The foundation is made of reinforced concrete pillars. Foundation supports for the summer cottage

Sooner or later, each owner of the house is faced with the question of the need to install a fence. Which type of fencing to give preference to - brick, mesh or wooden - is not a problem of choice, the main difficulty is the choice of the base.

About what reinforced concrete supports for power grids are, what are their advantages and disadvantages, what is the service life according to GOST and how to build it yourself, read on.

When the mortar is mixed, it can be poured into the formwork. The composition is poured carefully, in the process it is necessary to prevent the formation of air bubbles in the mixture, otherwise this will affect the strength indicator. To do this, when the entire mixture is in the formwork, it should be compacted as much as possible.

When the pouring of the mixture for the installation of an external pole of 110, 95, 35, 10, 105 kV overhead lines in accordance with GOST is over, using a trowel or a flat wooden board, it is necessary to level the surface as much as possible. Then the formwork remains to dry, this will take at least a week.

2.4 Production of supports without formwork

In accordance with the requirements of GOST, reinforced concrete supports of overhead lines can be installed in rounded concrete bases, thus you do not need to do the formwork. To do this, use an iron pipe, having thought in advance what diameter you need, which, in fact, will play the role of a form. Pouring with concrete mixture is carried out according to the following algorithm.

This article continues the series of publications devoted to the construction of foundations. It is time to pay attention to the columnar foundation, to figure out in what conditions it will show its best characteristics, to understand how it works and on what principle it works, to study the basic technological operations for its construction.

Features of columnar foundations

The columnar foundation can be considered the younger brother of the more industrial pile foundation, as it has a similar design and principle of operation. In both cases, a system of separate vertical supports of rectangular or circular cross-section is located along the axes of the building, which are present at all intersection points of the load-bearing walls, in the corners, under especially loaded areas (stone stoves, interior partitions of the base of staircases, columns). And here and there, a grillage can be used to tie the main elements of the foundation, the space between the racks is filled - the so-called "pick-up" is performed.

The main difference is the following - the pillars do not start below the freezing depth (these will already be piles, the length of which in the ground starts from 2 meters), so they only exert a plantar compressive effect on the soil, while the friction force in the zone of the side walls has insignificant indicators. Based on this circumstance, the technologically columnar foundation can be not only solid / monolithic, but also assembled from ready-made piece elements. Agree, it is simply unrealistic to carry out brickwork, for example, in a three-meter pit, and without any problems when deepened at 40–70 cm.

The columnar foundation has its own clear advantages:

· relatively low cost - it is about 1.5–2 times cheaper than its direct competitor, a shallow strip monolithic foundation (less materials and earthworks, no equipment needed);

· low labor intensity;

· you can even build it alone, gradually making individual elements.

Naturally, this foundation is not universal, otherwise everyone would be built on pillars, and there simply would be no other options. We will not call this his disadvantage, it would be more correct - specificity.

Due to the small total supporting surface, the columnar foundation cannot correctly transfer the mass of a heavy house to the ground. The compressive forces under the soles of the supports are so great that the base is not able to withstand the weight of the structure, an increase in the number of pillars and their cross-sectional area is required, which neutralizes the economic benefit from using such a foundation. Therefore, it is advisable to use columnar foundations only for light timber houses (frame, timber, log), for buildings made of lightweight mineral materials, only if they are small, low-rise, with wooden floors. In any case, the loads and resistance of the soil should be considered, this will be discussed below.

The restriction arising from the first point is that such a foundation cannot be laid on water-saturated, weakly bearing and heaving soils. Swampy and weakly bearing foundations cannot withstand concentrated loads and sink, and the possible forces of frost heaving easily overcome the slight load on the foundation from a light building (we have already decided on the weight moment). On loose unstable areas, piles work better, which either "reach" dense rocks, or, due to their length and large outer surface, cling to using friction forces.

It is dangerous to use poles on steep slopes (if the height difference under the house is close to 1.5–2 meters). In such conditions, horizontally directed shear forces are too active, which can simply overturn the structure. Moreover, the depth of the columnar foundation is small by definition, and, consequently, the house clings to the base relatively weakly.

Structurally, this foundation does not imply the construction of buried premises. If you need a basement or an underground garage, then it is better (in all respects more profitable) to build a monolithic or prefabricated tape, which by itself will form the walls in the ground.

Well, and in order to complete our introduction, we note that structurally and according to the material of manufacture, columnar foundations are divided into:

· wooden (there are logs in the pit with all kinds of extensions at the end - chairs);

· prefabricated (fired brick masonry, finished reinforced concrete products);

· monolithic (the most reliable, concrete is poured into the well directly on the site);

· rubble concrete (rubble stone is introduced into the solution).

Design of a columnar foundation

The development of the foundation structure is the most difficult and very responsible task for a private developer. After all, we need to take into account a lot of the most important points, the main among them will be the properties of the soil on which we are building the house, as well as the level of loads that will exert on the house during operation. In the article “Strip foundation. Part 1: types, soils, design, cost ”we talked in great detail about how to calculate the loads, as well as determine the type and, accordingly, the bearing characteristics of the soil. As for the columnar foundation, there are no fewer design issues here.

Columnar length

It has already been said that the columnar foundation is laid above the freezing depth. With a high-quality performance of each single support, even with a foundation depth of 40-50 cm, the house will normally hook onto the natural foundation. It makes sense to go deeper a few tens of centimeters only if more stable layers are located below and you can lean on them. Racks passing below the freezing depth, let's still refer to rammed piles and talk about them in the next article.

Now about the height above the ground. In order to remove the floor and wall structures from the ground at a sufficient distance, the pole heads are raised by about 30-50 cm above the surface. This has a positive effect on the moisture and thermal insulation of the first floor, allows you to create a base in the form of a pick-up, and thereby protect the lower part of the wooden walls.

Cross section of pillars

The prefabricated columnar foundation will have to be arranged in a rectangular or square pit, the monolith can be made of circular cross-section, and therefore, drills can be used for soil development, which facilitate work, and allow avoiding the use of removable formwork.

In most cases, the cross-section of the supports is made uneven - an expansion is organized at the bottom, and they come to the surface with a smaller transverse size. Thanks to this design, the total support area of ​​the entire foundation increases and the load on the ground decreases. There are several options:

For a wooden post, these are “chairs” (pieces of logs perpendicularly located to the posts), a spot of concrete at the bottom of the well, where the support is recessed with the butt-end, sometimes a large flat stone is simply placed in each sample.

For a brick foundation, these are extended 3-4 rows in two bricks, while the subsequent rows are laid in one and a half bricks or in one brick.

Monolithic pillars can start from a flat plate with a thickness of about 100–150 mm, which is 200–250 mm wider than the rack itself; in the well-known TISE technology, the support platform is spherical.

For the precast foundation of reinforced concrete, sometimes larger blocks are used, or, for example, FL elements.

The pillars are brought out to the head, as a rule, no more than 60 cm wide, then at least 200 mm (for racks with a non-removable steel shell). On average, the most common and technically justified is the column section of 40-50 cm.

Number of posts, distance between supports

In practice, the foundation posts are spaced 1.5 to 3 meters apart. Accurate figures can be obtained if we know how many posts to use. To make the necessary calculations, we need to understand how much weight is transferred from each sole, and how much weight the soil can support.

First, we calculate the pillar support area:

· for a square rack / slab with a section of 40x40 cm - this is 1600 cm 2 (we multiply the sides of the section);

· a round sole, for example, with a diameter of 40 cm, is calculated by the formula S = πr 2 (3.14 * 202 = 1256 cm 2), or as an option - S = 3.14D 2/4.

