Pile foundation with grillage. foundation strapping made of screw piles

Creating a pile-grillage foundation with your own hands

It is quite possible to do the construction of a pile-grillage foundation with your own hands. For the construction of small buildings (gazebos, country houses), a grillage on a columnar base is chosen, the pile option is suitable for buildings of permanent use. Work is best done in late spring, early summer or early autumn. First, the site is prepared, clearing it of vegetation and debris, then further stages of the work are carried out.

First, you need to prepare materials and tools, order concrete of strength class B17.5-22.55, or purchase ingredients from which it will be prepared in a concrete mixer. If necessary, it is necessary to add gravel or fine crushed stone under the future strapping.

Formwork

The formwork is mounted 10 centimeters higher than the height of the band grillage. The formwork is made of wooden boards or boards of a sufficient level of strength in order not to crack and not to disperse under the weight of concrete.

How is reinforcement done

The prefabricated monolithic grillage must be reinforced. For reinforcement, steel rods with a cross section of 12-18 millimeters are chosen, the depth depends on the project, but the mesh is laid evenly, in increments of 15-30 centimeters. The harness is mounted around the entire perimeter of the tape base.

The wire is cut in advance, the frame is installed in the mounted formwork, there they are tied to the reinforcement of the piles as rigidly as possible. Holes are drilled in the upper part of the piles protruding above the soil level, mortgages are passed through them, longitudinal whips of reinforcement are attached to them. Steel rods are driven inside the piles, the whips are tied together, with the upper whips. Inside the piles, the reinforcement is laid in a layer of 2-3 rods.

Concrete

The concrete is poured in equal horizontal layers, the thickness of which should be 10-15 centimeters. After pouring, each layer is sequentially rammed with a vibrating tool, then only the next one is poured.

For pouring the grillage, concrete grade M300 or M350 is suitable.

Rostwerk: weather and temperature-humid conditions

The grillage device is carried out in hot weather, preferably calm, no precipitation. Direct sunlight should not hit the surface either. If the air temperature is negative, the concrete must be provided with minimal heat loss at all stages - from preparation to laying. If work is carried out on heaving soils, the ground is first warmed up to a positive temperature, protected from freezing.

Dismantling the formwork

After completing the pouring of concrete, the formwork is dismantled, first removing the fasteners and spacers, only after that the boards. The formwork panels should easily move away from the frozen monolith, if such a situation is not observed, this indicates that the solution has not yet frozen and has not gained the required strength.

Drying and care

When a concrete grillage is poured, proper care of the monolith must be ensured. The design is reliably protected from sunlight, wind, precipitation. The surface is covered with plastic wrap, periodically moistened with water if the air temperature exceeds + 22C.

Waterproofing

The concrete grillage must be waterproofed, this is especially important when building pile-grillage foundations of a buried type. It is also advisable to isolate elevated grillages from moisture.

Waterproofing options:

Penetrating - a special mortar with excellent adhesion characteristics covers the foundation.
Coating - the strapping is covered with bituminous mastic.
Sprayed - liquid formulations with high water-repellent properties are applied using a spray bottle.
Roll - the tape is coated with mastic, roll material is placed on top.

The choice of method and material for waterproofing depends on the type of soil, groundwater level, type of grillage, financial capabilities and other factors.

What materials is the grillage made of

The strength of the structure also depends on the material of manufacture. For the grillage are used:

reinforced concrete;
metal;
wood;
concrete.

Wood grillage

The first of these materials is widely used in the production of grillages due to its reliability, rigidity and durability. The main condition is the creation of a sufficient protective layer for the reinforcement. The concrete structure does not imply reinforcement, but is used only in the construction of one-story buildings. When using metal in this type of work, anti-corrosion preparation is required. A grillage foundation made of wood is applicable for structures made of a similar material. Such a base is impregnated with special substances to slow down the process of decay of the tree.

