Frame made of reinforcement for the foundation

An important structure of each object is the foundation, the arrangement of which is given close attention. Subject to certain rules for performing work, quality, long operational period, and reliability of the structure as a whole are guaranteed. In each type of base, a reinforcement cage is installed for the foundation. A concrete base that does not have a metal frame does not have the required level of strength. Concrete absorbs only compressive loads, while steel rods compensate for tensile and deformation forces, thereby ensuring the integrity of the foundation.

Do-it-yourself calculation of strip foundation reinforcement

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

Determination of reinforcement thickness

Since the strip foundation in section has the shape of a rectangle, the cross-sectional area is found by multiplying the lengths of its sides. If the tape has a depth of 80 cm and a width of 30 cm, then the area will be 80 cm * 30 cm = 2400 cm2.

Now you need to find the total area of the reinforcement. According to SNiP it should be at least 0.1%. For this example it is 2.8 cm2. Now, using the selection method, we will determine the diameter of the rods and their number.

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

For example, we plan to use reinforcement with a diameter of 12 mm. Its cross-sectional area is 1.13 cm2 (calculated using the formula for the area of a circle). It turns out that in order to provide the recommendations (2.8 cm2), we will need three rods (or they also say “threads”), since two are clearly not enough: 1.13 * 3 = 3.39 cm2, and this is more than 2.8 cm2, which SNiP recommends. But it will not be possible to divide three threads into two belts, and the load on both sides will be significant. Therefore, they stack four, laying a solid margin of safety.

In order not to bury extra money in the ground, you can try to reduce the diameter of the reinforcement: calculate it at 10 mm. The area of this rod is 0.79 cm2. If we multiply by 4 (the minimum number of working reinforcement bars for a strip frame), we get 3.16 cm2, which is also enough with a margin. So for this version of the strip foundation, you can use class II ribbed reinforcement with a diameter of 10 mm.

Reinforcement of a strip foundation for a cottage is carried out using rods with different types of profiles

We have figured out how to calculate the thickness of longitudinal reinforcement for a strip foundation; we need to determine with what step to install vertical and horizontal lintels.

Installation step

There are also methods and formulas for all these parameters. But for small buildings it’s simpler. According to the recommendations of the standard, the distance between horizontal branches should not be more than 40 cm. This parameter is used as a guide.

How to determine at what distance to lay reinforcement? To prevent steel from corroding, it must be embedded in concrete. The minimum distance from the edge is 5 cm. Based on this, the distance between the rods is calculated: both vertically and horizontally it is 10 cm less than the dimensions of the tape. If the width of the foundation is 45 cm, it turns out that between the two threads there will be a distance of 35 cm (45 cm - 10 cm = 35 cm), which corresponds to the standard (less than 40 cm).

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

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

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

All. We calculated the reinforcement of the strip foundation with our own hands. But keep in mind that neither the mass of the house nor the geological conditions were taken into account. We relied on these parameters to determine the size of the tape.

Supporting meshes

These meshes are placed in areas with bending elements, perpendicular to the acting loads. They are formed from transverse and longitudinal distribution rods. If you need to use such meshes, the easiest way is to purchase ready-made welded flat frames of standardized sizes. Such meshes differ in pitch and steel diameter, allowing you to choose exactly what is needed for a specific object and significantly reduce the amount of work with reinforcement.

The process of knitting a reinforced frame on the ground

First, the straight sections of the frame are knitted on the ground, and only then they are installed in the foundation formwork and the connecting corners are installed.

Stage 1. To correctly determine the size of the frame, you need to remember that it must be filled with concrete on all sides by about five centimeters. Taking this information into account, you need to prepare the wire and rods. The length of the wire for one node is approximately 20 cm. It is better to start making the frame from the smallest section of the foundation.

Stage 2. Place the two lower rods on a flat surface and carefully align them.

Stage 3. At approximately a distance of 20 cm from the ends of the rods, you need to tie horizontal rods. To do this, a piece of wire is folded in half and the metal elements are connected using it using the usual scrolling movements. In this case, the tightness of the knot should be moderate - not too tight, but not loose either.

Stage 4. At a distance of approximately 50 cm, you need to tie the remaining longitudinal elements in the same way.

Stage 5. In the same way you need to make the upper part of the frame.

Stage 6. The finished parts need to be placed opposite each other on their sides so that the parts take a stable position. The distance between them should be exactly the length of the vertical rods.

Stage 7. Systematically tie the remaining side parts, while checking the dimensions of the workpieces to be sure. Connected one side? Great! Turn the frame blank over and continue.

Step 8. Based on the mini guide described above, make all the straight parts for the foundation.

Stage 9. Place the frame on the spacers in the formwork to a height of more than 5 cm.

Stage 10. Measure the corner areas and make according to the workpiece values.

Stage 11. Attach the lower rotating parts first, then the vertical and upper ones. Remember that the overlap must be at least 50 cm.

Non-standard way of knitting the frame

To simplify the process of creating a metal frame as much as possible, you can build a simple device from scrap materials. It will not only significantly speed up mating, but will also help you cope with it without outside help.