We deal with the type of soil (we pay special attention to the layers that will take the load - from 50 cm and below). According to the table, we determine the bearing capacity of the base. For example, loams of medium hardness / plasticity successfully resist loads of 2.5 kg / cm 2.

It turns out that a square-section pillar with a base of 40 cm should be loaded on dense loams by no more than 4 tons (1600 * 2.5 = 4000 kg).

So that you can see the relationship between the type of soil and the design load on a separate pillar, we will give more examples for a rack of the same section: if we build on plastic loams (the bearing capacity is on average 1.5 kg / cm 2), you can load no more than 2.4 tons , for very wet sands (1 kg / cm 2) - no more than 1.6 tons.

Knowing the total weight of all building structures of the building, adding to this the mass of possible snow cover and operational loads (people, interior items ...), we obtain the estimated mass of the structure. For example, let's take a house of 100 tons.

With a soil bearing capacity of 2.5 kg / cm 2, a house weighing 100 tons will need to be installed on at least 25 pillars (100 tons / 4 tons = 25 pcs.).

If our hypothetical building has an area of ​​10x10 meters, while there is one central bearing wall, then the total length of all the axes of the foundation will be 50 m. - this is a load of 2 tons per one running meter. Knowing how much one post should carry maximum (in our case, it is 4 tons), we can first calculate the minimum allowable distance between the supports - 4 tons / 2 tons = 2 meters.

Layout and preparatory work

Before starting work, it is imperative: to carry out soil studies, make measurements of elevation differences, create a foundation plan, carry out a temporary drainage in the form of drainage ditches, clean the site from turf.

When all the initial operations are completed, they begin to take out the design marks in nature. The markup consists in tying the structure to the red lines and breaking down the axes of the future building, as well as the outer and outer contour of the foundation. As for the strip, in the case of a columnar foundation, it makes sense to make a cast-off with several control cords.

There are two main points when doing markup:

Observe the rectangularity of the conjugation of the lines (use the Pythagorean theorem, the Egyptian triangle, laser angle builder, measure and compare the diagonals - they must be equal).

Maintain the top of the pillars at the same horizontal level (especially important for prefabricated options, since it will be extremely difficult to cut the heads off - pull the control cords exactly according to the marks of the hydraulic level or level).

We described in detail the technology of preparation and staking out marks in the field in the article “Strip foundation. Part 2: preparation, marking, earthworks, formwork, reinforcement. "

Excavation

The volume of excavation work for a columnar base is one of the smallest among all types of foundations; the situation is, perhaps, better only with screw and driven piles. However, in most cases, pits or boreholes should be slightly larger than it seems at first glance.

To create a brick support at a depth of, say, 70 cm, you will have to manually dig a rectangular pit, and its size at the very bottom will be about 15–20 cm larger than the rack on each side. At the top, the excavation should expand, since the slopes will prevent the soil from falling into the pit. Approximately the same pits need to be prepared for the manufacture of monolithic square pillars, since it will be necessary to install and unfasten the formwork, and then dismantle it. The undoubted advantage of the enlarged pits is the ability, after stripping, to inspect the body of the post, to make it waterproof.

The situation is much simpler with circular supports; for their installation, wells are needed, which can be dug with the help of hand drills or special equipment - motor-drills, pit-drills. A clear advantage of this method is the ability to pour the monolith directly along the walls of the mine, without the use of formwork. However, the mechanized production of a well with a diameter of more than 40 cm is impossible due to the lack of a special tool, therefore, often round pillars with a support heel are installed in pits dug with a shovel.

Please note that a certain amount of depth is required, about 20 centimeters of the hole will be "taken" by the pillow.

Pillow device

If for foundations in which the sole is located below the freezing depth, a pillow as such is not needed (since the TISE technology even prohibits it), then for a columnar foundation, always laid half or even 1/3 of the height of the freezing soil, it is mandatory element. Since in case of possible frost heaving of the base, the soil will press on the pillars from below, we change it to a damper non-porous material - coarse sand, a mixture of sand with gravel (40/60) or to clean gravel, ten-centimeter layer rammed into the bottom of the well.

A sand pillow is made with a layer of at least 15–20 cm, while the material is placed in a sample from wall to wall. The mass must be spilled with water and carefully compacted.

Formwork application

If we decide to build a monolithic columnar foundation with rectangular posts, we cannot do without the use of formwork, because it will not be possible to dig a hole exactly in size. Formwork panels are most often assembled from edged boards, although sheet materials such as OSB or moisture-resistant plywood are also excellent. In any case, it is necessary to very carefully loosen the shields in the well in order to prevent distortions during pouring.

Note that all tolerances are clearly regulated by building codes, so the deviation of the pillars along the axis cannot exceed 5 mm (at the heads), along the bottom of the pit, the posts should not "diverge" from the axis by more than 30 mm, the permissible vertical drop is 1 cm per meter. The horizon line for all foundation heads must be maintained with a minimum error not exceeding 1.5 mm.

When developing a well with a drill, the formwork can be omitted and concrete can be poured directly along the walls of the working. However, it is still necessary to somehow form a part of the pillar protruding above the earth's surface. Usually the issue is solved by using a roofing felt shirt. It starts up to the very bottom of the well, the above-ground part of the jacket is reinforced with a mesh and fixed from the ground. On the surface, the roofing material will serve as a formwork, in the ground the concrete will press it tightly against the walls, and the shirt will act as a waterproofing material, in addition, it reduces the effect of friction forces arising from frost heaving.

Reinforcement, head device

Using concrete as a building material, it is necessary to reinforce it with steel rods with a variable cross-section - reinforcement. The rods with a cross section of 10 to 14 mm are combined into a frame with four longitudinal (vertical) threads, which are fastened between clamps made of thin smooth reinforcement with a diameter of 6 mm. The fixation of the frame elements is carried out with knitting wire or electric welding.

For reinforcing pillars with a circular cross-section (with a relatively small diameter), a frame of three working threads located inside triangular clamps may be better suited. The main thing is that we need to maintain the minimum reinforcement coefficient, which for monolithic columns is 0.4% (we consider the cross-sectional area of ​​the column), a normal indicator of 1–2% is considered.

If the foundation has a reinforced concrete grillage, then the longitudinal reinforcement rods are made 40-50 cm longer than the rack itself. The reinforcement is subsequently bent into a horizontal plane and tied to the grillage frame. If a wooden beam or ready-made reinforced concrete lintels is used as a grillage, then the head can be formed with one central rod, including a monolithic threaded rod.

Reinforced concrete pillars are not reinforced, here the stone reinforces the array, but such structures should not have a buta in the upper part, since in this part it is necessary to anchor the reinforcement designed to be connected with the grillage.

In order to form a protective layer of concrete (about 5 cm) and to securely fix the frame in the formwork, it is necessary to use special spacers. It is best to use factory-made plastic star stops for these purposes, which are put on directly on the reinforcing bars. Read about the nuances of working with reinforcement in the section "Reinforcement of the foundation" of the second article on monolithic strip foundations, types of rods and design of the frame, there is something interesting in the section "Calculation of the reinforcement belt" of the first article on strip monoliths.

