Pile-grillage foundation: classification, advantages and disadvantages, requirements and standards. Pile-grillage foundation: overview How to make a pile-grillage foundation

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

Ask a question to an expert

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.

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:

Hanging or tall. The distance between the ground level and the lower part 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.
Elevated. The base of the structure coincides with the zero level, and the structure itself rises 10 cm above the zero level. The construction 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.
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.
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:

A wooden grillage can only be hanging or raised. Once in the ground, the tree will quickly become unusable.
This type of strapping can only be used for light buildings.
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.
The boards for the structure must be chamber-dried, treated with an antiseptic and waterproof compound.
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.
The boards are installed strictly vertically!
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 installing 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

Professional builder. 18 years of experience

Ask a question to an expert

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 concrete mortar 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.

Step-by-step instructions for installing a reinforced concrete grillage:

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.

A pile-grillage foundation is a fairly strong and durable structure that is ideal for the construction of residential buildings on both normal and unstable soil. By creating a monolithic structure, this technology combines all the advantages of pile, columnar, and strip foundations. In addition, it is not difficult to build a pile-grillage foundation with your own hands. What is needed for this, and what installation subtleties do we need to know and we will try to figure it out.

What is a pile-grillage foundation

The technology for constructing a pile-grillage foundation was invented in Finland, where there have always been problems with the soil, and houses are made of wood (that is, they are quite light).

Important! Such a foundation is more suitable for the construction of low-rise light houses (for example,). It will also work for a brick building, the main thing is to make the correct calculations to distribute the load on the base.

The pile-grillage foundation combines all the advantages of its ancestors: the load is evenly distributed over the grillage, and the piles reliably secure the foundation, protecting it from destruction in heaving soils or groundwater passing close to the surface.

Foundation structure

Piles act as the basis of the entire structure. They sink to a depth below the soil freezing level (individually for each region), and take on the entire main load.
The edges of the piles above ground level are tied with grillage tape. Outwardly, it is no different from the classic strip foundation: reinforced concrete is located under all load-bearing walls, and takes on the main load. Ultimately, a monolithic foundation emerges, which securely secures the structure.

Interesting to know! Comparing the grillage type of foundation with its ancestors, it definitely wins. requires more financial costs and does not have such stability, but loses in terms of load distribution on the base.

For installation, you definitely need drawings and diagrams made by a professional, and for accuracy, markings are first made on the ground.

To resist soil movement, it is necessary to make a shallow foundation. It uses piles made of asbestos pipes, inside which reinforcement is laid and concrete is poured. Below we will take a detailed look at the step-by-step instructions using this example.

Pros and cons of a pile-grillage foundation

Any structure has its pros and cons; a pile-grillage foundation is no exception. Let's talk about them in more detail.

The strengths of this foundation include:

For installation you do not need to involve builders and special equipment; you can do it yourself.
It will take a little time to lay the foundation for it.
Low financial costs.
This is a universal foundation for different types of soil. It can also be done in areas with difficult terrain.
The foundation is highly reliable and does not collapse due to seasonal movement and soil heaving.

When compared with a classic strip foundation, the savings when constructing a pile-grillage foundation average 45-50%

Design disadvantages:

The basement and basement are excluded if a pile-grillage foundation is chosen.
The floors of the first floor require additional insulation.
The final mass of the building under such a foundation is limited.

Scope of application of pile-grillage foundation

Pile-grillage foundation in construction is usually used in the construction of light, one- or two-story buildings, in conditions of “unstable” soil (heaving, swampy, clayey). It is often used in.

This solution will also help during the installation of buildings on a site with non-standard terrain: for example, construction on a hillock.

If all requirements are met during installation, the grillage type of foundation will last for decades.

Foundation devices with a grillage: 1 - roofing felt, 2, 8 - bottom trim, 3 - anchor bolt, 4 - anchor immersion depth 100 mm, 5, 9 - grillage, 6, 10 - pillar, 7 - joists

Calculation of pile-grillage foundation

Calculation of a pile foundation with a grillage involves calculating the depth of immersion of the piles. It is recommended to entrust it to a professional. An error can lead to premature destruction of the entire structure.

In general, for this it is necessary to carry out a whole analysis: study the characteristics of the soil, take into account wind and snow loads, climatic features of the region and the mass of all building materials.

Correct calculations of the foundation are the key to high-quality and successful construction of a house

Let's consider the algorithm of actions

First, let's calculate the total mass of all building materials that will be used.
Next, we calculate the snow load, after which the total load on the foundation is calculated.
The final step is to calculate the total load on the foundation.
The result of previous calculations is multiplied by a coefficient.

