Pros and cons, technology for constructing a pile foundation with a monolithic grillage

Features of a pile-grillage foundation

The main feature of a pile-grillage foundation is that a foundation beam is placed on top of the piles - a grillage, which connects all the piles to each other. The grillage connects the entire foundation into one whole and thereby contributes to the uniform distribution of the weight of the house on all the piles. The latter, in turn, transfer the load from the weight of the house to the most durable layers of soil.

Most often, the grillage is constructed as a monolithic reinforced concrete structure, the strength of which is ensured by a metal frame made of reinforcement. To ensure uniform distribution of the load on the piles, the lower part of the grillage must necessarily be above the zero ground level (in weight).

The most popular type of foundation for a private home

When it comes to DIY construction, most owners give preference to strip foundations due to their reliability and durability.

As a rule, to build houses on unstable and waterlogged soils, the tape must be laid below the frost line, which leads to high labor and financial costs.

A pile foundation, in turn, solves this problem, but the supports themselves are capable of supporting the weight of lightweight structures, maximum frame buildings and low-rise buildings made of foam blocks.

An alternative to the two presented types of foundation is a pile-grillage foundation, in which the supports provide the necessary stability, and the piping is responsible for uniformly distributing the total loads on the soil.

Types of pile-grillage foundation that you can build on your own:

1. On screw piles.
2. On bored piles.
3. With a tape grillage (monolithic or block).
4. With a wooden grillage.
5. With metal profile strapping.

Three builders can screw in a screw pile of small diameter and height, but such a support structure has limited load-bearing capacity.

It is suitable for construction:

• garages,
• fencing,
• baths,
• terraces
• lightweight buildings.

For the reliability of the future structure, it is advisable to use screw piles with large dimensions, but then you will have to hire special equipment or gear units to screw in the rods. Therefore, for home construction, most owners decide to install bored piles with a grillage themselves.

The harness can be made of beams, metal, or choose a tape type . Wood has a short service life and low strength, so it is suitable for light wooden buildings.

To work with a metal profile, you need to be able to operate a welding machine. Based on the above, a tape grillage is the simplest type of strapping that can be made without the involvement of hired workers.

Advantages and disadvantages

The advantages of such foundations can be considered their following qualities:

- they require less time and materials for their installation, especially in comparison with the tape one; - they allow you to reduce the heat loss of the house through the foundation, since the grillage does not touch the frozen soil (provided that the space under the grillage is insulated); - they reduce the level of vibrations of the house (relevant if it is being built near transport routes).

True, such foundations also have disadvantages:

- the need to construct piles to a sufficiently large depth; - the space under the grillage must be filled and insulated.

Feasibility of the device

It is advisable to construct a foundation of this type for buildings made of light building materials (wood, foam blocks, aerated concrete, etc.) on fragile soils, which, at the same time, are subject to strong compression, that is, in those areas where the construction of a shallow strip foundation is impossible, and buried is too expensive.

In other words, a pile foundation with a grillage should be chosen when:

there is a desire to save up to 30% on the construction of the foundation (although savings can only be made if the estimated number of piles and their depth, and therefore the costs of their installation, are not too high); soil characteristics and conditions of their occurrence on the site (high groundwater level, heaving soil, large freezing depth) do not allow the construction of another type of house foundation in a minimum period of time; the load from the house on the foundation is relatively small.

Errors and recommendations

Errors made during installation work can compromise the strength of your building

There are big disadvantages to the functionality of the foundation if there is no connection between the grillage and the pile. When the winter season arrives, the generated force can shake the pile. It is worth noting that this situation is natural and occurs due to soil expansion. Errors made during installation work can damage the strength of your building and then all efforts and money will be wasted. To avoid such an unpleasant situation, we will familiarize ourselves with the main mistakes when installing such a foundation:

• There is no air gap between the base and the grillage. This nuance is especially relevant for the winter season, since in its absence, the pressure will increase and displacement of construction elements may occur.