Column assembly and concreting

The assembly of the posts of the columnar foundation must be carefully monitored in height after the installation of each row, this will be helped by correctly stretched cords, from which the necessary measurements can be made with a tape measure. If a reinforced concrete pile can be “cut down” to the required height and align all the heads in one horizontal line, then, for example, it is not so easy to cope with a brick. The same problems arise with foundations made of reinforced concrete blocks. A well is formed inside a prefabricated brick pillar, laid in one and a half or two bricks, which should be reinforced with a steel rod and poured with concrete.

Wooden poles are most often made from oak logs with a diameter of about 200-250 mm, which are burned over low heat until charring, treated with tar, bitumen or waste oils. Ready-made chairs are installed in pits or open pits and fixed with backfilling.

Rubble concrete foundations are assembled by alternately laying stone (diameter not more than 25 cm, compressive strength not less than the brand of coarse aggregate) and concrete. First, concrete is laid with a layer of 30–35 cm, then stones are placed on it and they are sunk until they are completely immersed. The approximate ratio of concrete / quarry should be no more than 3: 1. The minimum width of a rubble foundation is 500 mm.

For the convenience of pouring concrete into narrow boreholes, with or without formwork, it makes sense to pre-fabricate a hopper with a diameter of 700–800 mm from sheet metal. The concrete is placed in the formwork in layers of 30–35 cm and subjected to vibration or bayonetting. After the completion of concreting, the product is covered with polyethylene and, until the formwork is removed (about 5 days), it needs maintenance - humidification, heating, etc. In terms of compressive strength, concrete of class B15 and more will be most suitable, with a large aggregate with a fraction of up to 70 mm. For self-preparation of concrete mixture, it is worth taking as a basis the ratio 1: 3: 5: 0.5 (cement, sand, crushed stone, water). All the main points concerning the concreting of foundations were outlined by us in the article “Strip foundations. Part 3: concreting, final operations ”.

backfilling

This operation is mandatory, unless you poured concrete directly into a round hole dug with a drill. The borehole sinuses should be filled up in stages, with each layer about 20 centimeters thick should be compacted with a rammer. It is best if the material for filling the sample is coarse sand or a mixture of crushed stone and sand, which are non-porous, low-compressible soils.

Grillage device

The grillage is a system of beams or a solid slab that passes through the heads of all pillars and connects them into a single whole. The grillage structure allows you to evenly distribute the weight of the building on all supports (each axis of the house can be loaded in different ways). Note that for wooden houses there may not be a grillage in the usual sense, but then a beam or a log of the lower strapping plays its role.

In some cases, the grillage is welded or bolted together from steel beams. This design is very reliable with respect to the forces of compression and tension, but with flaws in the processing it is highly susceptible to corrosion.

Most often, the grillage is made of reinforced concrete - prefabricated or monolithic. The prefabricated grillage is obtained by laying over the pillars of ready-made reinforced concrete lintels, type 5PB-25-37 P, which are joined in the centers of the pillars and connected by welding the released reinforcing elements.

For the installation of a monolithic grillage, U-shaped boxes should be made for the entire perimeter of the building, they are installed on top of the heads and with struts reliably unfastened from the stakes driven into the ground. To prevent the structure from bending under the weight of concrete, props are made in the spans between the posts under the box. Some craftsmen prefer to create a ridge of sand around the perimeter, on which the formwork will rest.

Depending on whether there will be a gap between the ground and the grillage, or it will rest on the ground with its lower edge, a high and low grillage is distinguished. In the first case, the free space (at least 100 mm) ensures the movement of the heaving soil, and it will not act "for separation", raising the grillage. The second option is suitable for stable sandy soils, then the grillage transfers the load to the natural base, not only through the posts, but also in the spans. The low grillage is even deepened a little and a leveling sand cushion is made under it.

Obviously, a monolithic grillage must be reinforced, as a rule, 4 reinforcing threads with a diameter of 10-14 mm are enough for it. The manufacturing technology of the reinforcing cage, as well as concreting, is no different from the installation of a strip foundation or a monolithic belt, therefore we again recommend referring to the article “Strip foundation. Part 3: concreting, final operations ”.

As for the section of a monolithic grillage, it usually has the shape of a square, with a side equal to the width of the walls, but not less than the width of the pillars in the head area.

Zabirka

This element of the columnar foundation is mounted last, often already at the final stages of building a house. The draw-in is needed to isolate the space under the lower floor from external influences - moisture, snow, low temperatures. The essence of the filling is that between the posts, piece materials are laid (bricks, rubble, blocks ...), a concrete wall is poured, or a frame is created, which is sheathed with sheet panels, such as basement siding. Ventilation holes must be installed through the block of the filling.

This is how the technology for the construction of a columnar foundation looks like. This type of base has firmly taken one of the leading positions among all designs. And the point here is not only to save energy and material resources, just a correctly calculated and skillfully constructed columnar foundation is able to serve no less than the house itself without problems. This has already been tested by time.

Turishchev Anton, rmnt.ru

http: // www. rmnt. ru / - RMNT website. ru

From this article you will find out what are the advantages and disadvantages of supporting-columnar bases, we will take a closer look at the technological features of foundations of this type and deal with the main nuances of building support-columnar bases with our own hands.

Types of supporting columnar bases

In small-scale construction, when erecting small buildings made of wood or frame panels, they often resort to arranging support-columnar bases.

Rice. 1.1: Support-column foundation made of FBS blocks

There are several types of support-columnar bases, each of which has its own advantages and disadvantages. Let's consider the main ones:

• Brick;

This is the simplest option, which is perfect for the construction of light houses on dense soil (sandy loam or dry sandy soil) with a low level of groundwater. The bearing capacity of brick racks will be sufficient for any utility room and for small one-story wooden houses.

Fig 1.2: Construction of a support-column foundation made of bricks

• Columnar supports made of steel pipes;

Concreted metal pipes have the highest bearing capacity among all types of columnar supports. For the construction of a support-column foundation, pipes with a wall thickness of at least 4 millimeters are used, with the obligatory coating of pipes with an anti-corrosion primer for metal, which is necessary to protect steel from damage under the influence of groundwater.

• Column supports made of asbestos pipes;

• Made of wood;

Logs can be used for the construction of a support-column foundation, however, due to the many disadvantages of this material (susceptibility to decay, exposure to groundwater and low bearing capacity), this type of foundation is quite rare.

Fig 1.5

Support-column foundation pluses

To begin with, let's figure out in what conditions it makes sense to equip support-column foundations.

The use of any type of columnar foundations is limited by the weight of the building being erected - such foundations are not intended for the construction of heavy brick or concrete houses. This is a good option for light one-story buildings made of wood, panel boards and insulated frames.

Rice. 1.6: Construction of a house from a bar on a support-columnar foundation

Among the characteristic advantages of all types of support-columnar bases are:

• The minimum construction time - a full-fledged support-column foundation can be erected in 2-3 working days;
• The minimum cost, in comparison with strip and slab bases, due to the significantly smaller amount of materials required;
• The ability to arrange it yourself, without the involvement of special equipment;
• Good resistance to frost heaving of the soil, due to which it is rational to resort to the arrangement of support-columnar foundations when constructing auxiliary buildings on soils with a large freezing depth;

Disadvantages of a support-column foundation

• Low bearing capacity limits application potential - only suitable for light structures;
• Minimum resistance to horizontal movement of the soil, as a result of which there is a high risk of tilting the pillars - such a foundation requires reliable strapping with a grillage;
• The supporting-column foundation does not provide for the possibility of creating a basement floor or basement.