Stage 1. Make four blanks from boards the length of the reinforcing bars and connect them two at a time at a distance equal to the length of the vertical jumpers.

Stage 2. Make improvised racks - stops on which you can place the resulting workpieces. The main thing is that they stand on a flat surface.

Step 3. Secure the tied boards. So you have a wonderful layout of the future frame, from which you can easily create a metal copy of it.

Selection of material and reinforcement rules

Reinforcement is a mandatory procedure when constructing the foundation of a future building. The frame is assembled from metal rods of various diameters and with different surfaces. During the work, the following rods are used:

smooth;
equipped with ribs;
diameter 12-16 mm;
section 8-10 mm;
strength class A2 and A3.

In addition, to build a strong, high-quality structure, you will need tying wire or plastic clamps, as well as a device with which you will need to bend reinforcing bars for use in strengthening corners.

The main tape of the frame is assembled from ribbed rods with a diameter of 14 mm, which take on the maximum loads; the transverse jumpers are made from rods with a smooth surface and their thickness does not exceed 9 mm. Sufficient immersion of the frame in concrete avoids the destructive effects of corrosion. The thickness of the mortar layer in the upper part of the structure should not be less than 5 cm.

Concrete itself is not able to withstand deformation and compression; the reinforcement cage ensures the stability of the foundation to increased loads, creating a rigid fixation for the finished foundation structure. The guidelines for selecting reinforcing bars and assembling the frame indicate the need to carry out calculations that determine the level of loads on the base of the building.

An important condition for creating a high-quality, reliable foundation is strict adherence to the established distances from the metal parts of the structure to the surface of the foundation. The reinforcement frame of a strip foundation is a structure in which an important role is played by transversely fixed elements located at a certain distance from each other

Strict adherence to these distances (steps) guarantees the creation of a durable frame that can withstand increased loads and resist deformation

The reinforcement frame of a strip foundation is a structure in which an important role is played by transversely fixed elements located at a certain distance from each other. Strict adherence to these distances (steps) guarantees the creation of a strong frame that can withstand increased loads and resist deformation.

The steps in question are calculated in advance, and their magnitude is reflected in the design documentation. They depend on the depth of the foundation and do not exceed 25 cm. There are also restrictions on the size of the cells that make up the reinforcement cage. If the depth of each cell depends on the upcoming loads, then the length is at least 40 cm, and the width should not be less than 30 cm.

Recommendations

An armored belt for a foundation is a metal structure that takes on the resulting loads and deformations. Technological recommendations will help in its manufacture:

how to make an armored belt for aerated concrete;
what mesh to use for the screed;
what marking of fittings is used during manufacture;
what is marble concrete;
what types of couplings there are for connecting reinforcement;
what is a plasticizer and why is it needed?

Knitting of frame elements, depending on the conditions, is carried out directly inside the formwork or in another place on the construction site.

Strip foundation reinforcement scheme

Scheme of reinforcement of the strip base of the building

Almost all builders practice reinforcement using ready-made geometric shapes - a square or rectangle. Columnar foundations are reinforced in a circle. The reason here lies in the ideally correct forms of the reinforcement frame, because straight lines and precise connections guarantee the strength of the structure as a whole.

To make the frame correctly, you need to maintain the thickness of the cushion directly in the trench, taking into account the necessary margin for waterproofing and a protective layer of concrete. Therefore, even after pouring the reinforcement frame with concrete, the difficulties in constructing the foundation do not end. Now you need to properly and thoroughly cover the surface with waterproofing, and it is strictly forbidden to damage it.

It is the strip foundation that is considered the simplest and cheapest foundation in private construction. Such a foundation is cheap to construct, since a minimum of labor is used here, there is no need to rent powerful construction equipment, and there is also no need to use more expensive powerful and durable reinforcement.

The only difficulty is that you have to make complex mathematical calculations of the reinforcement, install the belts correctly and connect them efficiently.

Grillage

Another use of the reinforcement cage is in the manufacture of beams for laying under walls on columnar or pile foundations.

The grillage is made in formwork of the required dimensions, installed at the top mark of screw or monolithic columnar bases. In essence, this is the production of reinforced concrete spans at home using wooden panel formwork.

The selection of thicknesses and grades of reinforcement is made by analogy with the frame for the foundation. In the manufacture of a grillage you cannot do without reinforcement, but in general, the installation of runs on screw piles or concrete pillars is much cheaper than a monolithic strip foundation. This is especially true in the construction of lightweight houses.

Specifics of mating

The production of reinforcement frames with elements fixed with binding wire is carried out using the following methods:

tying reinforcement manually, which is characterized by increased labor intensity, requiring significant effort and high time consumption. The rods are fixed at the joining points using annealed wire with a diameter of 0.8-1.2 mm. With the manual method, pliers or a special hook are used to perform knitting, the use of which allows you to firmly twist the ends of the wire and ensure fixation of the rods;

Reinforcing bars are connected together with special wire

using an automated method involving the use of a special tying gun. The device guarantees high-quality connection of rods and fast execution of operations. The time required to fix a pair of rods does not exceed one second. The gun is used when performing significant volumes of work.

