Detailed description of foundation reinforcement. Foundation reinforcement schemes Transverse grillage reinforcement

The reliability and strength of a columnar foundation with a grillage largely depends on its correct reinforcement. The features of reinforcement of a columnar foundation, the sequence of work during reinforcement, requirements for reinforcement, the location of reinforcement in the corners of the building and at the intersection with load-bearing walls are considered. It also shows the regulatory documents according to which construction is being carried out and lists errors that should not be made during the work.

Features of reinforcement of a columnar foundation

Increasing the strength and reliability of the foundation is achieved by reinforcing it. Concrete can withstand high compressive loads. Bending or tensile forces, even small ones, tear it apart.

The following loads act on the foundation column:

• in compression - the weight of the building;
• to rupture - in winter, heaving of the soil compresses the walls of the pillar and tears it upward from the base;
• for fracture/shear, in winter - horizontal movements of the soil during freezing or in summer - shift of a dense layer over water-saturated or weak soil.

For compressive loads, they are not reinforced, and the effects of soil heaving are completely eliminated by wrapping the post in three layers of polyethylene or roofing felt. Shear loading is rarely possible, but it is protected from it by reinforcement.

The second reinforcement zone in columnar foundations is the grillage. Reinforcement of the pile foundation grillage is carried out only along its lower and upper surfaces, taking into account the thickness of the protective layer of concrete.

Requirements for reinforcement of foundation pillars and grillage

For horizontal longitudinal reinforcement of the grillage, rods with a regular profile and a diameter of 10 - 16 mm are used. The vertical and horizontal transverse sections of the frame are made of smooth reinforcement, with a diameter of 6 - 8 mm.

For pillars, vertical reinforcement is profiled, horizontal reinforcement is smooth. The diameters are the same.

Typically, rods of grades A I and A III (A 400 C) are used.

You can use a new type of reinforcement - composite. The practice is not great yet, but its characteristics are good.

Sequence of reinforcement of pillars and grillage

The pillars are reinforced with vertical rods. They are boiled or knitted with wire into frames.

Sand 200 - 250 mm thick is poured into the bottom of the pit and the same layer of sand and crushed stone is placed on top. At least 50 - 100 mm of concrete is laid to protect the metal from ground moisture and corrosion.

The finished frames are lowered into the holes of bored piles or holes for pillars.

The cross-sectional dimensions of the frame should be 35 - 50 mm less than the diameter of the well on each side. This layer of concrete is called protective. By its alkaline reaction it protects the metal from corrosion.

During the manufacture of the frame, the outlets of the pillar reinforcement are bent horizontally to a length of 30 - 40 rod diameters. If a certified welder knows how to weld reinforcement correctly and without overheating, bends are not made.

The rods are laid in the grillage in two layers:

• the top layer is below the top cut by the thickness of the protective layer;
• in the bottom layer, the same thickness above the sole.

The middle is not reinforced, there are almost no loads here.

The arrangement of reinforcement bars is determined by the requirements for parts of the foundation:

• for bored piles or reinforced concrete pile pillars - the shear strength requirements are determined by the load from the horizontal displacement of soil masses;
• for a horizontal, usually monolithic grillage, the load will be bending, since the grillage beam is located at its ends on supports, and there is almost no support under its middle part.

How are the reinforcement placed in the corners of the grillage?

Reinforcement of the corners of the pile foundation grillage and the intersection with load-bearing internal walls must be carried out by bending the rods to a length of at least 0.4 - 0.8 m. The bent parts of the horizontal rods of one side of the grillage should extend onto the other side perpendicular to it and vice versa.

It is not always possible to weld - some grades of steel cannot be welded with conventional electrodes, overheating of the rods, leakage of metal and weakening of joints, seams, etc. are possible.

Regulatory documents on columnar foundations

The number of rods, grades of reinforcement, and diameter values ​​are obtained as a result of the calculation of a columnar foundation by a professional civil engineer. As well as drawings for its reinforcement.

For this purpose, the following regulatory documents are used:

• SP 20.13330.2011 (SNiP 2.01.07-85*) “Loads and impacts” - terminology and loads on a columnar foundation;
• SP 50-101-2004 (updating SNiPs 2.02.01-83 and 3.02.01-87) - Set of Rules for foundations of buildings and structures, clauses 12.1 - to 12.8 - general requirements for calculations, calculation of columnar foundations - clause 12.3 ;
• SP 22.13330.2011 (updated SNiP 2.02.01-83) “Foundations of buildings and structures” - loads, depth, groundwater accounting, features of design stages;
• SP 63.13330.2012 (updating SNiP 52-01-2003) “Concrete and reinforced concrete structures”, design requirements in clauses 5, 7, 10.

Calculation based on documents allows you to more accurately determine the price of reinforcement for a columnar foundation.

Errors in reinforcement

The most common errors:

1. The reinforcement frame is installed on the ground. The metal corrodes, expands in volume and tears the concrete in the most important place - the base of the pillars.
2. When installed in a well, the frame is not centered. The reinforcement may come out of the post or a small thickness of the protective layer may remain.
3. Reinforcement for connections with the grillage frame is not available. A monolithic grillage will not be able to withstand horizontal soil movements, and the foundation may collapse.
4. When welding rods, connections should not be at corners or at intersections of walls.
5. When bending rods, the bend area is not heated - the rod gives microcracks.
6. Reinforcement in the middle part of any reinforced concrete product is a gross mistake - a concrete beam or slab is stretched either from above when there is a load on the edges and the support is in the middle, or from below - when the supports are at the edges and the load is in the middle. These tensile forces must be withstood by the reinforcement. In the middle part of the product there are almost no loads, and the reinforcement there is wasted money, time and labor.
7. When pouring concrete, use the deep vibrator only in the internal zone of the frame and carefully so as not to disturb its configuration.

Questions and answers on the topic

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In the field of individual construction, when using a pile foundation, a monolithic reinforced concrete grillage is the most popular option, since even with significant dimensions it can always be made on your own.

The materials used for this can be delivered to the construction site by ordinary freight or even passenger transport without the use of special platforms or cranes.

However, the installation of a monolithic grillage is more complex than a prefabricated grillage, and the main difficulty lies in the correct reinforcement of the pile grillage.

You can often hear about the similarity between the structure of a grillage and a conventional strip foundation, but this statement is only partly true. Indeed, in its appearance and function, the grillage is very similar to the strip base, however, the operating conditions of these structures differ significantly:

• If for a strip foundation the occurrence of a bending moment in the vertical plane is rather an out of the ordinary phenomenon, then for grillages, which are beams laid on piles, this is the norm. The span located between the supports takes the weight of parts of the building and other loads, while being, as it were, suspended in the air, which causes deflection;
• Another difference is that the load on a strip foundation is less predictable. The underlying soil under various sections of the foundation may “float” or swell. This causes multidirectional deflections, in which both the upper and lower parts of the cross section can be stretched. And the stretched zone that occurs when a reinforced concrete element deflects is, as is known, precisely the zone in which the reinforcement should be located. Thus, a conventional strip foundation has to be reinforced equally in both the upper and lower parts.

In the case of a grillage, the impact from the soil is completely eliminated, so the stresses arising in it are quite predictable: in the spans between the piles, the lower part of the cross section is always stretched, and in the zones of support on the piles, the upper part is always stretched.

This determines the reinforcement scheme for the pile foundation grillage. The lower chord of the reinforcement frame in the areas between the piles is made more powerful, and at the points of support on the piles the upper chord is strengthened.

Selection of reinforcement frame materials and determination of its parameters

The diameter of the reinforcement used and the parameters of the frame are selected based on calculations that take into account permanent and temporary loads.

