation, watch a video on the topic, and handle it yourself, it’s still possible. 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 the building has a 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 diagram. 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 an 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 the total cost of construction.

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 a light one-story house, a shallow foundation is 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 prefabricated 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 binding is most often used, in mass production - welding. 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

To reinforce a monolithic foundation, you will need from 2 to 4 rods in the lower chord and upper chord. 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

Reinforcing a strip foundation with fiberglass reinforcement is 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 the reinforcement of 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:

Even if we roughly calculate the costs of pouring a strip foundation for a private house of any size, it becomes clear that up to 30% of the total construction estimate is spent on the construction of the foundation. But this is the case if the developer buys absolutely everything - from concrete and its delivery and pouring to the labor of workers on the site. This also includes the cost of steel or fiberglass reinforcement and reinforcement frame knitting. But a correctly drawn up reinforcement scheme for a strip foundation or reinforcement for a pile-screw structure plus independently completed work (meaning all construction work that can be carried out on your own) allows you to save your budget by 100-140%!

Reinforcement Basics

Reliable is the error-free process of strengthening a concrete structure in accordance with the standards of SNiP 52-01-2003, SNiP II-21-75 and SN 511-78 and other regulatory documents. What are the most frequently repeated errors that affect the reliability, strength and service life of the strip base:

It is recommended to make the reinforcing frame for the concrete strip of the foundation of a low-rise building from corrugated metal rods Ø 10-24 mm or from fiberglass rods;
It is strictly prohibited to connect reinforcement intersections by welding; rods can only be connected with soft knitting wire Ø 3-5 mm. Electric arc welding is ultra-high temperatures, when exposed to which the metal overheats and loses its strength properties by 150-200%, especially in areas of connections of perpendicular intersections;
If there is homogeneous soil on the foundation laying area, it is allowed to use thinner rods of metal or fiberglass reinforcement - Ø up to 14 mm. For heterogeneous soil layers, reinforcing rods must be at least 16 mm in diameter;
Only corrugated rods are used - smooth rods adhere worse to concrete, and all mathematical calculations related to strength and loads on the foundation are designed specifically for the use of corrugated rods. Smooth rods are allowed to be used in a reinforced frame only to form transverse fastenings, since in these areas the load on the concrete and reinforced frame is small;
The longitudinal reinforcement bars in the body of the concrete strip must be located at a distance of ≥ 5 cm from the side, top and bottom walls of the formwork. If the reinforcement is exposed, then it will quickly be eaten away by corrosion, while the concrete will deteriorate in parallel with the corrosion of the metal - crumble, crack, swell;
A distance of 30-45 cm is maintained between transverse reinforcement;
Strengthening the corners of a strip-type foundation is carried out according to a different pattern from the standard knitting. This issue will be discussed separately below;
Also, the reinforcement of the strip foundation involves laying longitudinal reinforcement every 40 cm along the height of the strip. That is, if the height of the foundation is 160 cm, then you need to lay four longitudinal rows of rods.

Self-assembly of formwork

Properly installed will not only save the construction budget by reducing the consumption of concrete mortar, but will also make the work of reinforcing the base much easier and faster.

The material for assembling formwork decks (panels) can be very different: if the height of the base is no more than 1.5 meters, then use thick plywood, slabs (unedged boards), OSB sheets, fiberboard or chipboard, slate, sheet metal, etc. . The main requirement for formwork is that it withstand the pressure of the mortar and soil. For foundations with a height of more than one and a half meters, it is recommended to do so only because of the high pressure on its walls;
Preparatory work for the installation of formwork begins with compaction of the base of the trench. To do this, a sand cushion is made with a layer of 15 cm, moistened and compacted, and a 5 cm layer of concrete mortar is poured on top of the sand to level the base. If utility lines (plumbing, sewerage, heating or communications) will pass through the body of the foundation, then holes for them will be pre-equipped in the tape. To do this, embedded pipes are attached to the formwork in the right places through which the pipelines will pass;
According to the project plan, the site is marked with pegs with a cord stretched between them along the outer width of the foundation. To ensure that the lower part of the formwork panels collapses, the panels are propped apart with slats or bars at 70% of the height of the base. The length of the spacer should be approximately twice the height of the trench;
The spacers are attached to the panels with self-tapping screws or nails. If the base height is ≥ 1.5 meters, the formwork panels should be tied together with soft steel wire in 1-meter increments in a checkerboard pattern;
The gaps in the formwork should not exceed 2-3 cm so that the solution does not seep through them into the ground, reducing the strength of the concrete strip.