Reinforcing cages, the elements of which are fastened with knitting wire, are characterized by strength and ensure the durability of the foundation being built.

GOST and SNiP requirements

The execution of work on the manufacture and subsequent installation of reinforcement cages can be divided into two regulated areas:

production of welding works. The main regulatory document is SNiP III-4-80, which describes the safety requirements, primarily fire safety, for welding work. They are dangerous and affect the safety of human life, therefore they are controlled especially carefully;
any reinforcement work, including manufacturing and installation. They are regulated by GOSTs 19292-73 and 23279-85, as well as several SNiPs - 23-81, 3.03.01-87, 3.09.01 - 85, 2.03.01-84.

The basic requirements are as follows:

welders must have valid certification;
work can be carried out in strict accordance with the previously developed work permit for welding work;
reinforcement cages are manufactured in accordance with the drawings on them.

Knitting reinforcement with your own hands

With all the variety of specialized construction tools, not all private developers have the opportunity to buy or rent them. Knitting rods does not require expensive tools; moreover, you can do it yourself.

To do this, you need to purchase steel binding wire. It is quite flexible and durable, has a diameter of 2-3 mm. To bend it, you will have to use pliers or a specially made hook, which subsequently twists around the reinforcement and fixes it. Some craftsmen who perform reinforcement with their own hands sometimes use a screwdriver as a simpler and easier way to knit. If you knit with wire, you will need:

One of the options for knitting the base frame using a hook. Craftsmen sometimes use a screwdriver as an easier way to knit reinforcement bars with their own hands. cut a piece of wire about 30 cm long. You can do more if you don’t mind it, but the ends will get in the way (including excess waste);
then fold the wire in half to increase rigidity and strength;
bend it diagonally around the reinforcement joint and make a small loop;
Place the hook in the loop and twist clockwise evenly, without unnecessary effort, until it becomes difficult to wrap or the connection becomes strong enough. The main thing is not to use force, since it is easy to break the wire and then you will have to start all over again;
Cut off the ends of the wire with pliers and discard.

In the case of reinforcement of a columnar foundation, the reinforcement cage can be bent and then fixed to the heads with special clamps. Some manufacturers already supply metal or wooden piles with special clamping brackets and couplings. In this case, it is enough to bend the rod and insert it into the bracket. Clamp the bracket and boil it on top; you can do all this yourself, using a minimum of tools. In the case of using smooth reinforcement, the tying process is more labor-intensive, since the hooks will constantly bend and cannot be done without a specialized tool at hand, as well as without outside help.

It is better to knit the reinforcement cage for a slab monolithic foundation from several belts. For the horizontal tier, spiral rods with a cross-section of up to 16 mm are used, and for vertical links, smooth rods with a cross-section of up to 10 mm are used. When installing the lower mesh, it is recommended to use plastic expansion joints that will create a uniform pitch

Then, when knitting vertical rods, it is important not to forget to take them outside the foundation, due to the fact that load-bearing walls will be connected to them

Using plastic ties for knitting is a more expensive option for replacing wire, but clamps (ties) can be found in any household. The principle of tying is similar, but the plastic for the ties is less durable. Therefore, it is better not to use force during installation. The most popular clamps have a special core at the end of the tie; they are used to secure cables and pipes to vertical surfaces. Plastic showed excellent results when knitting with your own hands in warm weather; in cold weather it quickly loses its elasticity and bursts.

Knitting video:

Tape

A strip reinforced concrete foundation is the most difficult to reinforce: the essence remains the same, but the number of manipulations and the labor intensity of the frame formation process becomes more complicated. You can knit the frame either directly in the formwork (if its width allows) or separately (we knit and lower the structural element). It’s better to involve at least one assistant in the process - it will be much easier. The sequence of work can be represented as follows:

first, the required number of transverse rods of the selected length is laid with a calculated step between them (we remind you that the length of the rods should be 100 mm less than the width of the future tape - 50 mm on each side for the protective layer of concrete). For transverse rods, smooth reinforcement with a diameter of 6-8 mm is used;
then two longitudinal rods (ribbed reinforcement with a diameter of 12, 14 or 16 mm) are laid on the transverse reinforcement - the lower chord of the frame;
at the junction of the longitudinal and transverse rods, smooth reinforcement is mounted vertically, the length of which is 100 mm less than the height of the tape;
the upper transverse rods are tied to the “vertical” reinforcement (according to the same principle as in step 1);
then the working longitudinal reinforcement is laid on the upper transverse rods (two rods, as in step 2) - this will be the upper chord of the frame
do not forget to carefully tie each connection with wire. In some cases, if the frame will not be walked on while pouring concrete, you can tie it with plastic clamps - the kind that are used to bundle cables.

When using reinforcement clamps, the formation of the frame is somewhat simplified (see figure below).

The frame is installed on special attachments, concrete preparation, pieces of concrete, or any deformation-resistant polymer material. One of the most affordable options is to use pieces of PVC pipes or ordinary “ruble” socket boxes. Do not forget that the perpendicular tapes must be connected to each other by the releases of longitudinal reinforcement, previously bent with a special tool. Those. The longitudinal rods of one tape in the corner are connected by outlets with the longitudinal bars of the other, and the length of the outlets should be equal to 30 diameters of the reinforcement. This approach will make it possible to form a single rigid frame that will be ready for uneven deformations even in cases where they arise at the angles of the base of the house.