Calculation of the pile foundation grillage reinforcement should be carried out by an experienced civil engineer with a good knowledge of the topic of reinforced concrete structures.

Standard solutions

In practice, in individual construction the following rules are followed:

• in the stretched areas of the grillage, several longitudinal reinforcement bars of class AIII with a diameter of 20 mm or more are laid;
• reinforcement with a diameter of 8–15 mm is placed in the compressed belt. The pitch between the rods of the longitudinal reinforcement, also called working reinforcement, is 80 - 100 mm.
• To absorb transverse tensile forces, as well as to combine longitudinal reinforcement into a single frame, transverse rods are attached to it - smooth AI class reinforcement with a diameter of 6 to 8 mm. The distance between them should not be less than 250 mm, but usually it is taken equal to 3/8 of the height of the grillage section.

If the height of the grillage exceeds 150 mm, vertical bars are installed in the reinforcement frame, the pitch of which corresponds to the pitch of the transverse reinforcement.

Most often, instead of separate longitudinal and transverse rods, clamps are used - parts made of reinforcement in the form of a closed rectangle or an inverted letter “P”.

Reinforcement of abutment zones of grillage tapes

Where the grillage strips form an L-shaped or T-shaped intersection, simply fastening the intersecting rods of the working reinforcement is not enough.

Here rods bent at right angles are placed, each part of which fits into one of the adjacent tapes and extends into it by at least 40 diameters.

Clamps are installed twice as often in these areas.

Manufacturing jobs

Reinforcement of the pile foundation grillage is carried out immediately after the construction of the formwork. A mandatory element of the latter must be transverse jumpers in the upper part, to which, ultimately, the reinforcement frame will be suspended.

Work on installing reinforcement in the future grillage can be divided into several operations.

Construction of the lower chord of the reinforcement cage

At the bottom of the formwork, special plastic bosses are placed on top of the waterproofing, on which the lower chord of the reinforcement cage will then be located.

If there are no bosses available, they can be replaced with fragments of brick or wooden blocks 40 - 50 mm high:

• the height of all pads must be the same so that the reinforcement bars take a strictly horizontal position;
• the spacing between the bosses or elements used as an alternative depends on the diameter of the working reinforcement: it must be such that the rods do not bend;
• it is necessary to lay the working reinforcement of the lower chord on the bosses with equal spacing. The distance from the outer rods to the side surfaces of the formwork should be 30 - 40 mm.

When constructing the frame, the contractor must be guided by the requirements of the documents describing the reinforcement of the pile foundation grillage: a design drawing with all the necessary instructions is given in the construction project.

If the grillage strip is of considerable length, each thread of the working belt is assembled from several reinforcing bars connected with an overlap of 1 m.

Transverse reinforcement bars or clamps are attached to the lower chord, combining transverse and vertical reinforcement.

Upper belt device

The working reinforcement of the upper chord is suspended on the formwork lintels, which were mentioned at the beginning of the section. The length of the hangers should be such that after pouring the grillage, a protective layer of concrete with a thickness of 30 to 40 mm is formed above the reinforcement.

The rods of the upper chord are connected to transverse and vertical reinforcement or to clamps, if any are used.

Then both working belts should be tied to the reinforcement protruding from the piles. The reinforcement frame can be considered ready.

Methods of knitting reinforcement

The most common fastening method is to tie the reinforcement together using a special wire. Electric welding is used very rarely and only for fittings marked with the letter “C”.

It is not allowed to connect conventional reinforcement by welding, since due to exposure to high temperatures it becomes less durable.

For knitting reinforcement, only annealed round wire with a diameter of 1 mm is used. Unburned wire is less flexible, so it bends poorly and breaks easily.

The fastest way to knit reinforcement is with a special gun equipped with a battery. But its purchase is only advisable for large volumes of work; moreover, it is not very convenient when tying reinforcement in hard-to-reach places.

Reinforcement of a pile-grillage foundation for a private house is mainly carried out using another tool - a special hook. Professionals prefer homemade hooks, but for one-time work, purchased ones will do.

On sale you can find both regular and screw hooks, also called semi-automatic.

The latter allow you to knit the reinforcement somewhat faster, but due to their design, after tightening the knot, they leave too long free ends of the wire, which often protrude from the concrete and begin to rust.

The simplest and most common types of knots are the so-called “loop” and “two loops”. The first is used when connecting reinforcement with overlaps, the second - for butt joints. In practice, the loop is often used not only for overlap joints, but also for corner joints.

At the final stage of installation of the reinforcement cage, the bosses on which the working reinforcement of the lower chord were installed should be removed. After this, the entire frame will be suspended on a wire wrapped around the upper formwork lintels. Now you can start pouring concrete.

Video about reinforcing the grillage of a pile foundation

A pile foundation is a universal foundation for the construction of brick (read about the reinforcement of brickwork separately), wood, aerated concrete (read about the reinforcement of aerated concrete separately) and foam concrete low-rise buildings in any ground conditions. Such bases are also used for other structures (for example, fences, columns). The strength and reliability of the pile foundation directly depends on the grillage, the reinforcement technology of which we will talk about in this article.

Grillage reinforcement

You will learn why reinforcement of a pile-grillage foundation is necessary, what materials are used for this and how the process itself is performed. Diagrams and drawings will be provided that explain all the nuances of reinforcement of a monolithic grillage.

What functions does the grillage perform and why is its reinforcement needed?

The grillage is a strip structure (read separately about how a regular strip foundation is reinforced), connecting free-standing piles to each other. By tying the supports, they receive additional spatial rigidity and resistance to overturning loads. The grillage also acts as a supporting surface on which the walls of the building are erected.

Read also: what is reinforcement anchoring, and why is it necessary?

There are several types of strapping based on the material of manufacture - steel (from a channel or I-beam), wood (from timber) and reinforced concrete. It is in the case of installing a monolithic pile grillage, which is used in the construction of houses made of heavy materials, that it is necessary to reinforce the piping.

The need to strengthen a monolithic grillage with reinforcement is determined by the fact that concrete as a material has high resistance to compressive loads, but at the same time it has weak resistance to bending and tensile loads, which can cause its deformation.

Scheme of a pile-grillage foundation

The reinforced frame placed inside the monolithic grillage takes on the above loads, preventing the risk of its destruction, which significantly increases the reliability and durability of the structure. Reinforcement is necessary not only when installing a pile-grillage foundation, but also in a columnar foundation, which has a similar configuration.

Read also: what mesh is used to reinforce the floor screed?

Note that foundations that use two types of piles are subject to reinforcement - driven and bored. Driven piles are prefabricated structures that, upon completion of installation, are cut using a pile driver using a special hydraulic pile cutter.

After trimming, the reinforcement at the end of the pile is exposed, which is subsequently connected to the frame of the monolithic grillage. When installing bored supports, their reinforcement frame is made so that there are reinforcement protrusions 30-40 cm high above the concrete body of the pile.
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What and how to reinforce?

Reinforcement of the strip grillage is carried out using a spatial reinforcement frame, consisting of two longitudinal reinforcement belts (upper and lower), connected to each other by horizontal and vertical jumpers.

Longitudinal belts are made from reinforcement bars of class A3 (hot-rolled corrugated profile), the diameter of which is 13-16 mm. It is possible to use fiberglass reinforcement, which is confirmed by reviews of the successful operation of such pile-grillage foundations on specialized forums.

Connecting vertical and horizontal jumpers can be made in two versions - in the form of separate rods of reinforcement welded to the longitudinal chords (the diagram shows the configuration). In this case, it is necessary to use rods of the same standard size as when arranging the longitudinal belt.

