When manufacturing a monolithic underground load-bearing structure, it is necessary foundation reinforcement to absorb tensile loads. Horizontal frames are used in strips and grillages, while vertical frames are used in pillars and piles. The slabs are reinforced with meshes, and in certain areas of the reinforced belt they are reinforced with anchors.

Why are foundations reinforced?

Foundations experience compression, torsion, shear and tension loads. The structural material concrete copes with all of them except the last one. To absorb tensile forces without destroying concrete, it is used foundation reinforcement on two levels. The lower belt compensates for prefabricated loads, the upper - for swelling forces acting on the base of the underground structure.

Attention: It is mandatory to calculate the reinforcement to calculate the thickness of the rods, their number in each belt and the minimum content of reinforcement in the section of the concrete structure.

What fittings are used?

According to SP 20.13330 and SP 22.13330, the main elements of frames and meshes (longitudinal rods) are made of 10 - 16 mm “corrugated” tape. This is a periodic section reinforcement with a side notch of class A400. All other elements are created from 6 - 8 mm smooth reinforcement A240.

Attention: Metal reinforcement should be used in load-bearing structures. Composite materials are not suitable for foundations.

Wire twisting of frame/mesh parts is more reliable than welding joints and plastic clamps. Welding weakens the steel in adjacent areas, and the polymer clamps break and shift when moving inside the concrete formwork.

Foundation reinforcement schemes

Under ideal conditions, foundations can be reinforced only near the base to prevent destruction from prefabricated loads. This is possible on non-heaving soils or by compensating for heaving forces by drainage, insulation and the use of non-metallic materials in backfills and underlying layers.

In practice, designers play it safe by installing two reinforced belts. In addition to working fittings, installation and technological equipment is required:

Depending on the foundation design, reinforcement technologies differ significantly.

Plates

The simplest reinforcement scheme is a floating slab. Two grids are placed inside it, subject to the following conditions:

For ribbed slabs, the schemes become more complicated; a reinforcement cage is placed inside each stiffener, rigidly connected to the meshes.

In coffered slabs, a basement of a monolithic structure is added, the walls of which are reinforced with frames similar to MZLF, and the floor with grids, like a conventional slab.

Attention: In slab foundations of complex structure, the reinforcement of different elements must be tied together with wire twists.

Depending on the slab foundation technology, the protective layer will be different:

• smooth slabs are cast on top of the concrete base, so 2.5 cm spacers under the bottom mesh are sufficient
• USHP and ribbed slabs are often concreted on top of extruded polystyrene foam; a bottom layer of 3–4 cm is recommended
• lack of insulation and footings, the thickness of the gaskets should increase to 5 - 7 cm
• the thickness of the side protective layer is more stable, ranging from 2.5 to 5 cm depending on the diameter of the rods

Attention: In non-recessed and shallowly recessed slabs there are always hatches for wiring communications. If the diameter is less than 15 cm, there is no need to strengthen the structure. For large holes, rods should be placed around the perimeter and over the corners to strengthen them.

Ribbons

The strip foundation rests completely on the base. Therefore, due to the weight of the building and other operational loads, its upper edge is compressed and the lower edge is stretched. Heaving forces, on the contrary, compress the sole and stretch the upper part.

The classic reinforcement scheme for a shallow tape looks like this:

When the belt width is small, two longitudinal rods are used in each belt. As the size of the concrete structure increases, their number also increases.

Attention: If the frames are knitted in place, it is forbidden to overlap the rods at the corners. They need to be bent at a right angle (40 - 80 cm from the edge), laid with their long ends on adjacent sides of a common corner.

Grillages

Unlike MZLF tapes, the grillages do not have contact with the ground, and heaving forces do not act on them. But they rest on pillars or piles with a smaller area. Therefore, despite the external similarity, the reinforcement schemes for strips and grillages differ:

Technological and installation reinforcement are also used in transverse reinforcement. These are lintels and clamps made of smooth rods that give the structure a spatial shape.

Attention: The armored belts of the grillage can be rigidly connected to the frames of the vertical elements of the foundation (column, pile) or not touch each other with a hinged joint pattern.

Pillars

A columnar foundation is considered the least stable, therefore in 75% of cases it is equipped with support plates at the base of each column. Therefore, the reinforcement scheme differs from other foundation structures:

The reinforcement is made of concrete in order to later bend half of the bars at the level of the lower reinforced belt of the grillage, the remaining ones at the height of the upper belt and tie them to them with wire.