Important rules for tying reinforcement and basic SNiP

Before you start embroidering your future foundation with reinforcement or wire, you need to roughly calculate the load on it in order to decide what cross-section of rod you will need. You don’t need to know exactly, since they always take it with a reserve. For example, when building a temporary metal structure with a wall weight of up to 400 kg/1 m2, you can use reinforcement with a diameter of 8 millimeters. When building a cinder block garage with walls up to 3 meters in height, a rod with a cross-section of 12 millimeters is used. If you are building a two-story cottage, then you will have to embroider it with more serious metal - a diameter of 14-18 millimeters.

Of course, you can give this project to experienced specialists for calculations, who will save money and select the minimum acceptable value, but if a few thousand rubles do not play a big role, take it with a reserve. Often there is a desire to complete a floor with an attic or make a multi-level heavy roof - the foundation must be prepared for such a “turn of events.” There are several SNiPs that regulate the manufacture of this design. Let's take a closer look at them.

SNiP 7.3.4 states that the minimum distance between two vertical rods should be no less than the cross-section of the reinforcement itself, and preferably 2-3 times larger. The maximum value is not indicated, since it is selected individually for each project and depends on the masonry method, the presence of a sealant, the brand of cement, the quality of the aggregate and other factors.
SNiP 7.3.6. The distance between two parallel longitudinal rods should be no more than 40 centimeters. The greater the load on the base, the shorter this distance will be. The minimum distance for a strip foundation is 10 centimeters with a reinforcement diameter of 14 mm.
SNiP 7.3.7 regulates the spacing of transverse reinforcement. The value should be no more than half the working height of the section, but in no case should it exceed 30 centimeters.

By adhering to these SNiPs, you will get reinforcement according to “book standards”. But there are several rules that were developed specifically by builders to facilitate the process of establishing a foundation. These recommendations are time-tested and will significantly improve the physical and mechanical properties of your structure, as well as save a little on the purchase of materials.

You cannot weld fittings together. Heating the metal significantly worsens its properties, but there is no need for strong connections at all - they are held together by the concrete, not the metal that you will fuse for hours.
The reinforcement is subject to corrosion, so you need to deepen it on all sides into concrete so that it lasts for decades. On the sides, the metal should “go” into the concrete by at least 8 centimeters, from below by 10, from above by 10.
You cannot make cross joints at the corners; the rods should not intersect perpendicularly; it is better to take and bend the metal into the required shape so that the next joint is no closer than 100 centimeters from the corner. They always bear the heaviest load, and a connection on a short section of the site will not provide the required strength.
The corners should be additionally reinforced with crossbars and verticals. Very often, people simply do cross-stitching, believing that the mass will, for some reason, rest on the rod itself. But such a knitting of reinforcement for the base is simply unacceptable, because you will end up with 2 separate blocks that will not have any connection with each other. The sense of this action is exactly 0.0%. U-shaped and L-shaped reinforcements are needed at the corners and at the first crossbars from them.

We have discussed the basic rules of how to make high-quality foundation reinforcement, the diagram for which is located below. Now you can move on to the phased construction of this structure and analyze all the nuances in more detail.

Features of fittings

Since, for many reasons, it is quite difficult to accurately calculate the foundation, experts have developed recommendations for the reinforcement of the foundation strip.

They are like that:

the diameter of the longitudinal rods must be at least 12 mm;
the number of working rods in the frame must be at least four (maybe six);
The pitch of transverse reinforcement is from 200 to 600 mm. The cross-section of steel rods is 6-8mm;
The strip foundation should be at least 300 mm thick.

In the upper part of the foundation, which is subject to compressive forces, reinforcement of a smaller diameter can be laid than in the stretched lower part. After all, part of the loads at the top will be taken over by concrete

T-shaped intersections and places that may be subject to deformation must be reinforced with embedded products (for example, reinforcing haunches or tabs). They must match the diameter of the working rods.

How much reinforcement is needed for a strip foundation?

Reinforcement frame diagram with calculation of the length of the strip base

For calculations, you need to know several parameters of the future foundation. For example, the base parameters are as follows: width 3.5 m, length 10 m; height 0.2 m, width 0.18 m.

Calculation steps:

Calculation of the total volume of the casting. To do this, we take into account the volume of a typical parallelepiped, namely, we use all the parameters:

P = AB + BC + CD + AD = 3.5 + 10 + 3.5 + 10 = 27 V; 27 x 0.2 x 0.18 = 0.972.

Calculation of the internal volume of the foundation: 10 x 3.5 x 0.2 = 7 m³.

Subtract the volume of the casting: 7 – 0.97 = 6.03 m³.

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

Calculation of the amount of reinforcement. To facilitate calculations, the average metal diameter is assumed to be 12 mm.