Fig 1.7

Columnar foundation made of concrete blocks

The most common type of support-columnar bases is a foundation made of concrete blocks, for the creation of which reinforced concrete or expanded clay concrete blocks of industrial production are used.

Reinforced concrete block structures have a large weight (up to 3 tons), which is why they are laid with construction cranes (special loop-shaped hooks are provided on the block surface). In small-scale construction, such blocks are rarely used.

Expanded clay concrete blocks are much smaller in size and weight, the creation of a columnar base using such blocks can be done by hand.

Fig 1.8

The technology for erecting a support-columnar base provides for a pillar pitch of 2-3 meters (the step may be smaller if the building is being built on problem soil), while the support pillars should be evenly placed along the perimeter of the walls of the building and must be present at the intersection points of the walls and at the corners of the house ...

The height of one pillar may vary depending on the slope of the construction site - according to the technology, on terrain with a natural slope, the supports should have uneven deepening into the ground, there are often cases when on one side of the building the support pillar is made of two FBS blocks, and on the other - from five ...

Fig 1.9

Pillar-support foundations made of FBS, as a rule, are created with a minimum level of immersion in the soil (within 15-30 centimeters). A prerequisite is the presence of a compacting cushion of sand and gravel, the thickness of which must be at least 20 centimeters (10 centimeters for each layer).

When laying concrete pillars FBS, the blocks are connected using a cement-sand mortar or a special adhesive composition. Upon completion of the installation, the pillars are covered with waterproofing material - roofing felt or roofing felt and the arrangement of the piping begins.

The grillage on support pillars from FBS blocks can be made in the form of a monolithic reinforced concrete tape, or it can be a prefabricated structure from a bar, an I-beam or a channel.

Do-it-yourself support-column foundation

Let's consider the main stages of building a support-column foundation from FBS blocks with our own hands:

• Preparatory work - the site is cleared of vegetation and debris, the top fertile soil layer is removed to the depth of one shovel bayonet;
• Marking - according to the design data, the contours of the walls of the house are transferred to the soil, along which the locations of the support pillars are marked. The marking is carried out using pegs driven into the ground from reinforcing scraps and twine stretched between them;

Fig 2.0: Layout of the site for the foundation

• Earthworks - then it is necessary to dig holes in which the support pillars will be located.

• Backfilling - a 10-centimeter layer of sand is poured into the pits, which is spilled with water and compacted, a layer of fine gravel of the same thickness is placed on top of the sand;

Fig 2.1: Diagram of compacting bedding under the foundation

• Concreting - a cement-sand mortar based on cement grade M300 is poured into the pits, the surface of which is carefully leveled, after which it takes 2-3 days until the residual hardening of the concrete;
• Block masonry - FBS masonry is performed using a similar cement-sand mortar, upon completion of the masonry, the height of the pillars is leveled at one level and the blocks are covered with roll waterproofing material or coated with bitumen mastic. Then, the free space in the pits is backfilled, while the soil is additionally compacted with a manual rammer;

Fig 2.2

The foundation is the foundation of the foundations of any structure. Although summer cottages are not very heavy structures and do not exert significant pressure on the ground, it is still not recommended to assemble them directly on the ground. In most cases, a light point foundation is made under the buildings. At the corners of the future structure, support points are installed in the ground, which are short concrete piles or columns made of bricks, extending into the ground by 0.5-1 m. These can also be asbestos-cement pipes dug in vertically or even pre-waterproofed wooden supports.

With a tree, unfortunately, not everything is so simple. You can wrap wooden posts in the underground part with tar paper or roofing felt, as some builders recommend, but this will not bring any benefit. Moisture can freely penetrate through the joints of the winding, no matter how many layers there are, and the wooden posts will still get wet. The old way to grind the butt of a log is more effective, but it is necessary to follow a certain technology.

Earlier in 1889, the following recommendation was published in the journal "Agriculture and Household Management": "The most common means of protecting the underground or underwater part of pillars and stakes from decay is, as you know, charring or smearing with resin the corresponding part of the pillar. But the use of one of these methods without the assistance of the other does not give good results ... ".

This is a good method, proven over the years. However, instead of the previously used resin, a mixture of molten bitumen with diesel fuel is now successfully used. This mixture is much more reliable. When using refractory bitumen, more diesel fuel is needed, for less refractory bitumen - less. The mixture of bitumen and diesel fuel is used hot, so the temperature of the charred part of the wooden posts does not matter. A mixture of bitumen with gasoline or kerosene is made and used cold, but in any case, the coal layer will be soaked through and through. At the same time, do not forget that the part of the pillar that rises 25-30 cm above the earth's surface should also be charred and tarred.

In addition, it will not be superfluous to remove the top layer of soil 15-20 cm thick under the gazebo and instead make a bed of gravel and sand. Thus, a kind of drainage cushion will be created, which drains water from the supports.

Factors that determine the type of foundation structure

The foundation serves to evenly distribute the pressure of the mass of the structure on the ground. The design of any foundation depends on the mass of the building, the depth of freezing of the earth and the type of soil on which it is erected, and in addition, on the level of occurrence of groundwater. The quality of the soil is determined on the basis of engineering and geological surveys, which are carried out before the start of construction. The bearing capacity of the soil is important for the construction of the foundation. From this point of view, there are good soils (rocky, coarse, coarse dry sand), mediocre (wet clay, fine sand) and bad (loess-like, silt, bulk soil).

Rocky soils are reliable and durable. They are not subject to swelling, subsidence and erosion. Coarse soils containing fragments of crystalline or sedimentary rocks (streaks of gravel or stones) are weakly compressed and not eroded. Sandy soils, depending on the size of the particles, are divided into large, medium, small and silty. They sag and thicken. Fine and silty sands with clay impurities, being saturated with water, become fluid, which further reduces their bearing capacity (they are also called quicksand).

Clay soils (loess, loess) are subject to compression, swelling and erosion. They have pores - cells in the form of vertical tubes. Moistening, such soils are compacted and form subsidence, therefore they are called subsidence. Sandy loam and loam - a cross between sandy and clayey soils. They are distinguished by the content of clay: sandy loam contains up to 10% clay, loam - from 10 to 30%.

Fill soils are formed as a result of filling ravines, ponds, dumps, etc. with waste rocks, slags, garbage (containing organic impurities and production wastes) with a heterogeneous structure and degree of compressibility. Such embankments, depending on external conditions, self-compact in 5-7 years.

Another extremely important indicator is the depth of soil freezing. This value directly depends on the geographical location of the area. Freezing is the main reason for the instability and deformation of foundations: at a certain moisture content, some types of soils begin to swell. Foundations laid in such soils above the freezing depth are simply squeezed out of them if the forces of frost heaving are not balanced by the load (the mass of a building or other structure). These forces are quite significant and can reach 1 t / m2. But that's not all. The danger for the structure also lies in the fact that the soil is deformed unevenly, which leads to a distortion of the foundation, the formation of cracks in the walls and, ultimately, to the destruction of the entire building.

Finally, the choice of the foundation design is also influenced by groundwater, more precisely, the level of their occurrence. This level can be determined using geotechnical and hydrogeological surveys. The best for laying the foundation is the occurrence of groundwater below the freezing depth. The worst is when the water table is well above this mark. It is then, as a result of the swelling of the soil under the sole of the foundation, forces are formed that push it upward. To neutralize them, it is necessary not only to lay the base of the foundation below the depth of soil freezing, but also to compensate for the effect of tangential (lateral) heaving forces. This can be done by building a reinforced concrete foundation with a base in the form of a wide platform and tapering upward (inclined) walls.