Since the earth tends to move, be washed away by groundwater, and swell when frozen, it is advisable to conduct a qualitative assessment of the soil. This study plays an important role in the construction of any type of foundation.

DIY pile-grillage foundation

The construction of such a foundation does not require special skills and experience, so those who want to build a house can cope with this task on their own. Let's look at the step-by-step instructions for installing a pile-grillage foundation with your own hands.

Cleaning and marking the area

Site preparation is one of the most important stages of construction, the quality of which will determine the comfort of further work. The first thing you need to do is remove all excess debris and plants.

Important! Trees and bushes must be uprooted, otherwise they will sprout again and cause problems during the operation of the home.

If the territory is provided for, it is necessary to carefully remove all weeds. If you plan or beds, the top layer of soil (4-5 cm) is removed.

Also at this stage, the site is marked. It is necessary for more precise execution of installation work (even pouring of the grillage and installation of piles in a predetermined location).

To make the correct markings, the drawing from the drawing must literally be transferred to the ground. It is important that all dimensions exactly correspond to the parameters specified in the drawings.

For work you will need the following materials:

level;
hammer;
roulette;
rope (fishing line);
pegs.

Separately marked places for piles. They are distributed over the area in a certain order so that each support bears a certain level of load (from 800 to 1600 kg).

Important! Supports are installed at each corner of the future building, as well as in places where load-bearing walls or partitions will pass.

Drilling a hole for piles

Sometimes the grillage is made at a certain distance from the ground, then there is no need to dig trenches, but this somewhat complicates the process of pouring the grillage.

Wells for piles are drilled with a garden or hand drill. You can also resort to the services of drilling crane machines, but it is worth taking into account that this will lead to an increase in the estimated cost of construction by about 10%.

The depth of each hole is 50 cm greater than the freezing level of the soil. The diameter of each hole should be slightly larger than 1/3 of the width of the foundation strip. The first 30 cm must be covered with sand and compacted thoroughly. This will help protect metal parts from soil moisture.

Important! The distance between piles should not exceed 3000 mm. The smaller the diameter of the pillar, the smaller the minimum permitted distance between piles becomes.

Installation of foundation piles

Now we form a “pile field”, that is, we install the piles in their places. For the construction of simple buildings, they can be evenly distributed around the perimeter in rows.

Sometimes piles are installed in a staggered pattern. This order of placing supports is often used for installing fences.

At the stage of designing a pile field, you should remember the following details:

The choice of piles depends on the type of soil;
How close to the surface does groundwater flow;
The diameter and length of the piles depend on the final mass of the structure (the larger the house, the more powerful, which means the larger the piles should be). It also depends on the type of grillage.
The bearing capacity of the supports must be calculated.

We proceed directly to the installation of piles. Formwork and reinforcement are made for them, and after that the holes are filled with concrete mixture. It is recommended to start pouring concrete only after all excavation work has already been done.

You can use screw piles, for installation of which you do not need to carry out excavation work. Installation of piles into the ground occurs in several stages:

In a pre-marked place for the piles, we make a hole 10-15 cm deep.
We put the pile screw in it and start screwing it in. This will require 3-4 people.
As you screw in, be sure to check that the support is evenly inserted into the ground using a building level.

When purchasing ready-made concrete supports, you will have to use special equipment; such piles are driven into the ground.

For each support, you must make a “heel” on which it will stand securely. To do this, sand is poured into the well, the pile itself is placed in the well and filled with concrete (about 40 cm). Then the support is raised (by 30 cm) so that the concrete flows under it and creates a support cushion.

Foundation formwork

Before installing the formwork, it is necessary to make a cushion at the bottom of the trench. To do this, 10-15 cm of sand is placed on the bottom, it is filled with water and thoroughly compacted. Crushed stone is poured on top of the sand.

You can buy formwork in a store or make it yourself from ordinary boards or chipboard panels. So that the material for the construction of formwork can be reused, it must be wrapped in plastic film.

Initially, along the perimeter of the future growth, we drive stakes every meter, to which we mount formwork panels so that the supporting stakes are on the outside.
To prevent the shields from falling apart, additional support is nailed at the top and bottom. Particular attention should be paid to the formwork elements at the lower corners.

Important! The height of the formwork should be 10-15 cm greater than the expected height of the grillage.