The casting will have two horizontal chords, and the vertical rows will be spaced at 500 mm intervals. The perimeter of the strip foundation is 27 meters. Thus, you need to use 54 meters of horizontal rods and 114 rods of 0.5 meters each for vertical piping. Taking into account the factory configuration of the rods, 114 x 0.7 = 79.8 m of reinforcement will be needed for the vertical.

So, to build a strip foundation with these parameters, you need to use 1 cubic meter of concrete, 6 cubic meters of filler (sand and crushed stone), 134 meters of reinforcement, which will then need to be cut into specified pieces with a grinder. The volume of wood for formwork is not included in this calculation.

Technological process of reinforcement

Installation of formwork for arranging a reinforced frame of a strip base
First, the formwork is installed, the inner surface is covered with parchment or roofing felt.

Reinforcing bars with a calculated length and diameter of 10 mm are driven into the trench soil. Smooth rods can be used. The pitch between the vertical bars is 400 - 600 mm.

A stand is installed at the bottom, on which several rows of horizontal rods are arranged. The upper and lower rows are connected by longitudinal jumpers and tied together with wire or ties.

When erecting a frame, you must strictly adhere to the permissible distance to the foundation surface. There should always be a supply of concrete that will cover the ends of the rods and prevent corrosion processes inside the base.

After installing the frame, you need to provide ventilation holes at the bottom of the trench and fill the entire structure with concrete.

The principle of operation of the reinforcement cage

The quality of the frame affects the properties of the foundation

During construction on an industrial scale, the correct installation of the reinforced frame is monitored quite strictly. In this case, the integrity of reinforcement in foundations with a reinforced concrete frame is checked by special commissions, which are armed with collections of building standards and rules specially developed for this case.

However, when building a private house with your own hands, the developer does not always approach the reinforcement of the reinforced concrete foundation with full responsibility. The result is deformation and premature destruction of the base of the building, which often also entails the destruction of the entire structure.

Properties of concrete structures

To better understand the need for reinforcement of the base, you need to delve a little into such a complex subject as strength of materials. Any foundation of a building is subject to several multidirectional forces, and these forces are not constant, but change their magnitude, direction and place of application over time.

First of all, the mass of the building being erected presses on the concrete foundation, and this pressure force is not the same everywhere. No matter how hard you try to evenly distribute the mass of the house over the entire area of the foundation, you will not be able to do this - in some places the pressure will be stronger.

If the house stands on moisture-saturated soil, the deforming forces of “heaving” press on the concrete foundation from below in winter. Expanding when freezing, the soil begins to bulge onto the surface in the form of mounds, lifting and squeezing up the foundation elements. When the soil thaws in these places, swampy holes can, on the contrary, form, and entire sections of the foundation can simply hang in the air.

Concrete, being a fairly strong material, is not at all elastic - although it copes well with compression, it cannot work in tension and bending. Thus, the resistance of concrete to compression is 50 times greater than to rupture. This is manifested to a greater extent in the design of the strip base: due to its large length, it can have several bending or stretching zones. As a result, the concrete inevitably bursts and cracks, and the foundation of the building collapses.

Technical features of reinforced concrete

Reinforced concrete foundation combines the best qualities of metal and concrete

To avoid these significant disadvantages of concrete structures, a reinforced concrete foundation was invented. Improved technical characteristics were achieved by combining the best qualities of two building materials - concrete and metal. A supporting frame made of steel or fiberglass reinforcement is mounted inside the formwork, which is then filled with concrete.

As a result, reinforcement makes it possible to transfer tensile and bending loads to frame reinforcement, which copes with them much better than concrete.

Frame for columnar and slab foundations

For a foundation in the form of a flat slab, the assembly of the frame is much simpler, since it is performed in a horizontal plane. The assembly process itself is similar to a strip foundation.

The frame for the foundation pillars is made outside its installation location. For production it is possible to use various devices and special tools.

For small buildings, instead of volumetric frames in the foundation, it is possible to use reinforced surface belts to strengthen the building.

Design Features

The reinforcement frame for a strip foundation ensures the strength and reliability of the foundation of the building, preventing it from cracking and collapsing under the influence of loads and many negative factors. The choice of fittings is carried out at the project development stage. The service life of the building and its reliability depend on the quality of the selected grade. The preparatory stage includes several types of work, including:

conducting soil analysis;
determining the depth of groundwater;
calculation of the mass of the future building;
choosing the type of future foundation.

The fabrication of the reinforcement frame of the foundation is carried out both before the start of construction-related work and during its implementation.

This feature of the reinforcement bars used for strip foundations ensures reliable adhesion to the mortar used to fill the foundation. How durable the structure will be depends on several factors:

brand of metal rods used for installation;
cross section of rods;
range of fittings;
compliance with norms and rules while working on the diagram of the future frame;
the chosen method of fastening the rods.

A high-quality frame made of reinforcement will provide full resistance to compression of the structure.

Reinforcement of the foundation requires the use of metal rods with a cross-section of at least 12 and no more than 16 mm when installing the frame. The necessary strengthening of the structure is ensured by the use of class A 2 or A 3 rods, the strength characteristics of which guarantee the reliability and durability of the foundation and, accordingly, the entire building.

Reinforcing a strip foundation with your own hands cannot be called a very complex operation, but it must be carried out in a strictly established order and in compliance with all the subtleties of the technological process. This concerns the correct choice of rods to create the frame and the method of attaching them.

How to knit a frame correctly

So, how to properly make a reinforcement cage for a foundation?

The design drawings are studied in advance, since the operational life of the structure depends on the reliability of the foundation.

To avoid mistakes, it is recommended to follow certain rules while working:

minimum overlap - from five centimeters;
in corner areas, rods located perpendicularly are connected to each other. Blocks that are not connected to each other are prohibited from being used. An excellent option is corners prepared from bent reinforcement. This frame design is considered to be of higher quality. True, certain equipment will be required to bend rods whose cross-section exceeds fourteen millimeters;
if the connections are made with binding wire, they must differ in density. Using a special hook, the wire should be tightened until it stops, leaving no free spaces between the clamps and reinforcing bars. Be sure to check the clamp for mobility. If it is easy to move it by hand, it is necessary to perform an additional ligament;

the spacing between the reinforcing bars must correspond to the design drawings;
the reinforcement frame for a slab or other foundation in the formwork structure is installed evenly, the metal must be surrounded on all sides by a concrete solution that protects against corrosion;
The reinforcement is bent cold, without preheating, so as not to reduce the strength of the metal.

Basic criteria for choosing reinforcement for foundation construction

Reinforcement of the foundation is necessary primarily to prevent its rapid destruction and ensure its durability. The “correct” material for reinforcement, thanks to which the foundation of a house will last for decades, must meet clear requirements and standards. It must be corrosion-resistant, have high strength, fatigue life and ductility, and adhere well to concrete. In addition, to strengthen foundations, this material of a certain diameter and class is used.

The fittings existing on the modern building materials market come in two varieties - metal and non-metal. The first is made from special hot (rod) or cold (wire) rolled steel. Non-metallic is also called composite, since it is made from fibers of glass, basalt, carbon or aramid using thermoplastic or thermosetting polymer impregnation. In domestic construction, the first type of reinforcement is used more often than the second, due to the relatively recent introduction of the latter. Therefore, it is better to choose a “proven” option.

Corrugated fittings

According to the method of formation, wire, rod and rope reinforcement are distinguished. Its surface can be either smooth or corrugated (with a periodic profile). For the construction of foundations, rods with a ribbed surface are used, as they allow stronger adhesion to concrete. Round smooth reinforcement serves mainly as a structural element; its diameter should be smaller than that of profiled reinforcement.

The next parameter that you need to clearly know when choosing reinforcement is its thickness, or diameter. It can largely determine the strength of the reinforcement frame and, consequently, the foundation as a whole. The thickness of the reinforcing bars usually depends on the type of soil and the expected load on the foundation. Most often, products with a diameter of 8-16 mm are used, but it is better to choose at least 10 mm.

The type of fittings will also depend on where exactly it will be used. Thus, to prevent the occurrence of vertical cracks, longitudinal cracks are used, and for inclined cracks, transverse cracks are used. According to their purpose and areas of application, the following types of building reinforcement are also distinguished:

working - used to reduce external loads and reduce the stress exerted by the block mass;
distribution - as the name implies, it is used to distribute the load and maintain the stability of the working rods;
clamps – protect the concrete structure from the appearance of cracks at the supports, and are also used to tie together rods in the reinforcement frame;
mounting – necessary for assembling the reinforcement “skeleton”, supports steel bars in the desired position during concreting; produced in the form of a frame, structure or mesh;
piece - also used when assembling the frame, but on the condition that the amount of work is small.

Foundation reinforcement

Definition and scope

Typically, a distinction is made between volumetric and flat reinforcement frames (mesh). In addition, in the manufacture of the structure in question, two connection options can be used - by welding or using wire knitting.

In modern conditions, in order to meet the high requirements set by customers and regulatory documents, the use of reinforcing cages is carried out almost everywhere.

Thanks to such outstanding qualities, reinforcement cages have an extremely wide range of applications:

monolithic concrete works. When performing them, the use of reinforcement cages is almost always not only desirable, but mandatory, in accordance with the requirements of current regulatory documents;
Finishing work. Flat reinforcement cages are used when plastering to prevent the appearance of cracks as a result of mechanical damage or temperature changes. An additional advantage is the ease and ease of attachment to the wall surface;

masonry using bricks or various blocks. Reinforcing mesh in the masonry increases its strength and reliability of the wall structure;
installation of screeds and floor coverings in various rooms and buildings. Reinforcing mesh is often laid both during screeding and before laying some finishing floor coverings, such as ceramic tiles;

work on the construction of heating mains and pipelines. Reinforcement frames are easily and conveniently attached to a variety of thermal insulation materials, significantly increasing their strength and durability;
cladding with various finishing materials. The use of reinforcing mesh increases the adhesion of the wall surface and the cladding being performed.

The use of reinforcement cages is not limited to the areas listed above, but the examples given are enough to understand how often this type of reinforcement is used.

Frame design

Choose a metal profile of class A-400

Before you begin to install the frame, you should make a series of mathematical calculations. First of all, you should decide on the diameter of the steel bars and their number.

When creating a reinforced frame for a strip foundation of a building, steel reinforcement from a periodic profile of class A-400 is most often used. This rolled product has a special design, equipped with protrusions on the sides that spirally encircle the metal rod along its entire length. This design was specially designed for better adhesion of the reinforcing frame to concrete.

Fiberglass reinforcement

Recently, fiberglass reinforcement is increasingly used as a material for frames. Among the main advantages of fiberglass compared to steel are:

low weight;
corrosion resistance;
lower cost.

Among the disadvantages, it should be noted that the tensile strength is worse than that of standard steel reinforcement.

When creating a three-dimensional frame of a strip base, the reinforcement scheme looks like this: horizontally, along the future walls, threads of corrugated rolled steel run. They are arranged in several rows: both horizontally and vertically.

Between them there are transverse round rods connecting the longitudinal horizontal threads to each other.

Frame installation

Next, we will step by step consider the work on reinforcing the strip base. It is much more convenient to perform reinforcement before installing the formwork. In this case, the formwork will not interfere with your welding or knitting of a frame structure from individual elements.

The frame elements are rectangular volumetric structures of a certain length, which are laid in a trench dug for pouring the foundation. The length of these frame elements should be from one corner of the future building to the other. At the corners they are connected by special L-shaped connecting elements into one continuous frame structure. For more information about installing the frame, watch this video:

Preparatory work

Before you begin installing the frame, you should mark the site area and dig trenches in the right places along the perimeter of the future walls. At the bottom of the trench there should be a cushion of gravel, coarse sand or crushed stone. Our metal structure will be mounted on top of this pillow.

Such a pillow acts as additional protection against winter heaving of the soil, taking on a significant part of the pressure, and also plays the role of drainage, removing excess moisture from the concrete base.

Frame making

The frame must lie in the formwork in such a way that its longitudinal, “working” threads are completely hidden by concrete. The layer of concrete on top of the main reinforcement should be at least 2 - 3 cm. The standard width of strip foundations is 40 - 50 cm, respectively, our frame should be about 35 - 40 cm wide.

When starting to manufacture elements of a frame structure, first of all, we produce the required number of metal blanks. We cut the working reinforcement into pieces of the required length in the required quantity (depending on the number of threads).

We also cut transverse connecting elements from smooth round bars of smaller diameter than the working corrugated fittings. In this case, the width of the future foundation should be taken into account - the horizontal connecting elements should be equal in length to the width of the foundation.

Observe a clear arrangement of workpieces

Vertical connecting reinforcement must correspond to the height of the foundation. In this case, these pins, protruding beyond the longitudinal threads, will serve as a limiter for the formwork, allowing you to maintain the required distance between it and the working reinforcement of 2 - 3 cm.

After this, we proceed to welding or knitting flat blanks for future reinforcement.

We lay two threads of the corrugated rod parallel to each other and connect them to each other with transverse metal pins using a welding machine or knitting wire. In this case, a clear arrangement of the workpieces should be observed:

the pitch between the transverse connecting elements should be 20 - 30 cm;
the transverse pins should protrude beyond the edges of the future structure by 2 - 3 cm on each side.

Carrying out welding work requires a certain amount of experience, especially in such a matter as making a frame for the base of a building. If you are not sure of the quality of your welds, it is best to entrust this work to a specialist.

As a result, we get flat structures similar to metal ladders. The next step is to combine them into three-dimensional rectangular structures using vertical connecting pins. By welding or tying “ladders” with wire at certain distances to vertical pins, we obtain three-dimensional openwork structures, which are the main blanks for future reinforcement.

Assembling a single frame

The resulting volumetric elements are placed in trenches on top of a sand and gravel cushion. In this case, the frame should not lie on it - for high-quality reinforcement, it should be raised by 5 - 7 cm. For these purposes, we place stones or pieces of brick under it in several places.

The next step is to join all these individual elements located on straight sections of the trench. This can be done by using L-shaped clamps made from the same reinforcement as the horizontal threads. With their help, all adjacent horizontal threads of two adjacent frame elements are connected in pairs.

This is the final stage of reinforcing the reinforced concrete base of the building. After all the frame blanks are connected at the corners, you can begin installing the formwork and pouring concrete.

Features of fiberglass frame structures

When knitting fiberglass reinforcement, the step should be longer.
Fiberglass has appeared on our construction market relatively recently, so many developers are still prejudiced against this material. However, according to the technical qualities declared by the manufacturers, fiberglass is somewhat superior to steel in strength. Therefore, based on strength calculations, the step between structural elements in this case can be 1.5 times greater than when using metal reinforcement.

Rolled fiberglass for reinforcing reinforced concrete, like steel, is produced in two versions: smooth and corrugated. Their purpose is also similar: corrugated rolled steel is used as the main, working reinforcement, and smooth rolled steel is used to connect the main threads into one volumetric frame.

