Pile foundation with grillage. Pile-grillage foundation: how to design and build a reliable structure

The design of pile-grillage foundations is much cheaper than popular strip foundations and gives excellent results in terms of reliability and durability. Wherein technological process so simple that it is possible to do all the work with your own hands.

Pile-grillage foundations in construction

Pile-grillage supporting structures for buildings and structures are increasingly replacing the popular tape ones. This is especially true for construction in the regions of the Far North, where they are the only possible option foundation devices for any building.

Building a foundation is a costly business. In the estimate of construction costs, this item is up to 45% of the total cost for the installation of the most popular supporting base of the tape structure.

The pile-grillage foundation is a monolithic structure (grillage) located on pile supports.

What is a pile-grillage foundation

The main feature of the pile-grillage foundation is the use of piles as the main bearing element. They are buried in the ground different ways until a reliable ground layer is reached, but in any case below the level of its maximum freezing.

To connect the pile system in the horizontal direction, horizontal beams made of various materials:

cast concrete. They are made simultaneously with pouring piles or separately. Such foundations can be used in the construction country houses up to two floors high;
wooden. Wooden grillages are used in the construction of log and lumber buildings, baths or outbuildings. They are also used in the construction of frame buildings and the installation of greenhouses in combination with screw metal piles;
metal from various profiles - beams, channels and corners of large sizes. They are popular in the installation of non-residential buildings, such as workshops or garages.

The main purpose of the grillages, in addition to the horizontal strengthening of the supporting base, is the uniform distribution of the load from the structure located on it to the piles. This design prevents distortion of the building during operation.

Photo gallery: types of pile foundations

Pros and cons of grillage foundations

The positive qualities of grillage foundations include the following qualities:

The inherent disadvantages of the design do not outweigh the positive qualities listed above. The disadvantage is the fact that with such a foundation it is impossible to arrange a basement or underground. The second negative point is that to close the opening above the piles, you need to arrange a pick-up. But this is easily solved with inexpensive vinyl siding.

Video: the pros and cons of pile foundations

Scope of pile-grillage foundations

Pile foundations are used under unfavorable landscape or hydrogeological conditions for the construction of any objects from fences and outbuildings to residential buildings with a small number of storeys. It is economically beneficial to choose a strip foundation using bored piles in such cases:

A high grillage rises above the ground, the heaving force practically does not affect the foundation. The support is transferred through piles to the ground with high bearing capacity.
A pile foundation with a metal grillage from a channel is an excellent solution for the construction of wooden buildings.
Bored piles with a monolithic concrete grillage cope well with the load from two-story brick and aerated concrete buildings.

Pile foundation with grillage

When designing foundations, the two main tasks are to ensure the bearing capacity and counteract the forces of swelling of the soil when it freezes. In other words, it is impossible to allow the structure to subside under its own weight and to skew it with uneven heaving. The main sustainability measures are:

Let's make a reservation that the pile-grillage foundation should not be confused with the tape, based on piles. The difference lies in the fact that the grillage rests only on piles at nodal points, while the tape is fully supported both on pile devices and on the ground.

There are three types of grillage by location:

High. Regardless of the method of manufacture and material, the grillage is located at a distance from the ground. Such structures are used in the construction of overpasses, bridges, residential buildings and outbuildings on slopes. A separate area of \u200b\u200bapplication is the construction of piers or piers.
Elevated. The sole of such a grillage is at ground level, not resting on the ground. The support device of this design allows you to keep the air cushion under the building, protecting it from the wind. The disadvantage is the lack of access to the space under the house.
Recessed grillage. A very common and popular design due to its low cost and functionality. The difference from others is that the tape is located below the ground level. The tape is poured into a grooved formwork.

Unlike a strip foundation, a pile-grillage foundation has supports only at nodal points.

Production of a pile-grillage foundation

It is quite possible to make a pile-grillage foundation with your own hands with minimal experience in performing construction work.

Piling manufacturing

The type of piles is selected based on the specific hydrogeological conditions at the site. Before construction begins, preliminary exploratory drilling is usually carried out at the site of the construction of the building. In the case of private suburban housing, this can be done independently using a small-diameter auger drill. The purpose of the study is to determine the nature of soils and the depth of the bearing layer.

We will consider the manufacture of a pile using the example of a bored support device. Work is carried out in the following order:

Types of standard piles

Several types of piles are used in construction. If we classify them according to the material of manufacture, the main ones are:

Concrete or reinforced concrete.
Metal from various profiles: beams, channels, pipes.
Wooden from a bar or round timber.
Plastic from the corresponding pipes.
Asbestos-cement.