Drawing of connecting belts with separate jumpers

The frame can also be connected by jumpers made of rectangular reinforcement bent into clamps (diagram below). With this approach, smooth rods of class A2 (diameter 8-10 mm) are used. Bent clamps are labor-intensive to install, but due to the smaller number of welds, they are more reliable and durable. Fiberglass reinforcement that cannot be bent is not used to create clamps.

Drawing of connecting belts with clamps

According to the provisions SNiP No. 2.03.01 “Manual for the design and arrangement of pile-grillage foundations”, when installing the reinforced frame, it is necessary to observe the following step between the constituent elements:

• the number of rods in the longitudinal belts is at least 4, the distance between them is up to 10 cm;
• the pitch between the transverse jumpers of the longitudinal belt is 20-30 cm;
• the step between the vertical connecting jumpers is up to 40 cm;
• protective layer of concrete - at least 5 cm.

The protective layer is the distance between the outer contours of the reinforced frame and the walls of the concrete body of the monolithic grillage. If the protective layer does not have the required thickness, two problems will arise - the frame will not be able to correctly redistribute the loads acting on the grillage and the reinforcement will be excessively susceptible to corrosion under the influence of moisture penetrating into the micropores of the concrete.

Plastic stand for fittings

To create a protective layer along the bottom edge of the grillage, special plastic mushroom stands are used, which lift the reinforcement above the formwork. The use of pieces of brick for these purposes is not permitted.
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As an example, we give the calculation of the amount of reinforcement for a monolithic grillage with a perimeter of 8 * 6 m. We use the conventional dimensions of the strapping 40 * 40 cm. The reinforcement frame for such a strapping will consist of two longitudinal belts of 3 A3 rods with a diameter of 14 mm in each (the pitch between the rods is 10 cm , 5 cm on each side eats up the protective layer of concrete). The belts are connected by jumpers made of A1 reinforcement with a diameter of 11 mm, located in increments of 20 cm.

The calculation is performed using the following algorithm:

1. We determine the total length of the rods in the upper longitudinal belt. To do this: a) determine the perimeter of the grillage: 8+8+6+6 = 30 m; b) we calculate the length of 3 rods: 3*30 = 90 m; c) calculate the length of reinforcement A3 for both belts: 90*2 = 180 m.
2. To connect the rods of the longitudinal belt, we will need jumpers 30 cm long, which will be located in increments of 20 cm. We calculate their number for both contours of the grillage: 2*(30/0.2) = 300 pcs, after which we calculate the total length of the transverse jumpers: 300* 0.3 = 100 m.
3. It remains to calculate the length of the vertical jumpers connecting the upper and lower contours of the frame to each other. But since in the example a rectangular grillage is calculated, their number and length will be identical to the transverse lintels. If a grillage of rectangular configuration is used, the calculation is performed according to the formula specified in point No. 2.

As a result, the calculation showed us that the grillage reinforcement requires 180 m of A3 class reinforcement and 200 m (100+100) A2 rods with a diameter of 11 mm. You may also need to calculate the binding wire if you do not plan to use a welded joint. It is carried out taking into account the fact that about 40 cm of material is required for one connection: we determine the number of connections: 4*(30/0.2) = 600 pcs; and calculate the material consumption - 600 * 0.4 = 240 m.
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Features of grillage reinforcement (video)

Monolithic grillage reinforcement technology

The amplification of the grillage begins after all the previous stages of arranging the pile foundation have been completed - installation of piles, their trimming and arrangement of formwork. You must have a ready-made formwork, inside which the reinforced frames of the piles protrude to a height equal to the cross-section of the framing.

Formwork and piles before reinforcement

When assembling the frame, the reinforcement can be tied together using wire or the rods can be connected by welding. There is no significant difference in the joining method - it is often argued that a welded frame, due to the lack of elasticity, resists deformation worse than a ductile structure, however, in industrial multi-story construction, the frames of pile-grillage foundations are always welded, so these fears are groundless. In addition, welding is a more practical and quicker method to implement.

Read also: how are stairs reinforced, and is it necessary to do it?

Grillage reinforcement - step-by-step instructions:

Assembling the reinforced frame on straight sections of the grillage is quite simple to perform. Difficulties arise when reinforcing the corners, which must be further strengthened, since this part of the frame experiences maximum loads.

Scheme of correct reinforcement of grillage corners and junctions

Corners and places where the internal walls of the frame meet the external ones cannot be reinforced with overlapping reinforcement. In these areas it is necessary to lay solid rods curved in an L or U-shaped configuration. A diagram of the correct reinforcement of the corners of a pile grillage is shown in the image.

Related articles:

Reinforced concrete monolithic structures are one of the prerequisites for the strength, reliability and durability of an object. A reinforced concrete structure means that the concrete is reinforced using a special frame tied or welded from reinforcing bars. You should learn how to properly knit reinforcement for the foundation before reinforcing concrete on your personal plot, building a house, garage or other durable objects.

Options for knitting reinforcement

Basics of proper tying of reinforcement

Basically, in individual construction, a reinforcing frame is used when laying a strip foundation. A strip base is a monolithic structure made of concrete and a reinforced frame inside, in which the frame takes on tensile loads and lateral shifts of the soil. Due to multidirectional loads on the reinforcement frame, it is important to correctly calculate it, as well as find out the parameters of a house or other building that uses reinforcement in the structure, the amount of building materials and their characteristics.

To tie a reinforcing belt with your own hands for any type of foundation in which it can be used, you need to be able to tie the transverse and longitudinal joints of the rods in the correct way. Welding is very often not recommended for assembling reinforcement cages due to the connection being too rigid, which, under sufficiently strong loads, can burst and weaken the entire structure. Therefore, you should use a special factory or homemade hook, plus know the basic layout of reinforcing bars in concrete.

Reinforcement parameters when calculating a frame for a strip foundation

The knitting steel wire must be soft or annealed, and in order to properly crochet the reinforcement, it is necessary to study the requirements for the knitting wire, which are regulated in GOST 3282.

Professional builders categorically deny knitting metal reinforcement with plastic clamps, which are allowed to knit fiberglass reinforcement, since the mass of concrete poured into the formwork displaces the knitting points along with the mortar. Slab concrete foundations are a separate topic, and in them the reinforced frame can be welded. There are ready-made industrial reinforcing mesh welded from rods. But such a frame is much more expensive than a home-made one, and besides, the end joints need to be additionally reinforced with U-shaped clamps in place, which makes the welded frame even more expensive. Therefore, for the foundation of a private or country house, it is easier to knit the reinforcement frame manually, using a coil of soft wire, a special crochet hook, and instructions for work.

Hook for tying reinforcing bars

When knitting a frame for a foundation, operations are performed in the following order:

1. A piece of knitting wire 20-25 cm long is used for knitting reinforcement rods Ø 8-16 mm. A piece of this length must be cut from the bay;
2. The segment is bent in half in the center, brought under the intersection of the rods diagonally;
3. The sharp end of the crochet hook must be threaded into the loop that was created by folding a piece of wire;
4. The clamp, which is made from a piece of wire, should be pulled tight;
5. the free end of the clamp is placed on the working end of the crochet hook;
6. Now we knit two intersections together: when you rotate the hook 3-5 turns, you will get a strong but flexible twist;
7. After removing the crochet hook from the loop, the remaining free ends of the wire clamp must be bent inside the reinforcement frame.

Important: If reinforcement Ø 25 mm or larger is used for the aroma frame, the intersections of the rods must be welded and not tied. Connected joints can break during operation of a finished reinforced foundation under the weight of concrete and the building.