Requirements for arranging a brick base on screw piles

A pile foundation is the best option for a two-story brick house, the construction of which should be carried out in a region with problem soil. The dynamic loads on the basement, even without the insulation of the base structure, after the arrangement of the screw elements, will not affect the structure. The depth of the foundation for a one-story house also depends on the characteristics of the soil, therefore, it is necessary to make indentations for the supports, guided by the established standards.

The base of a house on piles resembles a monolithic foundation in its properties. It is able to prevent the impact of groundwater on the structure. Neither tape nor slab can compete with screw piles in terms of reliability. These elements, installed during soil drilling, are made of steel, which is corrosion resistant. The structure is pre-fabricated, as it can be done within 1-2 days.

A pile foundation with a grillage has its own negative characteristics. Even if the width of the foundation on the screw piles is acceptable, the thermal insulation of the house may be low. As a result, the loss of thermal energy will be significant. To prevent this from happening, it is necessary to observe all the nuances of the technology for installing a brick two-story house with a plinth on piles. It is required to insulate the base at the stage of building a house.

An obligatory stage of warming the foundation is the installation of a false basement and a blind area - a zabirka, which protects the free space under the house from wind and precipitation. To insulate the foundation of a two-story brick house on piles, you will need to prepare the following types of thermal insulation materials:

extruded polystyrene foam (penoplex);
regular foam.

Various types of foundations can be insulated with these materials. Heat insulators have a long service life, are durable and reliable. Before insulation, it is necessary to waterproof the brick foundation if the house is planned to be built with a basement.

The upper part of the grillage should be covered with a layer of waterproofing, where the walls of a two-story brick house, its lower and side parts should be placed. It is also necessary to waterproof the pile heads adjacent to the grillage.

Combined pile-slab foundation: step by step instructions

Pile-slab foundation (SPF) is a combined type of foundation that can withstand increased loads for a long time. Such a foundation consists of two supporting structures: a pile field and a concrete slab.

The main purpose of the combined SPF is multi-storey construction. For example, 90% of the buildings in the Moscow City complex are built on pile-and-slab foundations.

In low-rise construction, such a design is rarely used due to its inexpediency and high cost.

Installation of an SPF during the construction of a cottage or a country house is justified in the following cases:

In areas with increased seismic activity.
On heaving soils, it is recommended to additionally strengthen the bearing piles before the construction of a monolithic slab.
In places where the depth of soil freezing is below 2.5 m.
Groundwater layers are located high to the surface of the earth.
When erecting structures that are sensitive to vibrations (foam concrete, glass).
Construction of an extension to an existing building on a monolithic or strip foundation.

Often a pile-slab foundation is used in the absence of data from hydrogeological surveys of the site. In many cases, the cost of an SPF device turns out to be lower than conducting research. For safety net, future owners of a private house choose this type of foundation as the most reliable and durable.

Pile-slab foundation on bored piles

In addition to screw piles, bored supports can be used for the SPF device. This is a type of pile, when installed, holes of the required depth are drilled in the ground, and then filled with concrete and reinforcement. The most popular option is the I-shaped barrette type supports. The lower part of the pile rests on bearing dense soils, and the upper one protrudes above the surface.

The use of bored piles is advisable where screw piles cannot be used. For example, in soils with high alkalinity, because in this case, the metal screw supports will quickly become unusable due to corrosion and lose their bearing capacity.

Advantages of SPF with bored piles in comparison with screw:

able to withstand 20% more load with the same support diameter;
non-susceptibility to corrosion, aggressive environments;
drilling does not affect neighboring buildings, therefore, these piles are often used when erecting an extension to an existing structure;
long service life - at least 100 years.

If it is necessary to build an extension, bored piles will successfully coexist with screw piles in the same building, fully performing their functions.

