How to knit reinforcement for a foundation: the best ways. Subtleties of the process of reinforcing a strip foundation How to use a crochet hook for crocheting reinforcement

Any building cannot do without a reliable and strong foundation. Construction of the foundation is the most important and time-consuming stage. But in this case, all rules and requirements for strengthening the foundation must be observed. For this purpose, a strip foundation is erected, which can make the foundation of the structure strong and reliable. It is worth considering in more detail the features of the strip foundation, as well as the technology for reinforcing the structure.

Peculiarities

The strip foundation is a monolithic concrete strip without breaks at doorways, which becomes the basis for the construction of all walls and partitions of the structure. The basis of the strip structure is a concrete mortar, which is made from M250 cement, water, and sand mixture. To strengthen it, a reinforcement frame is used, made of metal rods of different diameters. The tape goes deep into the soil a certain distance, while at the same time protruding above the surface. But the strip foundation is subject to serious loads (groundwater movement, massive structure).

In any situation, you need to be prepared for the fact that various negative influences on structures can affect the condition of the foundation. Therefore, if the reinforcement is not done correctly, at the first slightest threat the foundation may collapse, which will lead to the destruction of the entire building.

Reinforcement has the following advantages:

prevents soil subsidence under the building;
has a positive effect on the soundproofing qualities of the foundation;
increases the stability of the foundation to sudden changes in temperature conditions.

Requirements

Calculations of reinforcing materials and reinforcement schemes are carried out in accordance with the rules of the functioning SNiPA 52-01-2003. The certificate has specific rules and requirements that must be met when reinforcing strip foundations. The most important indicators of the strength of concrete structures are the coefficients of resistance to compression, tension and transverse fracture. Depending on the established standardized indicators of concrete, a specific brand and group is selected. When reinforcing a strip foundation, the type and controlled quality indicators of the reinforcing material are determined. According to GOST, the use of hot-rolled construction reinforcement of a repeating profile is allowed. The reinforcement group is selected depending on the yield strength at extreme loads; it must have ductility, resistance to rust and low temperature indicators.

Kinds

To reinforce the strip foundation, two types of rods are used. For axial ones that carry a key load, class AII or III is required. In this case, the profile should be ribbed, because it has better adhesion to the concrete solution, and also transfers the load in accordance with the norm. For superstructural lintels, cheaper reinforcement is used: smooth class AI, the thickness of which can be 6–8 millimeters. Lately, fiberglass reinforcement has become in great demand, because it has better strength properties and long service life.

Most designers do not recommend using it for residential foundations. According to the rules, these must be reinforced concrete structures. The features of such building materials have long been known. Specialized reinforcing profiles have been developed that help ensure that concrete and metal are combined into an integral structure. How concrete will behave with fiberglass, how reliably this reinforcement will be connected to the concrete mixture, and whether this pair will successfully cope with various loads - all this is little known and practically untested. If you want to experiment, you can use fiberglass or reinforced concrete reinforcement.

Calculation

The consumption of reinforcement must be carried out at the stage of planning the foundation drawings, in order to know with accuracy in the future how much building material will be required. It is worth familiarizing yourself with how to calculate the amount of reinforcement for a shallow foundation 70 cm high and 40 cm wide. First, you need to establish the appearance of the metal frame. It will be made of upper and lower reinforced belts, each with 3 reinforcing rods. The gap between the rods will be 10 cm, and you also need to add another 10 cm for a protective concrete layer. The connection will be made by welding sections of reinforcement of identical parameters in increments of 30 cm. The diameter of the reinforcement product is 12 mm, group A3.

Calculation of the required amount of reinforcement is carried out as follows:

to determine the consumption of rods on the axial belt, you need to calculate the perimeter of the foundation. You should take a symbolic room with a perimeter of 50 m. Since there are 3 rods in two armored belts (6 pieces in total), the consumption will be: 50x6 = 300 meters;
Now you need to calculate how many connections are required to join the belts. To do this, it is necessary to divide the total perimeter by the step between the jumpers: 50: 0.3 = 167 pieces;
observing a certain thickness of the enclosing concrete layer (about 5 cm), the size of the perpendicular lintel will be 60 cm, and the axial lintel - 30 cm. The number of separate types of lintels per connection is 2 pieces;
you need to calculate the consumption of rods for axial jumpers: 167x0.6x2=200.4 m;
consumption of products for perpendicular jumpers: 167x0.3x2=100.2 m.

As a result, the calculation of reinforcing materials showed that the total amount to be consumed would be 600.6 m. But this number is not final; it is necessary to purchase products with a reserve (10–15%), since it will be necessary to strengthen the foundation in corner areas.

Scheme

The constant movement of soil puts serious pressure on the strip foundation. In order for it to firmly withstand such loads, and also eliminate the sources of crack formation at the planning stage, experts recommend taking care of the correctly chosen reinforcement scheme. The foundation reinforcement scheme is a specific arrangement of axial and perpendicular rods, which are assembled into a single structure.

SNiP No. 52-01-2003 clearly discusses how reinforcing materials are laid in the foundation, with what steps in different directions.

It is worth considering the following rules from this document:

the step of laying the rods depends on the diameter of the reinforcement product, the dimensions of the crushed stone granules, the method of laying the concrete solution and its compaction;
working hardening step is a distance that is equal to two cross-sectional heights of the reinforcing tape, but not more than 40 cm;
transverse strengthening - this distance between the rods is half the width of the section itself (no more than 30 cm).

When deciding on the reinforcement scheme, it is necessary to take into account the fact that the frame assembled into one piece is mounted into the formwork, and only the corner sections will be tied inside. The number of axial reinforced layers must be at least 3 along the entire contour of the foundation, because it is impossible to determine in advance the areas with the heaviest loads. The most popular are schemes in which the reinforcement is connected in such a way that cells of geometric shapes are formed. In this case, a strong and reliable fundamental foundation is guaranteed.

Work technology

Reinforcement of strip foundations is carried out taking into account the following rules:

for functioning fittings, rods of group A400 are used, but not lower;
experts do not recommend using welding as a connection, since it blunts the cross-section;
at the corners, the reinforcement is necessarily tied, but not welded;

It is not allowed to use threadless fittings for clamps;
it is necessary to strictly implement a protective concrete layer (4–5 cm), because it protects metal products from corrosion;
when making frames, the rods in the axial direction are connected with an overlap, which should be at least 20 rod diameters and at least 25 cm;
when placing metal products frequently, it is necessary to maintain the size of the aggregate in the concrete solution; it should not get stuck between the rods.

Preparatory work

Before starting work, it is necessary to clear the work area of various debris and interfering objects. Using pre-prepared markings, a trench is dug, which can be done manually or using specialized equipment. To ensure that the walls are perfectly level, it is recommended to install formwork. Basically, the frame is placed in a trench along with the formwork. After this, concrete is poured, and the structure must be waterproofed using roofing felt sheets.

Methods of knitting reinforcement

The scheme for strengthening the strip foundation allows the connection of rods using the tying method. The bonded metal frame has increased strength compared to the welded version. This is explained by the fact that the risk of burning through metal products increases. But this does not apply to factory products. To speed up the work, it is allowed to perform reinforcement in straight sections by welding. But reinforcement of corners is carried out only with the use of binding wire.

Before knitting the reinforcement, you need to prepare the necessary tools and building materials.

There are two ways to bind metal products:

specialized hook;
knitting machine.

The first method is suitable for small volumes. Laying reinforcement in this case will take too much time and effort. Annealed wire with a diameter of 0.8–1.4 mm is used as a connecting material. The use of other building materials is prohibited. The reinforcement can be tied separately and then lowered into the trench. Or tie the reinforcement inside the pit. Both methods are rational, but there are some differences. If you make it on the surface of the earth, you can do it yourself, but in a trench you will need an assistant.