Attention: Corners and joints are anchored similarly to the MZLF tape using L-shaped or U-shaped elements.

Piles

The easiest way to reinforce drilled piles. Depending on the diameter and the minimum percentage of reinforcement, 3–5 rods are used, tied with a triangular, square or pentagonal clamp, respectively.

Instead of clamps, individual developers use pieces of smooth reinforcement, but the consumption of knitting wire will increase. The ends of the rods also protrude from the concrete, similar to pillars for embedding into a monolithic grillage.

Attention: If steel beams are used for light walls of an outbuilding, there is no need to release the reinforcement; the upper protective layer is 5–7 cm. Steel products should be sunk to this depth to protect them from corrosion.

Reinforcement technologies

Construction estimates indicate the design characteristics of the reinforcement in relation to specific operating conditions. However, an individual developer should know some of the nuances of making frames and meshes from individual parts.

Mesh production

Due to the large size of the foundation slab, the reinforcing mesh is knitted at the site of use from intersecting rods or assembled from ready-made cards sold on construction markets. In the industrial production of meshes, high-performance welding joints are used. When knitting yourself, it is better to use knitting wire.

Knitting frames

When using clamps, the productivity of frame construction increases at least five times, and less wire is consumed. In this case, you should take into account:

• The clamps are suitable for grillage dimensions of 40 x 40 cm maximum
• the number of longitudinal bars in a row should not be more than 4

Therefore, grillages with a beam cross-section larger than the specified values ​​are constructed from two gratings installed vertically. They are tied together with transverse horizontal jumpers, taking into account the protective layers. The structure is laid on gaskets, the side protective layers are provided with polymer rings. They are put on the rods and prevent contact with the formwork.

Thus, foundation elements of different structures are not equally reinforced. It is necessary to take into account the given diagrams and recommendations in order to achieve the maximum quality and service life of the underground structure with the minimum possible budget.

To ensure the stability of erected buildings, various types of foundations are used, including pile foundations. This foundation has proven itself to be effective when performing work on frozen soils, on an inclined construction site, as well as on weak soils with nearby groundwater. Reinforcing the grillage structure with steel reinforcement allows you to form a solid foundation for the future structure. Reinforcement of the pile foundation grillage is carried out on the basis of the drawing and the results of preliminary calculations.

What is a grillage

Not all private developers are familiar with special construction terms. Among professionals you can often hear the word “grillage”. Let's look at what it is.

This is a loaded element of the pile base, which performs a number of important tasks:

• combines the heads of the supports with a common power contour, reinforced with reinforcement;
• prevents the possibility of displacement of supporting elements from the vertical axis.

Based on pre-developed documentation and special calculations, the dimensions and design features of the grillage are determined.

A grillage is a monolithic element of the base of a building that connects separate pillars or piles into a single system

For foundations with supporting columns, the following designs are used:

• tape It combines the supports located under the load-bearing walls into a power circuit using a solid concrete strip;
• slab The configuration follows the shape of the building and connects the pillar heads using a monolithic slab.

There are various options for a grillage foundation, each of which has its own characteristics:

• monolithic. The solid structure is formed as a result of hardening of the concrete solution poured into the prefabricated panel formwork;
• made. It consists of industrially manufactured reinforced concrete elements that are supported by columns.

Despite the differences in design, all types of grillage form a solid foundation that ensures the stability of the main walls of the building. Tying the heads of pile supports located in the ground provides an increased margin of safety. This makes the spatial system more rigid and less susceptible to the influence of loads. Reinforcing the pile and strip foundation with steel rods increases the service life of the structure, forming a monolithic base.

Grillage foundation design

The pile-type foundation grillage, which is a solid reinforced concrete strip, can be located at different levels relative to the ground.

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

For the construction of building walls, various types of grillages are constructed, differing in location relative to the zero level:

• towering. The lower plane of the power contour is located at least 15 cm above the soil level. A high structure is constructed for lightweight buildings, the construction of which is carried out on all types of soil. It is indispensable for problematic soils and requires reliable reinforcement with steel reinforcement. This is due to the presence of free space between the soil surface and the concrete edging;
• located at soil level or ground grillage. It is formed on a sand-crushed stone bed without immersion in the ground. The main feature of the above-ground structure is that the concrete monolith touches the soil surface with zero clearance. This design is used on stable soils that are not subject to deformation as a result of frost heaving. When the soil freezes, there is a high probability of compromising the integrity of the concrete contour;
• not deeply buried. The supporting plane of the concrete reinforcement rests on a crushed stone-sand bedding located below the zero mark in the depth of the pit. Structurally, such a foundation is similar to a strip foundation, which is built on pile supports. The construction process is quite labor-intensive and associated with significant costs. This design is used on soils with reduced bearing capacity for the construction of large buildings.

Pile foundations are constructed for the construction of lightweight buildings. The design of the foundation grillage, which is a concrete edging, ensures the stability of such buildings. The width of the tape corresponds to the thickness of the walls, and the height of the contour is no more than 0.4 m.

The grillage also acts as a supporting surface on which the walls of the building are erected

What is the purpose of reinforcing the grillage of a pile foundation?

The need to strengthen the foundation of a building using a reinforcement grid is associated with the properties of the concrete composition. Concrete is susceptible to the effects of deformation, causing tension and bending. As a result of such deformation processes, destruction of the base is possible, although the material is able to withstand significant compressive loads.

Reinforcing the pile foundation grillage with steel reinforcement strengthens the structure, increases its stability, and also has a positive effect on the durability of the structure being built. A powerful frame, concreted in a concrete strip, increases the strength of the base and compensates for various types of loads and torques.

In order to increase the strength characteristics of the pile base, it is also necessary to strengthen the supporting columns. The reinforcing bars located inside the supports are combined with the grillage tape into a common power circuit.

Strengthening the pile foundation grillage with reinforcement provides:

• stability of the concrete mass, which perceives the reaction of frost heaving forces;
• increasing the strength characteristics of the base on which the weight of the building acts;
• protection of the base, which is constructed of concrete of reduced strength.

Using steel reinforcement to strengthen the grillage base, you can prevent the influence of negative factors.

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 is characterized by weak resistance to bending and tensile loads

Strengthening pile and strip foundations - recommendations from experts

Professional builders recommend using a spatial frame for reinforcement, consisting of the following elements:

• strong horizontal rods with helical corrugation on the surface. Reinforcing bars with A3 marking, manufactured by hot rolling, are used. With a diameter of 1.2–1.6 cm, they are able to compensate for an extended range of loads;
• perpendicularly located jumpers, reduced diameter. They can be made of corrugated wire with a diameter of 0.6–0.8 cm. Steel jumpers encircling the longitudinal bars provide rigidity to the lattice and give it a square or triangular shape.

To form a spatial frame, along with standard reinforcement, the following can also be used:

• straight pieces of steel wire of the appropriate diameter;
• ready-made lintels without corrugation, having the required cross-section after bending.

When carrying out measures to strengthen the strip base resting on support columns, observe the following requirements:

• use at least four rods located in pairs in the upper and lower planes of the spatial frame;

Scheme of a pile-grillage foundation

• during assembly, place horizontal reinforcement bars at a distance of 100–200 mm;
• maintain an interval of 250–350 mm between vertically located connecting elements;
• provide a guaranteed gap from the reinforcing metal structure bars to the concrete surface of more than 50 mm;
• securely fix the assembled frame, ensuring that it cannot move when pouring concrete.

The gap between the bars and concrete allows:

• protect frame elements from moisture, which causes corrosion;
• correctly position the frame in the concrete and distribute the loads evenly.

To ensure a stable gap, special linings made of plastic are used.

Why is a drawing needed?

To correctly implement reinforcement measures, it is necessary to develop documentation. You can develop the drawing yourself or use the services of professional developers.

The drawing allows:

• determine the need for steel bars for assembly;
• manufacture the load-bearing structure in accordance with the documentation.

Reinforcement of Strip Foundation

A professionally executed drawing contains the following information:

• frame dimensions;
• rod diameter;
• rod profile;
• pitch between wire jumpers;
• spacing between power fittings;
• design features of the belt.

Based on the drawing, you can independently calculate the length of the rods in the belts and the total number of jumpers. After breaking down the reinforcement used by assortment, it is easy to calculate the total length by summing it up. To order bars, you need to know their total weight. To do this, the total footage for each standard size should be multiplied by the weight of a linear meter for a specific rod.

To ensure the necessary strength, instead of electric welding, tie wire should be used to connect the elements. Welding creates stress zones, and the binding wire firmly connects the rods without disturbing the structure of the metal. Knowing that 25–30 cm is required to ensure the fixation of two rods, it is easy to calculate the total need for binding wire. To do this, multiply the number of joints by the specified length.

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

What materials and tools are needed?

To perform reinforcement work, it is necessary to prepare the following materials, as well as tools:

• reinforcement, the diameter of which corresponds to the requirements of the drawing;
• a special device that facilitates bending of rods;
• wire for knitting elements of the spatial frame;
• crochet hook, speeding up work;
• a grinder that allows you to cut reinforcement into blanks.

The assembled reinforcement frame is placed inside the pre-assembled formwork on special supports and filled with concrete mortar.

Reinforcement of the pile-grillage base - stages of work

After completing the installation of the support columns reinforced with reinforcement and the installation of the formwork, you can begin assembling the spatial frame. It is attached to the parts of the reinforcing bars that protrude from the piles. Fixation is done using knitting wire.

Sequence of operations:

1. Cut the workpieces with a grinder, following the requirements of the drawing.
2. Install the lower tier of horizontal rods on plastic supports.
3. Connect the elements of the lower chord using transverse rods.
4. Attach special square clamps to the horizontal reinforcement.
5. Tie the longitudinally located reinforcing bars of the upper tier.
6. Reinforce the corner areas of the grillage using curved rods.

It is important to securely fix corner areas where significant loads are applied. To create a solid foundation for the future building, it is important to correctly reinforce the grillage connecting the piles with reinforcement. The drawing will allow you to calculate the need for material and make it easier to carry out the work yourself.

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.

Amplification of the grillage begins after completing all the previous stages of arranging the pile foundation - 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.

In order for the building to serve for a long time, it is necessary to reinforce the grillage of the pile foundation in accordance with regulatory requirements. House construction transfers the force of gravity to a concrete strip, which serves to evenly distribute the load on the piles, and through them to stable layers of soil. The need to strengthen a concrete monolithic grillage with reinforcement arises from the fact that concrete responds well to compression forces, but weakly resists tensile and bending loads. In the absence of a reinforcing frame, the structure may become deformed.

Why do you need a grillage?

The house carries an uneven load, with some parts weighing much more than others. It depends on the arrangement of furniture and other items.

The grillage is a structure that connects the supports into a single system. Serves to evenly distribute the load of the building and transfer it through piles (pillars) to the ground. Protects the building from uneven shrinkage.

It is made in the form of a monolithic concrete strip, which must be reinforced with a reinforcing frame, and can be made of wood, reinforced concrete, and steel products that are laid on poles and interconnected into a single whole.

The grillage can be located at a distance above ground level, lie along the upper edge of the soil, or be buried in the soil. For the base of a hanging structure, horizontal beams or a concrete strip can be used. For the recessed option, installation of a monolithic concrete structure is most often used.

Reinforcement technology

Reinforcement of the concrete strip is performed with two rows of metal rods laid along the structure. To obtain sufficient strength, the upper and lower rows of reinforcement are fastened together with vertical and horizontal jumpers.

The rods laid along the grillage must have increased strength. They are made from hot-rolled corrugated profiles of class A3, with a diameter of 13-16 mm. Sometimes fiberglass reinforcement is used; it is good because it is not subject to corrosion.

The following are used as jumpers between the longitudinal rows:

• Rectangular fittings, curved in the form of clamps, made of smooth class A rods with a cross-section of 8-10 mm. Such jumpers are more reliable and have a long service life due to fewer welded joints. In terms of labor intensity, this type of reinforcement is more complex and time-consuming.
• Separate steel rods are welded to the top and bottom rows. The rods must be made of the same material as the longitudinal strapping. Welded seams do not have sufficient strength and are susceptible to corrosion. Doing this kind of work is easier and faster than in the first case.

In longitudinal rows, rods are laid at a distance of 100 mm from each other; there should be at least 3-4 rows of rods in each belt. Transverse lintels of longitudinal reinforcement are installed in increments of 200-300 mm. Vertical rods are fixed at a distance of at least 400 mm from each other.

At the bottom of the grillage, space is left to pour the concrete solution. To do this, lift the steel reinforcement bars above the formwork, placing mushroom-shaped plastic stands under them.

There must be a layer of concrete at least 50 mm thick between the outer contours of the metal frame. If its thickness is less, the rods will be subject to corrosion, and the structure itself will be unable to evenly redistribute the load-bearing load.

Calculation of the base with a grillage

In order to correctly perform all calculations, it is necessary to take into account the characteristics of the soil, the proximity of groundwater and the load from furnished housing construction, taking into account the maximum force of gravity. It is better to show all calculations and diagrams to specialists so that they can check their correctness.

Based on the data obtained, the required number of piles and their burial depth are calculated. The support should be buried 20 cm below the freezing point of the soil. Piles or pillars are located at each corner, at the intersection of load-bearing walls with lintels, under the heaviest structures of the house (under columns, fireplace). The remaining supports are installed at a certain distance from each other.

After installing the piles, a grillage is installed; if it is arranged in the form of a monolithic concrete strip, it must be reinforced with reinforcement.

Calculation of the amount of reinforcement

As an example, a monolithic concrete grillage 8 m long, 6 m wide, 400 x 400 mm thick is presented. For reinforcement you will need two longitudinal belts with 3 rods each. You will need metal rods with a cross section of 14 mm, class A3. The distance between them should be 100 mm, taking into account the fact that a layer of concrete occupies 50 mm on each side.

To install jumpers you will need rods with a cross section of 11 mm, class A1. Install them at a distance of 200 mm from each other.

Calculation formula:

1. Calculate the length of the rods in the upper longitudinal row. Determine the length of the entire grillage. To do this, add up the length of all four of its sides: (8*2) + (6*2) = 16 +12 = 28 m. Since three rods are used in a row, the resulting number is multiplied by three: 28 m * by 3 pcs. = 84 m. Since two rows need to be laid, the resulting value is multiplied by two: 84 * 2 = 168 m of reinforcement will be needed to install two longitudinal rows.
2. Calculate the jumpers for both contours of the grillage. They are placed at a distance of 200 mm from each other. The length of the jumpers will be 300 mm. The quantity is calculated using the formula: (30/0.2) *2 = 300 pcs. Calculate the length of the metal rods: 300 * 0.3 = 90 m.

In a grillage in which the thickness is the same on all sides, the same number of vertical jumpers will be needed as transverse ones.

You will need 168 m of metal rods of class A3 and 180 m of rods of class A2.

Stronger connections are obtained if the reinforcement is fastened together with wire rather than welding. Each connection requires about 40 cm of wire. Its quantity is determined by the formula: (30/0.2) * 4 = 600 pcs. 0.4 m each = 240 m.

Installation of a monolithic grillage

After installing the piles, the installation of the grillage begins. Its device includes:

• installation of formwork;
• laying reinforcement according to calculated indicators;
• filling the form with concrete mortar;
• dismantling of formwork;
• waterproofing works.

The design of the formwork depends on how the grillage is located above ground level.

Installation of formwork

The strength and appearance of the grillage will depend on the correct installation of the formwork. The removable form is most often assembled from boards, sometimes plywood is used.

It is imperative to control the vertical level of installation of the side walls. Angles should be set at 90 degrees unless other parameters are specified in the project. The walls are reinforced with supports so that the concrete solution does not destroy the formwork.

If the grillage is located above ground level, you need to calculate the load from the reinforcement and concrete mortar on the lower wall of the form. If the bottom falls out, the work will need to start over.

After installing the formwork, pour a layer of sand 150 mm thick into it. Wet it and compact it well. Waterproofing material is laid.

Reinforcement

Reinforcement of hanging grillages is performed with metal rods. Fiberglass reinforcement, as experience shows, is good in cases where it rests on the soil. The type of reinforcement and type of beams for the grillage are determined at the design stage of the house.

After cutting the supports to the required size, the reinforcement will protrude from them. It will be used as a connecting element between the grillage and the support.

Before performing reinforcement, draw a drawing of the location of metal rods. All work is performed based on this scheme. If the reinforcement is installed incorrectly, the structure may not withstand the load and become deformed.

Metal rods, connected together by 3-4 pieces of wire, are lowered into the formwork. The reinforcement should not touch the edges of the wooden form for concrete, so that later it does not turn out that its edges protrude from the concrete base.

To ensure ventilation of the space under the floor of the house, vents are left in the structure by inserting pipes with a diameter of 100 mm into the formwork.

After installing the metal frame, remove all construction debris from the formwork using an industrial vacuum cleaner with high power.

Before pouring the foundation, you need to clean the future grillage from water and dirt. When weather conditions do not allow pumping out water near the foundation, a small hole is dug below its level with a bevel from the base of the house into which the water will flow.

Pouring concrete

The geometry and reliability of the fastening of the formwork and reinforced frame are checked so that the structure does not fall apart during filling with concrete.

Prepare cement mortar. It should be uniform, without lumps. The solution is mixed at the construction site using a mixer or ordered from the factory in a concrete mixer.

After the concrete has hardened, the formwork is dismantled and the sand is removed from under the grillage. You can disassemble the form no earlier than the concrete base is completely dry.

Waterproofing

A hanging grillage can be isolated from moisture by coating the structure with bitumen mastics.