By the type of construction, foundations are slab, strip, columnar and pile (Fig. 1), and depending on the materials used - rubble, concrete, buto-concrete and reinforced concrete. The foundation of any structure must rise above the ground by at least 30 cm. This part of it and the top of the underground part can be made of stone, brick or concrete blocks. Floor slabs are laid on the upper part of the foundation protruding above the ground, which will serve as the base of the floor of the first floor.

Slab (solid) foundations (Fig. 1, i) are built on heavy and subsiding soils located in river floodplains, in flooded and wetlands with a high groundwater table. They represent a rigid structure - a monolithic reinforced concrete slab along the entire load-bearing plane, withstanding vertical and horizontal movements of the soil. The slab is laid on sand-crushed stone backfill. Such foundations are also called floating. They have proven themselves well in low-rise construction, but they require significant costs, since a lot of concrete and metal is used for their manufacture.

Strip foundations (Fig. 1, b) are arranged under buildings with brick, stone, concrete and wooden walls, as well as in cases when it is planned to equip a basement under the house. If the strip foundation is laid in heaving and deep-freezing soils, then its sole should be at least 20 cm below the depth of their freezing. Such foundations are technologically uncomplicated and economically feasible, do not require large labor costs and are most often used in simple geological conditions. According to the production technology, strip foundations are monolithic and prefabricated. The former are made of rubble, iron and rubble concrete, the latter are made of ready-made concrete blocks.

To create a monolithic strip foundation (Fig. 2), you first need to dig a trench and prepare lean concrete along its bottom. The width of the trench, which is different from the width of the foundation, is determined using calculations that take into account the type and condition of the soil, the load on the foundation, depending on the weight of the building and other factors, information about which the designer receives from the geotechnical surveys.

A trench or foundation pit for the installation of a monolithic foundation cushion is prepared for the full width, then the formwork is exposed, reinforced according to the decisions made in the project and poured with concrete of the grade also specified in the project.
When laying the foundation of rubble, they use torn stones (of irregular shape), the voids and seams between which are filled with mortar. The masonry should be with bandaging of the seams and have a width of at least 60 cm. The creation of such a foundation is a laborious process, but in this case little mortar is consumed.

In the manufacture of rubble concrete foundation, small stone and crushed stone are used. A layer (5-10 cm thick) of the largest stones or crushed stone fractions is laid at the bottom of the trench, tamped and spilled with a solution. This operation is repeated until the foundation has reached full volume. In this case, the concrete must be constantly compacted (for example, with a vibrating screed) so that when pouring it is distributed evenly without leaving voids.

After the concrete mixture begins to harden, the open part of the foundation must be covered with burlap or straw mats and regularly moistened with water for 2-3 weeks so that the concrete does not dry out during the setting process. In the summer, in the first few days, such procedures are carried out every 4 hours, and then 2-3 times a day. In winter, the foundation should be protected from exposure to negative temperatures during hardening. The construction of such a foundation is less laborious than a rubble foundation, but a lot of concrete is spent on it.

Prefabricated strip foundations

Prefabricated strip foundations(Fig. 3) are used to speed up the installation of the foundation, they require less labor and are performed faster. To create them, ready-made foundation blocks of walls (FBS) and blocks of foundation cushions are used. The standard length of the FBS is 90, 120 and 240 cm, the width is 30, 40, 50 and 60 cm, the height is 60 and 30 cm.

Foundation blocks are laid on a layer of sand (up to 10 cm thick), leveled to the design level. Installation of foundation blocks on bases covered with water or snow is not allowed. A prefabricated shallow foundation is created by placing ready-made concrete blocks with a crane into a trench on a prepared foundation. They are placed on top of each other on a mortar with bandaging of vertical seams, the depth of which should be at least 0.4 of the block height for low-compressive soils and at least 1 block height for highly compressible, subsiding and swelling soils. The same rule for laying blocks with ligation is preserved for the places of abutment of the outer and inner walls.

Blocks of the outer walls of the foundation, installed below the ground level, must be aligned on the inside, and located above its level - on the outside. Erecting prefabricated foundations on highly compressible soils or with uneven stratification of soil layers, a belt is arranged over the last row of prefabricated blocks along the entire perimeter of the walls, which is reinforced with welded or knitted frames from rods of the design section.

The installation of prefabricated strip foundations requires less time, but it is impossible without the use of expensive lifting equipment.

Installation of a columnar foundation (Fig. 2, c) will cost half the price of a strip foundation. Such foundations are used for the construction of light buildings on heaving soils with deep freezing or when the soil layer serving as the base lies at a depth of 3-5 m. The pillars are made of stone, burnt bricks (iron ore), concrete, reinforced concrete, wood and asbestos-cement pipes filled with concrete. The section of rubble pillars can reach 60x60 cm, brick - 50 x 50 cm (two bricks). Sometimes verandas, terraces, baths and even light houses are installed on pillars made of wood, the so-called "chairs", which are burned before being buried in the ground and then impregnated with bitumen resin. Columnar foundations must be laid 20 cm below the level of soil freezing. The pillars are placed with a pitch of 1.5-2.5 m, but they must be installed in the corners of the house, at the intersection of the external and internal load-bearing walls, under the frame racks in wooden frame houses and in other places where the load is concentrated.

To support the wall on the pillars, they arrange (cast from concrete or lay standard) lintels or foundation beams with a height of at least M of its span. Lintels can also be made of bricks with a reinforced seam under the bottom row of bricks. Sometimes, in ordinary soils with normal bearing capacity, columnar foundations are laid in the form of drill piles. To do this, a well is drilled and an asbestos-cement pipe is inserted vertically into it, around which the earth is carefully tamped. Pouring concrete into the pipe at Uz height, it is slightly raised - part of the concrete is poured into the well, forming an expanded base of the pile, a kind of sole. Until the concrete has set, the pipe is set to the desired height, reinforced with metal reinforcement and everything is poured with concrete. For connection with other structural elements, the reinforcement is installed so that after pouring its ends protrude 15-20 cm above the concrete surface. In a few days, when the concrete gains a certain strength (the final setting of the concrete mixture occurs 4 weeks after pouring), on such a foundation you can install the beam of the lower frame strapping.

Pile foundations (Fig. 1, d) are used in the construction of multi-storey buildings in difficult geological conditions: on bulk soils of low density, soils with a low bearing capacity and a high level of groundwater. Piles are led through bad soil to soil with normal bearing capacity, after which a grillage (slabs or tapes) is laid on them to evenly distribute the load of the building.

Rice. 4. Incorrect foundation laying and the effect of soil buoyancy on it in the summer (a) and winter (b) periods: GWL - groundwater level; UPG - the level of soil freezing; B - forces of soil swelling; Г - tangential swelling forces soil; h - lifting height of the foundation	Rice. 5. Correct laying of the foundation: GWL - groundwater level; UPG - the level of soil freezing; A - foundation pressure on the ground; B - soil resistance; Г - tangential forces of soil swelling

The main mistake that can occur when constructing foundations is laying them above the level of soil freezing (Fig. 4). In the summer period (Fig. 4, a), the action of forces A and B is balanced, and since the soil does not freeze, the foundation does not rise. In the winter period (Fig. 4, b), when the soil freezes, the buoyancy forces of the soil swelling B and the tangential (lateral) forces D begin to act on the base of the foundation. Their total effect raises the foundation to a height h.