In addition, piles are distinguished by the way they are immersed in the ground:

Driven - their immersion is carried out by hitting special hammers, vibrators or by pressing into the ground. Hammers and vibrators are used only at a distance from active objects or residential buildings, since ground shaking can cause it to move under these buildings.
Hollow shell piles - immersion is carried out by vibration method with simultaneous removal of soil from the internal cavity and its replacement with concrete.
Drilling - are arranged by drilling a well, followed by reinforcement and pouring concrete directly into the ground.
Stuffed - are made by the formation of a cavity by compressing the soil and pouring it with concrete.
Screw - are immersed by screwing into the ground using special mechanisms or manually, if we are talking about individual housing construction.

It is not possible to talk about the disadvantages or advantages of certain piles. These support elements are always selected on the basis of specific conditions. For example, you can not use cheap wooden piles in conditions high humidity soils on the site, they will quickly fail. In places with acidic soils, metal piles should not be used, plastic or asbestos-cement piles are preferred.

Photo gallery: types of piles

Location of piles in the foundation

The number of piles for a particular building is determined by the weight of the building and the total area of the supporting surfaces. Data on the permissible specific load at the construction site can be found on the Internet or obtained from local construction organizations.

When planning the foundation, consider that:

The cross section of the foundation along the outer perimeter and for internal partitions should be the same.
Piles are installed at all intersections of the walls.
The distance between the axes of adjacent supports should not be more than three meters for individual housing construction.

The distance between piles may vary.

Placement of piles on the foundation plan

This operation must be performed according to the method described in the previous paragraph.

Drawing pile foundation represents the location of reference points with their binding to the axes of the reference base. On the internal walls and partitions, it is also necessary to install supports, observing the distance between them.

Grilled foundations on piles are more difficult to perform than other types of supports. But they are less time-consuming and economically justified. When choosing such a design, the drawing should contain not only the layout of the piles, but also an indication of the assembly sequence and information about necessary materials to make a foundation.

The pile field plan should contain the layout of the piles, the dimensions and material of the grillage, as well as the necessary data on the sequence of assembly of the foundation elements

The decision on the nature of the arrangement of piles is made on the basis of an analysis of the nature of the soils and their bearing capacity.

Table: average calculated soil resistance

Priming	Design resistance, kgf / cm 2
Crushed stone, gravel	5
Sands are large, gravelly	4
Sands of medium size	3
The sands are fine and silty dense	2
Fine sands of medium density	1,5
Sandy loam hard and plastic	2,5
Loams are hard and plastic	1,5
Clay hard	4
Plastic clays	1,5

With such data, it is possible to calculate the loads on the foundation and its individual parts and design it in such a way that all its parts are loaded equally. Otherwise, there will be local stresses in the supporting base, which are not conducive to long-term operation.

Ways of arranging piles

Ways of arranging piles are as follows:

Tape method - all piles line up along the same axis. It is used to evenly distribute the load on piles with an equilibrium structure of the structure.
The cluster method - piles are concentrated in a certain area, which is subjected to increased loads due to the peculiarity of the execution of the upper structure. To equalize the loads in this place, several piles are made, combined with a monolithic grillage.
Pile field - arranged when it is impossible to use a simple strip foundation, as calculations show excessive loads on piles. A series of additional tapes is created, the axes of which intersect. United by a grillage, they take part of the loads on additional piles.

Depending on the design features of the building, one of three methods for arranging piles is chosen for the construction of the foundation under it.

The procedure for calculating the pile-grillage foundation

When performing foundation calculations, you need to calculate the mass of all parts of the building:

Self weight of piles and grillage, including mass of concrete. To do this, you need to approximately select the diameter of the piles and the cross section of the grillage. Then the volume of a single pile is calculated. For calculations, the formula is used: mass is equal to density times volume.
Own weight of the foundation. To do this, we multiply the cross-sectional area of the grillage by its total length and by the density of concrete and add it to the mass of all piles.
House frame weight. The principle is the same - determining the total area of walls and piers, excluding door and window openings, followed by multiplication by the thickness. The specific gravity of various materials is easy to find on the Internet.
The total mass of the house, including ceilings and roofing. Produced according to the quantity of materials used on the basis of a draft design.
The total load on the ground, as the sum of all the results obtained in the previous stages.
Additional load from furniture and equipment. It can be taken equal to 150 kg for each square meter. The resulting value is added to gross weight Houses.