How to properly tie reinforcement in the corners of a strip foundation?

For corner walls, several bonding methods are used.

With a paw. To carry out the work, a foot is made at the end of each rod at an angle of 90 degrees. In this case, the rod resembles a poker. The size of the foot must be at least 35 diameters. The bent section of the rod is connected to the corresponding vertical section. As a result, it turns out that the outer rods of the frame of one wall are connected to the outer ones of the other wall, and the inner ones are connected to the outer ones.

Using L-shaped clamps. The principle of execution is similar to the previous variation. But here you don’t need to make a foot, but take a special L-shaped element, the size of which is at least 50 diameters. One part is tied to the metal frame of one wall surface, and the second to the vertical metal frame. In this case, the internal and external clamps are connected. The spacing of the clamps should be ¾ of the height of the basement wall.

Using U-shaped clamps. For the corner you will need 2 clamps, the size of which is 50 diameters. Each of the clamps is welded to 2 parallel rods and 1 perpendicular rod.

How to properly reinforce the corners of a strip foundation, see the following video.

How to perform reinforcement at obtuse angles?

To do this, the outer rod is bent to a certain degree value and an additional rod is attached to it to qualitatively enhance the strength. Internal special elements are connected to the external one.

How to knit a reinforcing structure with your own hands?

It is worth taking a closer look at how reinforcement is knitted on the surface of the earth. First, only straight sections of the mesh are made, after which the structure is installed in the trench, where the corners are reinforced. Reinforcement sections are being prepared. The standardized size of the rods is 6 meters; if possible, it is better not to touch them. If you don’t have confidence in your own abilities that you can cope with such rods, they can be cut in half.

Experts recommend starting to knit reinforcing bars for the shortest section of the strip foundation, which makes it possible to acquire certain experience and skill, and in the future it will be easier to cope with long structures. It is undesirable to cut them, because this will lead to an increase in metal consumption and reduce the strength of the foundation. The parameters of the workpieces should be considered using the example of a foundation, the height of which is 120 cm and the width is 40 cm. The reinforcement products must be filled on all sides with concrete mixture (thickness about 5 cm), which is the initial condition. Taking these data into account, the net parameters of the reinforcing metal frame should be no more than 110 cm in height and 30 cm in width. For knitting, you need to add 2 centimeters from each side, this is necessary for the overlap. Therefore, blanks for horizontal jumpers should have a size of 34 centimeters, blanks for axial jumpers - 144 centimeters.

After calculations, the knitting of the reinforcing structure occurs as follows:

you should choose a flat piece of land, put two long rods, the ends of which need to be trimmed;
At a distance of 20 cm from the ends, horizontal struts are tied along the outer edges. For tying, you will need a 20 cm wire. It is folded in half, pulled under the tying area and tightened with a crochet hook. But it is necessary to tighten it with care so that the wire does not break off;
at a distance of about 50 cm, the remaining horizontal struts are tied alternately. When everything is ready, the structure is removed to a free place and another frame is tied in an identical way. As a result, you will get the upper and lower parts, which need to be connected to each other;
Next, you need to install stops for the two parts of the mesh; you can rest them against various objects. The main thing is to ensure that the associated structures have a reliable profile arrangement; the distance between them should be equal to the height of the associated reinforcement;

At each end two axial struts are tied, the parameters of which are already known. When the frame product resembles a finished device, you can begin tying the remaining pieces of reinforcement. All procedures are carried out with checking the dimensions of the structure, although the workpieces are made of the same dimensions, an extra check will not hurt;
Using a similar method, all other straight sections of the frame are connected;
A gasket is placed at the bottom of the trench, the height of which is at least 5 cm; the lower part of the mesh will be laid on it. Side supports are installed, the mesh is mounted in the correct position;
The parameters of unconnected joints and corners are taken, and sections of reinforcement products are prepared for connecting the metal frame to the overall system. It is worth noting that the overlap of the ends of the reinforcement should be at least 50 bar diameters;
the bottom turn is attached, then the perpendicular posts and the top turn is tied to them. The distance of reinforcement to all sides of the formwork is checked. The strengthening of the structure ends here; now you can proceed to pouring the foundation with concrete mixture.

Knitting reinforcement using a specialized device

To make such a mechanism, you will need several boards 20 millimeters thick.

The process itself looks like this:

4 boards are cut according to the size of the reinforcement product, they are connected in 2 pieces at a distance equal to the pitch of the vertical posts. The result should be two boards of an identical pattern. It is necessary to ensure that the marking of the distance between the slats is the same, otherwise the axial arrangement of the connecting special elements will not work;
2 vertical supports are made, the height of which should be equal to the height of the reinforcing mesh. The collections must have profile corner supports that will prevent them from tipping over. The finished structure is checked for strength;
The legs of the support are installed on 2 nailed together boards, and the two outer boards are placed on the top shelf of the supports. Fixation is performed using any convenient method.

As a result, a model of the reinforcing mesh should be formed; now the work can be carried out without outside help. Vertical braces of the reinforcement product are installed in the planned areas, and their position is fixed in advance using ordinary nails for a certain time. A reinforcement rod is installed on each horizontal metal lintel. This procedure is performed on all sides of the frame. If everything is done correctly, you can start knitting with wire and hook. The design must be made if there are identical sections of mesh made of reinforcement products.

Knitting reinforced mesh in trenches

Carrying out work in a trench is quite difficult due to the tightness.

It is necessary to carefully consider the knitting pattern for each special element.

Stones or bricks no more than 5 cm high are placed at the bottom of the trench; they will lift the metal products from the surface of the earth and allow the concrete to cover the reinforcement products on all sides. The distance between the bricks should be equal to the width of the mesh.
Longitudinal rods are placed on top of the stones. Horizontal and vertical rods must be cut to the required parameters.

They begin to form the base of the frame on one side of the foundation. The work will be easier if you tie horizontal struts to the lying rods in advance. An assistant must support the ends of the rods until they are mounted in the desired position.
The reinforcement is knitted alternately, the distance between the spacer elements must be at least 50 cm. The reinforcement is tied in a similar way on all straight sections of the foundation tape.
The parameters and spatial location of the frame are checked, if necessary, it is necessary to correct the position, and also to prevent metal products from touching the formwork.

You should familiarize yourself with the repeated mistakes that inexperienced craftsmen make when performing reinforcement without following certain rules.

Initially, it is necessary to develop a plan according to which further calculations will be performed to determine the load on the foundation.
During the manufacture of the formwork, no gaps should be formed, otherwise the concrete mixture will flow out through these holes and the strength of the structure will decrease.
The soil must be waterproofed; in its absence, the quality of the slab will decrease.
It is prohibited for the reinforcing bars to come into contact with the soil; such contact will lead to rust.

If you decide to reinforce the frame by welding, then it is better to use rods with index C. These are specialized materials that are intended for welding, so they do not lose their technical characteristics under the influence of temperature conditions.
It is not recommended to use smooth rods for reinforcement. The concrete solution will have nothing to fasten to, and the rods themselves will slide in it. When the soil moves, such a structure will crack.
It is not recommended to arrange corners by direct intersection; reinforcement products bend very hard. Sometimes, when reinforcing corners, they come up with tricks: they heat the metal product to a pliable state, or use a grinder to saw down the structure. Both options are prohibited, because with these procedures the material loses its strength, which will lead to negative consequences in the future.

Increasingly, in the construction of private houses and other objects, monolithic foundation slabs for the entire house or floor slabs are used, which are cast directly on the construction site. The reason for this is practicality, reduced construction costs, as well as the high performance characteristics of monolithic reinforced concrete structures.