• Incorrect calculations. This error can lead to subsidence of the foundation of the building. Solving this problem is not a cheap process, so it is better to approach construction responsibly.
• Violation of installation rules when installing a pile. To avoid mistakes, their installation should occur at a depth below freezing of the soil.

Do-it-yourself pile foundation with grillage

It is quite possible to build such a foundation with your own hands. As an example, let's look at how you can make a pile-grillage foundation with your own hands using bored piles, which are made by concreting wells drilled under them. After the piles are made, a reinforced concrete monolithic grillage is installed on them.

But before the robot begins to construct a pile-grillage foundation, it is necessary to clear and plan the site and, in accordance with the project, mark the position of its axes and the locations for drilling the piles. After which you can start drilling wells.

Plan drawing of a pile structure with a grillage

Engineers and designers in construction companies are involved in drawing up the drawing plan. As a rule, the project is included in the cost of turnkey construction. If a developer plans to build a foundation with his own hands, then his skills in drawing and geometry will be useful.

A design drawing is needed to:

1. Accurately determine the installation points of the supports.
2. Maintain the distance between the piles.
3. Choose a suitable method for tying the piles with a grillage.
4. Calculate the amount of building materials.
5. Indicate the distance between the grillage and the zero level of the site.

When designing a pile foundation with a strip grillage, the following must be indicated in the drawing:

• places where utilities will pass;
• type and diameter of the support section;
• grillage type and section;
• depth of installation of supporting elements.

In the process of drawing up the drawing, it is important to indicate the coordinates for the first block from which construction will begin, since the remaining structural elements will be aligned with it.

Production of bored piles

Wells for piles are drilled along the perimeter of the future foundation of the house and in the locations of internal load-bearing walls with a step of not about 2 m. The depth of such wells should be greater by 0.5 m to the depth of soil freezing in this area (0.3 m for the pile itself and 0 .2 m for a sand cushion under it).

The drilling of the wells themselves can be carried out using a special drilling rig hired for this purpose or independently, using a hand drill, which allows you to drill wells with a diameter of up to 30 cm and to a depth of more than 5 m. The depth and diameter of the wells for piles are calculated depending on the characteristics of the soil and most often their depth is within 10 m and their diameter is about 20 cm.

Fig. 1 Making bored piles with your own hands for a pile-grillage foundation: 1 – well; 2 – hand drill; 3 – waterproofing (roofing felt, film, etc.); 4 – frame made of reinforcement; 5 – concrete; 6 – soil freezing depth; 7 – sand cushion. After the wells are prepared, we begin making the piles themselves.

To do this, we lay waterproofing material along the entire length of the well in the form of a pipe. For this purpose, you can use several layers of roofing felt, PVC film or galvanized steel. Asbestos-cement or plastic pipes can also be used for this purpose. But in this case, their outer diameter must correspond to the diameter of the well.

Waterproofing is installed above the soil level, along the height of future piles in one horizontal plane. To do this, you can use a level, a special water level or a modern laser level. After this, a reinforcement frame is installed in the well, which consists of 3 or 4 longitudinal rods connected by transverse clamps. The height of the frame should be such that the upper ends of the reinforcement extend above the level of the poured piles to connect with the frame of the future grillage. This is necessary for a reliable connection of the piles with the grillage. The frame elements are connected to each other with soft steel binding wire.

There must be a gap of at least 2 cm between the frame reinforcement and the waterproofing to completely cover it with concrete when pouring. After installing the frame, the piles are poured with concrete, which is prepared in a concrete mixer using quartz sand and crushed stone. When pouring concrete into wells, it must be thoroughly compacted. This is best done with the help of special vibrators. If they are unavailable, you can use available means. After pouring, the piles are left for a month for the concrete to finally set and acquire sufficient strength.

How to prepare for work?