Next, you need to determine the area of \u200b\u200bthe supporting surface. To do this, the cross-sectional area of one pile is multiplied by the total number of supports. Dividing the total mass of the house by the area of \u200b\u200bthe supporting surface, we obtain the specific load in tons per square meter.

Now you need to compare this indicator with the normative data for the soil at the construction site. If it significantly exceeds the recommended loads, proceed as follows:

increase the area of support by changing the bearing size of the piles;
increase the number of supports by reducing the distance between them;
revise the cross-sectional dimensions of the grillage in the direction of reduction;
once again analyze the design of the house, looking for the possibility of reducing its weight through the use of other, lighter materials.

For example, the total weight of the foundation and the upper structure of the house is 120 tons, the bearing surface area of the piles is 20,000 square centimeters. The verification calculation shows that the specific load is 120,000 kg: 20,000 cm 2 \u003d 6 kg / cm 2. The supporting soils for piles at the construction site are gravelly sands, the bearing capacity of which is 4 kg/cm 2 .

Conclusion: the number of piles must be increased by one and a half times (6: 4 = 1.5). As recommended above, it is possible to revise not the number, but the size of the piles.

Foundation pouring technology

The procedure for the construction of a pile-grillage foundation may look as follows.

Plot marking

In contrast to the marking of the strip foundation, the contour of the supporting base is not applied to the surface of the earth. The main operation is the installation of pegs at the location of each pile. The control operation is to check the equality of the length of the diagonals along the corner stakes of the outer perimeter and inside each rectangle of the inner partitions. Measurements must be made with a tape measure of the appropriate length.

It is necessary to drive pegs into the pile installation sites, and then check the equality of the diagonals at the extreme points of the foundation

Earthworks and piling

Excavation along the contour with a high grillage is not carried out. It is only necessary to drill holes in the places where the stakes were previously installed. To do this, you can attract a contractor with a pit drill, then all work will be completed within a few hours. When using a drill with a diameter of up to 30 centimeters, the pits can be made by hand if the immersion depth does not exceed five meters.

The pouring of each pile must be carried out without interruption. For this, concrete grade 300 is used, which is constantly prepared at the work site. It is better to supply the solution into the well through a wooden or metal tray.

The work is carried out in the following order:

Vegetation is removed from the construction site, including grass, bushes and trees.
A well is being drilled.
If the depth of the well does not exceed five meters, it can be done with an ordinary garden drill
At the bottom of the well, a drainage layer of sand (up to 15 centimeters) and gravel of medium fraction (up to 20 centimeters) is arranged. The layer is compacted with a rammer and spilled with water.
Pipes of the selected material are installed in the wells. All upper ends of casings should be at the same level along the horizon.
Before pouring concrete, it is necessary to set the heads of the casing pipes to one level vertically
Reinforcing gratings are made and immersed in the pits, ensuring the release of the ends of the reinforcement above the pipe cut to connect the pile with the grillage during its pouring.
Concrete solution is prepared and poured into pipes. A break in the pouring of piles is allowed, but the formation of a pile must not be interrupted until the pipe is filled.
The pouring of one pile must be completed before the concrete inside the pipe hardens.

Be sure to seal it during the pouring process. Otherwise, voids may form in the body of the pile.

You can use the services of a concrete pump, then you need to prepare all the wells for pouring at the same time.

Grillage device, concrete pouring

It is possible to start pouring the grillage after at least 7 days after the completion of concreting the piles. Therefore, the time for preparatory work quite enough for the grillage.

At the end of the pouring of the piles, you need to proceed with the installation of the formwork for the grillage. It runs from any available material, but most often from boards. The shape of the formwork is a tray, fixed on weight with props. When installing it, it is necessary to control the horizontalness of the upper edge, otherwise an uneven supporting surface may result, which will inevitably affect the performance of the building.

Video: making a pile-grillage foundation

Pile-grillage foundations at one time became a revolutionary solution for the construction of a wide variety of buildings. The use of screw metal piles generally eliminates the need earthworks, which significantly reduces the complexity and time of construction of the foundation. I wish you success!

The article will consider a pile foundation with a grillage. It is not always possible to apply traditional designs - slab or tape. Sometimes they become too expensive, only the foundation will take up to 50% of the total budget. As a rule, a pile foundation of this type is used in cases where construction takes place in an area where the depth of soil freezing is more than two meters. Often such foundations are erected on weakly bearing and unstable types of soils.