Installation of bored piles

The algorithm for constructing a monolithic slab on a pile foundation with bored supports is as follows:

Wells of the required depth are drilled in accordance with the scheme. The drilling method is chosen based on the financial capabilities of the owner, the location of the site, the type of soil, etc. When building cottages, an inexpensive and effective method of manual auger drilling is most often used.
Then the casing is stopped in the well, which will act as a formwork for reinforced concrete bored supports. The pipe can be metal, asbestos-cement, reinforced concrete. Soil is poured into the free space between the pipe and the borehole walls and compacted.
With the help of the building level, the casing pipes are aligned in height. As in the case of a screw foundation, it is recommended to make a raised type SPF. Pipes should rise 30-50 cm above ground level. Excess pipes are cut off.
The well is filled with cement-sand mortar on cement not lower than M300 grade. The mixture is compacted using submersible vibration equipment. If you do not have an electric vibrator, you can use a hand-held vibrator.
Before the cement-sand mixture hardens, a metal frame is lowered into the well under pressure. It is quite problematic to do this manually, therefore, in the absence of special equipment, you can install a reinforcing mesh inside the casing, and then fill it with cement mortar.

In this case, special attention should be paid to tamping!

The supports are connected with each other by a reinforced concrete grillage. After the grillage has hardened, a monolithic slab is mounted using standard technology.

Conclusion

Combined types of foundations: pile-slab, pile-grillage and bored piles are not common in private construction. There are no statistics on their use.

Rough calculations show that SPF is 50-80% more expensive than a conventional pile or slab foundation.

You can ask your question to our author:

The main types of screw and pile grillages

A grillage with a wooden base. It is used in the construction of small buildings where small loads on the foundation are provided. In some cases, half of the harness is made from logs, and the other from concrete beams. They are connected to the pile heads with anchors or studs. In such a base, waterproofing is necessarily provided.
Metal grillage. The base device is as follows: the structure uses metal connecting fittings or channels to connect the piles. Used for heavier buildings of several floors. The connection must be made strictly according to the layout of the load-bearing walls, and the thickness of the reinforcement is selected in each specific case individually, but it is recommended to use powerful metal to strengthen the main load axes. All connections are made by welding and additionally a bolted connection is used, then the chance of occurrence of breaks in the base is reduced and the load will be evenly distributed throughout the foundation.
Dolphin. The device of this foundation provides for the use of several nearby piles at the same time, which are then fastened together from above. The finished pile building block is immersed in the ground next to another. Such a foundation arrangement implies the distribution of a point load from the supporting structures of buildings. This type is often found in the construction of TV towers, radio masts and other tall and compact buildings.
Reinforced concrete grillage. This is the main type of foundation, it is used almost everywhere, it is distinguished by its high structural strength and reliability of the foundation. Given that concrete slabs are inexpensive, such a base is popular. It can be used in the construction of screw foundations on uneven sandy areas. Structurally, there is always an expansion gap between the grillage and the ground, which protects the supports from rupture as a result of soil swelling.
Shallow grillages. Unlike suspended concrete foundations, such structures distribute the load not only along the top of the piles, but also on the foundation. They are used in the construction of massive high-rise buildings without loss of stability and subsidence along single planes.

DIY step-by-step instructions for building a foundation

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

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 short step-by-step guide to quickly understand all the nuances of this process.

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

Drill out or dig holes under the support pillars according to the scheme "in the corners of the house and with a step of 1–2 meters under the tape."
Pour and tamp at the bottom of the “wells” a 30-centimeter sandy one, and then pour concrete on it for the support pillars with a thickness of another 20 cm.
Lower asbestos-cement pipes into the ground, reinforce them with rods with a cross section of 10–12 mm and fill them with concrete.
Make a formwork for the tape.
Lay the grillage reinforcement and fill it with concrete.
Perform waterproofing.

The lower edge of the supports should be below the freezing point of the ground. In this case, wells for piles are made 10–15 cm wider than the asbestos-cement pipes taken. To keep the pillars stronger in place, an expanding concrete sole is arranged in their lower part. Pits in the ground for supports in width are made just for its dimensions.