The correct laying of the foundation is below the level of soil freezing (Fig. 5). In winter, the forces of soil swelling do not act on the base of the foundation. The action of tangential forces is compensated by special methods and means.

In the early 1990s in Russia, the inventor RN Yakovlev developed a special popular, that is, accessible to the majority, construction technology - "Technology of individual construction and ecology" (TISE). It involves building a house on your own, without the use of hired labor. The author developed the idea of ​​manufacturing a columnar foundation of increased strength (Fig. 6 using a manual foundation drill of an original design, by means of which it is possible to obtain a support well with an expanded cavity at the bottom. The well is filled with reinforcement and concrete.

Drilling and concreting of one support takes about 1.5 hours. The foundation pillar, made using this technology, is not lifted by the forces of frost heaving due to the lower expansion of the pillar. However, if in the same season it is not supposed to load the foundation with a house (or other building, for example, a heavy gazebo), then such a pillar should have reliable reinforcement (4 rods with a diameter of 10-12 mm), which excludes the separation of the extended part of the pillar from the cylindrical one.

After installing all the supports, they proceed to the implementation of the grillage tape, cast from reinforced concrete in a conventional plank formwork. By location relative to the ground level, there are three types of grillages: high, elevated and low. The most common and convenient in construction is a high grillage, which is at least 10-15 cm above ground level. A low grillage is below ground level. The sole of the raised grillage is at ground level. In order for the heaving forces not to act on the grillage of the last two types, it is necessary to remove a layer of soil 10-15 cm thick from under them.

The bearing capacity of the supports is determined depending on the value of the calculated soil resistance. Table 1 shows the indicators of the bearing capacity of one foundation pillar, cast using the TISE technology. The bearing capacity is determined based on the strength of wet soil at a depth of about 1.5 m and the diameter of the support foot of the pillar. At the surface, the bearing capacity will be almost 1.5 times lower.

The step of the foundation pillars when erecting stone walls using the TISE technology should not be more than 2-3 m. This allows you to get by with a small cross-section of the grillage tape. Pillars along the outer perimeter of the foundation are placed, as a rule, at its corners and at the intersection with the inner walls of the house. But this is optional. When distributing supports along the perimeter of the foundation, it should be borne in mind that under the internal load-bearing wall loaded with floor beams (slabs) from both sides, the pitch of the pillars should be reduced by 10-15% compared to the pitch of the supports under the outer walls.

Table 1 Bearing capacity of one support according to TISE technology

Soil type	Design soil resistance, kg / cm2	Bearing capacity of the support, t, with the diameter of the support sole, cm
Pebble with clay
Gravel with clay
Coarse sand
Medium sand
Fine sand
Dusty sand
Loam
Subsidence soil
Bulk soil with compaction
Bulk soil without compaction

The advantages of the TISE foundation are high bearing capacity, the possibility of self-production and the fact that it can be left for the winter without loading from above.

In the article we will consider the columnar foundation of the house, we will describe the columnar strip foundation (columnar foundation with a grillage). We will tell you in which cases the construction of a columnar foundation is most applicable. Separate parts describe the arrangement of the columnar foundation, recommendations and errors when installing the columnar foundation.

General information about columnar foundations.

The stages of preparation and the technology for manufacturing a columnar foundation and a strip foundation are in many ways similar. Therefore, the general provisions typical for the manufacture of foundations (assessment of soils, freezing depth, the presence of groundwater and communications, preparatory work, installation of formwork, pouring concrete, possible errors in design and construction) in this article is not advisable to repeat. To familiarize yourself with them, just refer to the article.

Along with an overview of all options for columnar foundations, we will focus on foundations made of precast concrete and reinforced concrete blocks.

Columnar foundation is a system of pillars located at the corners and at the intersection of walls, as well as under heavy and load-bearing walls, beams and other places of concentrated load of the building. To create conditions for the joint work of the pillars, as a single structure, and to increase the stability of the columnar foundations, to avoid their horizontal displacement and overturning, as well as to arrange the supporting part of the basement between the pillars, a grillage is made (strapping beams, randbalki).

The main type of columnar foundations used in mass construction is monolithic reinforced concrete foundations.

As a rule, the distance between the posts is 1.5-2.5 m, but it can be more.

With a distance between the posts of 1.5-2.5 m. The grillage is an ordinary reinforced lintel. At the same time, it is impossible to tie the attached terrace, veranda, porch into a single constructive solution. These rooms must have their own foundation, that is, they must be separated by an expansion joint, since the load from the porch is not comparable to the load from the walls of the house, and accordingly they will have different draft.

You can read more about the device of such a seam in the topic. .

When the distance between the foundation pillars is more than 2.5-3 m, the grillage is made from a more powerful, so-called, randbalk. Randbalka is made in the form of a monolithic or precast reinforced concrete beam. It can also be metal (I-beam, channel, profile).

• for houses without basements with light walls (wooden, panel board, frame);
• under brick walls, when deep laying is required (1.6-2.0 meters, i.e. 20-30 cm below the depth of seasonal soil freezing) and the strip foundation is uneconomical;
• when the soils during the operation of the building ensure the settlement of the columnar foundation (at equal pressures of the pillars on the ground) is much less than that of the strip foundation;
• when it is necessary to exclude as much as possible the negative impact on the foundation of frost heaving, because columnar foundations are less susceptible to this phenomenon.

a - prefabricated-monolithic with the location of groundwater at the time of the work below the foot of the foundations;

b - prefabricated at any location of groundwater;

1. prefabricated reinforced concrete support post with a bar reinforcement cage;

2. the same with a steel pipe core;

3. the same, with a bar reinforcement cage and a sheath of asbestos-cement pipe;

4. the same, with a steel pipe core and an asbestos-cement pipe sheath;

5. prefabricated support post made of steel pipe;

6. backfilling with excavated soil;

7. base plate made of monolithic reinforced concrete;

8. base plate of precast concrete foundation;

9.Sand pillow.

Consider a few points in favor of using a columnar foundation:

• If the cost of other types of foundations is 15-30% of the cost of the whole house, then the cost of a columnar foundation will be no more than 15-18%.
• Columnar foundations in terms of material consumption and labor costs are 1.5-2 times more economical than tape foundations.
• Columnar foundations have another positive quality, which is that the base soils under free-standing supports work better than under solid belt supports, as a result of which the settlement under them at equal ground pressures is much less than that of belt ones. Reducing the amount of settlement makes it possible to respectively increase the pressure on the ground by 20-25% and, consequently, reduce the total area of ​​the foundation.
• The most dangerous forces acting on the foundation of low-rise individual houses are the forces of frost heaving. Therefore, almost all the options for the construction of foundations are considered from the point of view of their construction on heaving soils. It is generally accepted that when building on heaving soils, the depth of the foundations should be lower than the estimated depth of seasonal freezing. However, for lightly loaded foundations of small houses, the heaving forces usually exceed the total load from the house acting on the foundation, as a result of which various kinds of deformations occur.

Therefore, when building houses without basements on heaving soils, it is better to build shallow or shallow foundations. Let us explain their differences.

1. Shallow consider foundations with a depth of 0.5-0.7 of the standard frost penetration depth. For example, with a standard freezing depth of 140 cm, the depth of a shallow foundation will be 140x0.5 = 70 cm.
2. Shallow foundations- such foundations are considered, the depth of which is 40-50 cm, and averages half or a third of the freezing depth.