Foundation design features

What is a pile foundation? Everyone knows this - this is a certain number of pillars that are driven into the ground. Moreover, the lower edge is at the depth of soil freezing. But such a construction pure form rarely used in practice.

The reason is that it is quite difficult to distribute the load that the house creates on all the piles. On one there will be a large load, and on the second - less. It is for this reason that pile foundations are used, as a rule, in structures with low weight - for log cabins made of timber or logs, frame houses.

Bars or logs have one good quality- they allow you to redistribute the load evenly on all points of support. Buildings made of other materials cope with this task much worse. But here the device of the pile foundation with a grillage is such that it does not have the disadvantages indicated above. Therefore, it can be used without problems in brick or block structures. The structure consists of several piles and a tape (usually made of pure concrete or with metal reinforcement) that connects all the support points. It is this tape that is called grillage.

Features grillage

The grillage is part of the foundation, which unites the upper parts of the piles. It takes the entire load that the structure creates, and due to its closed-type device, it evenly redistributes it to all piles. Rostverk is of the following types:

Concrete.
Reinforced concrete.
Metallic.
wooden.

Also, reinforced concrete and concrete can be divided into two subcategories - high and low.

The first are located significantly above the level of the earth's surface. Very often, grillages are made of metal - square ones are used. metal pipes, channels with a large cross section. But the device of a concrete grillage is much more complicated.

Features of the grillage

As you understand, the house gives a different load in the premises. Indeed, in it furniture, decoration, various appliances and things are unevenly distributed. Of course, the load on the supports will also be different. With the help of a grillage, it turns out to transform all the loads in such a way that the same forces act on the piles installed under it. This quality is very useful, as it allows you to achieve the stability of the entire structure.

If the piles are loaded evenly, then the likelihood that they will shrink differently is reduced. If the foundation shrinks unevenly, then cracks will definitely appear on it and the walls. The device of the pile-grillage foundation is highly stable. But all the same, the structure did not get rid of the main drawback of the piles - it is not known what type of soil is located near them.

Is it worth using piles?

Architects do not really trust structures based on piles - it is almost unrealistic to predict their behavior in the ground in advance. Near one pile, the soil will be dense, and next to two neighboring piles - loose. And there will be uneven shrinkage of the whole house.

But there are more predictable designs, which we'll talk about next. In particular, with a grillage, which is highly durable. But its cost is quite high.

Strip foundations on piles

Low types of grillages are good because their behavior can be predicted. Grillages of this type begin significantly below ground level. And they are made of simple concrete or reinforced. It should be noted that the reinforcement coming out of the piles is mechanically connected to the reinforcement of the grillage itself. It is also worth noting that the pile foundation grillage is insulated in the same way as the strip one. The materials used are the same. The structures are very similar.

We have a grillage called a strip foundation of a shallow type. It is made using the same technology. And the difference is that in addition there is a connection with piles, which significantly increase the stability and reliability of the entire structure. Foundations of this type are called pile-tape or tape on piles. Without exaggeration, they are considered ideal, since they combine all the advantages of both types of foundations, and the disadvantages are compensated.

Foundation work

The work is as follows. All the load that the house creates affects the concrete tape. Since there is longitudinal reinforcement, the forces are distributed evenly over the entire support area. Part of the load goes into the ground, the rest is taken by piles. And one feature should be noted - shrinkage and load are uniform, since these parameters are aligned with the tape. It is desirable that a pile foundation with a grillage be installed to the freezing depth.

V winter time heaving forces act on the foundation - at this moment you can see all the advantages of a tape structure on piles. When the heaving soil acts on the structure tape, the piles do not allow the foundation to move. In this case, the likelihood of skew of the building is reduced. You can get rid of the effect of heaving soils if the foundation is poured below the freezing point. But the cost of such a design is quite large, it is not recommended to use it.

In what cases can pile-grillage foundations be used?