Laying a foundation is a responsible process , since the reliability and durability of the design structure depends on the choice of material and quality of installation.

Before drawing up a plan, it is necessary to study the regulatory requirements (SNiP 2.02.03-85), collect information about the geological features of the site and calculate the foundation.

Where to begin?

The selection of supporting elements and calculation of the foundation are carried out based on the results of geological survey. To obtain reliable information, you must order a service from an organization that specializes in this.

But to save money, you can use reference information and independently conduct a study of the soil and the depth of underground sources on the site.

What do you need to know before designing?

To calculate a reinforced concrete pile-strip foundation, you need to know:

• 
  soil type;

• degree of soil heaving;
• freezing point;
• occurrence of ground sources;
• bearing capacity of the soil;
• elevation changes on the site;
• climatic conditions for the region (amount of precipitation).

Before calculating the foundation, it is necessary to select the number of piles. As a rule, supports are installed at the corners of the building and in places where the partitions in the house according to the project will intersect.

The approximate distance between supports is 1.5–3 m . The cross-sectional area of ​​the piles is selected experimentally, based on the bearing capacity of the soil.

To select parameters, it is recommended to use the reference data:

Calculation of supports and grillage

To lay a reliable foundation, it is necessary to carry out a number of mandatory preliminary calculations:

1. 
   Determine the total loads taking into account the weight of walls, ceilings, roofing, snow flooring, etc.

2. Find the required support area, knowing the weight of the structure and the safety factor. Calculation formula: S support = (M * 1.4)/N, Where:
   M – total mass of the structure (from paragraph 1),
3. N – bearing capacity of the soil (reference information),
4. 1.4 – reliability factor.
5. Calculate the total cross-sectional area of ​​the piles, taking into account their number.
6. Compare the results of calculations in steps 2 and 3.

If the cross-sectional area of ​​the piles is larger than the supporting area, then the selected parameters are suitable; if it is smaller, it is necessary to increase the area of ​​the supports. Sometimes it is advisable to increase the number of pillars (the calculation algorithm will not change).

The length of the supports is selected taking into account the depth of soil freezing . As a rule, a reinforced concrete structure must rest against a solid load-bearing layer. For most Russian regions, the freezing point is at a depth of 1.5 m. To this value, you must remember to add the height of the base.

The grillage parameters are calculated using the methodology described in SNiP 2.03.01-84 A simplified version of calculating the minimum tape height (h): h = na + 40 cm, where na is the depth of embedding the pile into the grillage (approximately 15 cm).

The width of the grillage is selected so that this value exceeds or is equal to the thickness of the plinth or load-bearing walls.

Required tools and materials

To build a pile-grillage foundation, you will need the following tools and materials:

• hand drill or electric installation for making pits;
• mixture for concrete mortar: sand, crushed stone, cement, water;
• medium-fraction crushed stone for installing a drainage cushion under the grillage;
• bentonite solution for coating the walls of the well;
• roofing felt sheets for waterproofing piles;
• sheet waterproofing material for grillage;
• polyurethane foam insulation;
• metal reinforcement for reinforcing the upper and lower parts of the foundation;
• boards, beams, nails and screws for the manufacture of formwork;
• pegs, fishing lines for marking the area.

Making a grillage

The grillage for a pile foundation can be made with your own hands from prefabricated ready-made reinforced concrete elements or in the form of a monolithic belt. The second option is preferable, since a solid monolithic grillage is more reliable. In addition, individual reinforced concrete blocks of a precast structure are not so easy to install into place.

In order to make a monolithic reinforced concrete grillage, it is first necessary to manufacture and install formwork.

It can be made from edged boards in the form of a rectangular gutter and must be installed in such a way that there is a gap of 10-20 cm between the lower part of the future grillage and the soil. The height and width of the formwork must correspond to the design dimensions of the grillage. As a rule, its height is at least 30 cm, and its width is no less than the thickness of the wall of the future house.