Using the tables and SNiP standards, you can independently carry out the work of arranging the reinforcement of the strip foundation of a private house. For high-quality production of a frame structure, you only need to strictly follow the recommendations of building regulations and the articles of the relevant GOSTs.

Pile bored

Perhaps, for a bored foundation, a reinforcement cage is the easiest to make. For its manufacture, 2, 3 or 4 reinforcement rods are used (their number depends on the diameter of the support) of a periodic profile with a diameter of 12 mm. The length of the reinforcement is equal to the length of the bored pile + 300-500 mm for reinforcement outlets, subject to subsequent tying with a reinforced concrete grillage. To avoid shearing forces or eccentric loads, the frame is tied using round or triangular clamps. You can use factory-made triangular-section frames, which are used in the production of monolithic floor beams.

Slab

The frame for a slab foundation consists of two reinforcing meshes, the distance between which is determined based on the selected slab thickness. Each such mesh is a collection of longitudinal and transverse rods of the same cross-section (12-14 mm). Ribbed reinforcement is used to ensure maximum contact with the concrete mixture. The distance between two reinforcing meshes is maintained by jumpers, which can be made from metal corners, scraps of PVC pipes, sand-cement tiles - any materials that are not subject to rotting and are resistant to heavy loads. It is advisable to refrain from using wood. When making a frame for a slab base, as in other cases, be sure to leave space for a protective layer of concrete (50 mm): on top, bottom, on the sides.

Weldability

You can buy high-quality reinforcement cages if all the elements are securely connected, which is achieved when the metal meets the requirements of the work being carried out. The weldability of workpieces can be assessed using a special table:

group I has good weldability. This means that the maximum quality of seams can be achieved without the use of any special means and methods;
group II is characterized by satisfactory weldability. To create a high-quality reinforcement frame, it is necessary to strictly comply with a whole set of technical requirements. These include the use of additives, high-quality edge cleaning, optimal temperature up to heating the welding site to 100-150 degrees for some methods;
group III, limited weldability. Under normal connection conditions, such grades of metal give multiple cracks. To carry out work at the proper level, warming up to 250-400 degrees and vacation are necessary;
group IV is characterized by poor weldability. This means that it will be difficult to achieve a high-quality connection of the reinforcement frame, even if all techniques are followed, including preheating and temperature treatment at all stages of manufacturing the structure.

These aspects do not change regardless of what systems are intended to be created, be it reinforcement frames for bored piles or reinforcement frames for a wall in the ground.

Spatial reinforcement frame for the foundation in a few minutes

It takes a lot of time to manufacture a spatial frame from iron reinforcement. This is due to the fact that reinforcement with a diameter greater than 6 mm is almost never supplied in meshes, since it is very heavy and carrying it to the construction site is not a very pleasant task. Therefore, builders have to knit reinforcement at a construction site, which is quite time-consuming and expensive. But technology does not stand still; for more than 10 years, fiberglass reinforcement has been widely used in the domestic market for reinforcing concrete structures; GOST, the Code of Rules and other regulatory documents on the use of composite reinforcement have been approved.

Recently another pleasant new product has appeared - the BASIS . It consists of fiberglass or basalt plastic rods made in accordance with GOST 31938-2012, connected to each other at the intersection points with a special thermoplastic material.

BASIS mesh is needed for concrete reinforcement instead of traditional metal reinforcement. The connection of fiberglass rods into a mesh is carried out using patented technology. The thermoplastic that connects the rods together acts as a stool and forms a protective layer in the concrete.

The rod from which the BASIS is covered with sand, which significantly increases adhesion to concrete and increases the crack resistance of the structure, compensating for the low modulus of elasticity of the composite.

The main advantage of the mesh is that it is connected into ready-made cards that do not need to be knitted on the construction site; in addition, it has a number of advantages over metal:

9 times lighter
3 times stronger tensile strength
Speeds up the reinforcement process 7 times (no need to knit on site)
20% cheaper
No need for “chairs” for a protective layer
High corrosion resistance
Low thermal conductivity

In fact, BASIS opens up a new market segment, since the mesh consists of a rod up to 10 mm thick, it is suitable for reinforcing heavy structures, such as bridge decks, road slabs, floors with high loads, foundations of various structures.

The composite mesh is produced in cards measuring 2.2x6 m, while it is possible to produce cards of other sizes with a width of no more than 2.4 m and a length of no more than 6 m.

The BASIS composite mesh does not require the installation of linings to form a protective layer.

Unloading and laying of the mesh is carried out manually, without the involvement of machinery.

Cutting cards can be done with a grinder using a stone disc.

Replacement table with metal by strength

Composite BASIS	Metal AIII
4	8
6	10
8	12
10	14

It’s also very quick and convenient to make spatial frames from the BASIS mesh; it looks like this:

We take one BASIS card and two stripes as in the photo below

We connect the strips with a house and fasten them with ties

We repeat the operation several times, the recommended distance between the “houses” is 100-120 cm.

Then cover with another BASIS card on top

We get such a wonderful frame

You can safely walk on it when pouring concrete.

The frame straightens

The BASIS frame can now be easily lifted

and move to the place of concrete pouring, the weight of the spatial frame is no more than 20 kg