Waterproofing of concrete is carried out with roofing material or mastic. Even modified bitumen shingles will do. True, it will cost more than the usual roofing felts.

What piles to use

It is recommended to install pile-grillage foundations in the following cases:

When unstable and weakly bearing soils go to a sufficiently large depth. These are karst, forest, peat soils, quicksands, plant and fertile soils of great thickness (more than 1.4-1.5 meters). In this case, the load must be transferred to dense soils located below with normal bearing capacity. It is not always possible to get to the bottom of them, and if it is possible, then the foundation turns out to be too expensive. Therefore, transferring the load with piles is the best choice.
In areas with large elevation differences. In this case, it is often much cheaper to use piles of different heights than to carry out work on leveling the ground or pouring a deep tape that can compensate for the height difference.

One of the types of pile-growth foundation - with TISE piles

With a high level of groundwater. Pile foundations are the only ones for which the level of groundwater does not matter

It is important that there is a load-bearing soil under the heel. The level of the location of the waters affects only the type of grillage: if the water is close to the surface, the grillage is made high, if it lies deep, it can be made low.
When building in hard ground

In this case, small amounts of land work (in comparison with strip or slab foundations) have a positive effect.
If you decide to build a house using frame technology. To make a tape for it is a waste of money: it will turn out to be too large a margin of safety, which, in this case, is useless. In this case, a pile or pile-grillage foundation is the best choice.
With a large building mass (more than 350 tons). Then it turns out that the tape or slab must be very massive, and, therefore, expensive. In this case, the pile-grillage foundation is often cheaper.

Sometimes it's even simpler: they start from the lowest cost. But you always need to remember that any type of pile foundation is less reliable than slab and strip. And all because we cannot know exactly what kind of soil is under each of the piles. That is why, when calculating the parameters, an increased safety margin is laid in the design. Not 1.2, as is commonly believed, but 1.4. And still, no one can guarantee anything.

Any piles can be used in pile-grillage foundations. They are chosen based on the soil, the planned load of the house. Piles are made of metal, concrete, sometimes wood. They can be round or square. They also differ in the installation method:

Driving. They are installed without drilling or digging. Usually - they are hammered, that's why they are called so. They are rarely used in private construction: special equipment is required.

Driven reinforced concrete piles are used more often in the construction of multi-storey buildings
Bored. First, a well is drilled in the ground, then the formwork is installed and fixed in it. It contains reinforcement that increases the strength characteristics. Then the whole structure is poured with concrete.
Reinforced concrete drilling. In this case, wells are also drilled, but ready-made reinforced concrete piles are installed (hammered, but with less effort) in them.
Screw. These are metal piles, pointed at the end and having helical blades that cut the soil.At great depths, special equipment is required, small ones, up to 2-3 meters long, can be installed manually.

One of the types of piles is screw. They can be used with grillages from different materials for different houses (to increase the size of the picture, right-click on it)

In private construction, bored piles are most often used. They are especially popular in the construction of summer cottages or baths. They can also be used in the construction of small houses. But if summer cottages and baths can be done without calculation, then when building a house it is very desirable to order a project.

Different piles are in shape: square or triangular cross-section, round filled and round hollow, sometimes complex shapes are developed specifically for the project. By the way the piles transfer the load to the ground, they are:

hanging;
piles-racks.

What is the difference between piles by type of work (to increase the size of the picture, right-click on it)

Rack piles, on the contrary, transfer most of the load through the tip. In this case, the side walls are undeveloped and smooth, and it makes sense to expand at the end of the pile. One of the types of this type is TISE piles. They have a cylindrical extension at the bottom, which is why they transfer the load over a large area. Also, the heel prevents the heaving forces from raising the foundation.

Grillage and bored piles

This is the easiest option if the master plans to independently build a house, since bored piles are made immediately at the construction site. Therefore, there is no need for special equipment.