And now let's talk about the cases in which the use of foundations of such a design is simply necessary:

In cases where weakly bearing and unstable soils go to great depths. As a rule, these are soils of karst, peat, forest types, as well as vegetable, quicksand, fertile, in which the thickness is over one and a half meters. The load must be transferred to a denser soil, which is located much lower. As you understand, it is quite difficult to dig a trench and reach soil with a high bearing capacity. And the construction of the foundation will be quite expensive - so the use of piles is a way out of the situation.
When building on a site where there is a large difference in height. When building a foundation, it turns out to be easier to use piles with different heights than to level the surface or pour tape at a great depth in order to slightly compensate for unevenness.
If the groundwater is too high. In this case, only the height of the pile foundation grillage is important. It should be noted that when erecting a pile foundation, it does not matter at what depth the waters are located. The main thing is that under the so-called heel there is soil, which has a high bearing capacity. The level at which groundwater is located can only affect the type of grillage. If the water is close to the surface, you need to make a high grillage. And if the water is deep, it is allowed to make a low design.
If a building is being built on hard ground. When erecting a tape or slab foundation need to do a lot of earthworks. In this case, the use of piles is justified.
During construction frame houses it makes no sense to build a strip foundation - it's just a waste of money. The margin of safety turns out to be unreasonably high, it is best to choose a pile-grillage structure.
If the total mass of the structure is over 350 tons, it is best to build a pile foundation with a grillage. Tape or slab structures will be too massive, and expensive.

It is worth noting, however, that the most reliable types of foundation are tape and slab. But if there are no funds to build such complex structure, and a large margin of safety is not required, it is allowed to use a pile-grillage type.

What are piles?

As a rule, absolutely all types of piles are used in construction. When choosing, you need to pay attention only to the type of soil and the maximum allowable load that the building creates. Piles can be made of concrete or metal, very rarely they are made of wood. The cross section is either square or round. It is necessary to reinforce the grillage of the pile foundation so that the entire structure is as strong as possible.

The following types of piles can be distinguished according to the type of installation:

Driven - mounted without the use of excavation or drilling. They are driven into the ground using special equipment. It is for this reason that they are rarely used in private construction.
Bored - in the ground it is necessary to make a well into which the formwork is placed. After its fastening, reinforcement is mounted (it increases the strength of the structure. After the actions taken, concrete is poured inside.
Drilling reinforced concrete - as in the previous case, you must first make a well. After that, the already finished piles are driven into it. Efforts for this need much less than when installing driven.
Screw - somewhat similar to self-tapping screws. They are made of metal, the ends are pointed and there are blades. With their help, the soil is cut. If it is necessary to install piles to a greater depth, special equipment is indispensable. But when installing to a depth of up to three meters, you can do without it.

In the construction of private houses, bored-type piles are most often used. But, as a rule, they are installed as supports for small buildings - sheds, baths, etc.

Pile shapes

Piles differ in the shape of the section:

Round.
Square.
Triangular.
Hollow round.

More complex forms are often developed, it all depends on the specific project.

Ground load distribution

It should be noted that pile foundations with a monolithic grillage are the most durable and strong. But, as you understand, piles can distribute the load on the ground in different ways. There are such types:

Piles-racks.
Hanging.

The latter have quite a large side surface. It is with its help that they transfer the lion's share of the load to the ground (about 70%). Such structures are used in cases where it is impractical to go deeper, and the level reached is not enough to withstand the entire load. The design has a heel, but its presence does not change the picture - the entire load goes to the ground not through the tip, but through the side surface.

But the pile-racks transfer the load through the tip. The walls are smooth and undeveloped, but at the end a heel is made - an extension that allows you to increase the area of \u200b\u200bsupport. Thanks to such a support, heaving forces cannot lift the entire foundation. But in order for the support to be of high quality, it is necessary to calculate the pile foundation grillage. It is better to entrust this procedure to experienced specialists.

How are the piles in the grillage

As a rule, piles are located strictly vertically in the ground, but in some cases they are also mounted obliquely. Moreover, it is allowed to install several piles in one place. This method of construction is used in cases where there is a possibility of horizontally directed forces. Good example- if the construction takes place on a site with slopes.

Point location of piles under supports is also allowed. This is typical when erecting sheds or building a roof over open area. Piles are installed under those columns that hold the roof.

When building a private house with a small number of storeys, piles can be placed like a tape. They are installed in a row, and sometimes in two or three. Often, in places where a large load on the soil is planned, several piles are located at a small distance from each other.

In most cases, when the task of equipping basements is not set, best solution there will be a grillage foundation that has the ability to withstand a load greater than individual piles.

On stable, calm soils, it is placed for reasons of saving materials and time. Where there is a large freezing depth, heaving, weak soils, the construction of a foundation on piles with a grillage allows you to build not only light frame structures, but also large log cabins, brick or block houses.

Purpose and functions

Piles are optimal on a site with difficult relief

When designing your own private house, you definitely need to figure out what a pile foundation with a monolithic grillage is, and whether it is suitable for this particular case.