Ready reinforced frame

Common mistakes when knitting a reinforcing frame that do not need to be repeated:

1. Straight sections of rods at the corners of the frame are connected using the overlap method;
2. The reinforcing frame is installed not on pads, but on vertical frame rods;
3. In the section of the concrete tape, the reinforcing binder and reinforcing material is less than 0.1% of the total volume of concrete;
4. There is no protective layer on the sides of the formwork, which is why the rods can come into contact with the formwork material.

The angular intersections of the frame rods in a strip foundation cannot simply be tied together and left as an overlap of rods. The connection of the rods is done according to anchoring schemes specially developed for such cases, one of which is presented below:

Schemes for anchoring frame corners

Reinforcement of a concrete foundation must take into account some features of the strip structure:

1. The reinforced frame for a concrete strip can be tied both in the ground and in the finished formwork. For this, reinforcing bars, metal clamps and anchors are used;
2. The deep foundation is reinforced before installing the panel formwork - this option is preferable due to the fact that the heavy frame does not have to be lowered into the trench and deformed;
3. The reinforced frame needs to be reinforced with U-shaped or L-shaped anchors at the corners of the structure;
4. To ensure that the frame is protected from below with concrete, supports 5-7 cm in size are used, which are called glasses;
5. The lengthening of short longitudinal rods occurs with an overlap, the overlap should be ≥ 20 rod diameters, or ≤ 25 cm;
6. The reinforced frame should not be placed on stones, bricks or sections of reinforcing bars - only iron, plastic or concrete pads should be used;
7. The joints of the overlapping reinforcement must be spaced apart - more than half of the total cross-section of the longitudinal rods should not be connected in one section.

Important! Clamps in the reinforced frame are used to create and hold the geometry of the structure. Therefore, the diameter of long horizontal rods should be 6 for length ≤ 0.8 m and 8 mm for rod length ≥ 80 cm.

Reinforcement of tape with L-shaped and U-shaped reinforcements

Reinforcement of a slab floating foundation should take into account some design features and not repeat common mistakes:

1. The rods at the corners of the upper and lower levels must be connected with U-shaped clamps;
2. You cannot use one reinforcing mesh instead of two frames - the lower frame takes on tensile loads from the weight of the house, and loads from heaving forces are applied to the upper layer of the frame. One reinforced mesh is allowed for concrete slab thickness ≤ 15 cm;
3. Failure to provide concrete protective layers for the frame at the top and bottom. Concrete layers must be ≥ 5-7 cm thick;
4. The cell size of the reinforcing mesh should be ≤ 40 cm, the optimal cell size is 20 cm.

To assemble the reinforced frame of a concrete slab, the upper chord of the mesh is fixed using such bending devices as “tables”, “conductors”, “pawns”, “frogs”, “sticks”, “spiders”, and other supporting elements with straightened rods, which rest against the structure of the lower belt.

Bending products for reinforcing frames and meshes

Bending of reinforcing bars should not be carried out using gas welding. The rods are bent on special bending machines or clamps, in which the required radius can be set.

Near the load-bearing walls, the foundation must be reinforced with additional rods, since the size of the mesh cells near the walls is half the size of the others. If slabs with stiffeners are used for the base, then the reinforced frame is used the same as for a strip foundation or grillage.

Bending machine

Grillage reinforcement

Due to the fact that the grillage is similar to a foundation strip, many craftsmen make mistakes in its reinforcement. Tensile loads from the weight of the house are applied to the concrete strip in the area of ​​the base; the upper part of the foundation experiences loads from seasonal heaving of the soil. The grillage never experiences loads from heaving forces, since it rises above the soil and has an air gap or a layer of expanded polystyrene, which wrinkles when deformed. Only vertical bending forces are applied to the grillage in areas where the supports are pinched.

Important: In a grillage, the reinforcing frame must be reinforced with longitudinal reinforcement connected with steel clamps. Reinforcement is carried out for the upper columns, piles or pillars, as well as for the lower armored belt.

Grillage reinforcement for piles

The cross-section of the reinforcing frame is of different types:

1. If the formwork is tubular, then the frame can be tied round or square;
2. For a columnar foundation in formwork made from prefabricated panels, round or square clamps are used to tie vertical reinforcement bars;
3. One support must have at least four longitudinal rods.

Pile reinforcement

The bottom of the piles does not need to be reinforced. The head of the pile at a distance of 1 meter from the bottom must be reinforced and filled with concrete. Vertical reinforcement bars are bent at an angle of 900 and then tied to the grillage.

Pile reinforcement

A homemade reinforcing frame is made only using twists of soft knitting wire. Ready-made reinforced frames for floating, slab, pile and column foundations are fastened together using electric welding. It is prohibited to use gas welding, since the reinforcement rods become soft in the heating areas.

Using the above recommendations, you can tie the reinforcement cage or mesh yourself - on the ground or in the formwork. Each type of foundation has its own design differences that affect the thickness of the protective concrete layer, and the most difficult operation during reinforcement is anchoring the corners of the foundation, strengthening areas of tension and compression.

Laying the foundations for any building is a very responsible and important stage from which the main construction work begins. It is recommended that foundations be manufactured in strict accordance with the design documentation.

For monolithic structures, a fairly important part of the work is the grillage reinforcement. The strength of the entire structure largely depends on the quality of the associated reinforcement. You can carry out reinforcement yourself, having previously familiarized yourself with the technology of this type of work.

What is a grillage

A grillage is a monolithic element of the base of a building that connects separate pillars or piles into a single system. It is made in the form of a strip foundation, on which the load-bearing and external enclosing structures of the building are installed. The tape evenly distributes the loads across the entire base of the building, which in turn transfers them to the ground.

Grillage arrangement diagram

The grillage can be made not only in the form of a monolithic strip foundation. It is also made of wood, metal and reinforced concrete products located between columnar support structures. Such a device in the form of beams is used much less frequently than a monolithic one.

There are hanging and recessed structures

Depending on the height of the grillage foundation relative to the ground level, hanging and recessed versions of the device are distinguished. When constructing a recessed grillage, a monolithic design is selected. If a hanging one is made, then the grillage base can be made of horizontal beams.

A monolithic grillage contains concrete and reinforcement at its core. Reinforcement takes up the bulk of the time when constructing this type of foundation. When carrying out work on reinforcing a strip foundation, it is necessary to be guided by building codes and regulations 52-01-2003.

The grillage should serve as a reliable support and protect the structure from moisture. The pile-grillage foundation is suitable for the construction of buildings with no more than three floors.

Installation of a monolithic grillage

To make a monolithic grillage foundation, you will need to perform several stages of work.

1. Installation of formwork.
2. Grillage reinforcement.
3. Concreting.
4. Stripping.
5. Waterproofing tape.

Installation of formwork

The formwork must be installed strictly at an angle of 90 degrees

The grillage foundation is made suspended or buried in the ground. The design of the formwork directly depends on its shape.

Regardless of the design, the side walls of the formwork must be assembled at a strictly vertical level, and the angles must be 90°, unless the design provides for a different design.

When making a tape in the ground, you can use soil instead of formwork as a support for the future foundation. Above ground level, formwork is usually assembled from boards or plywood. It is knocked together or pulled together in such a way that the concrete does not squeeze out the boards or spread during the process of laying it. That part of the foundation that protrudes above the ground will be protected by such a structure.

If a hanging version of the grillage is chosen, then it is necessary to provide a high-quality foundation in the formwork. It needs to be calculated based on the load it must withstand. The load is determined by the mass of concrete and reinforcement. It is also necessary to take into account the mechanical effects on the structure from vibration of concrete during the pouring process.

The side walls of the formwork must be firmly assembled. For this, transverse ties, spacers, tubes with studs and other materials can be used that will ensure the reliability of the structure.

Poor quality formwork can lead to failure of the concrete laying process. This is unacceptable in construction, but often occurs due to negligence in this part of the work.