When installing a buried concrete strip and before pouring concrete, roofing felt is placed on the bottom of the formwork, and after dismantling the formwork, the entire grillage is covered with roll insulation.

Rules for grillage reinforcement

By adhering to the following rules, you can avoid many mistakes when building a grillage:

• the reinforcement frame and formwork are installed strictly according to the level;
• the top part of the piles is cut off so that all the heads are in a horizontal plane;
• when installing a metal frame, the jumpers are installed at a distance of 200-400 mm from each other;
• corner elements are connected by bent L- and U-shaped elements;
• the cross-section of the support must be at least 300 mm, the number of rods in the longitudinal belt is 3 or more, the allowance for reinforcement under the grillage must be 50 cm or more;
• welded joints are less durable than wire joints.

You cannot skimp on the quality and quantity of metal rods.

You can learn more about how to reinforce a pile-grillage foundation from specialized books or videos:

Reinforcement of a monolithic concrete grillage is a mandatory technological process. If all standards and reinforcement technology are observed, the building will last more than half a century.

Pile foundations allow the construction of buildings in difficult soil conditions. They are indispensable when constructing facilities on weak or heaving soils, with high groundwater levels or difficult terrain. Tying the piles with a grillage combines free-standing pillars into a single structure that receives and distributes loads from the ground part of the structure.

What types of grillages are there?

The materials for the grillage can be metal beams, wood and reinforced concrete. Channels and I-beams have excellent strength, but they are heavy, expensive and not very convenient when installed on the heads of multi-level piles. Logs and timber beams serve as the lower crown of a wooden house. Prefabricated structures are supplied ready-made and only require installation in the designed position.

Monolithic reinforced concrete grillage is considered universal and technologically convenient. Unlike prefabricated beams, it does not require the presence of lifting mechanisms at the construction site, is made in various configurations in the form of slabs or strips, and can have non-standard sizes, bends and refractions. Depending on the design features of the structure and soil conditions, grillages are:

• tall;
• low;
• buried.

The strength and durability of a monolithic grillage is ensured by a correctly selected and installed reinforcement frame. For a structure rising above the ground surface, the installation of a more reinforced metal frame is required than for a grillage resting on a soil cushion.

The reinforcement frame for the grillage is calculated taking into account the distance between the piles, permanent and temporary loads, taking into account the shape of the structure, correction factors and much more.

Grillage reinforcement

The installation of fittings is preceded by:

• leveling the top of the piles horizontally with the exposure and bending of the reinforcing bars required to create a reliable connection between the grillage and the pile pillar;

• installation of formwork (in the case of a recessed grillage, concrete is often poured directly into the trench);
• geodetic layout, which determines the location of reinforcing mesh, as well as embedded parts (on unimportant objects, marking can be done without the use of high-precision instruments);
• assembly of reinforcement using welding and knitting into a three-dimensional frame (ready-made structures are often delivered to the construction site).

In industrial conditions, reinforcing mesh is made using resistance spot welding. Electric arc welding is used on construction sites, which increases labor costs and the amount of reinforcement waste when cutting it. The best option is considered to be a combined method of assembling reinforcement into a frame, when a welded metal mesh is delivered to the site, and the enlarged installation with the installation of embedded parts is carried out by a specialized team already on site.

In the case of manufacturing a frame for a grillage on a construction site, the following work is carried out:

• unwinding and straightening of reinforcement;
• cleaning the surface from contaminants of various origins;
• cutting, selection and bending of rods according to design documentation;
• assembly of flat meshes or frames (spot welding is used for small-diameter rods, and electric arc welding is used for reinforcement 40 mm or more);
• preparation of volumetric frames by knitting or welding;
• installation of embedded parts and anchors;
• placement of frames in formwork with fixation in the design position.

For the grillage, two rows of grids are provided - lower and upper. They are connected to each other by vertical rods, resulting in the formation of a spatial frame. In one plane, the mesh is laid overlapping, and the outlets are welded. For a more reliable connection, the meshes are fastened with knitting wire using special hooks.

Laying the reinforcement cage directly on the bottom of the formwork or trench is not allowed.

Under the bottom mesh there must be a protective concrete layer 5-7 cm thick, which protects the reinforcement from corrosion. To do this, concrete clamps or traditional bricks are installed over the entire area of ​​the grillage. On the side of the vertical walls, the frame is rigidly fixed in the desired position to prevent it from moving from the design position and to ensure the correct thickness of the protective concrete layer.