Piles are used as load-bearing supports. the best option in difficult geological conditions, when heaving forces have a significant impact on underground structures, and a high level of freezing will require deepening of the monolithic tape over 2 m.

The diagram shows how the pile grillage design works:

The manufacturing technology differs from the usual installation of a building on piles in that all the supports are connected into a single base with a solid belt that receives and distributes loads on the columnar supports.

Types of grillage

The grillage connects the piles to each other

Design calculation, based on site conditions and total weight buildings, choose which type of pile-grillage foundation it is advisable to use.

The decision is influenced by the need to install a ventilated underground under the crown, the possibility of flooding by flood waters, the slope (relief) of the site.

Based on these conditions, determine the height of the pile foundation grillage:

A low grillage has the advantages of a strip foundation

A low grillage is a combination of an unburied strip foundation with piles, which significantly increases the reliability, rigidity, and stability of the entire supporting structure.

This option combines the advantages of pile and strip foundations, while the combination significantly compensates for the disadvantages that appear separately:

the weight load of the building is transferred to the foundation concrete strip and, due to the presence of a reinforcing frame, is redistributed to the entire support area;
a monolithic low tape rests with its lower part between piles on a pillow (soil), providing a contact area with a support along the entire perimeter;
in winter, the impact of forces near the surface is compensated by buried piles.

Elevated grillages are used on difficult unstable soils

Level Up ground water the height of the concrete grillage relative to the soil surface increases.

The elevated type is used on quicksand, peat bogs, karst, forest, fertile soils, more than 1.4 m thick.

This arrangement eliminates the effect of lateral forces on the monolithic grillage, and the piles are not only supports, but also an anchor in moving rocks.

The device of such a foundation reduces the volume of earthworks, will require fewer materials and cash costs than a concrete tape or slab. During installation, a monolithic reinforced concrete grillage will require precise observance of the design dimensions and work technology.

Material

wooden beam- most cheap material

The basis for the grillage under the pile foundation is selected raw materials that, according to their characteristics, can withstand constant and variable loads for a long time, which are included in the design calculation of the house.

A durable grillage on piles is made from the following materials:

steel profiles (channel, I-beam);
wooden beam (rounded log);
concrete (reinforced concrete) casting.

A low pile-buried foundation can only be with a concrete grillage.

Concrete structures are used for heavy houses

Metal grillages are made high, since, with their great strength, they need protection from moisture.

The reinforced concrete type, which rises above the ground, is used in the construction of fairly heavy houses, since concreting at a height will require good formwork.

Another criterion is the service life of building wall materials. The selected grillage foundation must meet or exceed the performance of the structures located above it.

How to support a pile foundation with a grillage from different materials on piles is shown in the diagram:

Pile selection

It should be considered what a foundation grillage device is from different types of piles. For such structures, any type of support can be used, based on the characteristics of the geology of the site and the total weight of the materials and internal equipment of the house.

The cross section (width), raw material, method of installation to the depth of the stable stop must correspond to the calculated load.

In private do-it-yourself construction, the use of bored piles, which are made by pouring cement mortar into the formwork, is common. It is practiced to install asbestos-cement pipes, reinforced depending on Ø 4 - 6 vertical rods.

The load of such metal-reinforced supports can be significant and depends on the bearing capacity of the natural base:

Screw models are used for lighter buildings

When erecting light buildings (a bathhouse, a barn, a one-story cottage), a bored-type grillage foundation does not require complex calculations, it is important right choice support points.

Driven piles are installed using special mechanisms without drilling and earthworks. They are used in the construction of large multi-storey buildings.

Screw models are screwed to the desired depth and cut along set level. They are available in lengths from 2 to 11 m. different types screw, so on large slopes of the surface it is possible to maintain the required dimensions of the grillage using various models products.

General rules

When choosing a pile grillage foundation, it is quite simple to take into account the pros and cons. The disadvantages include:

the need for special equipment if it is necessary to install heavy modifications, driving models;
requirements for anti-corrosion protection for steel products, antiseptic - for wood;
lack of underground facilities near the house. Recommendations of experts on the device of this type of foundation, see this video:

The design size of the grillage in width should be slightly larger than the supported wall, beam, crown.

According to SNiP, the step for piles in a strip grillage, including a stuffed foundation, is at least 3 Ø of a support. In this case, the chosen distance can also be 5 Ø, if the strength that the grillage foundation has in cross section allows.