Preparation and installation of piles

Traditionally, they first clear the site, then mark it in accordance with the project, mark the places for future piles. They are located around the entire perimeter of the building, in its corners, under the internal (bearing, non-bearing) walls. The maximum pitch between the supports is 2 meters, but the recommended distance is less - 1.5 m. Then they proceed to earthworks.

Pile holes are drilled. Formwork is installed in the wells. Its role is played by asbestos-cement or plastic pipes, PVC film, roofing material, which guarantees waterproofing of concrete pillars.
The depth of the wells depends on only one factor - the level of soil freezing. The pile should be 500 mm below it. 200 mm of them are allocated for the arrangement of a sand cushion. The diameter of the holes is about 200 mm.
After filling and tamping the sand cushion, pipes are installed in the wells. They should rise above ground level at the same distance. The verticality of all elements must be checked.
A reinforcement cage is laid in the pipes. It is made from 3-8 metal rods. These elements are connected to each other by knitting wire or welding. Reinforcing pins should rise above the surface by 300-400 mm.
The distance from the reinforcement cage to the walls of the "formwork" is 200 mm. Concrete is poured into the prepared pipes. Seal it with a vibrator. If there is no tool, then the solution is bayonetted using a long rod.

They act differently if water has accumulated in the pipes. To displace the liquid from the bottom, first pour a third of the solution, then it is carefully rammed. Water after such an operation is taken upward. Then add the remaining concrete.

To ensure the reliability of the structure, pouring concrete into all elements of the grillage foundation should be carried out within one day. Therefore, there is no need to wait until the solution grasps in the support pipes.

Reinforced concrete grillage

First, a gutter formwork is made from edged boards, chipboard sheets or plywood. Other possible options are metal shields or fixed formwork, which at the same time becomes a heater and a waterproofer. For example, a prefabricated foam structure is popular.

The width of the formwork is not less than the thickness of the walls (400 mm are optimal for the tape), the height is about 400 mm.In this case, props are installed under the gutter, which will "hang" above the ground. Their minimum step is one meter. The horizontality of the formwork is tested with a tensioned rope, it is pre-checked with a level.

For reinforcement, rods with a diameter of 10-12 mm are taken, they are placed along the entire structure.
The elements of the space frame are tied with a knitting wire, the thickness of which is 6-8 mm.
The upper and lower belts are connected by vertical ribs. Pieces of stone, fragments of bricks or small wooden blocks are placed under the frame.
With the same knitting wire, it is connected to the vertical elements of the pipe racks. An alternative, but not the best, option is welding.

In the grillage case, in contrast to the massive strip foundation, the pouring does not take place layer by layer, but immediately, therefore, a large amount of mortar is prepared. After distributing the concrete, it is leveled and compacted. After a few hours, the solidified surface of the mortar and the walls of the formwork are moistened. For a uniform set of strength, the surface of the grillage is covered with dense polyethylene. Further work is postponed for a month.

Types and calculation of the load-bearing element of a brick building

Monolithic base, as well as FBS blocks are able to withstand the load of a brick structure

Many people do not know which foundation is best for a brick house, for this reason they start to panic. Before you start calculating the foundation for a house, you need to decide on its appearance.

Nowadays, there are many types of load-bearing elements of a building. But not all of them can withstand the direct impact of heavy loads from a brick building.

The foundation should be chosen correctly, based on the level of climatic influences in a particular region. It is also necessary to determine the structure of the soil structure, the location of groundwater types and the level of loads that will arise from the residential building itself.

According to experts, a monolithic foundation is considered good, since its bearing capacity is quite large. The downside of this type is the high cost, which is unacceptable for the device of a private country house.

You can make a foundation from blocks, it also has many positive characteristics, but the FBS device is expensive due to delivery. For this reason, the block type of construction is omitted. The best option would be a foundation on piles, since in addition to a large number of advantages, this type of foundation is cheaper than the previous types.