Reinforcement of piles and grillage

Reinforcement is a mandatory stage in foundation construction, which helps strengthen the entire structure as a whole. To do this, after preparing the formwork, a three-dimensional mesh is assembled inside it from metal rods.

The rods are laid in several directions, and at intersections they are tied with strong steel wire.

Piles are also necessarily reinforced. To do this, take three rods and connect them in the shape of a triangle, and then place them in place.

The rods should protrude 20 cm above the pile. Sometimes, to further strengthen the structure, a complete circle is assembled from rods.

Pouring the solution

When pouring concrete, you need to consider some subtleties:

The density of the finished solution should be medium.
Before pouring concrete, all reinforcing rods must be connected.

Procedure

First of all, all support piles are poured. They are left for 1-2 days so that the structure dries out a little and becomes more durable.
After this, the tape itself is poured. To do this, it is recommended to use several concrete mixers and pour the mixture simultaneously at several points.
We leave the foundation to dry for a week. If necessary, the surface of the grillage is leveled.

Important! In rainy or cloudy weather, pouring concrete is prohibited, as this will reduce the strength of the entire structure.

Waterproofing insulation

Thermal and waterproofing of the foundation helps protect the foundation itself, as well as the foundation materials of the house, from moisture and dampness.

Metal and asbestos piles also need to be covered with waterproofing, since over time their strength decreases due to corrosion. To do this, you can use the same material as for waterproofing the foundation strip.

Subtleties of waterproofing:

To protect the piles, roofing material is rolled up and placed in the hole in this form. In the trench for tapes, the walls and bottom are completely covered with this material. For reliability, the top of the roofing material can be coated with hot resin.

The pile-grillage foundation provides for insulation of the side walls of the foundation, which act as a plinth. For this purpose: polystyrene foam or polystyrene foam, bitumen, etc. are used.

To protect the base from dampness and mold, it is also important to take care of the ventilation holes. They are made using small pieces of plastic pipe.

It is laid at a certain level of the tape during pouring of concrete, the pipe contour is sprinkled with sand so that it can be easily removed. When the foundation is completely dry, the pipe is removed.

Now you know how to make a pile-grillage foundation with your own hands, using the knowledge gained from studying this article.

Until recently, only four types of foundations were common in construction: pile, strip, slab and columnar. Moreover, preference was given mainly to the strip type - it is laid below the freezing point of the soil, thanks to which the building stands reliably, but this zero level is expensive. How long? By as much as 45% of the estimated cost of all work! That is why the new Finnish type of zero-level device - the pile-grillage foundation - began to gain popularity so quickly. Especially its subtype, which is constructed in permanent formwork. And it comes out within 10-25% of the total estimated cost for the bathhouse - all thanks to the fact that there is no need to install shields and mount them with wooden blocks, and dismantling of hardened concrete is also not necessary.

And the pile-strip foundation (it is also called that) copes with its task perfectly on slopes, areas with uneven terrain and on unstable soil. If the bathhouse is planned to be massive and not have one floor, just such a zero level will withstand everything.

What is a grillage and why is it needed?

A grillage is slabs or beams that connect piles to each other already on the surface of the earth. This foundation design is simply ideal for baths that are built using frame technology and their main elements are connected to piles, and when the width of the strip foundation is planned to be too wide.

So, in such a foundation for a bathhouse, the grillage can be monolithic, prefabricated, or prefabricated-monolithic. If it is monolithic, made of concrete with formwork, it is also a strip foundation on bored piles, which is no less strong and durable.

Which piles are best for such a foundation?

According to the materials, piles can be reinforced concrete, concrete, metal and occasionally wood. There are also hanging piles, which transfer the load of the bathhouse to the side surfaces, and rack piles, which transfer the same weight to the parent soil.

A modern pile foundation with a grillage is made today with both cast-in-place piles, which are conveniently laid in prepared holes right on the construction site, and injection piles - they are poured into narrow holes up to 12 cm with single reinforcement. A good alternative is driven piles - ready-made pillars that are driven into the ground using special equipment.

How to properly position piles in a grillage?

In total, there are 5 ways to arrange piles in a pile-grillage foundation:

Single - when the piles are each under their own support.
Tape - when they are evenly located around the entire perimeter of the bath.
In the form of strips - when piles are placed in 2 or more rows in a long grillage. This is for huge and massive baths with pools and floors.
Bushes - piles are located in places of high load and under load-bearing columns.
In the form of a field, the piles are arranged in rows or in a checkerboard pattern under a large grillage.