It is recommended to lubricate the inside surfaces of the formwork panels with machine oil or petroleum distillation products so that when dismantling the formwork it is easier to tear off the concrete. This is done if the formwork will be used as a reusable structure.

Rebar weight calculator GOST 5781-82

Installation of reinforcement cage

After preparing the trench and installing the formwork, reinforcement of the shallow strip foundation begins. Reinforcing the foundation with fiberglass or iron reinforcement is technologically no different, so let’s consider a more familiar option - knitting a frame from steel rods. For work you will need the following materials:

Corrugated reinforcing bars Ø 14-18 mm (choice of diameter - according to calculations in the project);
Vertical and transverse smooth reinforcement Ø 10-12 mm;
Soft knitting wire Ø 3-5 mm;
Pliers, pliers, pliers, a narrow pry bar or other metal lever Ø 20-25 mm, or a special crochet hook that you can purchase or make yourself.

Important: the fastening of steel or fiberglass reinforcement is carried out using annealed steel wire, since it stretches well and has a good strength margin.

The first step to creating a reinforced frame is to carry out calculations to determine the diameter of the rods, their length and weight. Calculating the correct reinforcement of a strip foundation is quite simple: transverse rods are laid in increments of 30 cm, longitudinal rods in increments of 40 cm, vertical rods in increments of 50 cm. The total number of connections is calculated as follows: the size of the long side of the foundation must be divided by the number of transverse rods and the number vertical rows of longitudinal reinforcement bars.

Let's say a house is being built 10 x 10 meters (base perimeter) with a foundation wall height of 120 centimeters:

The length of one foundation wall is 1000 cm. The step of laying transverse reinforcement bars is 30 cm, therefore 1000 / 33 = 33 (transverse reinforcement in one row);
33 x 3 = 99 (cross bars for one side);
99 x 4 = 396 (total number of reinforcing bars on all four sides).

The number of fiberglass reinforcement rods is calculated in the same way.

Further actions: the total number of reinforcement (396 rods) is multiplied by the width of the tape (let's say the tape is 0.6 meters wide): 396 pcs. x 70 cm = 237.6 meters - this is the total length of the reinforcement used in the frame. The footage of longitudinal rods is calculated in the same way:

1000 cm x 2 = 2000 cm (one row);
2000 cm x 3 = 6000 cm (one side);
6000 cm x 4 = 24000 cm (240 meters).

Calculation of vertical rods (knitting through a jumper, i.e., after 60 cm):

2 x 17 = 34 units per side;
34 x 4 = 136 units for the entire foundation;
136 x 1.20 m = 163.2 meters.

In order not to purchase additional reinforcement bars (in case of erroneous calculations), add 5-8% to the total result.

You can knit a frame both on the ground and in a trench, but if the trench is narrow, this will be inconvenient. On the other hand, you won’t be able to lower the huge frame alone - you need help.

More information about reinforcing a strip-type base with your own hands:

The beginning of the knitting is the lower transverse rods: they must be laid at a distance of 30 cm from each other, two long rods should be placed on top, and tied with wire at the intersections;
Vertical rods are installed through one transverse rod and tied together;
In this way, two or three more rows (as needed) are knitted at a distance of 40 cm in the upward direction;
Upon completion of assembling the entire frame, there should be four nodes.

Now you need to learn how to correctly tie them together, as well as correctly tie the rods at the corners of the foundation.

How to reinforce corners

The corners of the foundation are constantly subjected to multidirectional compressive forces, so reinforcement at the corners must be carried out equally and without errors, so that each corner evenly absorbs the same loads, and does not create a separate local area with different load-bearing values. There are several methods for strengthening corner foundation structures:

Using welded metal coarse mesh. Such a ready-made rigid structure has cells ≤ 200 x 200 mm, and the thickness of the reinforcement bars in the mesh can vary from 8 to 24 mm - this depends on the mass of the building and the length of the foundation. After 05-0.6 meters, horizontally laid rows of reinforcing mesh are connected to vertically located reinforcing bars, as when knitting a rod frame, with an overlap of about 0.8 meters at the corners of the frame.
Reinforcement with individual rods:
1. Using L-shaped bent rods with an overlap of ≥ 60 cm;
2. U-shaped rods are usually used to reinforce right angles and foundation junctions;
3. Reinforcement of connections with L-shaped brackets.