If the design of the house and the slab is calculated by the designers, and the concrete is supplied from the factory, then the most responsible work falls to the builders - tying the reinforcement of the monolithic foundation and floor slab and pouring it. It is the quality of workmanship that lays the foundation for the strength and durability of the structure.

Concrete itself is fragile; it is impossible to construct a slab of large area or length from it without cracking even under its own weight, and without requiring an increase in its thickness. Reinforcement with steel or polymer reinforcement helps to complement the properties of concrete, from which the skeleton of the future structure is made.

Reinforcement - steel or polymer rods mixed with glass or basalt fiber provide the monolithic slab with elasticity and significant freedom of deformation without destruction of the concrete.

The reinforcement holds the slab under lateral forces, which constitute the lion's share of the entire payload.

A skeleton, a frame for future reinforcement, is assembled from rods of strictly calculated thickness. This is one or more planes in which segments of reinforcement are laid crosswise and form a grid. The planes, if there are several of them, are tied together with transverse vertical posts.

This entire structure is completely filled with concrete using formwork so that the minimum distance from any edge of the slab to the internal reinforcement is at least 20 mm. The last requirement primarily applies to steel reinforcement.

Ferrous metal is used, which in the presence of oxygen and water vapor begins to rust, which is why reinforcement in monolithic slabs is not allowed to come out, with the exception of specially prepared embedded elements.

The design of the reinforcement, materials, spacing of rods, and cell size are determined by the designer based on the distribution and magnitude of the load that will act on the slab. The determining factors are the option of supporting the slab on walls or soil, constant loads in the form of partitions or stationary equipment, and so on.

The diameter of the reinforcement is selected for each section and for places where additional reinforcement is required, the method of knitting the frame and permissible deviations are determined. The last two points must be checked in accordance with the requirements of the standards.

SNiP and GOST requirements

wiring diagram and device

Regarding the construction of monolithic buildings, foundation slabs and floors, there are standards and requirements that cover almost all possible options for using concrete monolithic structures and elements.

The two key documents for reinforced slabs are:

SNiP 3.03.01-87;
GOST 10922-2012.

They stipulate the grades of concrete, the process of preparing the formwork site, options for binding and assembling the reinforcing frame and reinforcements, and the procedure for installing embedded elements.

Actually, there are no special instructions regarding the design of reinforcement, since calculations are performed individually in each project based on the assigned tasks.

The standards specify especially strictly the permissible deviations from the dimensions and distances between the reinforcement bars established by the project.

There are several rules for tying reinforcement for monolithic slabs:

In one plane, cross reinforcement must be laid in strict accordance with the spacing established by the project.
Tying of reinforcement at all intersections is carried out only along the perimeter of the entire structure and along the boundaries of reinforcement, embedded elements or prepared openings. In the rest of the volume of the reinforcing frame, the intersections are knitted in a checkerboard pattern.
When laying several layers of reinforcement, co-directed rods are shifted relative to each other so that in the upper projection the rods of one row are located between the rods of the second.
The key requirement of SNiP concerns the joining of reinforcement. An overlap with a length of 35d to 75d is necessarily formed, where d is the diameter of the reinforcement used.
At the point of overlap, bandaging is carried out several times with a distance of no more than 10 cm to impart rigidity and strength to the frame, especially if it is first assembled on a prepared site and then transported to the installation site.

Knitting step

The usual step for distributing reinforcement under a monolithic slab is 150x150 mm or 200x200 mm, however, there may be deviations from these dimensions depending on the requirements of the design documentation.

Reinforcement tying can be done at all intersections, however, it is enough to perform it in a checkerboard pattern with offsets in different planes and only along the perimeter at each intersection.

Technology

Welding of reinforcement is rarely used and only in exceptional cases during the construction of large monolithic structures.

It is important to know that welding at the connection point of the reinforcement weakens the material, makes it unstable to loads and exposes it to an additional risk of accelerated corrosion.

In private and low-rise construction, the only option left is to tie the reinforcement with wire or other mechanical fastening materials.

For tying reinforcement the following is used:

Special baked steel wire with a diameter of 0.8 to 1.5 mm. Annealing the wire gives it toughness and softness, due to which it can be twisted and tied even by hand;
Ready-made clamps made of unfired steel wire for cross-connecting reinforcement;
Polymer clamps and ties.

Annealed knitting wire has become more widespread, but more as a historical fact, it is polymer clamps or ready-made spring-loaded steel wire clamps that can speed up the knitting process.

The task of tying the reinforcement frame is as follows:

The boundaries of the future monolithic slab are marked along the prepared site, indicating all boundaries and angles. Next, bosses are laid - special clamps, supports, on which the first layer of reinforcement is laid out in order to maintain a given distance from the lower boundary of the slab being poured, so that the reinforcement is completely covered with concrete;
The reinforcement is laid first in one direction, with obligatory overlap at the points where the reinforcement is made to cover the entire length;
Transverse vertical elements are distributed to connect with subsequent layers of reinforcement;
Knitting is performed at all points of triple intersection, where there are vertical transverse drains, along the entire perimeter of the reinforcement and inside in a checkerboard pattern or at each intersection;
Next, bosses are installed for the second row of reinforcement. The entire procedure is repeated, only on the condition that the checkerboard knitting pattern in the central part of the slab will be shifted diagonally relative to the first row.

Crochet

The simplest and most accessible knitting option. A hook made of thick, strong steel wire (even a slate nail) of a special shape is used. The end of the hook is pointed, the bend of the hook itself has a turning diameter of approximately 3 cm and an end extension of 3-4 cm.

The handle of the hook is made rotary and shifted relative to the hook to the side so that they are not located on the same axis.

You can make a crochet hook yourself, but it is better to purchase a ready-made tool at any hardware store.

The purchased version will be stronger, more reliable and incredibly more convenient, since a convenient ergonomic shape of the tool and a grip option have long been found so that the hand does not get tired.

For knitting, a piece of wire about 20-25 cm is used. It is folded in half and then bent again in the middle at an angle of 90 degrees. The result is a curved hook on one side with a loop and two free ends on the other side.

The wire is hooked under the intersection or overlap of the reinforcement. The hook is inserted into the loop on the wire so that its tip catches on the second end. If you twist the hook around the axis several times, the ends of the wire twist and tighten the loop around the reinforcement.

The last step is to bend the protruding piece of wire towards the plane of the frame, so that in no case does it protrude beyond the limits of the harrowing volume. If this is not done, the protruding metal will rust over time, which will affect the strength of the slab and will even show through further finishing.

As an improvement to crochet, other options are used:

The hook is made with a straight base and is clamped in a screwdriver chuck or drill with a force limiter. By inserting the hook into the loop of the wires, you can quickly twist and tighten it, while focusing on the force on the screwdriver limiter. This will speed up the knitting process by about half;
Semi-automatic hooks for knitting reinforcement are available for sale. This is a hook made of steel wire, mounted on a thick cylindrical shaft, which has a special spiral thread with a large angle of inclination. The handle is designed specifically for this thread. By hooking the hook onto the loop and pulling the handle towards you, the shaft rotates around the axis, tightening the wire.
It is noteworthy that the knitting is more accurate than in previous versions due to stable tension. However, users complain about the short service life of such semi-automatic hooks.

With a pistol

Even the binding of reinforcement has already been fully automated. Wrap the intersection of the reinforcement with wire, pull the ends together and twist them; this can be done in 0.5-0.8 seconds if you use a special gun.

The wire for tying is fed from the reel to special gripping claws, which rest against the crosshairs of the reinforcement. Next, just pull the trigger and in a split second the mating is completed.