Construction of such a foundation in a step-by-step manner

Piles for such a foundation will need to have a round cross-section, and they will be driven into the ground thanks to the work of a construction drill. After drilling the wells, a sand cushion will be laid in them in a layer of 30 cm. Prepare for the fact that there will be a lot of piles - both at the base of the walls and at the corners of the strip, and at a distance of at least 1.8-2 meters from each other. Asbestos-cement pipes and those made from ordinary roofing felt using fishing line are traditionally used as waterproofing for such a foundation.

The simplest version of a pile-grillage foundation is piles buried 2 meters and 3 m apart from each other, and a grillage in the ground 20 m deep. And then inside the grillage you can build an underground floor on a sand cushion or screed - then there will be no need for waterproofing . Cheap and cheerful, as they like to say in Russia.

Step 1. Geological exploration work is carried out, which allows us to understand what kind of soil is on the site and how homogeneous it is. Moreover, if it is not possible to bring a specialist, you need to at least do all this in a primitive sense - after all, it is known that the characteristics of the soil can be different within a very small area. In addition, such parameters as wind load, the weight of the building materials of the bathhouse and the magnitude of the relief slopes are also important - all this is also taken as a basis.
Step 2. A sand cushion is prepared for the reinforced concrete foundation strip - so that the entire structure is maximally protected from the mechanical influence of the soil.

Step 3. Traditional formwork is made, as for a strip foundation - according to the same principles. As for the pile-grillage foundation with permanent formwork, the role of “dishes” in it is played by extruded polystyrene foam “Penoplex” or “ThermoMonolit”. As a result, the foundation itself turns out to be warm and even waterproofed. And all cold bridges will be eliminated by fiberglass reinforcement and SVT ties.

Step 4. Piles are made. The holes for them are drilled with special equipment, then they are lined with roofing felt or similar sheet material - with the expectation that the upper part is located at ground level. Moreover, an asbestos cement pipe can be used as casing. But four threads of reinforcement are placed inside the hole - connected to themselves so that their upper part comes out of the pile and is connected to the grillage reinforcement. This is where the concrete is then poured.

But before reinforcing the grillage, the upper part of the piles is first waterproofed from it - the amount of material is calculated individually. But the reinforcement that is released from the piles is tightly connected to the grillage reinforcement. After it reaches 50% strength, the bedding can be removed and a grillage above the ground will be obtained - it should not rest on the ground.

Step 5. The piles and strips are reinforced together and filled with concrete - for these purposes it is best to use construction vibration equipment. This is, in fact, a strip foundation on piles, which is officially called “pile foundation with a monolithic grillage.” Moreover, the piles are poured first - and only after a long period of time can the entire reinforced concrete strip be concreted. And, more precisely, exactly a week later, when the concrete has already gained half of its brand strength, work on the grillage begins. So, first, formwork is constructed, where sand is poured or polystyrene foam is laid. This is necessary to raise the grillage above the ground and align the bottom of the formwork with the top of the piles. By the way, this foundation can be filled with self-produced concrete.

But the pile-grillage foundation also has its disadvantages. Firstly, the steam room will not have a basement floor; such a structure cannot be installed under heavy walls, and the calculations themselves for a pile-grillage foundation are quite complex. But for an ordinary Russian bath, the option is almost ideal.

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, 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.

Sandy soil. It has good drainage properties, does not heave and compacts tightly. Foundations on such soils are easy to construct and durable.
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.
Clay. Clay soils are prone to severe swelling. To build a foundation, an anti-heaving cushion is required.
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

Produced area cleaning.
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.
The turf layer is removed under future construction, and the soil surface is leveled.

Step 4 - Marking

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.
Then between the pegs the fishing line is stretched or twine, thereby denoting foundation installation line.
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:

Conducted well drilling below soil freezing by at least 0.5 meters.
If it is necessary to strengthen or drain the load-bearing soil layer, sand cushion is being installed.
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.
Then, using a level, it is made horizontal control And pipes are cut to the required level.
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.
The fittings are located in such a way that it upper part performed above fill level slightly lower than the height of the grillage.
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.

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.
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 buildings by 5-10 cm.
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.
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.
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.
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.
Horizontally located along the perimeter the rods are tied with tying wire for greater durability.
Then it is produced pouring concrete form using a concrete pump.
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.
When the concrete will harden(usually it takes 2-3 weeks) the formwork is removed, A sand cushion is removed.
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

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.
Imprecise definition soil bearing capacity. Result - incorrect calculations, instability and immersion of the foundation into the ground.
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:

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

One of the most cost-effective types of foundation is a pile-grillage foundation. It, like others, has its own construction features, advantages, and disadvantages. This will be discussed further.