With a great depth of freezing in heaving soils, anchor columnar reinforced concrete monolithic or prefabricated foundations are effective. On such foundations, the influence of frost heaving forces acting on the lateral surface is insignificant, since the pillars are made with a minimum cross section. If the foundation is erected from stone, brick, small blocks, monolithic concrete without reinforcement, its walls must be made tapering upward, this will save material and evenly distribute the load from the walls.

Additional measures to reduce the influence of frost heaving forces can be: coating the side surfaces of the foundation with materials that reduce soil friction, such materials are bitumen mastic, plastic lubricants (synthetic solid oil "S", CIATIM-201, BAM-3, BAM-4), organosilicon compounds , epoxy resins, furan-epoxy composition, polymer films as well as insulation of the surface layer of the soil around the foundation. The feasibility and options for such insulation are set out in the question.

Conditions under which columnar foundations are not recommended to be used:

• in horizontally moving soils and soft soils, since their structure lacks resistance to overturning. To repay the lateral shift, a rigid reinforced concrete grillage is required (its device will negate the cost savings on the difference between the columnar and the tape).
• Their use is limited on weak soils (peat, subsidence rocks, water-saturated clay, etc.) and in the construction of houses with heavy walls (massive brick more than 510 mm thick, standard reinforced concrete slabs and blocks);
• If you have limited financial resources or time period for the installation of the base. If, with a strip foundation, the basement is formed as if by itself, then with a columnar filling the space between the pillars with a wall (zabirka) is a difficult and time-consuming task;
• It is not recommended to arrange columnar foundations also in areas with a sharp difference in heights (the difference in heights in the area under the foundation is from 2.0 m and more).

Consider what materials can be used for making a basement, depending on the design of the house (first of all, its mass and number of storeys):

• The stone foundation is made of rubble stone or medium-sized flagstone. It is advisable to select a stone of the same size, and the flatter it is, the better.
• It is advisable to make brick foundations of well-fired red brick (black), preferably iron ore. Poorly fired bricks collapse quickly.
• Concrete foundations are made of heavy concrete grades B15-B25;
• Concrete;
• Monolithic reinforced concrete (monolithic foundation has increased strength, has the highest service life - up to 150 years);
• Prefabricated precast concrete and reinforced concrete blocks. In the prefabricated version, the poles are manufactured separately and assembled during installation.
• asbestos-cement or metal pipes filled with concrete mixture.

• concrete and rubble concrete - 400 mm;
• masonry - 600 mm;
• brickwork above ground level - 380 mm, and when bandaging with a pick-up - 250 mm;
• from rubble - 400 mm;

Photo of a columnar foundation for a small private (country) house.

Information about the depth of laying the supports of the columnar foundation

It is necessary to pay attention to three main points when determining the depth of laying a columnar foundation:

• the depth of soil freezing in your area in which the house is being built; (The best option is to lay the pillars below the freezing depth of the soil, thus eliminating deformation of the foundation)..
• determination of the type and composition of soil (Fixed soil or mobile, clayey or sandy. The best soil can be sand, since water leaves through it instantly and it has a high bearing capacity, it is impossible to build on silty and peaty soils, it is necessary to arrange a partial or complete replacement of soil on sandy);
• the level of the location of groundwater (is there a reservoir nearby, a river, if there is this indicates the presence of a high level of groundwater, it is necessary to do waterproofing or drainage)

These factors must be taken into account in the project of the house ordered by you.

Also, when calculating the depth of laying the foundation, the designer should take into account not only the natural influences on the foundation, but also the following indicators:

• the weight of the future home;
• the weight of the foundation supports;
• the weight of the furniture in the house and the number of people who will live in this house;
• seasonal, temporary loads (snow).

It is advisable to contact a designer who has all the necessary data to carry out such calculations (the level of groundwater in your area, the depth of freezing, the structure of the soil, etc.). The value of the designer's participation in the design process lies in the fact that he will calculate the depth of the foundation with absolute accuracy (without excess margin in depth). This will allow you to obtain savings in building materials, financial resources without compromising the quality and safety of the house.

Columnar foundation device

In this section, we will consider the construction technology of a monolithic reinforced concrete columnar foundation as the most common type in private construction.

1. Preparatory work

The work should start with cleaning the construction site. To do this, it is necessary to cut off the vegetation layer, preferably at least 2.0-5.0 meters in each direction from the planned location of the foundation. Its thickness is 10-30 cm, and it is not suitable for the base of the foundation. This soil needs to be cut and transferred to a vegetable garden or garden.

If the soil under the cut layer consists of sand mixed with fine stone (gravelly sand, sand of coarse or medium grain size), then it is used as the base of the foundation, regardless of humidity, groundwater level or freezing depth.

If clayey soils are found (clay, loam, sandy loam), then a sand-gravel cushion is necessary. The thickness of the pad depends on the geological characteristics of the soil.

If under the cut layer you find peaty or silty soils, then it is necessary to carry out a complete replacement of the base, in which case a geologist's consultation on the composition and arrangement of the artificial base is needed.

Garbage and all foreign objects are removed from the construction site.

After the construction site is cleaned, it is flattened. Bumps are removed, soil is poured into the existing pits. The horizontal control of the site is carried out with a level that is installed on a 2-2.5 meter flat board or rail. The preparation ends with the delivery and storage of building materials to the site.

2. Breakdown of the foundation

The breakdown of the house plan on the site consists in transferring from the drawings to the land plot and fixing the axes and main dimensions of the foundation.

Before breaking down the foundation of the house, pillars (cast-off) are installed around its perimeter, at a distance of 1-2 m from the building. Wooden boards or slats are nailed to the pillars from the side of the future walls of the house and parallel to them, on which the dimensions of the individual parts of the pit (trenches and pits) and the foundation itself and future walls are marked. The accuracy of the division of the center lines is controlled by accurate measurement of the distances with a tape measure. It is imperative to check the corners of a rectangular or square foundation, they must be strictly straight at 90 degrees. Be sure to check the elevation of the bottom of the trench with a theodolite, at least at the corners of the house and at the intersection of the bands. It must correspond to the design one (that is, if you decide to deepen the foundations by 1.4 m, then the bottom of the trench should be 1.4 m below the zero mark of the house).

Check the correctness of the leader of the axes, their intersections, the angles should be strictly the same as on the plan of the house.

As mentioned above, the pillars should be under each crosshair of the walls.

The pillow is poured abundantly with water and rammed by hand tamping. To prevent water from leaving the poured concrete, polyethylene or roofing material is placed on the pillow.

4. Formwork installation

For the manufacture of formwork, boards of any wood species, 25 ... 40 mm thick and 120 ... 150 mm wide, are used planed on one side (the planed part is installed facing the concrete). Timber for formwork should have a moisture content of up to 25%. Wide planks for formwork, as a rule, are not suitable, since gaps appear during their installation. You can also use chipboards, metal structures, waterproof plywood.

Wooden formwork is preferable to metal formwork, as it is lighter and has less adhesion to concrete. The disadvantages of wooden formwork include the possibility of its deformation, hygroscopicity. The formwork is installed close to the walls of the pit, strictly perpendicular to the base of the foundation, checking it with a plumb line.

In some cases, if the pit walls are dry and do not collapse, concrete can be poured without formwork. At the same time, polyethylene is laid around the perimeter so that water does not leave the concrete.

Also, in the form of formwork, asbestos, ceramic, iron pipes can be used. Depending on the structure of the building, pipes with an internal diameter of 100 mm and more can be used. The concrete is poured directly into the pipes and they remain in the ground along with the foundation.

