Tie a frame from reinforcement. How to properly pour a foundation for an extension to a house. The disadvantages include

Construction of a house begins with laying the foundation. The main requirement for a concrete foundation is its strength. It is achieved by laying a frame of reinforcement bars tied together inside the concrete. Such a frame is called reinforcing. This article will discuss such an important stage of construction work as tying reinforcement for the foundation.

It is necessary to first consider what methods of tying reinforcement for the foundation generally exist. They differ from each other by type:

tool;
material;
knitting patterns;

By instrument type- this can be either knitting reinforcement for the foundation manually or using a special tool. As the latter, special crochet hooks, screwdrivers, special guns, produced just to perform this operation.

As a material which is used to connect reinforcement bars to each other used:

knitting wire- This is the most common and reliable technology for tying reinforcement for the foundation, because it is performed with tying a knot.
paper clips- are wire tacks, which, unlike ligation with knitting wire, are made without tying a knot.
clamps small size made of plastic- this new material has become widespread due to its ease of installation and high knitting speed, and besides, it is not afraid of corrosion. However, such a bundle of reinforcement for the foundation causes a certain skepticism among professionals. Read more.
clips— made in the form of latches that fix adjacent rods to each other.
welded joint- this old method has not become widespread, since the welded joint, due to its fragility, is susceptible to cracking during concrete pouring and does not have the necessary reliability. To perform a high-quality welded joint, you need a highly qualified welder.

Required wire

When choosing wire, the following factors must be considered:

Manufacturing accuracy class. The accuracy class is determined by the production method. There is a wire of a higher accuracy class, its deviation of the actual size, diameter, from that declared by the manufacturer along the entire length of the wire is less than that of a wire of a lower accuracy class. However, for knitting reinforcement, the accuracy class is not particularly important.
Wire rolling method. There are two types of rolled products: cold-rolled and hot-rolled. Cold-rolled steel is rolled out from blanks by presses without heating. With the hot rolling method, rolled steel is rolled out in a heated state, which gives greater strength.
Which tensile strength group does it belong to? wire (there are the first and second groups);
Degree of corrosion resistance. On this basis, there is only one difference - whether there is a galvanized coating on the wire or not.

The criterion for choosing wire is very simple, you need wire, which is called “knitting”. It has a full set of necessary characteristics: sufficient softness with the declared strength, abrasion resistance and reliability when fastened.

Galvanized wire is considered overkill.
The optimal diameter of the knitting wire is 1.2-1.4 mm. A wire with a diameter of 1.6-2 mm takes a lot of force, as a result of which construction slows down, and the piece is too weak, it will simply burst.

Attentively you need to ensure that the connection of the reinforcement remains rigid after tying the knot: during pouring, the frame must remain motionless. This will ensure the reliability of the structure after hardening.

You need to check the rigidity of the connection of the reinforcement by touching the rods - if they are rigidly fixed, they will not move, which means everything is in order. You should not test the strength of the knot itself, otherwise there is a risk of loosening the binding.

The length of wire recommended for one knitting point is from 30 to 50 cm. The wire itself is extremely cheap - about 50 rubles. for 100 meters. To avoid running out of it at the wrong time due to loss or excessive consumption, it is recommended to buy it with a double supply. 100 rubles for 200 meters is quite inexpensive.

How to bend reinforcement correctly, all the ways

You should choose how to bend foundation reinforcement based on its diameter: with your own hands It’s quite easy to bend a small diameter, but for thicker reinforcement you’ll have to use special devices, homemade or specialized.

Among homemade devices, two methods are common. The first is when an ordinary pipe of suitable diameter is installed vertically and its base is poured with concrete so that it stands firmly.

The fittings are inserted inside all the way, and now the end protruding from the pipe can be bent by simply leaning on it. If this presents certain difficulties, then a second pipe is additionally put on the free end of the reinforcement, and now, due to the increased leverage, the thick reinforcement is easily bent.

Welding is also often used. By softening a section of the rod with heat, it becomes easy to bend. The same is done with a blowtorch and a hammer. After heating the bend point with a lamp, bend the reinforcement with a hammer.

The most radical way is to make an incision with a small grinder and then bend it completely using available tools.

It should be noted that methods using welding and notching are not the best - at the bend, in these cases, the strength of the reinforcement is reduced by up to 10%.

Crochet

The design of the hook for these purposes may be different, but this is not so important. The meaning lies in the presence of a hook as such, because it is used to thread the wire. The rules for tying reinforcement for the foundation are shown schematically in the figure.

Pay attention to the sequence of actions:

Bend the wire in half;
Follow the arrow, as in the figure, bring it into position for threading;
Insert the hook into the loop that will now be wound;
Place the hook loop inward between the free ends of the wire;
Without removing the hook, twist until tightened, but do not pinch;
Ready!

There are motorized screw hooks in which the wire is tightened by rotating a screw. It turns out very quickly and conveniently.

For strip foundation

The strip foundation reinforcement has two patterns for laying rods:

4 rod system: two at the base of the foundation, two at the top (used if the width of the foundation does not exceed 50 cm),
6 rod system: an additional longitudinal rod is placed between the two main ones (used in cases where the foundation width is more than 50 cm).

Bent reinforcement is laid at the corners, and the ends should protrude from the corner by at least 40 cm. Reinforcement connection nodes should be located apart from each other at a distance of no more than 60 rod diameters. For example, if 12 mm reinforcement is used, then the strapping should be every 72 cm or more often.

For columnar

This is a foundation that is placed on pillars that act as piles.
A tied one is placed inside the pillars before pouring. The tying of reinforcement for a columnar foundation is the same as for a strip foundation - either 4 rods, or 6 for large columnar foundations.

For vertical rods in this type of foundation, 12 mm reinforcement is used, since this is a vertical foundation. The cross rods can be thinner and smoother.

For wooden houses, it is allowed to use longitudinal and vertical reinforcement thinner than 12 mm. Sometimes, for the foundation of small wooden buildings, a welded frame is constructed from vertical rods connected with hoops like a barrel. This is incorrect, because with this bonding method you can only use welding, and this is not a completely reliable method. We have already talked about this above.

For slab

A reinforcement frame for a foundation can take the form of a two-dimensional plane, a mesh formed from reinforcement bars. The second option is volumetric, in the form of two meshes of intersecting reinforcement, located one above the other and connected by transverse rods.

Reinforcement - from 12 mm and above, up to 16 in private housing construction. The mesh cell size is 200x200 mm. The distance from the lower reinforcement belt to the pillow (or insulation) is 50 mm. The top belt is also protected from external influences by a 50 mm layer of concrete.

Cost calculation (price for work and materials)

Let's take as an example a strip foundation 10 by 10 meters. This is the perimeter of the house. In addition, there will be a foundation for internal load-bearing walls - two walls of 10 meters each. It turns out 60 m.p. foundation.

How much knitting wire will be required with the right approach?
Let's say the foundation is less than 50 cm wide - it will use a scheme with four longitudinal rods. In this case, in 1 linear meter of the foundation the following will be used:

4 longitudinal rods. That means at 60 mp. will be 240 meters.
4 vertical. With a foundation height of, say, 50 cm, their height will be no more than 45 cm.
4 x 45 cm = 1.8 m. 60 meters of foundation - 108 m.
4 transverse. With a foundation width of 45 cm, the width of the cross sections will not exceed 35 cm.
4 x 35 cm = 1.40 m. 60 meters of foundation - 84 m.

How much is it?

For longitudinal rods we use 12 mm reinforcement costing 25-30 r/m.p. 240 x 35(30) =6000 (7200)
For vertical and transverse rods, take 6-8 mm at a cost of 12-16 r/m.p. (108+84) x 12(16)=2304 (3072)

So, the purchase of reinforcing rods for this foundation will cost from 8304 to 10072 rubles.

Now let's calculate the required quantity wire. 4 ties for a 4-bar foundation per 1 m.p. This, based on a maximum consumption of 50 cm per tie, is 2 meters of wire per meter of structure. We have 60 meters, so we need 120 meters of wire.

Attention: Wire is sold in kilograms. It is necessary to convert from meters to kg.

1 m of wire with a diameter of 1.2 mm weighs 9 grams, respectively, 120 m of wire with a diameter of 1.2 mm weighs about 1 kg, which costs about 50 rubles. The wire is cheap, so it can and should be taken with a double reserve of 240 meters for 100 rubles. All that remains is to calculate the cost of installation and knitting of the frame. As a rule, it is not calculated separately and is included in the total cost of pouring the foundation. In the regions, such work is cheaper, but the price range is approximately the same - 1000-2000 rubles per cubic meter. This price includes the construction of a trench, installation of formwork, binding of the frame, pouring concrete and removing the formwork.

The total length of the foundation we are calculating is 60 meters, width 0.4 m, height 0.5 m. Let's calculate the volume: 60 x 0.4 x 0.5 = 12 m3. With this volume, the cost of foundation work will be 12,000 - 24,000 rubles.

Useful video

How to knit reinforcement in the video below:

In contact with

The need to connect the old and new foundations arises when constructing extensions or other structures in order to increase the size of the usable area of the building.

In the immediate vicinity of the building being used, a concrete slab, strip is poured, or supports (pillars, screw piles) are installed.

Some of these types of foundations need to be “connected” to the foundation of the structure. This task can be accomplished in several ways.

Important points before docking

Before you begin work on increasing the area of your home with extensions, you need to obtain the appropriate permits. All distances from nearby buildings and neighboring properties must be taken into account and maintained.

The extension can be built as an independent building or integrated into an existing one. It is important to note that the building already in use must be older than 1 year. During this period of time, it will give the necessary shrinkage and will not carry away the new foundation built nearby.

The old and newly constructed foundations must be of the same type. If a residential building is installed on a strip foundation, the extension must be built on the same one. This will significantly reduce the risk of deformation of the combined, docked base.

Tools and materials for work

To build the foundation, a significant amount of excavation work will be required, as well as reinforcement and concreting.

Tools you will need:

Bayonet and shovel shovels;
A stretcher or garden wheelbarrow for moving soil;
Hook for tying wire;
Tape measure, marker, pegs, rope for marking the site;
A bubble or water level, but a level is the best choice.

Materials you will need:

Reinforcement bars with a cross section of 8-10 mm;
Knitting wire;
Cement grade not lower than M400;
Sand and crushed stone of the middle fraction for preparing cement-sand mortar and forming a shock-absorbing “cushion”;
Metal studs (you can use reinforcement with a cross-section of 12 mm) to connect the new foundation to the old one.

Connection steps

In order to properly combine the two foundations, you need to think through in advance all the nuances of each stage of work. It is necessary to choose a method for “ligating” the bases. Several options are possible.

Method number 1: “tape-tape”. Used to build a foundation of similar width and depth. It is carried out in several stages.

They are marking the site for the construction of an extension.

A ditch is dug around the perimeter of such a width that it can accommodate the formwork for pouring the tape of the required parameters. Level the bottom and walls of the dug trench using shovels.

A sand-crushed stone fill is made, consisting of 5-7 cm of compacted sand and 10-15 cm of crushed stone, which is also compacted.

Tamping is done with a vibrating plate and available materials. For example, a barrel half filled with stones, a piece of timber.

Formwork is assembled in a trench from any suitable lumber.

A reinforcing belt is made, consisting of two tiers of mesh with a mesh size of 15x15 or 20x20 cm, connected to each other by vertical metal rods.

A gap of 1.5-2.5 cm wide is left between the foundations, which is filled with mineral wool. The formwork is limited at the junction of the bases with a wooden or metal shield.

Using a concrete mixer, a cement-sand solution is prepared in a 1:3 ratio (1 part cement and 3 parts sand, water and filler in the form of crushed stone or gravel).

Concrete is poured into the formwork in layers. They pierce it repeatedly with a rod of reinforcement so that all the air comes out of the solution.
After the concrete has set, the formwork is dismantled.

The damper joint of the foundations is closed with a rubber band or waterproofed in another way.

This method of tying the bases allows you to be sure that the new one will shrink and carry the old one with it. After the strip foundation shrinks, it is increased in height so that it is in the same plane as the base of the residential building.

Method number 2: “plate-tape”. It is carried out similarly to the previous one, with the only difference that the damper seam is made longer: along the entire slab.

This joining method is optimal only for stable soils, when there is confidence that there will be no significant subsidence of the extension after its construction.

Rigid connection

To rigidly tie two foundations, you will need to connect them using reinforcement bars. You will need at least 20 rods per 1 m2.

To install metal rods, holes are drilled in the old foundation, reinforcement is placed in them and concreting is carried out.

Rods are also laid on the side of the new foundation and the joints are filled with concrete.

Construction of a columnar foundation

The best choice for building an extension would be to install it on poles. The soles of the supports should be located 15-20 cm below the freezing point of the soil, which will prevent them from moving during soil movements during periods of freezing and thawing.

If a columnar base is built, the house and the extension are connected at the level of the lower floors.

Possible difficulties

If the construction site has a high groundwater level (groundwater level), it is first necessary to make wall or ring drainage.

For more tips, watch the video:

When building a new foundation on moving soils (sand or sandy loam), the corners of the old one are strengthened with piles buried at least 100 cm into the soil.

For reinforcement, hot-rolled construction reinforcement of a periodic profile, heat-treated or mechanically strengthened, is used. For the foundation, reinforcement of class A 400 is used. The use of classes A 240 and A 300 is unacceptable. Using reinforcement of a class higher than A 400 for reinforcement is neither economically profitable nor advisable from the point of view of using the strength potential. The diameter of the reinforcement is usually used 12mm for working longitudinal reinforcement, 6-8mm for vertical and transverse reinforcement.

The laid reinforcement must be connected.

There are several types of reinforcement connections. Most often it is knitting using knitting wire. Welding and fastening with plastic clamps are also used.

Wire is a time-tested, reliable option.

For knitting, wire processed by firing, the so-called burnt wire, is used. Burnt wire is more flexible and stronger than regular wire, and is also more resistant to tension. The diameter of the wire depends on the diameter of the reinforcement. As a rule, for reinforcement with a diameter of 8-12 mm, 1.2 mm wire is used; for thicker reinforcement, thicker wire is used. However, using wire larger than 1.6 mm is not advisable since it is very inconvenient to knit and will be difficult to tighten. Wire with a diameter of less than 1.2mm will burst when tightened.

There are several ways to knit with wire:

Knitting using reinforcement pliers;
Crochet;
Knitting using a drill with an attachment;
Knitting using a knitting gun.

Method 2.

The wire is also folded in half, pressed with your fingers to the reinforcement, the ends are bent towards themselves, a hook is inserted and tightened. After tightening, the hook is removed and the ends are bent.

Method 3.

The wire is also folded in half, threaded under the reinforcement, and the loop is inserted into the hook. The second end is also inserted into the hook and bent down. Pull the hook towards you and tighten.

This method is considered the most convenient.

Tying with reinforcement pliers

The disadvantages include its bulkiness, just like that of a drill. And the need for consumables special for this pistol, or the need to load cassettes.

The technology of operation of all tools is identical - knitting wire on reinforcement. Accordingly, the choice of tool will be based only on your personal preferences.

Recently, most builders have begun to pay attention to the recently introduced plastic clamps. The advantages of clamps include: ease of installation, speed of strapping, and low cost.

Also on sale are plastic clamps with a heart made of steel wire. They are more expensive, but also more durable.

The disadvantages include fragility in the cold and the inability to bear additional load. From frost they immediately become brittle and burst.

Connecting reinforcement by welding– This method has its advantages and disadvantages. The main disadvantage of this method is that it requires the involvement of an experienced welder. The second disadvantage is the weakening of the metal at the welding points and a change in ductility along the entire length.

Fiberglass is a relatively new material, which has both pros and cons.

The advantages include low weight, corrosion resistance, high compressive and tensile strength. Resistance to aggressive environments.

The disadvantages include much lower elasticity compared to traditional reinforcement; when heated, it loses its reinforcing properties.

Tying fiberglass reinforcement is not particularly different from tying metal reinforcement; it should be noted that plastic clamps are most often used for these purposes.

In conclusion, I would like to note that the process of tying reinforcement is not quite complicated, but it requires attention.

The reinforcing frame inside the foundation is a structure that works in bending and tension. After all, the concrete itself under such loads becomes covered with cracks, and in the end it simply splits. Therefore, the reinforced frame is a necessary and integral part of the foundation. In this case, the connection of the rods to each other should be carried out not by welding, but by wire knitting.

Because when welding under the influence of high temperature, the crystal lattice of the steel changes, which leads to a decrease in the strength of the joint. Therefore, the question of how to properly knit reinforcement for the foundation is relevant today for those who are trying to fill the foundation of a house with their own hands. Let's look at all the processes in more detail.

Types used

Before starting to analyze the topic of how to properly knit reinforcement for a foundation, you need to understand the reinforcement itself. Indeed, today the market offers two varieties of it:

This is regular steel.
Composite.

Everyone has long been accustomed to using ordinary steel. But what is the second model, how does it differ from the first, and is it better?

Steel

Metal reinforcement consists of six classes, which differ from each other in the percentage of alloying additives. And the more of the latter, the higher the class, the higher the characteristics.

The reinforcing bars themselves are rods with a smooth or grooved surface. The first class is smooth, the rest are grooved.

The relief structure is an increase in the area of adhesion between reinforcement and concrete mortar. In addition, the protrusions act as restraining sides when the reinforcement structure begins to work in tension.

As for the choice taking into account the strength of the reinforcing bar, for foundations, hot-rolled material of class A III with a diameter of 10 - 18 mm is usually used.

Rods with higher characteristics and sizes are too expensive, but they perform the same functions with not the heaviest loads. And the lower class reinforcement for foundations is rather weak. But we must add that even smooth reinforcement is used in reinforcing frames. It is not the main one, but it is used for jumpers, braces, ligaments and other non-loaded units.

When choosing, you need to pay attention to the product labeling, especially the indices. Here are just two of them:

“C” is a designation that the reinforcement can be welded.
“K” - anti-corrosion additives were added to the steel. This type is the most expensive, so it is not used in private housing construction.

As for welded reinforcement, it is also not the cheapest option. Therefore, for private owners, the best option is knitting with steel wire. As for the question of what kind of wire is used to knit the reinforcing frame, we will talk about it below.

Composite

This variety is a relatively new material. It is based on plastic, to which filling components are added: glass, carbon, basalt.

The most popular is the fiberglass variety, because it is simply cheaper than the other two with almost the same strength characteristics.

If we talk about the technical characteristics of this material, then:

The tensile strength of plastic reinforcement is 1000 MPa, and that of steel reinforcement is 390.
It is 3.5 times lighter than metal.
Steel corrodes, plastic does not.
It does not conduct electricity.
It has low thermal conductivity.

As for the negative aspects:

Metal reinforcement is better in elasticity.
Plastic belongs to the category of slightly flammable materials.
When heated, it softens.
Fiberglass reinforcement can only be tied with clamps or wire; steel can be welded.

Wire

For reinforcement cages, it is necessary to use wire produced in accordance with GOST 3282-74, which indicates that this material is classified into several positions.

Processing method: untreated or annealed.
Processing precision.
With or without protective zinc coating.

The diameter of the product varies in the range of 0.16-10 mm. It can be black or steel. Since we are interested in knitting wire, that is, soft wire with a large bending cycle, it is better to choose the annealed version.

Someone may say that galvanized wire will last a long time, and no one will argue with this. But it is more expensive than usual, and besides, practically no corrosion processes occur inside hardened concrete.

To knit the reinforcing frame for foundation structures, wire with a diameter of 1.2 - 1.4 mm is used, less often 1.8, unless the diameter of the reinforcing bars is chosen for the frame to be the largest (18 mm).

Today, coils of knitting wire have appeared on the market, which are cut to a length of 80 - 180 mm, and loops are already made at the ends. That is, these are already ready-made sections for knitting. There are 1000 segments in one bay.

Its advantages and disadvantages

The connection of reinforcement for the foundation is primarily determined by the strength characteristics of the foundation. And this is the main advantage of the reinforcing frame. But taking into account wire knitting, other positive aspects of the design are also determined.

The wire connection preserves the volumetric and linear shape of the frame structure.
In this case, the joint is not firmly fixed, as is the case with welding. There remains room for balancing the reinforcing bars among themselves, which is very important when pouring, vibrating and hardening the concrete solution. That is, the connection of the reinforcement makes it possible to shift by millimeters in the area of the binding, taking an ideal position when loads arise from the concrete mixture.

As for the disadvantages, they mainly relate to the time characteristics and labor intensity of the process itself. That is, welding a frame is faster than knitting it with wire. And the difference here is significant. Tying foundation reinforcement cages is not an easy task. This requires knowledge of methods and the ability to use special tools. Although, as practice shows, several knots already provide the necessary experience, which reduces both the complexity of knitting and the time spent on it.

How to knit?

There are several options and schemes for how to manually tie reinforcement. Due to the rigidity of the wire itself, knitting cannot be done with your fingers. Therefore, various tools and devices were invented for this process. Knitting is carried out with a crochet hook (homemade or factory-made), a semi-automatic inertial crochet hook, or pistols. The craftsmen even adapted a drill for knitting. Today, metal staples, clamps or wire are used as knitting material.