For a long time I wanted to ask the question for a very popular topic.
We will accept that "piling" is a "piled grillage" distorted in the mind
Thanks to the book of Mr. Yakovlev and TISE, it has become customary to say that "de facto" - should be hanging. With it, everything is more or less clear, the air gap protects against heaving of the soil.
In the literature, there are 3 types of grillage.
1) recessed
2) not buried
3) hanging
Moreover, I did not find a more or less intelligible description of what is what and what it is used for.
With p3, everything is clear - there is a lot of information on the forum.
With p 1, not everything is clear, except that the grillage seems to be buried almost to the depth of freezing and is used in "large" construction. In general, this view is not very interesting.
But at the moment, I'm most interested in option 2. Since it is often called "pile tape" and is done by some builders.
Dear ALEX2626, in response to my statement, he described the following design - "pile strip foundation"
And what do you think to call it, filled with, if not pile-tape, and what does the inflamed brain of the builders have to do with it. Pile-tape (or pile-grillage) - exit in almost any soil, subject to the conditions, it turns out to be cheaper simply. For example, the most common type of shallow foundation - tape - 300 mm in the ground, 500 above the ground, width 400 mm - cross-sectional area \u003d 0.32 m2, multiplying by for 10 * 12 m - tape length 64 m, TOTAL FOUNDATION VOLUME \u003d 20.48 M3, at the same time it is necessary to put sand with crushed stone 300-400 mm under the tape, therefore dig to a depth of 600-700 mm, and this is 18 m3 of land work. Now we consider the pile-tape - we drill with a gas drill (or a hand drill with nozzles) to the freezing depth (in Samara 1.6 m) in one day 42 holes, put PGS 100 MM right on the ground and make a tape of 500 * 400 mm on it, volume foundation \u003d piles 3.3 m3 + tape 12.8 m3 \u003d 16.1 m3 - in total we get a foundation arranged according to all standards, i.e., to a freezing depth at a lower cost
That's how they often do it. on any soil motivating the fact that the pillars are below the freezing depth and that means everything is ok. I believe that such a design is safe only on non-rocky soils - for the following reason:
As water expands when it freezes, the volume of soil saturated with water increases. Roughly speaking, the earth, expanding, presses on the foundation from below.
If you just have posts, then they are affected by lateral grip with the ground and press from below - if the post is above the freezing depth.
In the case of "pile tape" according to the ALEX2626 version - adding 10 cm of ASG "right on the ground" the frost heaving force will not go anywhere. It turns out that when the soil freezes, the expanding soil will put pressure not only on the posts, but also on this "tape" and the fact that the posts are below the freezing level is not at all important here.
Since the tape is rigidly connected to the piles, this entire structure will begin to extrude. And the most unpleasant thing here is the following - when extruding, the piles will rise in their "wells" and a void will form between the bottom of the well and the bottom of the pile. Soil from the walls can easily crumble into this void, or a lot of other unpleasant things can happen.
As a result, the void will be filled, and in the spring, when the soil "leaves"
The pile may not get back into its place, and still remain "raised", and since it is rigidly connected to the "tape", it will warp the tape.
Accordingly, this is a direct path to potential problems with such a foundation on heaving soils.
I specifically highlighted the word potential - because this is one, but a probable path for the development of events. Moreover, this may not happen immediately, but let's say after 2 years or 5 years or 10. Or maybe it will "carry" ...
It’s just not clear why to play such roulette when you can do it differently
So I would like to understand - what is a "piled strip foundation" without an air gap and how much it has the right to live in heaving soils.
Note. al185. Topic summary

Domestic builders of private houses usually prefer to make a foundation in a monolithic tape design. But with large values of the depth of soil freezing, this option is expensive. After all, his similar situation it is necessary to lay very deeply, and these are additional significant costs for reinforced concrete. In order to reduce the estimate for the construction of the foundation of the cottage, now private developers have increasingly begun to give preference to a pile grillage foundation, the deepening of the supporting piles of which is much cheaper.

What is a pile foundation with a grillage?

Structurally, a pile-grillage foundation is a series of supports immersed in the ground below the freezing point, and connecting them on top with a "strapping" of steel or reinforced concrete. The first rows of bricks or timber (logs) are already laid on the latter. This design provides a uniform redistribution of loads from both the house and the ground.

Foundation scheme

The point impacts arising from heaving from the piles diverge along the entire grillage tape of such a base. Walls do not experience excess pressure at any one point. Distortions and destruction of masonry on a similar basis are practically excluded.