Correct formation of angles is based on following several recommendations:

The length of the overlaps is calculated as 50 diameters of the reinforcement bars;
When knitting corners more than 160 cm wide, the rods must be solid and bend along the corner;
The distance between the transverse rods should not be less than 0.75 of the height of the tape, but not more than 50 cm;
The reinforcement is attached to concrete with special claws, hooks, loops or straight ends. Welding and overlay cementation cannot be used.

Reinforcing the foundation of any structure with your own hands poses a certain problem for a novice craftsman, but if you follow the above recommendations, common mistakes can be avoided, and the foundation will be strong and durable.

Strip foundation reinforcement scheme updated: February 27, 2018 by: zoomfund

The foundation is the most vulnerable part of the structure. Due to the fact that the upper part of the building is subject to compression loads and the lower part is subject to tensile loads, proper foundation laying plays an important role. To perform the correct reinforcement of a strip foundation with your own hands, you need to perform a calculation according to the diagram.

Such a base is, in fact, a reinforced concrete strip running 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 experience overloads, 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 foundation must be reinforced. After all, the foundation is subject to various loads. This includes the weight of the entire house and various movements of the soil. The reinforcement scheme for a strip foundation resembles the skeleton of a structure, which is assembled from steel rods. In order to choose the necessary scheme for it, you need to understand what it is.

Reinforcement of a strip foundation can be easily done with your own hands, without the involvement of specialists. It is important, first of all, to correctly select the required diameter of the reinforcement

Reinforcing material

The choice of material is a fairly important step. To reinforce a strip foundation with your own hands, use steel rods of different sections or fiberglass reinforcement. But most often metal is used.

The main horizontal reinforcement has a cross-section of rods from 12 to 24 mm. The rods that will be positioned vertically 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 variation in loads on the foundation 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. Knitting wire and a hook are used to connect the rods. 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 strip foundation reinforcement

The number of reinforcement elements must be calculated based on the size 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 row of frames in a strip base measuring 6x6 m, you will need, on average, 24 m of reinforcement. If you lay 4 rods at a time, you will need 96 m of longitudinal rods.

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

If the mounting step of the clamps is 0.5 m, the number of connections will be: 24/0.5+1=49 pcs. This means, 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 be calculated from the table:

Diameter of fittings, mm	Calculated area of the transverse rod, mm 2, with the number of rods									Theoretical weight of 1 m length of reinforcement, kg
Diameter of fittings, 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 strengthen the foundation for low-rise buildings:

four rods;
six rods.

In accordance with SNiP 52-101-2003, adjacent reinforcement bars should 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 reinforcement scheme with six rods.

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

Typically, for a strip base, the rods are laid “in a cage.” In this case, all the rods are attached at an angle of 90°. For longitudinal arrangement, reinforcing materials of class A3, having a round shape, are used.

How to reinforce corners

The corners bear a lot of load. Therefore, when reinforcing, care must be taken to strengthen them.

AtThe following rules must be taken into account:

the rod must be bent so that one side of it is buried in one wall of the foundation, and the other in 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 fittings are used for this.

How to do reinforcement yourself

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

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

The frame is installed as follows:

bricks are laid at the bottom of the trench, the height of which is 5 cm (in order to create a gap between the lower part of the base and the frame);
to install rack rods, it is necessary to make a sample in advance, according to which the rods will be cut;
longitudinally shaped rods 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 in increments of 50 cm using knitting wire;
rods are attached vertically to the corners of the formed cells, 10 cm long less than the height of the base;
the upper longitudinal rods are mounted to the vertical reinforcement;
The upper transverse rods are tied to the resulting corners.

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 concern 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 selected according to the number of longitudinal rods. For a strip foundation, it must be at least 0.1% of the working sectional area 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.

You can see the minimum diameter of the reinforcement more clearly in the table of examples:

Terms of use of fittings	Minimum diameter of reinforcement	Regulatory document
Longitudinal working reinforcement along a side 3 meters or less	10 mm
Longitudinal working reinforcement along a 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 bending 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	Guidelines for the design of concrete and reinforced concrete structures made of heavy concrete
Clamps for knitted frames with a section height of more than 80 cm	8 mm	Guidelines for the design of concrete and reinforced concrete structures made of heavy concrete

Reinforcing a strip foundation is easy to do with your own hands; all you need to do is follow the technology and perform the calculations correctly. If it is difficult to do this on your own, it is better to seek the help of professionals. After all, a reliable and solid foundation is the price and guarantee of the stability of the entire building.

More information about reinforcing a strip foundation with your own hands can be seen in the video: