Pile grillage foundation construction stages. Pile-grillage monolithic foundation

This page provides information about the types of pile foundations with a grillage. We will look at the types of grillage - hanging, shallow and recessed, and study the performance properties of different types of foundations - screw, bored and monolithic.

A feature of the construction of houses in central Russia, and especially in the Moscow region, is the frequent need to construct pile foundations.

Our company carries out pile driving in those areas where, due to the condition of the soil, a foundation with a grillage on piles is the most preferable option.

Foundation on driven piles

A reliable and durable foundation for any small and medium-sized structure in conditions of weak, water-saturated soils will be a foundation on driven piles.

The construction of such a foundation begins with the preparation of the site, which, if necessary, is planned and then marked. At the same time, the location of the future structure, its load-bearing walls is determined and the points for driving piles are marked.

Bored pile-grillage foundation

Bored foundations consist of supports formed by pouring concrete into wells drilled within the building site. Such piles can be manufactured using two technologies:

• Rammed - initially a well is drilled, then a reinforcement frame is placed in it and the cavity is filled with concrete through a special pipe;
• Injection - concrete is injected into the cavity through an auger drill string, immediately upon completion of its development. The reinforced frame is placed in a well already filled with mixture.

Rice

The final strength, load-bearing capacity and stability of supports are influenced by the technology of pile manufacturing. The tying of bored foundations can be done using a reinforced concrete slab or strip grillage, depending on the layout of the supports in the foundation.

Important: the reinforcement frame of bored piles is always longer than the concrete body of the support - the protrusions of the reinforcement are subsequently connected to the framing frame.

Grillage foundation on driven reinforced concrete piles

Foundations on driven reinforced concrete piles are constructed using industrially manufactured structures, mounted on the construction site using pile drivers using the method of impact driving or vibratory driving.

Important: driven piles are always tied with reinforced concrete grillages - when creating foundations in the form of pile fields for multi-storey buildings - slab, for 1-3 storey buildings - strip.

Rice

To join the reinforcement of the pile and the grillage into a single reinforced concrete frame, the piles are immersed so that a section of the trunk 30-50 cm high rises above the ground. After installation, the concrete on the protruding part of the pillar is destroyed using a pile cutter, and the reinforcement frame of the frame is welded to the remaining reinforcement.

Rice

This type of foundation is characterized by maximum load-bearing capacity, stability in the ground and durability (over 100 years). The disadvantage is the relatively high cost.

Grillage foundation on support pillars

Columnar foundations are classified into two groups:

• Prefabricated - support pillars are created from brick or FBS blocks;
• Monolithic - pillars are filled with concrete.

Monolithic columnar foundations, in fact, are a makeshift analogue of foundations on bored piles. The pillars in them are created by pouring concrete into drilled wells (1-3 meters deep). Asbestos-cement pipes or rolls of roofing material assembled into a cylinder can be used as formwork for pouring.

Rice

Such foundations, like screw foundations, are used only for the construction of light buildings and auxiliary structures (garages, summer kitchens, baths). They are tied with tape-type grillages made of reinforced concrete tape, timber, I-beam or channel.

Often, in order to save money, developers undertake to build a foundation with a grillage themselves. As a rule, they use the bored method for constructing piles. The Internet is replete with similar instructions on this matter.

In fairness, it is worth noting that in some cases this option can ensure the reliability of the structure. It all depends on the condition of the soil, drilling depth and concrete quality.

But in most cases, it is better not to carry out construction without a preliminary study of the soil and strict adherence to the technology for manufacturing bored piles.

Our company loads piles for any type of pile foundation in strict accordance with the requirements of SNiP and the construction project. The level of training and experience of our specialists allows us to solve problems quickly and efficiently. high quality carrying out piling works.

Pile-grillage(or columnar-ribbon, both names are equivalent) the foundation is a structure consisting of pillars immersed in the soil and connecting them above the surface of the ground with reinforced concrete, wooden or metal tape. The peculiarity of this type of foundation is that they can be installed on any soil except rocky ones. SRF may vary in construction technology, material of manufacture and design features of piles.

Piles - types and features

According to the material of manufacture, reinforced concrete, wooden and metal piles are distinguished:

Wooden They are used mainly for the construction of buildings from the same material, often these are outbuildings, gazebos, and bathhouses. For the construction of residential premises, more durable foundations are usually installed. Installation can be done either singly or in groups of 3-4 pillars in a bundle to increase strength and load-bearing capacity.

Metal piles can be driven or screwed, but the second option is more common. A screw pile post is a metal pipe, the immersed end of which is made in the form of a cone with a screw blade for screwing. The cone-shaped tip can be cast or welded. Cast piles are more reliable and durable, since they do not have a welded seam, the strength of which is reduced. The steel product must be treated with an anti-corrosion coating, and during the installation process the pipe cavity is filled with concrete. The service life of such a foundation can reach up to 400 years.

Read more about types, types and features technologies of pile foundations.

Reinforced concrete piles are made from reinforced concrete, at the enterprise (drived) or directly on site (rammed).

DIY pile-grillage foundation

Step 1 - Soil Study

The purpose of a geological study of a site is to determine the type of soil, its bearing capacity, degree of heaving, level of groundwater, etc. The choice of foundation and the features of its construction depend on these characteristics.

For a full analysis, you should contact specialists, since independently drawn conclusions may turn out to be erroneous, which will affect the quality of the foundation itself and the building as a whole. This is especially true for columnar foundations, since it is not possible to thoroughly check the soil layers, reaching the level of solid soil. To conduct research, you can contact a geodetic company or send soil samples to a laboratory.

If for some reason this is not possible, then the type of soil should be determined.

Types of soil and their characteristics.

1. Sandy soil. It has good drainage properties, does not heave and compacts tightly. Foundations on such soils are easy to construct and durable.
2. Fine sandy. It has increased buoyancy and a tendency to swell. It is not recommended to build foundations on such soils, but in the case of pile-grillage foundations, the main thing is to carry out installation work in accordance with all requirements.
3. Clay. Clay soils are prone to severe swelling. To build a foundation, an anti-heaving cushion is required.
4. Rocky and clastic soils. They are difficult to work with, but they have no equal in reliability. The rock does not freeze, is not subject to swelling and buoyancy. However, this is the only type of soil that is not suitable for the construction of pile foundations.

Step 2 - Carrying out calculations

from the structure - the weight of pile pillars, grillage, future construction and additional elements (people, furniture, plumbing, etc.) is summed up.

Result divided by the total area of ​​the base piles The result of the calculations should not exceed the load-bearing capacity of the soil. Otherwise, the number of pile pillars increases.

Step 3 - Site Preparation

1. Produced area cleaning.
2. Determined location of the future foundation. It is important that the remaining buildings on the site are located at least 3 meters from the construction site. You should also choose an area free of tree rhizomes and stumps, as they make it difficult to drive the piles.
3. The turf layer is removed under future construction, and the soil surface is leveled.

Step 4 - Marking

1. To a cleared and level area from the drawings the layout is being transferred buildings - first, use pegs to mark the outer corners, then the intersections of the walls. Piles will subsequently be installed at these points.
2. Then between the pegs the fishing line is stretched or twine, thereby denoting foundation installation line.
3. Along the perimeter of the stretched twine there are marks places for installing additional piles. They should be located approximately 2 meters from each other.

It is important to make the markings accurate. Permissible deviation – 2 cm.

Step 5 - Installation of piles

Driving and screw piles are driven using the necessary equipment or devices.

Installation of bored piles consists of several stages:

1. Held well drilling below soil freezing by at least 0.5 meters.
2. If it is necessary to strengthen or drain the load-bearing soil layer, sand cushion is being installed.
3. Into the well asbestos cement pipe is placed, the upper part of which should protrude above the surface to the height of the grillage. If this is a hanging option, then the length of the protrusion is about half a meter on a flat surface. If the landscape is sloping, then the length of the ground part varies.
4. Then, using a level, it is made horizontal control And pipes are cut to the required level.
5. After that the pile is being reinforced, most often using reinforcement with three or more (depending on the diameter of the piles) rods. For increasing strength, the vertical frame is pulled horizontal jumpers at a distance of approximately 0.5 meters.
6. The fittings are located in such a way that it top part performed above fill level slightly lower than the height of the grillage.
7. After this, using a gas pump or manually (in private construction) Concrete is poured inside the pipe. In some cases, concreting of piles is carried out along with pouring the grillage.

Step 6 — Arranging the formwork and pouring the grillage

Applicable only to poured reinforced concrete foundations.

1. For installation of hanging type strapping under formwork a layer of sand is poured, the so-called sand cushion. It serves to maintain and stabilize the form for pouring concrete and raising the grillage above the ground.
2. Formwork being constructed made of wooden boards and is a rectangular trench for subsequent pouring concrete, which connects all the piles of the structure with one tape. The formwork must be constructed in such a way that grillage tape was wider than the walls future the buildings by 5-10 cm.
3. The formwork is being installed at a distance of 20 cm from the ground level for hanging grillages and 20-30 cm below the level for shallow ones.
4. At erection of formwork, special attention is paid to its fixation. The immobility of the form for concreting is the key to a high-quality grillage tape and clear geometry of the structure. The fixing spacers should be located at a distance of approximately 0.8 meters from each other.
5. Inside the formwork a reinforcing frame is placed which is necessary connect to the pile frame knitting wire. It is also important to make the correct bends of the reinforcing bars at turns - they must be made at right angles.
6. Reinforcing frame should be located at least 3 cm from the walls and bottom of the formwork, so that when pouring it will be completely concreted.
7. Horizontally located along the perimeter the rods are tied with tying wire for greater durability.
8. Then it is produced pouring concrete form using a concrete pump.
9. To distribute the mixture as evenly as possible, parallel to pouring, a deep vibrator is used. The principle is as follows: 1-2 people direct a stream of concrete into the formwork, and the third assistant distributes just arrived mixture using a vibrator.
10. When the concrete will harden(usually it takes 2-3 weeks) the formwork is removed, A sand cushion is removed.
11. IN hot dry weather, to avoid cracking, throughout the entire drying period grillage necessary moisten with water.

For self-preparing concrete mixture You will need to mix (proportions are indicated by weight):

• cement(M400) – 1 part;
• sand– 2.8 parts;
• aggregate(crushed stone) – 4.8 parts;
• water– is added in such quantity that the mixture turns out to be elastic and of medium viscosity.

From a mixture of ingredients in such proportions, concrete grade M200 is obtained.

The binding of metal piles is carried out using an I-beam or channel beam by welding. A wooden grillage is usually used for houses made of wood; in this case, a metal pin is placed in the pile post, with the help of which a transverse wooden beam is fastened.

Common mistakes

1. Lack of space between the grillage and the ground. This happens if you don't delete it. sand cushion. In this case, the foundation will be be under pressure during soil freezing, which can lead to its deformation.
2. Imprecise definition soil bearing capacity. Result - incorrect calculations, instability and immersion of the foundation into the ground.
3. Insufficiently deep immersion of piles. If the piles are located at the freezing level, then in winter pressure on the poles may intensify to such an extent that supports Just will tear.

What determines the cost of SRF?

The price of a pile-grillage foundation is determined by a combination of several factors:

1. Number of piles and them characteristics– material of manufacture, diameter, length.
2. Difficulty level works For example, a foundation with a suspended grillage will cost less than one with a recessed grillage, since the latter option involves excavation.
3. Installation method piles If screw piles can be installed independently, then for driven piles it is necessary attract equipment.
4. Dimensions being built foundation.
5. Quantity additional material– sand, cement, formwork, etc.

On average, 1 m 2 of grillage strip requires 350 kg of cement, 1000 kg of sand and crushed stone and 8 meters of reinforcement. The approximate cost of construction, taking into account the work, is from 2000 to 3000 rubles.

The price of some construction companies for the construction of a driven or bored foundation can reach 4,000 rubles.

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Under certain conditions, the construction of a pile foundation becomes advantageous. The pros and cons of this design make it ideal for a private home on difficult soils.

The installation of a pile-grillage foundation requires, in most cases, lower costs. This is due to a decrease in the volume of earthworks. Before making piles, you need to study their advantages and disadvantages, scope of application, description of the technology.

Types of piles

There are several ways to make such a pile-grillage foundation. The pros and cons in this case will depend on the technology and materials used.

Based on material, supports are divided into:

• wooden;
• reinforced concrete;
• metal.

The former are rarely used, since their main disadvantage is low durability. Wood is destroyed by moisture, rot, and microorganisms.

Reinforced concrete piles have high load-bearing capacity. Typically, the laying depth for your home is 1.5-3 m. The cross-sectional dimensions are chosen depending on the characteristics of the soil on the site.

Metal supports for pile foundations are an option for private housing construction. They are not designed for high loads, so they are used for wooden or frame buildings.

The following classification is carried out depending on the technology of immersion of elements. Installation of a pile foundation can be done in three ways:

• driving;
• bored;
• screw.

To make a pile-grillage foundation with your own hands, the driving method is not always suitable. It allows the construction of powerful structures, but has a significant drawback - the need for special equipment (heavy duty, pile drivers). Another disadvantage of a pile-rammed foundation is its strong impact on the surrounding buildings. When the mechanisms operate, shock impacts occur on the ground, which can cause damage to nearby buildings.

Pouring concrete

Pile foundation technology involves the use of concrete of classes B15-B20, depending on the load. It is not economically profitable to use a material with greater strength. You can make concrete yourself or order it from a factory. The second option is preferable, since in this case you can be sure that the resulting mixture has a certain strength. When mixing concrete by hand, be sure to study the manual for this process. Usually instructions are on the cement package.

Piles should preferably be poured in one go. Interruptions in the production of one element will lead to its weakening. Concrete pouring is recommended to be done at an outside temperature of 15-25 degrees Celsius. In this case, the concrete will gain strength faster and be durable. After every 30-50 cm of filling in height, a short break is taken, during which the solution is compacted with a vibrator or bayonet.

It takes an average of 4 weeks for the material to harden. In rainy and cold weather it takes longer. You can make a monolithic grillage after the concrete has gained 50-70% of its strength.

DIY screw pile foundation step by step instructions

Do-it-yourself pile-strip foundations are easy to do this way. The work is carried out in this order:

1. clearing the site and preparing building materials;
2. marking the area for the building;
3. screwing piles using a manual or mechanized drill to the required depth;
4. cutting off the supports one level at a time, at which the grillage on piles will be located;
5. filling pipes with class B15 concrete;
6. installation of a grillage on pile foundations.

Grillage options for screw piles

In this case, building a pile foundation with your own hands does not require time for the concrete to gain strength. The next stage of work can begin immediately.

Strip foundation on piles

A pile-strip foundation is a structure of separate supports rigidly connected to each other. The grillage prevents the structure from settling unevenly. The tape can be made from:

• wood (only for a wooden or frame house);
• metal;
• reinforced concrete.

Each strip foundation has its pros and cons. When choosing a material for a strip foundation with piles, you should pay attention to the material of the supports and walls of the building. For a wooden house - a wooden grillage. For metal piles, it is reasonable to make a structure from rolled metal or wood, for reinforced concrete piles - from concrete.

The strapping completes the column-and-strip foundation. First of all, the depth of the grillage is determined. He can be:

• buried;
• ground;
• hanging.

The choice largely depends on the characteristics of the soil. Particular attention should be paid to a do-it-yourself columnar-strip foundation on heaving soil. In this case, there is a high probability of damage to the structure due to frost heaving. The grillage should not come into contact with the soil. Use two methods:

• hanging strapping (for this, 10-15 cm of sand is poured onto the ground, an element is poured over it, after which the bulk material is removed);
• recessed trim with low-density foam pad.

The construction of a pile foundation and a monolithic grillage is not very complicated. Provided the calculations are carried out correctly and the technology is followed, even a non-professional can handle the work.

Unlike superficially similar shallow strip foundations, grillages always transfer loads to piles. There are slab, strip, and glass grillages. They come in hanging, ground, and buried types. They are made of concrete (monolith, prefabricated), profile assortment (I-beam, channel), timber. When designing, wall and roofing materials, number of storeys, region of construction, and other factors are taken into account.

Slab grillage on piles

For large dimensions of a heavy building of complex configuration, the pile fields are tied with large-format slabs. Monolithic construction is preferable; the thickness of the slabs is based on the shear force. Low grillages are laid on a standard “pie”:

• sand and gravel cushion - two layers of 20 cm each with vibration compaction every 10 cm and moistening with water
• ring drainage – at the level of the grillage base
• concrete preparation – 5 cm screed without reinforcement
• waterproofing is a standard procedure for reinforced concrete products used in the ground

Due to the slight depth of the low grillage slab, it is necessary to take measures to compensate or prevent heaving forces:

• replacing soil with non-metallic material - the technology is indicated above
• thermal insulation of the sole - by analogy with the USHP foundation, stiffeners are not needed

Hanging monolithic slab grillages are rare due to the complexity of manufacturing. Prefabricated modifications consist of one or several slabs supported on bored (less often screw) piles.

Tape pile grillage

To reduce the construction budget, a strip-type grillage is made. Dimensions depend on factors:

• width of the walls - masonry can be hung 10 cm in each direction in several rows
• number of piles in diameter - in individual construction, piles are usually mounted in one row
• height - the grillage is calculated as a beam (one span), this size is calculated in accordance with the standards SP 63.13330

Low strip grillages are laid on a concrete preparation with standard waterproofing of the base before pouring. The requirements for materials of monolithic structures are as follows:

Heaving forces are present exclusively in low grillages; they are compensated in several ways:

• cushions made of non-metallic materials + backfilling of the buried belt with sand, crushed stone
• insulation of the sole, blind area, edging - by analogy with MZLF, XPS expanded polystyrene sheets (manufactured by URSA, TechnoNIKOL and others) are laid over the waterproofing layer

Regardless of the level of the grillage relative to the surface, a drainage system is required to remove moisture from the bored piles.

Monolithic tape

Foundations, the grillage of which is poured into the formwork, have greater spatial rigidity in comparison with prefabricated structures. The grillage beams are reinforced with two chords, each of which uses at least two reinforcing bars of periodic cross-section.

In 90% of cases, a monolithic grillage is used on bored piles because:

• materials have the same resource, linear expansion
• in a monolithic grillage it is easier to wall up the heads with reinforcement bars sticking out of them
• the same waterproofing compounds are used

Regardless of the position of the monolithic grillage above the ground, it is necessary to lay drains that drain ground and surface water from the concrete piles.

Collection tape

Prefabricated pile-grillage foundations are ideal for wood construction technologies. Beams made of timber, I-beams, and channels are laid on the heads and joined in half a tree or by welding. The absence of concrete work allows:

• reduce the budget
• start building walls the next day

Prefabricated tape of reinforced concrete beams is rare and is practically not in demand in individual construction. The complexity of the design lies in the junction of two beams to the head of one pile.

The most difficult thing is to tie screw piles with a monolithic grillage. Therefore, they are usually tied with timber, I-beams, or channels. For brickwork, grillage beams made of two welded channels mounted on an edge are used.

In buildings with reinforced concrete frames, a glass grillage can be used. It has the form of a kneecap mounted on a slab with dimensions that are multiples of 15 cm, 30 cm (height, width, respectively). In this case, the total height should be 40 cm greater than the depth of the glass. Standard design calculations:

When reinforced, the spatial frame of the glass widens at the bottom - it is connected to the flat mesh of the slab. Each glass rests on 4 piles and is used for the installation of columns. Therefore, the technology is more in demand in industrial and agricultural construction.

Hanging grillage

The disadvantages of a high grillage - complex formwork, the need for removal - are compensated for on heaving soils by the absence of bending forces, cushions made of non-metallic materials, and excavation work. For monolithic grillages, bored piles are more often used. The beams of prefabricated grillages are often joined at the ends of the SHS.

The advantages of a hanging grillage are:

The disadvantage is the impossibility of making a floor on the ground - all other technologies (joists, slabs) are more expensive. When building a cottage using frame, log, or half-timbered technologies, the construction budget is always minimal. Therefore, the costs of removing and insulating communications underground cannot seriously increase the cost per square meter.

Underground grillage

The underground option is economically beneficial if the project includes a technical underground or a basement floor. The main advantage of a grillage over a strip foundation is its support on piles:

The gap under the sole of the monolithic structure in the ground is protected with sheet materials. This cannot be done for standard MZLF tape. Waterproofing and a drainage system can increase the service life of any reinforced concrete structure, therefore they are necessary for any low grillage.

Ground grillage

If the depth of the swelling layer in the building area is less than 12 m, it is more rational to use a low-type ground grillage. To compensate for heaving forces, it is enough to leave a 10 cm gap between the soil and the slab/tape. The gap is covered on both sides with sheet material to prevent soil from being packed into it or applied by storm drains.

In practice, the technology is produced in the following order:

The ribbon rising above the ground is also the base of the building. To ventilate the underground, vents in a monolithic structure are required. Therefore, it is recommended to increase the height of the grillage to 0.6 m in order to make vents no lower than 0.4 m from the zero level, otherwise in winter these holes will be clogged with snow.

Thus, a grillage on piles is in most cases preferable to other types of foundations in low-rise construction. The piles pass through heaving soils and rest on the bearing layer. The grillage collects operational and structural loads, distributing them evenly. There is no heaving silt at all, which guarantees the maximum possible service life of the building.

A grillage is an element of a pile foundation that serves to connect piles into a single structure.

The strapping is arranged for various types of pile supports: screw, reinforced concrete, bored.

Main functions of the grillage:

• connecting piles into a single structure;
• uniform redistribution of load on piles;
• increasing the bearing capacity of the foundation;
• giving additional rigidity to the base;
• preventing uneven subsidence of the house;

The installation of a grillage is recommended for the construction of private houses and cottages, regardless of the type of soil. It is not advisable to arrange a grillage for log houses, in which the lower crown will perform the piping function, and for frame houses, where the lower metal piping is made. When building cottages from piece materials on a pile foundation, the installation of a grillage is mandatory. For light small houses, outbuildings, gazebos, the grillage can be a full-fledged ground part of the combined foundation.

Expert opinion

Sergey Fedorov

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Important! Many people confuse the concepts of “strip foundation” and “grillage”. In design, these elements are indeed often very similar (especially monolithic ones). However, the functions of the elements are different: the grillage redistributes and at the same time absorbs part of the loads from the structure, and the strip foundation rests on the ground and absorbs the bulk of the weight of the structure.

Advantages and disadvantages of a pile-grillage foundation

A pile-grillage foundation is one of the most commonly used types of foundation in private construction. The demand for the design is explained by the presence of many advantages:

• low cost and the possibility of self-installation are the main advantages that help reduce the estimated cost of construction;
• versatility - suitable for all soils, subject to the correct choice of pile type;
• installation can be carried out at any time of the year;
• long service life, depending on the material of the piles - from 25 to 100 years;
• the possibility of constructing a foundation in areas with differences;
• load-bearing capacity up to 20 tons per pile;
• a small amount of excavation work and the ability to preserve landscaping on the site.

This type of foundation is excellent as a foundation for a house made of light foam and gas blocks, but a brick house requires the construction of a pile-monolithic foundation, which also includes a grillage.

The grillage foundation has its disadvantages:

• a detailed calculation of the pile field is required;
• the base requires insulation and waterproofing;
• the difficulty of repairing a metal grillage.

The need for repairs largely depends on the correct choice of piles. Problems are most often caused by screw supports, which corrode and lose their load-bearing function. In this case, it is necessary to replace them with partial dismantling of the grillage and the use of retaining walls.

Types of grillages for pile foundations by location

There are many options for constructing a grillage for a combined pile foundation. When choosing, you need to decide how the structure will be located relative to the ground. Based on this criterion, the following types of grillages are distinguished:

1. Hanging or tall. The distance between the ground level and the bottom of the structure is at least 30 cm. Suitable for houses on heaving, swelling soils, areas with a risk of flooding, and with high groundwater levels. To install a hanging grillage, a complex calculation of the load-bearing capacity of piles is required, because they will take up to 70% of the load.
2. Elevated. The base of the structure coincides with the zero level, and the structure itself rises 10 cm above the zero level. The installation of such a piping is possible only on soils with good bearing capacity. The disadvantage of this type is the lack of an air gap between the grillage and the soil, which leads to increased heat loss at home. To minimize heat loss, 10-15 cm of soil is excavated under the grillage to form an air cushion.
3. Shallow. The grillage is buried 10-20 cm into the ground. This is the best option, because... in this case, the structure evenly distributes the load on the piles and foundation. A shallow grillage can only be made on stable soils. If the soils on the site are loose and watery, then adding a layer of soil 0.5 m thick will be required, which increases the cost of construction.
4. Recessed. More than half of the grillage is underground. The design is reliable, but its implementation requires a large amount of excavation work. Therefore, this type of strapping is rarely used, mainly for the construction of massive 2-4-story townhouses and brick cottages.

Types of grillages by material of manufacture

To make a foundation with a grillage, metal beams, wooden beams or reinforced concrete can be used. The choice of material for tying depends on the type and weight of the structure, hydrogeological characteristics of the soil, and the financial capabilities of the owner of the future home. Let's look at the main types of grillages made from different materials.

Wooden grillage for foundation

This is the easiest and cheapest type of binding. For wooden light buildings, the first crown can perform the piping function, but when building a frame bathhouse or outbuilding from gas silicate blocks, a grillage is required. The technology for installing the structure is simple: pre-prepared boards are laid along the future walls and connected to the pile heads. More information about the installation and requirements for the grillage can be found in the SP standard “Wooden structures”. When performing wooden strapping, it is important to follow the following rules:

1. A wooden grillage can only be hanging or raised. Once in the ground, the tree will quickly become unusable.
2. This type of strapping can only be used for light buildings.
3. It is desirable that the piles be screw. For supports made of concrete, you will have to make metal heads, because... It is impossible to bind concrete to wood rigidly.
4. The boards for the structure must be chamber-dried, treated with an antiseptic and waterproof compound.
5. The section of the boards is selected depending on the weight of the structure: for one-story buildings - 15x15 cm, for houses with an attic - 15x20, 20x20 cm.
6. The boards are installed strictly vertically!
7. After installing the structure, a bench is installed - a horizontal board that improves the geometry of the structure.

The advantages of wooden strapping include ease of manufacture and no need for insulation. Waterproofing of the structure is necessary: ​​a film of foamed polyethylene is placed at the junction of the piles with the tree, as well as under the bed. Disadvantages of a wooden grillage: limited use, service life 10-15 years.

Metal grillage for foundation

Metal grillage is reliable and suitable for massive houses. A pile-grillage foundation with metal elements is made primarily on screw supports, but it can also be connected to bored and driven piles using reinforcement allowances. The metal grillage is made from an I-beam, channel or square profile. In terms of cost and ease of use, the channel is best suited.

The size of the channel depends on the diameter of the piles:

• channel 12, 14 and 16 are used for supports 108 mm, and the heavier the structure, the larger the metal structure should be;
• channel 16, 18 and 20 are used for supports 108 and 133 mm.

For a 2-story cottage, the best option is channel 20, for a one-story cottage - 16 or 20, for an outbuilding or bathhouse - 14, 16. The metal grillage relative to the ground can be located higher, shallowly or deeply buried. When installing a buried pile-grillage foundation, the metal structure must be treated with an anti-corrosion compound or purchased galvanized products. The grillage is connected to the heads of screw piles or the outlet reinforcement of concrete supports by welding, forming a strapping unit. Welded seams are treated with a primer.

The main advantage of a metal grillage is its strength; the structure forms a rigid and reliable bond. Disadvantages include labor intensity, the need for welding, and susceptibility to corrosion.

Concrete grillage for pile-grillage foundation

The concrete grillage has the form of a reinforced concrete tape that connects all the piles along the perimeter of the foundation and along future load-bearing walls. According to their design, the following types of grillages are distinguished:

• prefabricated, consisting of ready-made reinforced concrete structures, for example products RS1, RB, etc.;
• monolithic, poured on site into prepared formwork.

A prefabricated grillage is more expensive; when constructing it, difficulties often arise with connecting the pile and ground parts of the foundation. Therefore, in most cases, monolithic strip piping is chosen for the construction of private houses.

Expert opinion

Sergey Fedorov

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On the Internet you can often come across the concept of “monolithic slab-type grillage”. This definition is erroneous, because in this case we are not talking about piping, which is the main function of the grillage, but about a full-fledged pile-monolithic slab-type foundation. It is also important to understand that when talking about a concrete grillage, we mean a structure with reinforcement, i.e. reinforced concrete. A grillage made of concrete alone cannot be used for strapping, because the structure must bend, and a concrete solution without reinforcement will not last very long.

Calculation of pile-grillage foundation

The calculation of a combined base with a reinforced concrete grillage consists of two parts:

Pile field calculation

The structure and principle of calculation depends on the type of supports used. For screw supports, the calculation determines their diameter, the size of the blades, the depth of installation, and the distance between the piles. When calculating bored supports, it is necessary to determine the depth, diameter and pitch, as well as make an additional calculation of reinforcement.

Calculation of reinforced concrete monolithic grillage

The purpose of calculating a monolithic pile foundation grillage is to calculate the punching capacity of the structure, its ability to withstand bending loads and determine the strength of the section when exposed to shear forces. The calculation process is described in detail in SNiP 3.03.01-87, SP “Design and installation of pile foundations” and GOST R 52086-2003. In the field of private housing construction, it is not advisable to make these complex calculations. It is enough to determine the main dimensions of the piping for the pile foundation:

Grillage depth

The depth of the foundation directly depends on what type of foundation was chosen. Let us recall that, relative to the ground level, a pile-grillage foundation can be suspended, elevated, shallow and deeply buried. The pile part of the combined pile-grillage foundation is laid at least to the depth of soil freezing. The optimal depth for laying the grillage is 10-30 cm below the zero level. The heavier the mass of the house, the deeper the grillage should be buried.

If the grillage is not deep enough, the foundation may shrink, which will lead to the disappearance of the air gap between the soil and the monolithic strip.

Width of pile foundation grillage

The width of the monolithic strapping tape is determined by the formula:

where: B is the width of the tape;
M - mass of the house (materials + loads);
L is the length of the grillage;
R is the soil bearing capacity coefficient, determined from the tables in SNiP.

The length of the grillage is the sum of the perimeter of the foundation and load-bearing walls. The formula is suitable for calculating the width of an elevated and recessed base. Another way to calculate the width of the strapping tape without using a formula: the width is equal to the diameter of the piles used plus 25-35 cm. The width of the hanging grillage is determined through complex calculations that can be made using special engineering programs.

Height of the pile foundation grillage

The height depends on the type of building material from which the house will be built. For aerated concrete, a height of 40 cm is sufficient, for silicate blocks - 50 cm, for heavier materials - 60 cm. Relative to the width, the height of the grillage should be 90-110%.

If the grillage will also serve as the base of the house, then it should be made higher - 50-60 cm. This is necessary for the installation of vents, which are located at a height of 30-40 cm from the zero mark.

An example of calculating a grillage for a pile foundation: a house is being built from aerated concrete with a length of load-bearing walls of 100 m on dense sand using screw supports with a diameter of 108 mm. The weight of the house is 55 tons. The depth of the grillage, taking into account the weight of the structure, is taken to be 0.2 m. We calculate the width: B = 55 t/100 m * 75. The width is 41 cm (according to another calculation, 10.8 cm + 30 cm = 40, 8 cm). The height of the grillage will be 40 cm, of which 20 cm will be buried underground.

Reinforcement of the strapping is necessary to withstand bending loads. The reinforcement used for reinforcement must comply with the requirements of SP “63.133301.2012”. To determine the cross-section of reinforcing bars, it is recommended to use the table:

Minimum cross-section of reinforcing bars

For reinforcement it is necessary to use class A3 rods. The simplest reinforcement scheme is suitable for 4 or 6 rods with vertical inserts every 30-40 cm.

DIY pile-grillage foundation

The installation of a pile-grillage foundation begins with site preparation, which includes clearing and creating a trench for a buried grillage. The next step is the installation of pile supports. The technology for installing piles depends on their type. Screw piles are screwed vertically into the ground. A well is prepared for bored supports, which is then concreted. After the pile field is ready, you can begin to build the grillage part of the foundation.

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When mixing concrete yourself, it is important to strictly follow the recipe for the selected class. For example, to prepare a mixture of B22.5 (M300), it is necessary to maintain the cement/sand/crushed stone ratio = 1.2/4.4/3, and for the water/cement ratio = 0.53...0.55/0.60.

Waterproofing of pile-grillage foundation

The foundation with grillages needs waterproofing, which protects the foundation from moisture. The installation of waterproofing for buried pile-grillage foundations is especially important. For raised grillages, it is also advisable to waterproof them. The following waterproofing options are available:

• coating - the piping is covered with a layer of bitumen mastic;
• rolled - a monolithic tape is coated with a thin layer of mastic, and a roll of waterproofing is laid on top;
• sprayed - a liquid composition with water-repellent properties (such as “liquid rubber”) is applied with a spray gun;
• penetrating - a solution with high adhesive properties, which is used to treat the foundation to protect it from moisture.

The choice of waterproofing depends on the groundwater level, soil type, type of grillage, financial capabilities and personal preferences of the owner. Different types of waterproofing have their own advantages and disadvantages, which are recommended to be taken into account when choosing.

Insulation of pile-grillage foundation

Thermal insulation of the grillage helps prevent heat loss through the floor of the house. The following can be used as insulation:

• polystyrene foam or extruded polystyrene foam in slabs;
• sprayed polyurethane foam thermal insulation.

It is impossible to use mineral wool insulation for the foundation, because... they actively absorb moisture and become unusable. The main parameters that you need to pay attention to when choosing a heat insulator for a foundation on piles: thermal conductivity - must be at least 0.035 W/μ and water absorption no more than 4%. Also, the insulation must have noise-insulating properties, be resistant to rodents and aggressive environments. The insulation boards are attached to the top and bottom of the grillage using glue and dowel-nails. A reinforcing mesh and a plaster layer or other type of finishing are mounted on top. To remove moisture and maintain the integrity of the foundation, it is necessary to make a blind area.