In order to properly perform the foundation for a brick house, it is imperative to perform a detailed calculation of the supporting structure. Such actions can be performed according to such principles as:

a complete calculation of the mass of the structure is carried out, taking into account: partitions, roof structure, bearing walls made of bricks, and also the weight of finishing materials should be added;
the mass of the base is calculated, while its variety should be taken into account;
the total value of the mass must be divided by the area that is used for the future foundation, as a result, a weight number is formed that affects the soil. For more information on calculations for a brick house, see this video:

Slab grillage - constructive options

The slab grillage is made in various versions, classified according to the following criteria:

used material. Along with reinforced concrete, steel profiles, timber and ordinary concrete are used;
design features. Execution can be monolithic, prefabricated or monolithic-composite;
location height relative to the ground. The structure can be in contact with the ground, as well as displaced in different directions from the zero mark.

Consider design options that provide for the use of the following materials:

reinforced concrete.The use of strong reinforcing cages allows you to increase the bearing capacity of the base and, accordingly, the stability of the structure. Such a plate has increased rigidity, can be operated for a long time;
concrete. The concrete connecting contour is made without the use of steel reinforcement, which significantly reduces the strength properties. All loads are absorbed by the concrete mass, which can crack under the influence of bending loads;
rolled metal. The union of the column heads is carried out using I-beams or channels that form a single load-bearing frame. The use of rolled metal is justified in the construction of screw-pile foundations for small buildings;
wood. Wooden beams mounted on columns form the basis for lightweight timber panel buildings

It is important to reliably waterproof wooden elements, as well as treat them with antiseptics to increase durability.

A monolithic slab along with a grillage has recently become a very popular way to install a foundation.

A slab with a grillage can be manufactured in various versions:

whole. It is the most durable monolithic reinforced concrete structure used on problem soils. A distinctive feature is increased strength and durability. The disadvantages include the complexity of the work;
national team. The grillage base is formed from ready-made elements that are connected by electric welding. The rigidity of the structure is lower than in the one-piece version. To carry out the work, lifting equipment is required, which increases the level of costs;
prefabricated monolithic. The reference contour, corresponding to the configuration of the building, is formed from individual elements. They are connected to each other, then concreted. The implementation of this method of forming the foundation requires increased costs.

The one-piece base surpasses all the above options in terms of strength and durability.

Insulation of a columnar foundation

After the columnar foundation with the grillage has been erected, a pick-up should be made. It is a replacement for a plinth. The fence protects the space between the ground and the base of the house from snow drifts and drafts.

Wooden pick-up is an affordable and easy-to-install option for lining the basement. It is made of boards that are placed vertically or horizontally. The work process includes:

a 40 cm deep trench is dug between the supports;
one third of the depth is covered with fine sand and gravel;
wooden bars with a groove 40-60 mm wide are attached to the pillars of the base;
grooved boards are attached to each other;
from below, the filling is poured with expanded clay.

With the vertical position of the boards, the first beam is laid on the pillow in the trench. The second is fixed at the bottom of the building. Boards are vertically inserted into the grooves made on the bars.

To make a brick or stone filling between the supports, you should also dig a trench into which the pillow will be poured. The thickness of the filling in this case will be 1.5 bricks. Stone walls should not be more than 30 cm.

With a support height of 0.7 m, the filling is made of heat-insulating plates. They create it in the following sequence:

a structure in the form of a frame, which is made of a steel profile, is fixed on the supports;
from the inside, heat insulation is fixed - expanded polystyrene;
from the side of the street, corrugated board is fixed on self-tapping screws;
the resulting gap between the elements of the corrugated board and the ground level is sealed with thermal insulation material.

With any option for creating a filling, remember about the ventilation windows through which the space under the house will be ventilated. The diameter of these holes ranges from 100 to 150 mm. In winter, the vents are covered with rags.