Types of foundation on piles

The grillage of this type of pile foundation is made of monolithic reinforced concrete or a steel channel. The most commonly used concrete structure with reinforcement. It can withstand significant loads. The option, where the strapping is metal, is more intended for light buildings (garages, outbuildings, buildings from SIP panels and baths).

Pile foundation with metal framing

Pile foundation with monolithic piping

According to the type of supports used, the pile-grillage foundation can be of two varieties:

Screw.

Boronabivnaya.

In the first case, this is an almost complete copy of the foundation on screw piles. Only on the supports he has a more powerful monolithic grillage. At the same time, steel “screws” for such a design have to be chosen stronger, in which the wall thickness and diameter are larger.

Those who are going to make the foundation with their own hands often prefer to use bored piles in fixed formwork in the form of asbestos-cement pipes. This technology is simpler and cheaper when performed independently.

Advantages and disadvantages

The piles of the considered supporting structure, due to the large immersion depth, provide excellent stability to the entire mini-strip foundation from above. And they cost much less than a reinforced concrete monolith of the same height. And if supporting pillars from above to tie not with a concrete tape, but with a metal grillage, then you can save a little more. This option is one of the most inexpensive ways creating a support for a private house.

This foundation has the following advantages:

The possibility of arranging on slopes and in swampy areas;

Comparative cheapness of the construction of a pile grillage structure;

Minimum time spent on the construction of the foundation;

No need to attract lifting vehicles;

Simplicity of technology for installing bored and screw supports, as well as pouring concrete;

Excellent stability performance in moving heaving areas.

In terms of the speed of the device, a pile foundation with a grillage is inferior only to an analogue of only screw supports. Plus, the foundation of the foundation blocks of the wall will be ready to give odds to the design in question. In both cases, the high speed of work is due to the lack of concrete work, when it is necessary to wait several weeks before the completion of concrete curing.

If the building site has a slope, then pouring a monolith on it is problematic and expensive. It will be difficult to do without this type of foundation on such a site. Only with the help of piles will it be possible to make a stable and even horizontal base for the structure. This is one of the main advantages of the foundation. All other options for him on construction sites with difficult terrain lose immediately.

Another indisputable plus is the extreme simplicity of execution. It is not difficult to make your own stuffed supports from asbestos-cement pipes and concrete inside. It is even easier to make a reinforced concrete tape, small in size and weight, on them.

Small difficulties here can arise only when mounting the formwork on weight. You can't bury it in the ground. The pillars must raise the grillage part above the ground by at least 30 cm, otherwise, with strong heaving, it can “float” from the supports along with the building from above.

The foundation with a concrete grillage on piles also has disadvantages, but there are frankly few of them:

The inability to make a basement;

The cost of additional floor insulation.

The underground space of the cottage on a pile foundation with a grillage must be closed from the wind, otherwise the constant drafts under the floor will blow out all the heat from the building. To do this, you can use facade panels from various materials or make masonry from beautiful facing bricks. Plus, the floor in such a house will definitely have to be insulated. It is better to include these expenses in the general estimate of the construction of the dwelling.

Do-it-yourself step-by-step instructions for building a foundation

The calculation and preparation of a foundation project for a house, whether it be a pile-strip foundation, is best entrusted to a professional designer. If the piles are chosen incorrectly in height and thickness, then for a long time reinforced concrete support and the building on it will not serve.

Marking on the site

At the same time, it is also not worth laying the parameters “in reserve”, this will only lead to an increase in the cost of work. As such, a do-it-yourself foundation device of the type in question should not cause difficulties. Below is a brief step-by-step instruction allows you to quickly understand all the nuances of this process.

To make a foundation of bored piles and a monolithic grillage, you must:

The lower edge of the supports should be below the freezing point of the soil. At the same time, wells for piles are made 10–15 cm wider than the taken asbestos-cement pipes. In order for the pillars to stand more firmly in place, an expanding concrete sole is arranged in their lower part. Pits in the ground for supports in width are made just to fit its dimensions.

Waterproofing of concrete is carried out with roofing felt or mastic. Even flexible tiles from modified bitumen. True, it will cost more than ordinary roofing felts.

Usage

Comparing the pros and cons of the pile-grillage foundation structure, it is immediately clear that the former are much larger than the latter. Such a base is suitable for both small outbuildings and one-story private houses made of foam concrete or brick. At the same time, you can do everything yourself without any problems. Earthwork and concrete work will not have to be done so much, and the device of the structure itself is extremely simple.