Grillage reinforcement

Structural reinforcement

Reinforcing the grillage of a pile or columnar foundation is one of the most critical stages in constructing the foundation for a building.

Periodic metal reinforcement is used as the main material for reinforcing foundations. Recently, it has begun to be replaced with composite fiberglass. It is worth noting that fiberglass reinforcement is not suitable for hanging structures. It is good where there is support on the ground.

Reinforcement is welded into beams

The reinforcement is tied or welded in some cases into frames, so-called beams. There are several types of beams. The type of reinforcement, and therefore the type of beams, is determined at the design stage.

During self-construction, when there is no project and there is no opportunity to contact specialists, there is an option to use an online reinforcement calculator. It is advisable to find several such online programs on the Internet and make calculations in each in order to compare the data and determine the error in the calculations. Having calculated the reinforcement based on the entered foundation parameters, you can begin work.

The reinforcement of a monolithic grillage in its most common form consists of straight longitudinal and transverse rods, which are connected to each other by binding wire or welding. In order to properly connect the structure, clamps and U-shaped products are made from reinforcement. They are connecting elements in the nodes of the reinforcement frame.

To find out how reinforcement frames and their assemblies are correctly manufactured, you need to familiarize yourself with the manual for the design of concrete and reinforced concrete structures made of heavy concrete (without prestressing).

Reinforcement of pile-grillage foundations is impossible without connecting the pile reinforcement to the grillage frame. When constructing a pile field at the reinforcement stage, vertical rods are made with allowances in height. When installing the reinforcement frame of a strip foundation, the rods released from the piles are bent at the required horizontal level and connected to the main frame. Thus, the integrity of the structure is achieved. For all the details on pouring a pile-grillage foundation, see this video:

You cannot heat metal reinforcement in order to bend it. For bending it is necessary to use special devices or a pipe bending machine.

Concreting tape

You need to pour concrete into the formwork without interruption to get a high-quality monolith

The grillage foundation is poured with concrete at the same time without interruption in the work until it is completely completed. It is strictly forbidden to make breaks along the length of the foundation. The only permitted action is a gap in the height of the grillage. After pouring a 150-200 mm layer over the entire volume of the tape, a break in work is taken.

Before continuing construction work, it is necessary to wait until the concrete reaches the minimum permissible strength. Then you need to clean off the top layer, the so-called concrete milk, and only after that continue concreting the tape.

It is important to carry out the work so that there are no pores in the concrete mass. It is required that the concrete fills the entire space in the formwork. There should not be a single air pocket left inside the grillage.

Stripping

It is important not to remove the formwork ahead of time

You can neglect this process once and carry it out ahead of time in order to incur losses that will significantly affect the construction budget.

If the formwork is removed prematurely, the foundation may crack, which will leave virtually no options other than dismantling it. In this case, a new foundation will be required, and accordingly construction costs will increase significantly.

Concrete gains strength depending on its grade and ambient temperature. The ideal temperature is 20°C; under such conditions, concrete grades M200-300 will gain 100% strength in 28 days.

Data on concrete strength gain are presented in the table.

Concrete grade	Hardening time, days	-3°C	0°C	+5°С	+10°С	+20°С	+30°С
	1	3	5	9	12	23	35
	2	6	12	19	25	40	55
M200-300 on Portland cement M-400 and M-500	3	8	18	27	37	50	65
	5	12	28	38	50	65	80
	7	15	35	48	58	75	90
	14	20	50	62	72	90	100
	28	25	65	77	85	100	-

The table shows that at low temperatures it is advisable to use concrete with additives to quickly gain strength. This slightly increases its cost, but will also significantly speed up the construction process.

It is allowed to remove the formwork when the concrete has reached at least 50% strength.

Waterproofing tape

With a hanging grillage, you can use coating waterproofing. In the recessed version, it is possible to lay roll waterproofing in the ground before pouring concrete and, after stripping the upper part, completely cover the foundation with it. For more information about waterproofing a grillage structure, watch this video:

It is important to protect the base from moisture. If the foundation absorbs water, then in winter at subzero temperatures, microcracks will form in it during the expansion of freezing water. This must be avoided.

Mistakes when reinforcing and how to avoid them

Do not reinforce corners by crossing reinforcement

There are a number of mistakes related to reinforcement that inexperienced builders make in order to save money or simply due to ignorance of building codes and regulations. Below are the most frequently repeated ones.

1. Reducing the diameter of a bored pile, according to some builders, should be accompanied by a decrease in the number of vertical reinforcement bars to which the grillage frame must subsequently be attached. Reducing the allowance of vertical bars.
2. Reinforcement of corner sections by crossing straight reinforcement bars. Many people do this so as not to complicate the knitting of the frame.
3. Failure to follow the steps for installing lintels when reinforcing the grillage. Skipping required connections. This often happens in order to save money.
4. Deviation of the reinforcement cage from the central axis. This will lead to uneven load-bearing capacity of the foundation. Such things often happen due to simple negligence. See all the details of reinforcing a pile foundation in this video:

The solutions to the above errors are given below.

1. The diameter of the pile should not be less than 300 mm, the number of vertical rods should be less than 4, the allowance for reinforcement under the grillage should be at least 0.5 m.
2. To properly connect the beam assemblies, you should make bent U- and L-shaped parts with which you need to connect the corner elements.
3. When installing the reinforcement frame, a step of 200 to 400 mm between the lintels must be observed. The exact step size is determined at the design stage.
4. It is necessary to make all measurements using building levels so that the frame is aligned relative to the central axis.

Reinforcement is a significant part of the construction process. Everything is important: the quality of materials, the experience of the builders, and the availability of working documentation.

Failure to comply with reinforcement rules can lead to the most serious consequences. This stage of construction is one of the most critical.

During construction work, any mistake leads to a decrease in the life of the building without the need for repairs. This is the best case scenario. At worst, even at the stage of construction of the building, it is subject to reconstruction.

To achieve maximum service life, it is necessary to comply with building codes and regulations, avoiding deviations from the design. Construction combines a set of measures that must be followed to achieve the desired result. If possible, it is better to entrust such work to professionals.

A pile-type foundation is used as a reliable foundation for the construction of buildings. A foundation on supporting elements is necessary when constructing objects on problematic soils. A pile foundation is the optimal solution in many situations, including if the structure is being built on permafrost or weak soil with nearby aquifers, as well as if there are significant elevation differences at the construction site. Reinforcing the grillage of a pile foundation allows you to ensure the strength of the foundation and form a reliable base for the building being constructed.

The grillage is a critical, horizontally located part of the load-bearing frame, connecting the supporting columns into a single contour. It ensures the verticality of the pillars and prevents them from moving. Ensuring the strength characteristics of the supporting structure is achieved by strengthening it with steel reinforcement. To strengthen the support contour, a drawing is required, and calculations of the expected forces acting on the foundation during operation of the structure are required.

Pile foundation is a universal foundation for the construction of brick, wood, aerated concrete and foam concrete low-rise buildings

Let's look at how a grillage foundation is strengthened. Let us dwell on the features of the main stages of work, the professional implementation of which will ensure the reliability of the foundation being built.

What is a grillage?

For those who do not know construction terminology, we inform you that the grillage is a critical part of the pile foundation, connecting the pile heads into a single power circuit.

There are different types of grillages used in pile foundations:

• tape type, representing a monolithic concrete tape. It is located along the perimeter of the supports, successively located under the load-bearing main walls;
• slab structure, in the form of a monolithic slab, the dimensions of which correspond to the contour of the base of the building and cover all supports.