Fig. 2 Manufacturing of a pile foundation grillage: 1 – frame made of reinforcement; 2 – releases of pile reinforcement; 3 – grillage; 4 – formwork base; 5 – piles. A frame of reinforcement tied with knitting wire is installed inside the formwork. Such a frame can be made in the form of one or two rows of reinforcement rods connected by crossbars, or in the form of an armored belt, in which both rows are connected using specially curved clamps. The bottom row of reinforcement should be laid on stands 2.5-3 cm high, ensuring the possibility of its complete immersion in concrete when pouring.

The same minimum distance should be from the frame to the side walls of the formwork. The grillage frame reinforcement is connected using the same binding wire to the reinforcement outlets from the piles. After this, the required amount of concrete is prepared using a concrete mixer and poured into the formwork in a continuous cycle. During the process of pouring concrete, it is necessary to ensure that it is placed tightly so that unfilled cavities and shells do not form.

For better shrinkage of concrete, it is necessary to use a vibrator or even a regular bayonet shovel. After the grillage is completely filled, its surface is leveled and left until the concrete dries completely. In hot sunny weather, the surface of the grillage must be periodically moistened. After the grillage concrete has dried (after at least two weeks), the formwork can be removed and the pile-grillage foundation is ready.

How to do it yourself?

Each type of pile-grillage foundation requires its own order of technological stages. For example, to install driven and screw piles you do not need to drill wells, but you cannot do without renting equipment or special equipment (with the exception of small screw supports). Below is the procedure for constructing bored piles with reinforced concrete tape.

Determining the distance between piles

Too frequent placement of piles will lead to higher construction costs, and infrequent placement increases the risk of deformation of the grillage and, as a result, leads to the formation of cracks in the load-bearing walls of the structure.

In private housing construction, they usually do the following:

• Be sure to install supports at the corners of the building and at the intersection points of load-bearing walls;
• if the pillars are located at a distance from each other of more than 3 m, then intermediate supports are placed between them.

Before designing, it is useful to familiarize yourself with the requirements for the placement of supports, which are described in documents SNiP 2.02.03-85 and GOST 27751.

Marking and excavation work

Before construction work, construction debris is removed from the site and, if necessary, the site is leveled. Then markings are applied using pegs and fishing line.

Be sure to compare the diameters with the design values . Mark places for future supports using pegs, rods, or make small depressions in the soil as marks.

Installation of piles

Using a hand drill, holes are drilled for the piles. The manual device is suitable for making pits with a diameter of up to 30 cm. If the site is dominated by waterlogged soils, then a sand cushion 10–20 cm high is placed at the bottom of the trench, making sure to compact the load-bearing layer.

To prevent the collapse of the well walls, coat the surface with bentonite solution.

A reinforcement frame made of steel rods is installed inside the pit . The length of the rods should be 15–20 cm greater than the height of the well (reserve for connecting the support and the grillage). Fill the inside of the well with concrete solution. Bayonet the mixture to remove air bubbles. The concrete will take 2-3 weeks to harden before moving on to the next step.

There is no need to dig trenches for screw and driven posts. The supporting elements are screwed or driven into the soil according to the established marks.

Construction of formwork

A crushed stone cushion is placed under the grillage, which will protect the foundation from vertical forces resulting from frost heaving.

Experts advise raising the grillage above the ground level of the site , but this technology will significantly complicate construction.

Panel formwork is built under the monolithic strip. For this you can use plywood sheets or knocked down boards. It is advisable to support the structure on the outside with beams so that the formwork does not fall apart under the weight of concrete.

Reinforcement

A frame made of reinforced rods will add strength to the foundation. As a rule, rolled metal from steel AI – AIII is used. The reinforcing frame for the grillage is rigidly connected to the rods that protrude from the surface of the supports.