The shape and repeatability of the pistol's knitting is ideal. The tension force and wire consumption are adjustable, so this approach has no disadvantages, except for the high cost of the equipment itself.

The gun will cost the contractor or owner of the house being built approximately 35-50 thousand rubles. If necessary, you can find stores or companies that can offer a pistol for rent, which will be much more economical.

All work on knitting a frame for a monolithic slab performed with a gun an order of magnitude faster than manually. In fact, what a team of workers with hooks can do in 10 days, one person can do with a gun in one shift.

Wire clamps

The main task is not to firmly fasten the reinforcement, but to hold it in place without moving before pouring concrete.

Instead of burnt wire, you can use prepared clamps. They are made from springy steel wire up to 2 mm thick.

The wire is wrapped around two pipes with a diameter slightly larger than the fittings. The result should be a clamp in the form of a segment folded in half with two free edges bent around the circumference.

It is enough to hook one of the rods at the intersection with a wire and, bending it over the transverse reinforcement, hook it again to the first rod. There are ready-made forms for clamps in case of triple intersection and for overlapping reinforcement.

Plastic ties

It is not at all necessary to use steel wire and crochet it or use wire cutters. Plastic ties ranging from 50 mm to a meter in length are already widespread and available everywhere, which are easily tightened by hand and at the same time provide a reliable fixation.

It is better to wrap long ties once on each side of the crosshair reinforcement and then tighten it, but even a diagonal girth is sufficient in strength. The ideal solution would be plastic ties when reinforcing a monolithic slab with polymer reinforcement.

Price

The work of knitting a frame from reinforcement for pouring monolithic foundation and floor slabs is assessed separately from the general work of arranging formwork or pouring and maintaining concrete.

On average, the cost of manual knitting work can cost either 40% of the cost of the reinforcement, or in the range from 3,500 to 7,500 thousand rubles. per ton of reinforcement.

The price greatly depends on the design of the frame and its complexity, so professional installers will be able to provide detailed prices only after visiting the site and reading the design documentation.

Do-it-yourself reinforcement tying includes the cost of tying wire and tools. An important factor is the time spent on work.

So, if you use a gun, you can handle it in one shift or several, but the cost of even renting a tool will not be cheap. It will take about two to three times more wire. But the result will be of the highest quality.

For a monolithic slab, tying reinforcement is much simpler than for a strip foundation. The meshes are created from rods on the construction site; to work you need an angle grinder with a metal disc, a tying device or a cordless tool.

Technology for manufacturing reinforcing mesh for a foundation slab

Knitting reinforcement begins with the purchase of metal, the amount of which must first be calculated with the minimum possible margin. For the reinforced belt of the slab, it is necessary to take into account the following factors:

To create the lower protective layer, exclusively concrete or polymer pads are used. It is forbidden to lift the mesh with pieces of reinforcement, pipes, or lay crushed stone or brick.

Calculation of the amount of reinforcement

The reinforcement is knitted according to a standard pattern; calculating the number of rods is quite easy:

standard length of reinforcing bars 6 m
0.4 – 0.6 m overlap in joints
minus 8 cm for each rod for a protective layer of concrete
cell 15 x 15 cm or 20 x 20 cm
as the thickness of the slab increases, the cell decreases, the rods become thicker

It is more difficult to take into account the configuration of Z-shaped tables made of 6 - 8 mm reinforcement to support the upper chord. The upper U-shaped part usually measures 20 x 40 x 20 cm for a 30 cm slab. The support legs are about 40 cm on each side. One table requires 1.6 m of smooth reinforcement, their quantity is calculated depending on the project.

Thus, the number of rods is determined by the formula:

Then it remains to take into account that there are two armored belts in the design, with overlaps when connecting. In principle, there can be no problems with converting lengths into kilograms - every construction market has a conversion table. You can also buy knitting wire there, knowing the number of joints and the length of the piece for each of them (30 cm - twice 15 cm).

The most popular wire is 1.2 - 1.4 mm for 8 - 12 mm rods, respectively. Thicker wire is more difficult to form into a knot; the twists stick out above the upper reinforced belt, reducing the protective layer of concrete. Thin wire rod is easier to work with, but it can break when the torque increases. The margin recommended by experts is 15%, both for reinforcing bars and wire. For smooth fittings from which the tables will be bent, a 10% margin is sufficient.

Bar cutting

It is more convenient to cut the reinforcement using a template. Separately, longitudinal pieces of two meshes and transverse rods of structures are cut. For large formwork dimensions, pieces are cut out for extension, taking into account a 60 cm overlap, and screwed with wire to the long elements of the slab.

The most economical is cutting with abrasive equipment. An angle grinder with a metal disc can easily cope with fittings of any diameter. In addition, this is the most affordable power tool for an individual builder. At the same stage, it is easiest to clean the fittings from possible rust. This will be much more difficult to do later.

Making stands

To support the upper mesh made of reinforcement, stands - tables are needed. They are bent taking into account the thickness of the slab and reinforcement. For example, for a 40 cm monolithic structure, the calculation looks like:

slab thickness – two protective layers – thickness of the upper and lower mesh rods (4 overlapping rods)
40 cm – (4 cm+4 cm) – (4 x 1 cm) = 28 cm

Then you need to make a table, calculate the bending radius or calculate it experimentally. First, the U-shaped structure is bent, then the legs are bent in opposite directions. The table acquires spatial rigidity and a large supporting surface.

Installation of the lower mesh

The best option for fixing reinforcement bars to each other is knitting with annealed wire. Depending on the budget and volume, work can be carried out using several tools:

To reinforce one large-format slab, individual developers can use a screwdriver with a regular hook, partially mechanizing the process, and avoiding the cost of purchasing a professional binding gun. In this case, the handle will have to be cut off so that the hook can be inserted into the quick-release chuck.

When working with a conventional mechanical hook, the wire is wound manually by the operator. The cordless gun does everything on its own; the purchase budget is 40 thousand rubles for the most budget models. Therefore, a mechanical tool is more often used, costing 500 - 700 rubles, or a regular hook, which is even cheaper.

The technology for knitting a mesh of reinforcing bars is as follows:

layout of reinforcement along one wall every 15 - 20 cm depending on the cell size
laying out the rods on top of them with a similar step
knitting overlapping joints with special wire

A piece of 30 cm wire is bent in half, the resulting structure is additionally bent in half and placed under the joint where the rods intersect diagonally. The hook tip is inserted into the loop, the free side goes around the rod. By rotating (usually clockwise), the wire is tightened at the junction of the reinforcing bars, giving the spatial structure the necessary strength.

In the manual method, the tightening force is controlled by a wire tensioner. If a mechanical device is used, the torsional moment is more difficult to determine (usually a visual assessment). When using a screwdriver, you can set the required tightening force (21 - 9 positions in different models). The cordless rebar tying gun also has torque adjustments.

Installing the top chord

Before laying the upper chord of reinforcement, it is necessary to place tables on the lower grid. They are installed according to the following scheme:

the support legs rest on two rows of rods
the top shelf is parallel to the bars of the covering mesh or located diagonally
the legs are connected with wire to two adjacent rows of rods
the top shelf is fixed with wire in at least two places to the top mesh

In practice, the tables are tied to the bottom mesh, standing on concrete, polymer pads, with paws every two rows. They are joined to the top mesh after it is leveled in accordance with the protective layer. The reinforcement should not protrude from the formwork above the design level of the slab.

All metal elements must be cleaned of rust, otherwise corrosion of the reinforcement will continue inside the concrete. It “eats” approximately 0.01 mm per year, so in a few years the thickness of the armored belt will decrease significantly. The slab will no longer be able to properly absorb loads, which threatens not only cracks in the masonry walls, but also the collapse of the load-bearing frame.