The grillage is a ribbon structure that connects free-standing piles to each other

Depending on the characteristics of the grillage foundation, it can be manufactured in the following versions:

• Whole version. Manufacturing is carried out by pouring concrete mortar into pre-prepared formwork. The formation of a monolithic base occurs after the concrete mixture has hardened.
• Composite form. The base is a prefabricated surface made of industrially produced reinforced concrete products, connected during installation with supporting columns, as well as with each other.

Regardless of the design features, the grillage forms a supporting surface intended for the construction of the walls of the building. The tying of columns located in the ground ensures high rigidity of the spatial system and resistance to the effects of existing forces.

Reinforcement of a pile-grillage base allows you to strengthen the monolithic base with steel rods, which contribute to the integrity of the structure and increase durability.

Design features

To form a strip foundation located on piles, grillages are made at different heights relative to the zero level. Depending on the location of the contour relative to the ground level, the following types are distinguished:

• high, the lower mark of which exceeds the ground level by 10 cm or more. Constructed for light buildings located on any type of soil. On problem soils, its device is especially important. The structure needs serious strengthening with reinforcement, which is due to the presence of cavities under the concrete monolith located above the ground surface;

It is in the case of installing a monolithic pile grillage, which is used in the construction of houses made of heavy materials, that it is necessary to reinforce the strapping

• ground version, made on a gravel-sand backfill without penetration into the soil. Its peculiarity is the absence of free space between the concrete monolith and the ground. Installation is carried out on non-problematic soils. When the soil is exposed to frost heaving, cracks may form and the hardened concrete mass may separate from the supporting columns;
• shallow type, formed by burying the lower part into the soil on a previously prepared sand and gravel backfill. The design of such a foundation resembles a strip foundation, the base of which rests on piles. The formation of a buried foundation is associated with significant costs and is used for the construction of massive buildings located on soils characterized by low bearing capacity.

Pile-type foundations are formed mainly for light buildings. That is why the construction of a grillage foundation is quite common, the base of which is a hanging ribbon of concrete reinforced with steel reinforcement. With a base height of up to 40 cm, its width depends on the type and size of the material used to build the walls, and is 30-40 cm.

On the feasibility of reinforcement

The need to strengthen the foundation of a building with steel reinforcement is related to the characteristics of concrete. The material has increased resistance to compressive forces, but is susceptible to bending moments and tension, which cause disruption of the integrity and deformation of the base.

Note that foundations that use two types of piles are subject to reinforcement - driven and bored.

Reinforcement of a pile-grillage structure allows you to prevent the likelihood of destruction, increase the stability and service life of the building being constructed. The reinforcement frame located inside the concrete mass absorbs tensile loads and bending forces, ensuring the stability of the constructed foundation.

Regardless of the design of the piles used, located inside the soil, the supporting columns are also reinforced with reinforcement. The steel rods located in the piles are connected into a common structure with the reinforcing frame of the supporting surface.

Reinforcement of the pile foundation grillage allows:

• Prevent destruction of the monolithic massif as a result of soil reaction.
• Significantly increase the strength of the base, which absorbs the load from the mass of the structure.
• Prevent shrinkage of the structure caused by low strength characteristics of the base.

Strengthening the grillage foundation allows you to avoid negative phenomena.

Specifics of reinforcement

Reinforcement of the pile foundation grillage is carried out by a pre-fabricated volumetric frame, consisting of two tiers of rods, combined into a single structure using steel lintels.

Reinforcement of the strip grillage is carried out using a spatial reinforcement frame consisting of two longitudinal reinforcement belts

For the longitudinal chords of the frame, corrugated rods are used, produced by the hot-rolled method, which corresponds to class A3 reinforcement. Depending on the load perceived by the base, the diameter of the rods is 12-16 mm.

The combination of connecting elements located in the vertical and horizontal planes into a common power circuit can be carried out:

• separate steel corrugated rods of rectilinear shape, the diameter of which corresponds to the range of longitudinal reinforcement;
• steel clamps of rectangular configuration, made of smooth rods of class A2 with a cross-section of up to 10 mm. Despite the increased complexity of manufacturing and installation, rectangular jumpers ensure the reliability and durability of the reinforcement structure.

When strengthening a strip foundation placed on piles, adhere to the following recommendations:

• Use at least 4 rods located in the upper and lower tier of the strip contour frame, ensuring an interval between elements of 10-15 cm.
• Maintain a distance of 15-25 cm when installing jumpers in the longitudinal belt.
• Ensure the pitch of the vertically located frame jumpers is 30-40 cm.

The amplification of the grillage begins after all the previous stages of arranging the pile foundation have been completed - installation of piles, their trimming and arrangement of formwork

The need for a protective layer between the metal frame structure and the concrete surface of the grillage is determined by the following factors:

• the need for proper distribution of the current forces by the metal structure of the frame;
• the susceptibility of reinforcing bars to corrosion processes arising from moisture penetrating into the concrete.

Maintaining a fixed distance from the reinforcement to the formwork while providing a protective layer is achieved by using stands made of plastic.

Calculation method

To determine the need for reinforcement that allows for the reinforcement of the pile foundation grillage, it is necessary to first develop a drawing. The documentation contains the following information:

• Design dimensions.
• Number of reinforcement belts.
• Reinforcement profile.
• Diameter of the rods used.
• Distance between jumpers.

Scheme of correct reinforcement of grillage corners and junctions

Knowing the overall dimensions of the grillage foundation, it is easy to calculate the length of the steel reinforcement bars in the upper and lower chords, as well as the dimensions of the lintels.

Having summed up the obtained values, we obtain the total length of each standard size of the reinforcement used. Knowing the footage and weight of one linear meter of a certain rod, it is not difficult to determine the need for reinforcing bars, expressed in kilograms.

If you do not plan to connect the elements using electric welding, you will need knitting wire. Having a drawing that shows information about the number of connection points, you can calculate the required amount of binding wire. Considering that about 30 centimeters are needed to securely fix two perpendicularly located rods, the total need for wire is determined by multiplying the number of connections by the length of the material.

Carrying out the calculations is not difficult. The main thing is to first develop a reinforcement drawing.

Grillage reinforcement technology

If the reinforced piles have been installed and the formwork has been installed, then you can begin to form the reinforcement frame. Please note that the frame is fixed to the reinforcement protruding from the concrete piles to the height of the formwork. Fastening steel rods can be done by welding, as well as using binding wire.

The algorithm for performing the work is as follows:

• fix horizontally located longitudinal rods at a distance of 5 cm from the bottom of the formwork;
• place and secure the perpendicularly located rods of the lower chord;
• install rectangular clamps or vertically located rods for fastening the bars of the upper tier;
• secure the longitudinal rods of the upper chord;
• Perform angular reinforcement of the grillage by installing curved rods in the corners of the structure.

Reliably strengthen the corners with reinforcement, since in these places the frame absorbs significant forces.

Conclusion

Reinforcing the grillage of the pile foundation with steel reinforcement makes it possible to form a reliable base that ensures the stability of the structure being built. The work is not difficult to carry out independently, having previously developed a drawing according to which the pile foundation grillage is reinforced.

Reinforcement of pile foundation grillage: drawing, technology, calculation

How to reinforce a pile-grillage foundation? Correct calculation method. Features of grillage strengthening technology. Drawings and diagrams of grillage reinforcement.

Often, when building a house, a pile type of foundation is used. Moreover, the relevance and popularity of reinforcing the grillage of a pile foundation today does not raise any doubts. In this article we will understand the main important stages, characteristics and features of this direction.

In what cases is it advisable to use a pile foundation?

First of all, this type of foundation becomes relevant in the case of construction on heaving and soft soils. Also, this option will be the best when significant differences in height are obvious at the construction site or there is groundwater. In addition, the construction of such a foundation becomes a necessity when building a house in permafrost areas.