Tools

Tying the foundation with reinforcement requires assembling the frame into a single structure. Of all the designated tools, the hook has been used for a long time, which is why knitting patterns were invented for it at one time. Therefore, first of all, let’s look at how to use this simple tool.

Hook

Making a hook for tying reinforcement with your own hands is not a problem. Because it has a different bend shape and the length of the rod itself.

Therefore, each master adjusts these parameters exactly to suit himself, to suit the convenience of the work. It must be added that the hook is a universal tool.

It is convenient for them to work both inside the trench, getting under the lowest grates, and outside the pit. The most important thing is to follow the knitting pattern exactly. Typically, a homemade tool is made from thin reinforcement, bending it in a vice. A plastic hose or tube is used as a handle, which is heated after inserting the rod.

After cooling, the plastic envelops the rod, firmly adhering to the corrugated surface of the rod. Until recently, handles were made of wood; some craftsmen wrapped the rod with electrical tape. Reinforcing bars are knitted with wire using a hook by rotating the latter. At the same time, we rotate the ends with a crochet according to a special pattern, which will be discussed below.

Inertial action device

This is still the same hook, only with the opposite end inserted into a special handle. It has a screw thread cut into it, and inside there is a spring that is responsible for returning the hook to its original position.

The ends of the wire are hooked with a hook; they must be pulled with a device from the connection point. The rod begins to rotate along the spiral grooves, rotating about its axis. This is how twisting happens.

In fact, a tool with a cartridge works in exactly the same way. For example, a screwdriver. That is, the hook can be inserted into the screwdriver chuck and turn on the latter. The rotating motion will create a twist in the wire. This method is often used by craftsmen.

Gun

This device belongs to the category of special tools because it is intended for only one action. Wire spools are inserted into the design of this power tool (they are replaceable).

That is, the device itself pushes out the wire and knits it itself according to a certain pattern. Convenient, fast, high quality, but expensive in terms of the price of the gun.

Its only drawback is that it requires electricity either for direct connection or for recharging batteries.

Methods and schemes

Tying a frame for a foundation by hand is not as easy as it might seem at first glance. This is a labor-intensive task that requires a lot of time. But among all the schemes there are simple options. Here's one of them.

A piece 25 - 30 cm long is cut from the wire coil.
It folds in half.
Wrapped around the junction of two rods.
The hook grabs a loop that needs to be rotated.
One end of the wire is added to the twist after two turns.
After two more turns, the second one.
Full twisting is carried out.

The tool for tying the reinforcement according to this pattern - the hook - must rotate until the wire tying becomes tight. But you shouldn’t twist it either, as the wire material itself will weaken.

With the help of one loop you can twist according to other patterns. That is, this is the simplest option. In addition, the use of hooks makes it possible to move away from complex schemes, which are most often used in large-scale installation construction. For private house construction, simple mating options are also suitable. Of course, it will be completely easier if you use ready-made pieces with two loops at the ends. They simply wrap it around the joint, put two loops on a hook, which they begin to rotate.

Options for different foundations

The easiest way is to knit a reinforced frame for. Essentially, it is a lattice of longitudinal and transverse rods, the distance between which is determined by the loads. More often these are cells of 20 x 20 or 30 x 30 cm. For this design, knitting with one loop is used.

The same can be said about the frame for, because its design is several gratings connected by transverse short rods. But there is one subtle point in knitting the reinforcement of a strip foundation - this is the joining of the corners of the structure. Here it is very important to evenly distribute the connection points along the entire length of the bent and mating rods, which create the corners of the reinforced frame.

Video

Video about how to quickly learn to knit.

The technology for constructing a frame structure is no different from a strip structure. Here are the same schemes and methods of knitting structures from reinforcement. As for the frame, one must take into account the fact that the frame itself in these structures is a vertical structure with vertically installed main rods, which are connected to each other by rods of smaller diameter.

This is if the frame has a rectangular cross-section. Therefore, exactly the same knitting is carried out here as in slab or strip bases. If the cross-section is circular, then the longitudinal rods are one rod rolled into a circle. It is tied to vertical elements in certain places of the frame, taking into account the installation step.

Conclusion

The process of foundation reinforcement involves several operations on which the quality of the final result depends. And here the binding of reinforcement plays an important role. Its main methods are associated with simple circuits, often single-loop. Therefore, anyone can handle this process. It just takes time and a little experience.

In contact with

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 fixture, 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.