The main mistake of an individual developer is the use of ready-made reinforcement mesh or pre-connected 6 m rods on a convenient site in the building area. When producing reinforcement cards industrially, manufacturers often use welding, which is dangerous due to the weakening of the metal near the welded joints and the occurrence of corrosion at the joints.

When making your own meshes 6 x 6 m (standard length of rolled metal), this size is often not enough for the slab. The grids are overlapped, but there is no spacing in adjacent rows; the slab in this area is weakened by default. The only correct way is to build up the rods locally with an overlap of at least 60 diameters in adjacent rows.

If the specified technologies for knitting reinforced belts for a monolithic foundation slab are followed, the maximum possible service life of a reinforced concrete structure can be achieved. Any violation will automatically lead to a decrease in quality, which is very dangerous for slab foundations that have zero repairability.

There are only two ways to attach reinforcement to a frame: electric welding and knitting. We will not open a debate about which one is preferable. Let’s just say that knitting does not reduce the strength of the working rods.

Any welding weakens the metal because it creates local stresses in it. This negatively affects the reliability of the entire structure.

Compared to welding, knitting work is more labor-intensive.

Despite this, in private construction with its small volumes it is better to choose them. Especially when it comes to such critical structures as foundations and floor slabs.

Methods of knitting reinforcement
Crochet technology
Materials
Norms and rules for performing work
Knitting the strip foundation frame
Approximate prices

In this article we will tell novice builders how to knit reinforcement correctly. Let's look at the tools, materials and technologies used for this work. We hope that the information received will help you confidently handle metal, assembling strong and reliable frames.

Methods of knitting reinforcement

There are two ways to fix reinforcing bars: manual and automated.

The manual method uses four types of tools:

Pliers;
Hook (simple and reversible);
Screwdriver with attachment.

Using pliers is not very convenient. Therefore, they are rarely used and only for assembling small frames. Crochet is used more often. This simple device, with some skill, helps to quickly connect steel rods.

There is an improved modification of the simple hook (reversible). Its basis is a screw that rotates when the handle is pulled back.

By combining a hook with a screwdriver, home craftsmen have created another convenient device for fixing steel rods in a frame.

Automated knitting is performed with a so-called pistol. This is a rather complex and expensive device used at large facilities. Its performance is such that tying one knot occurs in 1 second.

The device is equipped with a compartment in which a spool of wire is installed. The working body of the gun delivers it to the fittings and ties it into a knot.

Crochet technology

There is nothing complicated in this operation. After doing it several times, you will quickly get used to it.

The essence of the method is as follows: the intersection of the rods is covered with steel wire folded in half. The crochet hook is inserted into the loop and the other free end is grabbed with it. After this, the tool is rotated until it is tightened. The ends of the wire are bent inside the frame.

The craftsmen know one little secret that guarantees a tight contact: without tightening the loop a little, you need to pull it towards yourself and only then tighten it to the end.

Scheme for knitting reinforcement using a hook

Working with a screwdriver is not fundamentally different from crocheting. The advantage is higher speed and less labor intensity. When using a screwdriver, do not forget to set the rotation speed of its chuck to minimum.

You should not knit reinforcement with an electric drill. The large inertia of this tool does not allow you to accurately determine the moment of completion of tightening.

Methods for connecting steel rods and the main types of nodes are shown in the diagram below.

Materials

To assemble the frame, special annealed wire is used. It is durable, but at the same time quite soft. This allows you to tighten the knots without the risk of tearing it. The recommended diameter of this material depends on the cross-section of the reinforcing bars and ranges from 1.0 to 1.4 mm.

Cheap wire comes without coating and is called black. It is more resistant to corrosion and has a protective layer of zinc.

Knitting wire is produced in two versions: in coils and measured (in segments). Working with a skein is more difficult because it has to be cut into pieces by hand. The measuring material can be used immediately. Wire with loops at the ends is especially convenient.

Norms and rules for performing work

Guidelines for the design and manufacture of reinforcement cages are contained in two regulatory documents. GOST 10922-2012 stipulates technical conditions for knitted and welded connections of reinforced concrete structures. Set of rules SP 52-101-2003 regulates the requirements for the design of frames.

Based on these standards, standard patterns for tying reinforcement under a strip foundation, dimensions of overlaps, diameters of the reinforcement used and other rules for the execution of work have been developed.

When joining rods on straight and corner sections, the length of the overlaps is important. SNiP sets this parameter depending on the diameter of the working fittings (in millimeters):

300 mm for rods with a diameter of 10 mm;
380 for 12 mm;
480 for 16 mm;
580 for 18 mm;
680 for 22 mm;
760 for 25 mm.

Knitting the strip foundation frame

The estimated number of longitudinal rods (diameter 12-18 mm) are placed at the bottom of the trench on supports (bosses) 4-5 cm thick. The distance between them depends on the size of the foundation and can range from 5 to 20 cm. If the standard length of one steel rod (6 meters) is not enough for the entire “ribbon,” then several rods are used. They are connected to each other, observing the regulatory overlap.

Supports for reinforcement cage

Clamps made of smooth or corrugated steel with a diameter of 8-10 mm are attached vertically to the working rods. According to building codes, the pitch of the clamps must be at least 3/8 of the height of the foundation (20-50 cm).

Having installed the clamps, the upper chord of the working reinforcement is attached to them with wire, observing the design distance between the rods.

At corners and junctions, clamps are placed more often (1/2 step), and the working reinforcement is bent, connecting to the rods of the intersecting section of the “ribbon”.

The length of the bend must be at least 50 diameters of the working reinforcement.

Making a reinforcement cage in a trench is labor-intensive and inconvenient work. That's why experienced builders use this simple device.

Having laid the longitudinal whips on wooden stands, clamps and the lower belt of the working rods are tied to them. The finished structure is transferred and placed in a trench.

Assembly of the reinforcement frame of a monolithic slab is simpler than that of a strip foundation. The design here consists of two flat meshes. The lower rods are laid perpendicularly with a given pitch and connected to each other. Then, at the points of their intersections, stands made of steel rods are placed and the upper mesh is screwed to them.

Stand for mounting the upper frame of a monolithic slab

In recent years, fiberglass reinforcement has begun to be used to assemble frames.

You can knit it in several ways:

annealed steel wire;
plastic zip ties;
plastic clips.

Approximate prices

The cost of tying reinforcement, as estimators say, “sits” in the total price of 1m3 of reinforced concrete. In square or linear meters it is calculated individually for each type of structure. In this case, it is necessary to take into account various parameters (the width and height of the grillage, the thickness of the slab, the cross-section of the reinforcement, the level of complexity of the frame, etc.).

For approximate calculations, builders use prices in rubles per 1 ton of metal used. Today in 2017 it averages from 20 thousand rubles.

There are two ways to connect individual reinforcement elements of a strip foundation and a monolithic slab - binding and welding. The first is a more affordable option; it can be manual or mechanized. For this method, flexible fired round metal wire with a diameter of 1 to 1.4 mm made of galvanized low-carbon steel is used. Fired wire is soft in bending while maintaining tensile strength. If you only have a simple one on hand, it is recommended to hold it over the fire for about 30 minutes.

Pros and cons of technology
Foundation reinforcement scheme
What tools are used?
Knitting rods by hand
Mechanized tying

Wire for knitting can be purchased by the meter in coils or already cut, with rings at the ends. The latter option allows you to significantly speed up the work and reduce labor costs. This is due to the absence of the need to cut the material or use power tools.

Advantages and disadvantages of knitting reinforcement compared to welding

Advantages:

low labor costs;
possibility of carrying out work at the construction site;
no power supply or complex equipment required;
no electricity costs;
the work is simple and safe (compared to welding), it can be performed by a person with no experience;
the design has less weight;
flexibility of the frame with sufficient rigidity, which is of particular importance for the foundation in areas with high seismic activity;
the surface of the connected reinforcement does not require additional protection.

Flaws:

low strength;
mobility of nodes;
low labor productivity;
instability of connection quality;
low resistance to temperature changes.

Do-it-yourself knitting is used mainly in private construction, where high precision and strict conditions are not required.

Foundation reinforcement

A network of longitudinal and transverse rods intersected at right angles is called a belt. The reinforcement consists of several belts, horizontally located one above the other. Rules and scheme for reinforcement of a monolithic slab:

The first reinforcing belt is tied and installed at a height of about 5 cm above the sand and gravel cushion after installation of the formwork.
In corners, it is correct to make reinforcement more frequent. To do this, additional longitudinal rods are added. At the corners of the belts, rods bent at an angle of 90 degrees are placed.
To install the remaining belts, vertical rods are tied to the bottom one in increments of 20-40 cm.
The next belt is tied at a height of no more than 15 cm from the bottom one.
The number of belts and the distance between them depend on the thickness of the slab. The step between the belts can be less than 15 cm.
The top edge of the vertical reinforcement should protrude above the foundation. When drawing out the walls, it will be connected to their lower edge.

Strip foundation reinforcement scheme:

After placing the formwork, drive in the vertical rods.
Knit one after the other in parallel for a horizontal waistband.
If the width of the base is up to 40 cm, then two longitudinal rods are sufficient; if this width is greater, three, rarely four.
The distance between the belts is no more than 40 cm. Their number can be more than two.
The last upper chord is usually installed several cm below the top of the formwork.

For proper reinforcement of a strip foundation, like a slab foundation, not joints of rods, but entire curved ones are placed in its corners. The pitch between the transverse rods of the chords at the corners should be smaller.

Strapping devices

The rods are knitted by hand using the following tools:

hooks for knitting wire - you can purchase them or make them yourself from corrugated fittings or a long nail bent in the shape of the letter L;
wire cutters (reversible pliers) - for tying loops and trimming;
ordinary pliers or pliers;
forceps.

Ready-made hooks (wire twisters) differ in the shape and material of the handle, and the bending angle of the working part. A variety is a semi-automatic hook. It is pulled up, the handle slides along the spiral and turns the hook. Handles of all types of twisters can be made of galvanized metal, wood or plastic. Using a crochet hook for crocheting reinforcement, you can subsequently tie bags, tie grapes, and perform many other operations.

Another option is mechanized knitting. For it they use:

1. Knitting gun. The device is relatively expensive, so if you need it for one time, it makes more sense to rent it. The wire is not suitable; special cassettes are required.

2. Screwdriver. This tool is inexpensive, is always in demand in everyday life, and works with ordinary wire. Using a screwdriver, tying is several times faster than by hand.

Hand knitting technology

You can knit reinforcement with your own hands directly in the trench or outside. In the second case, a ready-made reinforcing mesh is inserted into the formwork. This method is more reliable. The mesh elements are placed on special wooden templates with grooves for longitudinal and transverse rods. The width of the template should be between 30-50 cm, length - no more than 3 m.

Procedure for hand crocheting:

Cut the knitting wire into pieces 20-25 cm long. The correct way to do this is with a grinder, cutting a whole coil across.
Fold each piece in half.
Place the workpieces at the joints of the reinforcement parts.
Insert the hook into the loop formed by bending the wire in half.
Grab the second end of the wire with a hook and bend it so that it does not jump off the knitting device.
Start rotating the hook clockwise.
Tighten the loop until it stops, but make sure that the wire does not break. Three to four turns are enough for a reliable connection.
Remove the hook from the loop and repeat all operations at the next intersection.

If pliers are used instead of a hook, then after completing steps 1-4, grab the ends of the wire with your left hand, and with your right hand with pliers, grab the ends of the loop and twist it several turns. A homemade nail hook works the same as a ready-made one.

You can knit fiberglass reinforcement not with crochet and wire, but with plastic clamps. Special elements are installed at the corners.

Features of mechanized knitting

The knitting gun works automatically. Advantages - low probability of breakage, many disadvantages of the manual knitting method are eliminated, the speed is several times higher. The disadvantage is that it is inconvenient to use the device in hard-to-reach places. There are two types of devices for mechanized knitting - battery-powered and mechanical. You need to bring the device to the intersection of the elements of the reinforcing mesh and press the button or lever (depending on the type of gun), in about 1 second it tightens the loop with the required force and cuts off the excess. As an addition to the gun, you can use an extension attachment, which allows you to work without bending over.

An ordinary household screwdriver with an adjustable number of revolutions can also cope with the viscous reinforcing mesh of the foundation. How to tie reinforcement correctly:

Make a special hook attachment. To do this, you need a long nail with a diameter of 4 mm. His hat is sawed off, the nail is bent into a hook. Instead of a nail, it is possible to use thick wire.
Cut the wire into lengths and fold in half, as if hand knitting. Place the workpieces at the joints of the parts.
Slightly bend the prepared loop and bring it diagonally (at an angle of 45 degrees) under the intersection of the elements of the reinforcing mesh.
Insert the screwdriver hook into the loop.
Turn on the tool at low speed.
After fastening the first node, check the quality of the connection. If the wire is torn, then reduce the speed; if the loop is not tightened, increase it. If the unit is reliable, then the number of revolutions is set correctly.
Knit the remaining knots with an adjusted tool.

Knitting reinforcement for a strip foundation or from a monolithic slab using any of the proposed methods can be carried out independently, even in the absence of extensive experience in such work.

Construction symbiosis. It seems like a concept from biology. Animals and plants enter into symbiosis, that is, mutually beneficial cooperation. One, for example, can serve as a home for another, receiving useful substances or protection from viruses from the “tenant”.

What is the construction symbiosis? Let's look at an example and. Steel rods give rigidity to the latter, saving it from destruction. Concrete saves the reinforcement from oxidation and rust, protecting it from the harmful effects of the atmosphere and moisture on the metal.

For symbiosis to work, you need to learn knit reinforcement correctly. Without preliminary coupling of its rods, walls and interfloor ceilings are not poured. Why? More on this and more below.

Why knit reinforcement

You can understand why to knit reinforcement by knowing the diagram for pouring reinforced concrete structures. First, the metal frame is installed. However, there are also composite reinforcement. The latter is lighter in weight and is rolled into coils.

The first is unbending and heavy. But the principle of operation of classic and modern frames is the same. A kind of network is made from rods in the center of the foundation, wall, concrete. The reinforcement should remain in the center.

By moving to the edges of the fill, the frame will redistribute the loads in the final structure and become vulnerable. Close to the concrete surface, water vapor can reach the reinforcement, causing corrosion of the metal. That is why the rods are tied together so that the base does not “float” under the concrete mixture being poured.

How to knit reinforcement for a foundation

Question, how to knit reinforcement for a foundation, is popular because laying rods in the foundation is always required. A metal network is needed even under a private house, not to mention multi-apartment high-rises.

Under the latter, it is customary to pour monolithic foundations, that is, solid slabs. For private houses, it is often enough strip foundation. How to knit reinforcement for both? Same. There are several ways:

Classic reinforcement knitting

We take steel wire with a diameter of 0.8 to 1.2 millimeters. The exact diameter depends on the width of the reinforcement bars. It ranges from 6 millimeters to 8 centimeters. The degree of strength that the metal will impart to the concrete pour depends on the diameter.

Classic crochet reinforcement

However, this strength is also related to the quality, as well as the type of knitting. In addition to manual connection of reinforcement, there is the option of welding. The latter is rarely resorted to, since the docking turns out to be rigid.