The presented comments and advice from leading experts from various construction companies highlight the main aspects of the construction of such a foundation.

What is a pile-grillage foundation

A pile-grillage foundation is a reliable structure made of piles and a grillage.

Piles are pillars sunk to a certain level into the ground. They usually have a rectangular or round cross-section and serve as the main support for the entire future building. Piles are usually made of concrete, reinforced concrete, metal or wood, depending on the complexity and severity of the structure.

A grillage is a reinforced concrete monolithic structure that connects piles. It is designed to distribute the load between the piles, and is a reliable and stable basis for the construction of walls.

The combination of piles and concrete grillage makes the finished structure more stable and reliable.

When choosing the type of foundation, it is necessary to evaluate all the pros and cons and, based on this, decide on further actions.

Advantages of a pile-grillage foundation

Igor Andreev from the Fundament company talks about the advantages of this type of foundation:

This foundation is suitable for work under different conditions and has the following advantages:

Significant stability and load-bearing capacity. These parameters may vary slightly due to the building materials used, but on average this type of foundation can withstand a load of up to 5 tons.

Suitable for erecting buildings on difficult soil. This is a very important feature. If there is mobile or unstable soil on the plot of land allocated for construction, this will not be a basis for canceling the plans and moving it to another area.

Pile-grillage foundation on a slope, when building in areas with heterogeneous terrain, is one of the most convenient solutions.

This point of view is valuable because it reflects the experience of the real work of a specialist. In addition, we can only add that for the construction of this type of foundation, no preliminary work is carried out, such as clearing the area of vegetation, removing the top layer of soil, etc., that is, there is no preparatory stage, which saves a lot of time.

A pile-grillage foundation is often used for aerated concrete. This is a separate big topic, we will touch on it in our next publications.

There are also several other advantages:

You can install the foundation yourself, without using the services of specialists or using equipment.
Low cost of project implementation, which makes this type of foundation very profitable.

Andrey Kudritsky, head of the cost planning department of the leading construction company in Moscow "StroyDom", emphasizes:

If you calculate the construction costs, then on average, the cost pile grillage foundation will cost 10-25% of the total planned estimate, while costs for other types of foundations reach 45% of the estimate.

Disadvantages of a pile-grillage foundation

The pile-grillage foundation also has disadvantages, and they must be taken into account when making a decision:

Such a foundation is definitely not suitable for a heavy, massive structure, since it has a relatively small maximum load.
A rather complex and labor-intensive process of calculating a pile-grillage foundation.
Difficulties that arise when arranging the basement.
Often there is a need to fill the space between the piles, which leads to additional material and labor costs.

Petr Matko, a specialist in calculations and work planning at MosArkhBuro, believes:

It is best to hire an experienced specialist for this. He will be able to competently take into account possible terrain features. When making your own calculations, there is a high probability of an error, which will cost you a “floating” foundation.

Construction of a pile-grillage foundation

The foundation is the basis for building a future home. This process is quite labor-intensive and includes a number of important steps.

The first stage, which underlies construction - calculation of pile-grillage foundation. It goes like this:

The maximum bearing capacity of the soil, its composition and density are determined.
All possible additional loads and risks are taken into account.
The number of required piles is determined.
A project for the future building is being drawn up.

Advice from expert Peter Matko from the MosArkhBuro company on calculating the number of piles required:

The loads must be summed and divided by the total area of support. The result should be no more than the load-bearing capacity. If this condition is not met, the number of support piles must be increased.

At the next, preparatory, stage of construction, the foundation is marked on the ground. The corners of the house, the boundaries of the internal and external walls are marked. Next, markings are made for the piles. They are located in the corners of the building, under load-bearing walls and in places where internal walls intersect with external ones.

There are five main options for the location of piles in the foundation:

Single - each pile is under its own support.
Tape - piles are evenly distributed around the perimeter of the future building.
In stripes - piles are installed in several rows.
In clusters - piles are installed side by side, several in number, in places that bear significant load.
Field - piles are inserted in a checkerboard pattern or in rows over the entire area of the grillage.

After design and marking, they proceed directly to work on the ground. Excavation work is carried out manually or using special equipment. In the first case, holes for the pile are first drilled with a hand drill; in the second, this happens automatically using special equipment. A reinforcement cage is installed in the well, which is filled with concrete on the same day.