Pouring concrete

For the grillage, concrete with a strength of at least M200 is used. Pouring is carried out at a time using gutters to prevent delamination of concrete from impact when falling from a height.

When the material fills the inside of the formwork, bayonet is carried out to remove air bubbles. The concrete is then covered with plastic film and left for 3-4 weeks until completely hardened.

In the case of a metal grillage, the strappings are welded to the rods , which have been left protruding from the supports. A grillage made of beams is fixed to the heads of the pillars, having previously made technical holes in the metal plates.

Waterproofing and ventilation

Soil moisture destroys the concrete foundation over the years, so measures are taken to waterproof the structural elements. To protect the supports before installing the reinforcement cage, a sheet of roofing felt or glass roofing felt material rolled into a pipe is placed in the well.

To waterproof a recessed grillage, roll waterproofing material is also used, covering the internal surfaces of the formwork before reinforcement.

To ventilate the space between the reinforced concrete structure and the ground, pieces of pipes of small diameter (20 - 25 cm) are embedded in the formwork. For a “hanging” tape, there is no need to arrange vents: ventilation is carried out due to the air space between the soil and the base.

In the case of a metal grillage, protection is provided by a coating hydrophobic composition , which is used to cover parts of the structure protruding above the ground, paying special attention to welds. Wooden beams are pre-impregnated with a hydrophobic liquid.

Thermal insulation

The role of a heat insulator for the grillage is performed by a film based on polyurethane foam, which at the same time protects the structure from moisture. The foam material is applied to the entire surface of the grillage using a special sprayer after the concrete has completely hardened. As an alternative, sheet expanded polystyrene can be used.

Features of soil analysis

The geological report includes data on heaving, thickness of soil layers, presence of groundwater and its depth. The main characteristic is load-carrying capacity.

Contact a geologist or send a sample of unloosened soil to a construction laboratory. You can find out on your own about the type of soil, its homogeneity and the presence of underground flows. It should be noted that independent observations are subjective.

Determine the type of soil using the comparison table.

Name Characteristics Fine-grained sand Floating, strongly swells and freezes.

It is impossible to build a foundation on it. Gerbil is well compacted and allows water to pass through. Doesn't swell. The foundation on sandy soil does not soak, is durable and can be quickly installed. Clay is the most “inconvenient” soil for construction, as it swells greatly.

With such soil, specialists either create an anti-heaving cushion or change the installation location. Dry clay without groundwater is processed without problems. Rock or clastic soil It is difficult to process, but the foundation on it is the most stable. Does not swell, does not freeze, does not change over time.

Look at the asphalt road leading to the site. If in the spring it becomes covered with cracks, the soil is heterogeneous. Pits indicate groundwater, therefore, high-quality waterproofing of the pillars is necessary.

Features of choosing piles

A pile is a wooden, reinforced concrete or metal rod buried as a support. Think about which poles to use correctly on the site. Classification of piles according to installation method:

Name Characteristics Pressed Poured at the site of foundation construction: the concrete mixture is placed in wells formed by displacement of soil.

Need waterproofing. For private housing construction, short bored piles are used. Driven Material: reinforced concrete, metal, wood. Installed with a vibratory hammer, hammers or vibratory pressing device without excavation.

They change the characteristics of nearby soil at a distance of 20-30 m, which reduces the stability of the foundation of neighboring buildings. Need waterproofing. It is impossible to do without specialized equipment. Screws are screwed into the ground without its preliminary preparation.

A device without specialized equipment. Convenient for self-installation. Made by hand.

Once you have decided on the type of support, pay attention to its characteristics. In particular, maximum load, wall thickness, barrel diameter and length. The bearing capacity and diameter of the piles are determined according to the table in the collection of rules 24.1333 based on the bearing capacity of the soil - contained in the geological report.

Calculate the pile foundation: determine the length and number of pillars.

Stages of work

The step-by-step technology for installing the support system looks like this:

1. Drilling holes.
2. Installation of piles.
3. Wire frame fastening.
4. Filling the solution.
5. Construction of a grillage.

The grillage itself is poured by first installing the formwork and performing reinforcement inside it.

It is recommended to connect the metal of the supports and grillage to clamp the supports, ensuring their joint work with the tape.

Selection of piles

Various materials are suitable for pile structures. The choice depends on the soil and the expected load of the structure. The supports are made of concrete, metal or wood. They have a rectangular or round cross-section.

According to the method of installation they are classified as follows:

1. 
   Hammers. Install without drilling or excavation. Used in the construction of multi-storey complexes.

2. Bored. First, a hole is made in the soil, into which the formwork is secured and reinforcement is inserted. Afterwards, the entire structure is filled with a high-strength concrete mixture.
3. Reinforced concrete drilling rigs . First, wells are drilled, driving reinforced concrete products into them.
4. Screw. Metal piles, at the end of which there is a point with a screw blade.

For individual construction, bored piles are usually used.

Monolith calculation

To perform an independent calculation of the required materials, first determine the length of the grillage . When using a metal or wooden belt, this value is the required amount of building material. When installing a concrete monolith, the calculation is somewhat complicated.

For example, let’s say that it is necessary to construct a building with dimensions of 6*8 m, which has two load-bearing walls inside - 4 and 6 m. In such a situation, the length of the grillage is determined as follows: (8+6)*2+4+6=38 m.

After this, the volume of the monolith is calculated by first calculating its cross-sectional area. With tape parameters of 0.3 * 0.4 m, this figure is 0.12 sq. m. Then it is necessary to prepare the following volume of concrete for the monolith: 38 * 0.12 = 4.56 cubic meters. m.

Production of monolithic pile-grillage foundation

Since the monolithic grillage is heavy, there are certain features of its installation. To guarantee maximum strength of the entire structure and allow it to withstand ground movements, it is necessary to correctly reinforce the structure:

1. Reinforcement of supports . When piles are made directly on your own construction site, you need to fix rigid metal rods vertically inside the formwork, and then connect them with horizontal wire belts. Such jumpers are made every 0.5 m, connecting them with bolts. The top of the reinforcement must protrude above the supports by at least 15 cm, or better yet, even more.
2. Monolith reinforcement . For the procedure, the reinforcement belts are placed evenly, with a ten-centimeter interval, at a vertical distance of half a meter. After this, they are connected, fastened to the protruding ends of the metal from the supports.

Site analysis and preparation

Level the cleared earthen base. Drill a well or dig a hole, measure the height of the top layer - this is a bulk layer that is removed before construction, since it is not used as a base for the foundation.

A pit is a vertical pit with a cross section of 0.8-4 m2. Due to greater soil extraction, it is more convenient for geological research than a well.

At negative temperatures, the soil swells: water freezes and soil masses increase in volume. When heaving, the foundation rises. Your task is to ensure that the rise is uniform over the entire area of ​​the base.

If you are building on clay, add a stable bed of gravel or medium-sized sand. This trick is also used for other difficult soils (peat, swamp): weak soil is completely replaced with a cushion.

The soil is deformed if heavy structures are erected nearby. In this case, increase the estimated load on the ground.

Water communications at the construction site are a source of possible accident. The accident will change the structure of the soil and cause the house to sag. Waterproofing the supports will reduce damage.

Measure the distance to neighboring buildings - at least 3 m.

and fences - at least 30 cm. The roots of trees and shrubs interfere with deepening the piles, so choose an area away from forested areas. Stumps with roots are uprooted from the site and the surrounding area.

Construction of foundation supports

Depending on the type, the installation of pillars occurs differently. Let's look at the example of short bored piles.

Drill a well 15-40 cm. Place an asbestos-cement pipe in the well.

Waterproofing: bitumen mastic or reinforced tape. Immerse the pipe 1 m into the load-bearing soil, leave 40-50 cm above the ground for a hanging grillage.

Trim off the excess with a grinder. You can control the horizontal position using an optical range finder or leveler. Fill the pipe 1/3 full with concrete. Lift the structure so that the mixture “spreads” and forms a sole.

The size of the expansion is calculated in advance. Install the internal reinforcement cage vertically to prevent refraction and failure of the pile. Fill the pipe with concrete. Pour in equal portions, compacting the mixture each time. The pipe is poured in one go. Form the top from an anchor bolt or steel wire.

In case of high heaving, bury the piles below the freezing level.

Into stone or sand at least 0.5 m. Additional waterproofing: galvanized steel, roofing felt, PVC film.

Construction of a grillage for the foundation

The construction of the foundation is completed by installing the grillage. A grillage is a reinforced concrete frame that connects the tops of the pillars into one structure.

It serves as a support for the load-bearing elements of the building. Think about what kind of harness is right for your home. Types of grillage:

Name Characteristics Hanging Rising above the ground by 15-50 cm. The swollen soil does not rise to the strapping and does not put pressure on it.

Optimal for unstable soil. Disadvantage: unsealed movable air cushion between the top layer of soil and the grillage. Ground: Located at the level of the plant layer. Only for stable soil.

It is recommended to additionally strengthen it with a sand and gravel cushion. Waterproofing is needed. Recessed: Deepened into the ground, placed on a sand and gravel bed. Rarely used, not rational.

Requires a lot of money and equipment. Only for stable soil. Need waterproofing.

Methods for making a grillage:

monolithic tape; assembly from separate parts.

Monolithic tape is preferable, as it is more reliable and easier to install. Let's consider the device using the example of a hanging monolithic grillage:

Calculate the grillage: standard section is 40 * 30 cm. Make formwork from edged boards in the form of a rectangular gutter that corresponds to the dimensions of the frame. Formwork is a wooden form filled with concrete. Install the formwork so that there is 15-20 cm between the plant layer and the bottom edge of the frame. Place a frame made of reinforcement in the gutter cavity, tie the rods with knitting wire.

The lower edge of the frame is placed on supports 3 cm high; the side edge of the frame should be at the same distance from the formwork so that the rods are completely immersed in concrete. Connect the reinforcement of the piles to the reinforcement of the grillage with knitting wire. Fill the formwork with concrete. For better shrinkage of the mixture, use a bayonet shovel or a vibrator. Make sure that the entire gutter cavity is filled. Level the grillage and leave until completely dry. Remove the formwork after 2 weeks.

Make the grillage 5-10 cm wider than the walls to make the house more stable. In hot weather, periodically moisten the binding until the concrete dries.

Install a drainage or water supply system to protect the supports from rain and melt water - waterproofing is ineffective against massive flows. Drainage is necessary if there is a body of water near the site. You can insulate the base of the house with permanent foundation formwork with expanded clay, foam plastic and mineral wool; waterproofing will also not hurt.

Prepare your own concrete mortar by mixing sand and cement in a 4:1 ratio. Add aggregates to increase strength: sand, crushed stone, gravel.

With reliable and stable support, the house is protected from weak soil, difficult terrain, moisture and cold. Ensure your safety by correctly making a pile-grillage foundation with your own hands, as the step-by-step instructions say.

A pile foundation with a grillage is a design that allows the construction of buildings in difficult soil conditions. Pile supports transfer and distribute the load emanating from the structure onto deep layers of incompressible soil, which protects the house from problems associated with heaving and low density of surface soil.

Bored foundation with grillage

This article presents the types of pile foundations. We will look in detail at a foundation made of bored piles, provide instructions for its calculations in accordance with SNiP and construction technology, following which you can make a pile-grillage foundation with your own hands.

Types of pile foundations and types of grillages

Depending on the type of supports used, pile foundations (according to SNiP No. 2.02.03) are classified into the following types:

foot foundations; bored foundations; driven pile foundations.

For the installation of screw foundations, metal piles with a diameter of 89 and 108 mm and a length of 3 to 6 meters are used. Such structures are suitable for the construction of 1-2 storey buildings made of wood, aerated concrete or frame panels. The main advantage of screw foundations is the rapid construction time and the ability to build a house on a slope, without leveling the site.

Features of a bored foundation with a grillage

A bored pile foundation with a monolithic grillage is the optimal foundation option for private low-rise construction. When arranging the foundation, deep columns are used, the bottom of which rests on a layer of soil located below the soil freezing line, which protects the columns from buoyant loads.

Read the same: what technology is used to reinforce the grillages of pile foundations?

Scheme of a bored foundation with a grillage

For drilling under piles, a manual drill of the TISE-F type or its analogues is used. Asbestos, PVC pipes or roofing felt cylinders are used as formwork for columns for pouring concrete, placed inside wells. The formwork material does not affect the final load-bearing capacity of the column.

Bored piles are subject to mandatory reinforcement, which is carried out using reinforcing bars with a diameter of 12-16 mm, installed inside the well. Due to the reinforcement, the columns receive additional resistance to deformation, and the reinforcement is also used to connect the piles to the frame of the strip grillage. Concreting of piles and piping is carried out using concrete grade M300-M400 filled with granite crushed stone.

What it is?

The design of such a foundation contains a complex of vertically buried piles and a strapping belt, which takes the load and then transfers it to the supports.

The technology for constructing this type of foundation is clearly described in SNiP 2.02.03-85. Different types of piping with all kinds of piles, materials and dimensions of the grillage have been designed.

A successful combination of elements results in an optimal design that guarantees the required range of parameters.

Design features

There are only two options for filling a monolith:

• connecting all piles into a single system;
• serial connection of all supports with a grillage.

The monolithic slab is poured under the entire building, and the tape is poured only under the load-bearing walls. For private housing construction, the strip type is used, since particularly heavy structures are rarely built on a suburban site.

The tape system has several varieties:

1. High location. The grillage is raised above the ground.
2. Ground location. The sole of the monolith rests on the soil.
3. Short. Filling is performed by immersing the grillage into a trench dug between the supports.

Most outbuildings are erected on pile foundations with a strip grillage - this is the cheapest and easiest to implement construction option.

Feasibility of use

A grillage poured from concrete on piles is recommended to be used when a dense ball of soil lies deep. This option is also preferable for difficult soils:

• high rise in soil water;
• all kinds of peat bogs;
• soil is too clayey.

Limitation of use - rocky or clastic soils where it is difficult to drill wells.

A foundation on supports is the only option when the site has a sloping or relief horizon. In such a situation, there is no need to level the ground; it is enough to set the heads of the supports to the same level. The tape forms a continuous foundation under the load-bearing and internal walls.

The foundation is practical for light buildings:

• wooden,
• frame,
• low brick or block houses.

If the structure is heavy, it is recommended to use a recessed grillage, which evenly distributes the weight of the building along its entire perimeter directly onto the ground surface. Pile structures are convenient for construction near other objects, since they do not require the transfer of communications.

Advantages and disadvantages

The undoubted advantage of such a pile system is increased strength. A building mounted on such a foundation will remain stable for many years.

The design has many other advantages:

1. 
   Not much earthwork.

2. Concrete consumption is significantly reduced compared to a traditional foundation.
3. Pillars are allowed to be installed even in winter.
4. The foundation does not sag after frost heaving or flooding.
5. Minor contact of the base with the ground reduces heat loss.
6. Laying the foundation takes less time.

The design also has some disadvantages:

• it is impossible to arrange such a foundation when the soil is horizontally mobile;
• it is impossible to build a ground floor or basement unless the gaps between the piles are filled (removal);
• It is not recommended to erect bulky buildings on this foundation.