What is a grillage and the process of its reinforcement in general?

In the cases described above, diverse piles can be used. They may differ regarding:

• The material used for their manufacture;
• The method of immersing them in the ground.

The grillage is the connecting element that unites them into a single strong and integral structure.

Reinforcement of the pile foundation, in turn, is carried out in order to impart the required strength to the grillage. To do this, a preliminary drawing must be drawn up and all the most important calculations regarding the upcoming loads during operation of the structure must be performed.

What features are typical for the grillage device?

1. The norm for grillages is the presence of a so-called bending moment in the vertical plane. After all, it consists of beams laid on piles. At the same time, the span that lies between the supports is susceptible to the weight of various parts of the building, as well as other loads. It seems to be suspended in the air. For this reason, deflection appears;
2. The grillage completely eliminates any impact from the ground. Therefore, it is quite easy to predict the occurrence of tension in it. For example, the lower part of the cross section in all cases turns out to be stretched in the spans located between the piles. The upper one is in areas where the structure rests on piles.

These features of the grillage are of decisive importance in the process of drawing up a reinforcement scheme for the grillage of a pile foundation. It is not surprising that much attention is paid to increasing the strength of the lower chord of the installed reinforcement cage in the areas between the piles. At the same time, it remains important to strengthen the upper belt at the support points.

Reinforcement scheme for pile foundation grillage

It should also be remembered that before proceeding with the installation of the grillage and its reinforcement, it is necessary to correctly and clearly determine the required type of pile foundation and the total number of piles required.

There should be at least 4 of them on the basis that each corner will have its own pile. It is on this pile-type foundation that the grillage will be laid in the future. Moreover, it can be in the form of a solid slab or it can be of a strip type.

Scheme of strip pile foundation

How to correctly select materials for a reinforcement frame and determine its parameters

In order to correctly calculate the required diameter of the reinforcement used, as well as the necessary parameters of the frame, it is necessary to correctly perform the calculation with mandatory consideration of temporary and permanent loads.

Let's take a closer look at the most important aspects:

• First of all, it is necessary to determine as accurately and clearly as possible the composition of the existing soil located at the construction site. It is worth approaching the depth at which the foundation is actually planned with special responsibility. Why is this so important? These points are of no small importance for calculating the length of piles, as well as planning their design features. In addition, these points will be important for planning the arrangement of the foundation.
• It is also necessary to correctly calculate the bearing capacity of the future pile being installed.
• It is necessary to determine possible loads that can affect not only the piles, but also the soil.
• In order to obtain the total weight of the future building, it is necessary to sum up not only its weight, but also the weight of the planned floors and roof.
• It will be useful to take into account possible natural loads (for example, the mass of people in the house, snow, various equipment, and furniture).

All further calculations must be carried out taking into account the total area of ​​the building.

In general, in the most common cases, a grillage is chosen for buildings with an area of ​​at least 300 square meters. Moreover, a construction engineer who has excellent knowledge and skills regarding reinforced concrete structures should calculate the reinforcement of a pile-grilled foundation.

After the foundation of the building is calculated (with the determination of the required number of piles, as well as the distance between them, installation depth), a corresponding diagram and drawing must be drawn up.

Let's look at typical solutions and rules that are recommended to be followed:

1. Several reinforcement bars of class AIII longitudinal type (diameter - 20 mm) and above must be laid in the stretched areas of the grillage being installed;
2. Reinforcement with a diameter of 8 to 15 mm is placed in a compressed belt. The pitch between the rods of the longitudinal (working) reinforcement should be from 80 to 100 mm;
3. In order to absorb transverse tensile forces, as well as to combine longitudinal reinforcement into a single frame, transverse rods are attached to it. In this case, use class AI smooth reinforcement with a diameter of 6-8 mm. Moreover, the distance between them should be at least 250 mm. However, it is usually 3/8 of the existing height of the grillage section.

If the grillage exceeds 150 mm, vertical bars must be installed in the existing reinforcement frame. Moreover, the step must correspond to the step of the transverse reinforcement.

In general, clamps are often used instead of separate transverse and longitudinal rods. They are reinforcement parts in the shape of an inverted letter “P” or in the shape of a closed rectangle.

Grillage reinforcement

In the process of carrying out work on laying the foundation for a building with a grillage, it is mandatory to carry out proper reinforcement of the structure.

Why are piles reinforced? In order to guarantee them the required strength.

What is the purpose of grillage reinforcement? In order to maximize its possible load-bearing capacity.

Moreover, that part of the reinforcement that tends to protrude from the pile structure will be used as a connecting element directly between the grillage itself and the pile.

Fastening, in turn, is carried out using welding in most cases.

In order to perform reinforcement, it is necessary to draw up a preliminary drawing. In addition, the reinforcement scheme is also important.

Strip foundation grillage diagram

Do not forget that the grillage elements, which are not properly reinforced, will not be able to withstand the loads during the construction of the floors of the house, as well as its walls.

1. In the case of installing strip grillages, the reinforcement frame must be made of two separate belts. Moreover, they must be connected as rigidly as possible to each other using vertical rods made of metal (with the required cross-sectional diameter - up to 8 mm). Why is this particular diameter relevant? This happens because these metal rods are actually not subject to load. Their main role is to give the frame the necessary shape.

Strip foundation

The required condition is that each belt must include at least two rods. Moreover, the belts must be connected to each other using rods that are positioned horizontally and connected using the so-called knitting wire.

When making reinforcement cages for foundations with a grillage within industrial enterprises, welding machines are used to fasten transverse connections.

But at the same time, transverse circles or squares with longitudinal rods are connected only using the knitting method.

2. If the base is installed in the form of a solid monolithic slab, the reinforcement scheme will remain the same as for strip-type foundations.

In this case, the upper chord of the frame is made in the form of a kind of mesh of reinforcement, which has a cross-sectional diameter of 10-14 mm. For the purpose of arranging vertical rods, reinforcement with a smaller diameter is used.

Possible grillage design options

Depending on the design features, grillages can be low or high. Regardless of the type of structure, the same principle of reinforcing the grillage of a pile foundation is applied.

• In the case where it is planned to construct a foundation of the so-called ruined type, its lower part is placed at the same level with the ground. However, in some cases it can be allowed to drop down to a few centimeters below.
• To properly organize the trench between the piles, it is necessary to make cushions from compacted crushed stone and sand.
• After this, the direct installation of the formwork is carried out, as well as the assembly of the reinforcement cage.
• The reinforcement frame, in turn, must be rigidly connected with the existing pile heads. Moreover, it is necessary not to reach the walls of the installed formwork by approximately 5 cm.
• After the above steps, you can proceed to pouring the foundation with concrete.

However, it is worth keeping in mind that this grillage option will become possible if the building is erected on non-heavy soil. In other cases, an important condition will be the installation of a higher grillage with utmost attention to the reinforcement of the structure.

Methods of knitting reinforcement

Let's take a closer look at how to knit reinforcement for a pile foundation.

The most common method is tying reinforcement using special wire. For its part, electric welding is used quite rarely (only in the case of fittings that are marked with the letter “C”). Welding joints with conventional fittings is unacceptable. Indeed, due to exposure to high temperatures, it may lose its strength.

For the purpose of knitting reinforcement, only annealed round wire with a diameter of 1 mm is used. After all, unfired products have less plasticity and tend to bend poorly.

To speed up the mating process, use a special gun, which is equipped with a battery. However, it is logical to purchase it only if it is necessary to perform a large range of work. In addition, many appreciate it for its ease of working with viscous reinforcement in a variety of hard-to-reach places.