The frame has no gaps for a step “right” or “left”. Such movements are necessary when there are critical loads on the foundation. Where welded joints break, knitted ones will only stretch, maintaining the integrity of the structure.

The main load in the foundation is carried by the longitudinal reinforcement bars. Transverse – their support. Connect the corners of the frame and the intersection of the rods. Usually, the fastening wire is worked with pliers. They twist the ends of the harness, securely fixing it. The shape of the fastening is a single loop.

Knitting reinforcement with a hook and a screwdriver

Crochet reinforcement does not imply a fishnet, as some ladies might think. The hook for the foundation frame is not so much a knitting needle as it is a pair of wire cutters that remove unnecessary ends of the wire.

Tying reinforcement using a screwdriver

Before this, the fastener is picked up and twisted into a bundle. A hook also helps to secure the loop. He picks up the wire. All that remains is to make rotational movements.

They are made manually or using a screwdriver. The latter speeds up the knitting process by about 5 seconds on each loop. For the method to work, the ends of the wire are inserted into the screwdriver chuck and turned on.

Knitting reinforcement with a gun

A rebar gun is a battery-powered electrical device. The device speeds up and partially automates knitting. One knot with a gun takes 1.5-3 seconds, as opposed to at least 10 with other methods of connecting rods.

Knitting reinforcement with a gun

A microchip in the gun regulates the tension of the wire during tying. Convenient, because with manual connection it is rarely possible to make identical nodes. One may be tight and the other flimsy. The wire for tying in the gun is wound on a drum. The part is removable. This saves working time. A new drum immediately takes the place of the old one.

You have to pay for the convenience of working with a pistol. The device is expensive. Therefore, a reinforcing gun is used, as a rule, on large construction sites that need to be completed in a short time. In private housing construction, they prefer hooks and pliers.

Tying reinforcement with staples

A staple is a piece of wire. It is already folded into a loop. All that remains is to tighten it. As a result, the process of knitting a joint is accelerated by 3-4 times. Minimal skill is required to work with staples, and a beginner masters the process in just a couple of hours.

Tying reinforcement with staples

In addition, each bracket is of a standard size, which ensures uniformity and stability of connections. The ease of drawing up an estimate is also attractive. One staple is needed for one joint of reinforcement bars.

When purchasing wire in coils, you have to take into account the footage and split it into the approximate length of one fastener. In general, if you plan knitting reinforcement with your own hands, staples are a convenient and affordable option. The price tag for blanks is slightly higher than for regular wire. But the time saved on mating covers the costs.

Tying reinforcement with clamps

Clamps are plastic “straps”. They have something like plaques on them. The end of the belt is inserted into the plaque and tightened. Fastening is not as reliable as wire fastening, but it is sufficient for fastening rods in the foundation of a private house.

Tying reinforcement with plastic clamps

In addition, plastic has advantages over steel reinforcement. The polymer does not rot, even if it comes into contact with water. In addition, working with clamps is simple and non-traumatic. With wire, you can still get hurt and scratched.

An additional advantage of clamps is self-sufficiency. No additional tools are needed to work with plastic belts. The only problem is that in sub-zero temperatures it is difficult to use polymer fasteners. Plastic hardens in the cold. The connections are poor. But you can work with wire in any weather.

Most often people think about clamps when deciding how to knit fiberglass reinforcement for a foundation. The design is 100% polymer, excluding the weaknesses of metal in terms of intolerance to atmospheric phenomena and moisture. However, there are also complex clamps.

A thin wire is implanted into these. Plastic protects it and makes it easier to work with. But clamps, even ordinary ones, are about 3 times more expensive than wire for the same number of fasteners.

Knitting reinforcement with a double knot

The tying methods already described provide sufficient fixation of the reinforcement rods laid in the foundation pit. However, if the frame needs to be made separately and then moved to the main place, it will fold. Welding provides rigid fixation, but its disadvantages have already been discussed.

It is advisable to leave minimal play in the rods. Double knitting comes to the rescue. It requires hard training and involves simultaneously tightening steel rods on both sides. The scheme is difficult to explain in words. It's easier to watch a training video. It should have 5 steps. Exactly as much in double knitting.

There is also a scheme for connecting two spatial frames into one volumetric one. It already consists of 6 steps. Having mastered them, you can prepare the reinforcement in advance while the foundation pit and formwork are being prepared. Then all that remains is to move the frame.

How to knit corners of foundation reinforcement

Knitting the corners is a separate issue, since they account for the lion's share of the load. In addition, angles are right, acute and obtuse. The acceptable method of knitting depends on the configuration. Blunt connections are made rigid, overlapping.

Correct knitting of foundation corners

It is produced by bending one of the free ends of the reinforcement. Afterwards, the inner horizontal rod is attached to the same outer one. An internal horizontal rod is attached to the resulting bundle.

Fasten with a paw. Its length is equal to 35-50 diameters of the longitudinal reinforcement. As for the step between the corner transverse rods and the vertical ones, it is equal to 3/8 of the height of the foundation.

The corners of the joints in the foundation are secured with U- or L-shaped clamps. 90-degree joints of reinforcement bars are usually fixed with L-shaped anchor elements. Almost always the process consists of 5-6 steps. To master them means to provide the house with a bright, that is, strong future.

Knitting wire as a building material is rarely given much importance. But in the construction of monolithic reinforced concrete structures it plays an important role. The main purposes of these products are to bind reinforcing elements into a strong and reliable frame and fix fasteners before welding. A bonded reinforcement cage, for example, for a foundation, is not only cheaper, but also often more reliable compared to a welded structure. Other areas of application of knitting wire are the production of steel ropes, masonry mesh, chain-link, barbed wire, securing cargo during transportation, installation and packaging work.

What kind of binding wire is needed for reinforcement

Belongs to the hardware category of steel building materials. Its production uses low-carbon steel with a carbon content of 0.08 to 0.25%. The workpiece is wire rod, the final product is obtained by cold drawing - pulling under high pressure through a hole of a smaller diameter. To impart the required properties, the knitting wire is annealed - heated to a high temperature and then slowly cooled. During this technological event, the crystalline structure of the product, deformed during pressure treatment, is restored. This significantly reduces internal stresses in the metal.

Heat-treated binding wire, made of low-carbon steel, has excellent performance characteristics:

high ductility combined with sufficient mechanical strength;
no cracks due to slow natural cooling;
low cost;
The products are easy to use, easy to bend, knit, and fixed in a given position.

Attention! Wire that has not undergone heat treatment does not have the required properties and is not recommended for tying reinforcement. Unannealed wire bends heavily and breaks and breaks when tying a knot.

Which knitting wire is better

Knitting wire is produced annealed without coating, galvanized, with a polymer coating.

There are two types of annealing - dark and light.

During dark annealing, which is carried out in the presence of oxygen, the binding wire acquires a dark color due to the formation of scale.

Advice! The presence of scale does not affect the mechanical characteristics, but it does get your hands very dirty. It is recommended to work with it wearing gloves.

Bright annealing is carried out in special bell-type furnaces in the presence of an inert gas. Therefore, the surface of such wire is cleaner, and the price, naturally, is higher.

If you want to increase the durability of the frame of a reinforced concrete structure, for example, a strip foundation, purchase galvanized binding wire. Galvanizing is used for binding wire. The protective coating provides increased corrosion resistance of the product. According to reviews on the forums, it is very easy to use.

In the marking of the wire, the presence of heat treatment is indicated using the letter “O”, light annealing - “C”, dark annealing - “H”. In zinc-coated wire, the coating class is indicated - “1C” or “2C”. Products of class “2C” have a higher density of zinc coating.

Knitting wire is supplied in coils, skeins, and rosettes. Manufacturers also offer products for knitting frames in the form of wire segments with rings along the edges. Packages of cut wire can have a mass of 0.5-10.0 kg.

What diameter of binding wire is better?

The diameter of the binding wire is determined by the diameter of the reinforcement. In low-rise construction, 8-12 mm reinforcement is used, for which wire with a cross-section of 1.2-1.4 mm is considered the most suitable. Products with a diameter of 1.0 mm are too weak and often break off. Larger diameter wire is difficult to work with.

How much wire will be needed for reinforcement?

To determine the amount of binding wire, they are determined with a reinforcement diagram. It is difficult to accurately carry out such calculations, and this is not required, since the price of these products is low.

At the junction of two reinforcing rods with a diameter of 10 mm, pieces of wire approximately 25 cm long will be required; for knots of three rods, the length of the segment is approximately 50 cm. As the diameter of the reinforcement increases, the length of the segment increases. More precisely, the wire consumption per connecting point is determined experimentally. A completely simplified version - the number of all connecting nodes is multiplied by 0.5 and the required wire footage is obtained.

Attention! When purchasing, it is recommended to double the calculated amount of wire. Such a reserve is necessary, since during the knitting process some sections may tear or get lost. The size of the purchase may be less than stated.

The table below will help you buy the correct amount of binding wire. From it you will find out how many meters of knitting wire are in a kilogram, and the reverse information - how many meters are in a kilogram.

Table of the ratio of the mass and length of the knitting wire of the most common diameters in everyday life

Diameter, mm	Weight 1 m, kg	Length of 1 kg wire, m	Weight of uncoated wire on a reel or coil, not less than, kg	Weight of galvanized wire on a reel or coil, not less than, kg
0,6	0,00222	450,45	5,0	0,6
0,8	0,00395	253,17	5,0	0,6
1,0	0,00617	162,00	5,0	0,6
1,2	0,00888	112,6	8,0	2,0
1,4	0,0121	82,6	8,0	2,0
1,6	0,0153	65,4	8,0	2,0
1,8	0,0200	50,0	8,0	2,0
2,0	0,0247	40,5	8,0	2,0

Note - the minimum weight of uncoated and galvanized knitting wire in coils and coils is in accordance with GOST 3282.

When purchasing wire in a coil, to determine its length, divide the mass of the coil by the mass of 1 m of the product of the diameter you need. We take the data from the table. For example, you bought a coil of wire with a diameter of 1.2 mm, its weight is 50 kg. We make the following calculations - 50 kg/0.00888 kg = 5630 m. Using the table, you can make these calculations differently. 1 kg of wire with a diameter of 1.2 mm contains 112.6 m, which means that 50 kg contains 112.6x50 = 5630 m.

Knit or weld reinforcement

When comparing a welded joint and a knitted knot, at first glance, the welded seam is more reliable. Is it so? Let's look at what problems a weld poses:

Welding degrades the characteristics of the metal in the heating zone. Therefore, during operation, either the seam itself or the metal exposed to high temperatures may burst.
When pouring a concrete mixture according to the technology, it is supposed to be subjected to vibration, which negatively affects the strength of the seam.
Welding work requires the involvement of a specialist welder.

Therefore, in monolithic construction, preference is often given to a cheaper method of joining reinforcement - connecting it using a tying wire and a hook.

DIY hook for fittings

A hook for tying reinforcement can be made independently from the reinforcement itself or simply a steel rod 6-8 mm thick and a bearing. The metal rod is bent into a hook, which allows you to conveniently grab the wire. A bearing is mounted in the handle, allowing the hook to rotate quickly.

You can buy a hook for fittings - with a straight or curved handle, with different angles of bending of the handle, shape and size of the hook. The optimal instrument design for each performer can only be determined experimentally.

Rebar hook, semi-automatic and automatic

You can purchase a semi-automatic or automatic hook model in the store.

Semi-automatic hooks have a spiral built into the handle. This hook does not require rotation. If you pull the handle towards you, the tip begins to rotate. This tool is more expensive than a manual one; purchasing it makes sense when performing large-scale work.
You can make a semi-automatic version of the hook yourself using a screwdriver and a metal rod with a curved end. The rod is secured in a holder, and work is carried out at very low speeds.
An automatic hook for tying reinforcement is called a gun. Its performance is a node per second. The wire does not need to be cut into measured pieces. It is simply tucked into the tool, and he himself ties the knots and cuts off the excess. The rebar tying gun does not require a power source to operate as it runs on a battery. Such a tool has one significant drawback - its high cost, which pays off with significant volumes of reinforcement work.

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Any welding weakens the metal because it creates local stresses in it. This negatively affects the reliability of the entire structure.

Compared to welding, knitting work is more labor-intensive.

Despite this, in private construction with its small volumes it is better to choose them. Especially when it comes to such critical structures as foundations and floor slabs.

Methods of knitting reinforcement

There are two ways to fix reinforcing bars: manual and automated.

The manual method uses four types of tools:

Pliers;
Hook (simple and reversible);
Screwdriver with attachment.

There is an improved modification of the simple hook (reversible). Its basis is a screw that rotates when the handle is pulled back.

By combining a hook with a screwdriver, home craftsmen have created another convenient device for fixing steel rods in a frame.

Automated knitting is performed with a so-called pistol. This is a rather complex and expensive device used at large facilities. Its performance is such that tying one knot occurs in 1 second.

The device is equipped with a compartment in which a spool of wire is installed. The working body of the gun delivers it to the fittings and ties it into a knot.

Crochet technology

There is nothing complicated in this operation. After doing it several times, you will quickly get used to it.

The essence of the method is as follows: the intersection of the rods is covered with steel wire folded in half. The crochet hook is inserted into the loop and the other free end is grabbed with it. After this, the tool is rotated until it is tightened. The ends of the wire are bent inside the frame.

The craftsmen know one little secret that guarantees a tight contact: without tightening the loop a little, you need to pull it towards yourself and only then tighten it to the end.

Scheme for knitting reinforcement using a hook

You should not knit reinforcement with an electric drill. The large inertia of this tool does not allow you to accurately determine the moment of completion of tightening.

Methods for connecting steel rods and the main types of nodes are shown in the diagram below.

Materials

Cheap wire comes without coating and is called black. It is more resistant to corrosion and has a protective layer of zinc.

Norms and rules for performing work

When joining rods on straight and corner sections, the length of the overlaps is important. SNiP sets this parameter depending on the diameter of the working fittings (in millimeters):

300 mm for rods with a diameter of 10 mm;
380 for 12 mm;
480 for 16 mm;
580 for 18 mm;
680 for 22 mm;
760 for 25 mm.

Knitting the strip foundation frame

Supports for reinforcement cage

Having installed the clamps, the upper chord of the working reinforcement is attached to them with wire, observing the design distance between the rods.

At corners and junctions, clamps are placed more often (1/2 step), and the working reinforcement is bent, connecting to the rods of the intersecting section of the “ribbon”.

The length of the bend must be at least 50 diameters of the working reinforcement.

Making a reinforcement cage in a trench is labor-intensive and inconvenient work. That's why experienced builders use this simple device.

Having laid the longitudinal whips on wooden stands, clamps and the lower belt of the working rods are tied to them. The finished structure is transferred and placed in a trench.

Stand for mounting the upper frame of a monolithic slab

In recent years, fiberglass reinforcement has begun to be used to assemble frames.

You can knit it in several ways:

annealed steel wire;
plastic zip ties;
plastic clips.

Approximate prices

For approximate calculations, builders use prices in rubles per 1 ton of metal used. Today in 2017 it averages from 20 thousand rubles.