Comment by Peter Matko from the MosArchBuro company:

At this stage, the timing of the work is important. It is better to prepare reinforcement cages in advance, and concreting the piles must be done on the day of drilling wells. Why on the day of drilling? Because the soil may crumble a little during the night.

3-4 days after installing the piles and completely hardening the concrete, you can proceed to the installation of the grillage formwork. Formwork is required to create monolithic pile-grillage foundation.

The boards are spaced at a distance equal to the thickness of the walls. After they are securely fastened, a layer of waterproofing and a reinforcement frame for the future grillage are applied. For reliability, the grillage frame must be fastened to the pile frame. After this, the structure is filled with concrete. After the concrete has completely hardened, the formwork is removed. Below is photo of pile-grillage foundation.

Main mistakes and recommendations when constructing a pile-grillage foundation

In the process of laying a pile-grillage foundation, the following typical mistakes may be made, which are best avoided:

1. Lack of reliable connection between the piles and the grillage.

In winter, as a result of varying degrees of freezing of insulated and non-insulated soil, an additional force arises that tends to overturn the support pillars. This occurs because the frozen ground expands and presses on the tops of the concrete piles towards the floor of the building. If the pillars were not securely fixed at the top, there is a high probability that they would simply be pushed under the building.

2. Absence of an air cavity under the grillage.

The presence of an air cavity is especially important in winter. If this is not taken care of in advance, the following may happen. The frozen ground expands and presses from below onto the surface of the support. Significant pressure leads to separation of the piles from the grillage, and, consequently, to a violation of the integrity and stability of the foundation. To avoid such a development of events, the pile-grillage foundation should be equipped with an expanded polystyrene slab at the bottom of the formwork during the process of concreting the foundation. These plates will act as a shock absorber.

3. Errors made when calculating bearing capacity.

Inattention and frivolity when calculating the load-bearing capacity of a structure are guaranteed to affect the result obtained. Mistakes in such an important matter will lead to subsidence of the foundation, and this process is irreversible and difficult to stop. Rocky soils are the most stable, while sandy soils are the least stable.

4. Small depth of support.

Insufficiently deep piles lead to shrinkage, and, consequently, the cavity between the soil and the grillage decreases. And this again brings us back to the problem of foundation integrity. To avoid this negative effect, the pile support must be laid below the maximum freezing depth, that is, buried pile-grillage foundation.

A video from the ForumHouse.tv channel perfectly demonstrates all the qualities of a pile-grillage foundation.

The cost of a pile-grillage foundation

The technology of a pile-grillage foundation itself is not very expensive. The main cost items in the overall estimate are construction materials, such as, for example, reinforcement, concrete, wooden boards and rental of special equipment. Naturally, the cost of work may increase due to the involvement of specialists or unexpected costs.

In general, price of pile-grillage foundation much lower than with other methods of foundation construction. This is a very important advantage, and for some - fundamental. If you are confident in your abilities and knowledge, if you have your own concrete mixer and hand drill, then making such a foundation will be very simple and cheap for you.

To summarize, we can highlight the main features of a pile-grillage foundation:

Houses on a pile-grillage foundation will be stable even in difficult soil or terrain conditions.
This is one of the least expensive ways to lay a foundation.
Requires special care when drawing up and implementing a project.
The entire process of laying a pile-grillage foundation takes less than a week.
If all rules and construction technology are followed, a reliable support for the future home is obtained.

From reviews of the pile-grillage foundation, you can learn its features, the positive and negative aspects of this type of construction, and also learn from construction experience from others. Only after carefully studying all the important points can any conclusions be drawn. The foundation is the foundation of your home and requires special attention.

Pile-grillage foundation: reviews

Sergey Inokhodtsev, entrepreneur, Moscow:

For the construction of a new summer kitchen, I chose a pile-grillage foundation. I didn’t dare to do it myself, so I hired a team of specialists. The whole process of laying the foundation took a week - they completed the piles in a day, they froze for 3 days, and the grillage was poured on the fourth day. Everything is very fast, good quality. Even taking into account the costs of workers and equipment, the price turned out to be very cheap for the foundation. If you want an inexpensive, but high-quality support for your home, this is a great option.

Veniamin Maslov, agricultural technician, St. Petersburg

5 years ago I completed the construction of a house based on a pile-grillage foundation. During this time there were no complaints or shortcomings. An engineer I knew helped draw up the plan; he did all the work himself - fortunately, we had all the necessary tools. The result is only pleasing, and with the money saved I made a small extension. The foundation is high quality, I recommend it to everyone!