In general, reinforcement of a pile-grillage foundation is often performed using a different tool - a special hook. Moreover, professionals often make them themselves, but for one-time work, a purchased option will also be useful.

At the present stage, if desired, you can purchase screw (semi-automatic) as well as regular hooks.

Reinforcement tying pattern

Moreover, screw options help speed up the reinforcement process. At the same time, due to their design features, after tightening they can leave quite long free ends of the wire used. Therefore, they tend to protrude from the concrete and begin to rust quite quickly.

What types of knots are considered the simplest and most convenient? The so-called “two loops” or “loop”. A loop is used to connect overlapping reinforcement, two loops are used in the case of butt joints. In practice, a loop is often used not only in the case of overlap joints, but also in the case of corner joints.

We should not forget that the final stage of installation of the required reinforcement cage should be the removal of the bosses on which the working reinforcement of the lower chord was installed. After this stage, the frame is suspended on a wire that wraps around the upper lintels of the formwork. After these operations, you can proceed directly to pouring concrete.

It is clear that reinforcing the grillage of a pile foundation is a rather complex multifaceted process that requires a thoughtful and competent approach. We hope that the tricks and tips in this article will help you complete all the work clearly and easily.

A grillage is a device that evenly distributes the load of a house on the pillars or foundation piles.

There are 3 most popular types of grillage: strip, slab and pile. The grillage reinforcement must be carried out exactly according to the project, which must be drawn up in advance. It should make a preliminary calculation and analysis of the foundation of the future house. Because if you neglect this data, you can make a mistake in the basis, which will lead to undesirable and irreversible consequences.

The process of reinforcing slab and monolithic grillage

Scheme of reinforcement of the glass part of the grillage: 1 - transverse reinforcement mesh; 2 - spatial frame; 3 - meshes of indirect reinforcement.

When reinforcing a monolithic grillage, it is necessary to lay 2 layers of horizontal mesh, and make a protective layer between them. Reinforcing bars must be installed at a distance (step) of 200 mm. The joints themselves cannot be welded, because heating them leads to a loss of metal strength. Therefore, for reinforcing connections it is necessary to use knitting wire, which is tied with special hooks. The reinforcement frame should be made spatial; for this, “vertical distances” are used, which are made from cut pieces of reinforcement. These segments are not made very long so that the resulting connection has a sufficient margin of strength and stability.

The vertical outlet from the foundation piles must be connected to horizontal rods. This is also done using knitting wire. Reinforcement can be considered complete only when all the rods are placed in the formwork and they do not sag anywhere when pressure is applied to them. After this, it is necessary to check the protective layer in the lower sections of the connections.

Once you are convinced of the reliability of the structure, you can begin the process of concreting it.

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The process of reinforcing a strip grillage

Reinforcement technology is practically no different and is similar to slab reinforcement. The differences will be in the formwork installed, because it will significantly limit the work area. Within the formwork itself, it is imperative to maintain layers of protection on all sides. This must also be done using a knitting wire. The rods must be overlapped. The amount of overlap should be equal to or slightly greater than 50 times the diameter of the rods used.

To do the reinforcement correctly, you must remember that the rods that will be laid horizontally should not sag. At the moment when the concrete pouring takes place, the rods must necessarily occupy the position specified in the project. In a strip foundation, you need to place the vertical rods correctly, because... they will ensure the rigidity of the rods. Therefore, their presence in the strip foundation is mandatory.

The main difference between slab and strip grillages is that in the first option, all the heads are connected at once. With the tape version, only adjacent structures are connected with a grillage.

If you are reinforcing a grillage with a pile foundation, this can be done from different materials. The material from which the piles are made is mainly concrete. The reinforcement process is quite simple. For a pile foundation, it is necessary to prepare reinforcing bars, the diameter of which should be 1.0-1.5 cm. In order to tie the piles, which can be 2 meters high, together, the reinforcement should be placed at a distance of 45-55 cm from each other. The frame made of reinforcement for the pile foundation must be made so that the protrusions of the vertical rods are 15-20 cm. It will be necessary to tie it to them.

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Features of the work

The main problem that arises during the construction and calculation of the foundation is the choice of the cross-section of the grillage itself. It is necessary to take into account the fact that an air gap must be made under the strip grillage, the size of which must be at least 15 cm. Very often during construction there may be a desire to combine a slab and strip structure. This can lead to sad consequences in the future, namely: when the soil freezes in winter, the foundation strip will rise, and the slabs will prevent this. Which will lead to the rupture of the supports, and this will subsequently cause the destruction of the entire foundation, and then the destruction of the house.

To decide on the size of the transverse, you first need to make a house design: decide on the thickness of the walls to be erected, and the type of the building itself (number of storeys). You need to know the slope of the construction site and the type of soil. If a strip foundation is used, it must match the thickness of the house wall itself. In this case, it is necessary to take into account the insulation of the wall and its finishing. If there is a slope at the construction site, then you must immediately take into account that the strip foundation will have different heights along its entire length.

If the slope of the construction site is very large, then the grillage can be made of a stepped structure. In this case, the support rods must be deepened by no less than 20-25 cm. The support must be inserted into it by 5-7 cm. When choosing the height of the steps, it is necessary to determine the thickness of the wall masonry. The steps should not depend on the location of the supports themselves; their location should be free. When the wall is being built at the very place of the step, it is necessary to lay rods to prevent the appearance of cracks. The location of this reinforcement should be in the same plane with the building and only in the area of ​​the steps.

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Calculation of slab foundation reinforcement

To calculate the amount of reinforcement, you need to be guided by the type and shape of the foundation. They can be determined based on the load on the foundation and the bearing capacity of the soil. As an example, it can be done for a house whose size is 6x10 m and has 2 internal walls.

Rods that have a ribbed surface will be used. Class A3 fittings meet these requirements. took a diameter of 10 mm. You need to remember the fact that the thicker the rods, the stronger the foundation will be. The thickness of the reinforcing rod must be selected taking into account the weight of the house and the type of soil on which it is located. If the soil on which the future structure will be located is quite dense and its bearing capacity is high, then the deformation of the foundation will be less. When building a panel, frame or light wooden house, where there will be soil with good bearing capacity, it will be possible to use rods with a diameter of 10 mm. If a slab foundation and soil with weak bearing capacity are used, then in this case it is necessary to use reinforcement with a diameter of 14-16 mm. The mesh pitch of the reinforcement frame is 20 cm (0.2 m). The quantity calculation will look like this:

((10/0.2)+1) = 51 pcs. rods 10 m each.

((6/0.2)+1) = 31 pcs. rods 6 m each.

51 + 31 = 82 pcs. rods

Since the foundation is slab, it uses 2 reinforced belts: lower and upper. It needs to double the number of rods. It turns out 164 rods, of which 102 pcs. 10 m long and 62 pcs. 6 m long. The result is:

102 * 10 = 1020 m.

62 * 6 = 372 mm.

1020 + 372 = 1392 m.

The lower grid of rods must be connected to each other. Connections are made at the intersection of the transverse and longitudinal rods. The number of connections is calculated:

51 * 31 = 1581 connections.

If a slab is used, 200 mm thick. And the distance of the slab surface to the frame is 50 mm, then 200 - 50 - 50 = 100 mm or 0.1 m.

1581 * 0.1 = 158, m.

158.1 + 1392 = 1550.1 m - the required number of rods for a slab foundation.

The knitting wire is calculated:

51 * 31 * 2 = 3162 connections.

You need to connect with double folded tie wire. The length of a piece of wire is 15 cm. Multiplied by 2, the result is 30 cm. The number of ties at the joints is multiplied by the number of connections and the result is 6324 pieces.

6324 * 0.3 = 1897.2 m of wire.