When installing wooden formwork, it must be remembered that the boards must be damp, for which they are well moistened. Otherwise (dry boards) will absorb water, which negatively affects the strength properties of concrete.

If it is possible to use ready-made panel formwork, then this is a plus. Such formworks have a large number of installation options, which is very convenient when building foundations with a large number of corners. Inventory formwork panels are rigid and flexible, their length can be from 0.5 to 3 m.

5. Fitting installation

The pillars are reinforced with longitudinal reinforcement with a diameter of 10-12 mm with a mandatory device, after 20-25 cm of clamps with a diameter of 6 mm They are installed vertically and clasped with clamps or annealed wire to prevent them from diverging to the side. It is advisable to provide an exit of the reinforcement above the top of the foundation (as shown in the figure) by 10-20 cm, so that later the reinforcement of a monolithic grillage can be welded to them.

Photo of the reinforcement of the columnar foundation.

6. Concrete supply

Here everything is the same as in strip foundations, concrete is laid in layers of 20-30 cm with vibration with manual vibrators.

Photo of concrete feeding into the post formwork.

7. Grillage device

The grillage can be made in the form of a monolithic or prefabricated reinforced concrete rand.

After the completion of the arrangement of columnar foundations, the marks of the top of the pillars are checked and, if necessary, leveled with a cement mortar of 1: 2 composition. After that, they proceed to the device of a prefabricated, prefabricated monolithic or monolithic reinforced concrete belt (grillage).

The construction of a monolithic belt will ensure proper longitudinal rigidity and stability of the foundation. Before the start of the belt device, it is necessary to securely connect the prefabricated jumpers to each other. To do this, the mounting loops are crosswise tied with a wire twist or connected by welding with a cut of reinforcement with a diameter of 8-10 mm. Then, on top of the lintels, formwork is arranged and a reinforcing cage is installed, concrete mixture M200 is laid.

Photo of the device of the pillar foundation grillage.

The concrete surface is leveled and covered with any waterproofing material to protect it from weathering. After gaining strength and waterproofing, you can proceed with the installation of floor slabs.

8. Pick-up device

When constructing columnar foundations for insulating the underground space and protecting it from debris, snow, moisture, dust, cold air, etc. a pick-up is arranged, a fencing wall between the pillars. The pick-up can be made of various materials, most often of stone or brick.

For the device of a pick-up between the supports of the columnar foundation, it is necessary to make a concrete screed, which will serve as a base for it. The concrete screed has no deepening, it is placed on a sand cushion, which has a depth of 15 to 20 cm.

The filling is laid on a concrete screed. As in the basement, technological windows are made in the trough for supplying various communications. The filling is not connected to the supports, since uneven settlement can lead to the formation of cracks.

The height of the pick-up should be at least 40 cm. The degree of moisture impact on the walls of the house depends on the height of the pick-up, the higher the pick-up, the less the effect of moisture on the walls of the house. Also, a house with a low plinth looks squat, visually it may seem that such a house has no foundation and is built right on the ground, but houses with a high plinth look much more attractive and reliable. In this case, the height of the supports must match the height of the base / plinth. For more information about the structure of the base, see the article

9. Foundation waterproofing

Foundation waterproofing can be done in one of the following ways:

• apply a layer of bitumen to the top of the supports and pick-ups. Lay a strip of roofing material on this layer and reapply a layer of bitumen, after which you lay another strip of roofing material;
• on the top of the supports and pick-ups, apply a layer of cement mortar in which the ratio of cement to sand is 1: 2. After you have leveled the mortar, sprinkle it over the top with dry cement - a layer thickness of 2 mm to 3 mm. Letting the cement "grab", lay a strip of rolled material (roofing felt or roofing felt).

How to perform such waterproofing, and what materials, you can read in the article .

Important points in the construction of a columnar foundation

• When constructing foundations on heaving soils, it is necessary to have a clear idea that the construction of a house and its commissioning should be carried out in one construction season. Foundations erected on heaving soils and left unloaded for the winter time (without walls, ceilings and roofs) can deform. This is true for all types of foundations, but it is especially important for columnar ones, since each pillar behaves like a separate foundation (due to the absence of a single rigid frame, in contrast to a strip or slab). Each pillar gives its own precipitation, which in the future (after frost - in spring) can complicate the construction of the grillage and walls.
• Unforeseen deformations can also occur in the case when the built house is not operated or heated in winter, and the depth of the foundation was calculated for the thermal regime of the heated house. A favorable time period for laying the foundation is considered the period of time when the soil "moved" from frost and groundwater descended to the lower layers. These can be summer months and early fall.
• In the event that you made the supports of the columnar foundation from monolithic concrete, then you should know that the "readiness" of the concrete is achieved after 30 days. During the entire period of "maturation", no loads should be applied to the concrete supports, and it is also worth taking care that the top layer of concrete does not dry out. To do this, you can cover it with a film or roofing felt. For even concrete setting, from time to time the supports should be moistened with water (two or three times a week, depending on weather conditions).
• For the preparation of concrete, it is best for you to use M400 cement. Fine gravel and coarse sand can be used for concrete aggregate.

  An example of calculating the components for preparing a concrete mixture:

  • cement 20 kg;
  • sand 50-55 kg;
  • gravel * (crushed stone) 80-85 kg.
  Water is added so that the concrete mix can be easily poured - but not poured!
• If the composition of the concrete mixture is too liquid or, on the contrary, too thick, then the strength of the concrete structure is reduced by 25% of the strength of the same structure, in the manufacture of which all the requirements for the proportionality of the components were met.

What mistakes can occur when laying the foundation and how to avoid them

Many developers who decide to build a house on their own often make a number of mistakes when laying the foundation, which lead to varying degrees of damage to the foundation and walls of the house. These errors can be systematized as follows:

1. An insidious defect in the foundation is the unevenness of its subsidence. This can occur for a number of reasons, which include:
   • the calculation of the depth of the foundation was not performed correctly;
   • supports have different depths.
   • The load on the foundation supports is uneven.

   To exclude such a phenomenon, it is necessary to perform an accurate calculation of the planned distribution of the load on the foundation. Do not forget to take into account the load on the foundation when adding to the second level of the house (for example, erecting an attic);

2. The material used was of poor quality - the wrong brand of cement, sand that contained an admixture of clay, etc. Or a material, such as cement, has a long shelf life (it should be recalled that when stored for six months, its brand decreases by 25%, and when stored for a year or more, by 35-50%);
3. The assessment of the bearing properties of the soil was not made correctly.

   A properly executed project by specialists and constant control of the construction by you or an independent expert will help to avoid these mistakes.

Estimated cost of a columnar foundation

Editors Note: Prices in this article are for May 2009. Be careful.

The cost of a columnar foundation is determined by the technology of laying the foundation and the depth of its laying and consists of the following components:

Foundation laying prices:

• the device of a sandy base with a thickness of 100 mm - 80-100 UAH / m2 (or 10-13 dollars. USA);
• crushed stone foundation (depending on the fraction) - 80-100 UAH / m2 (or 10-13 USD);
• device of concrete preparation (with a thickness of 10 cm); - 100-120 UAH / m3 (or 13-16 USD);
• laying of reinforced concrete cushions or blocks - 160-180 UAH / piece (or 21-24 US dollars);
• installation of monolithic reinforced concrete foundation walls - 1300-1500 UAH / m3 (or 179-198 US dollars).

Masonry prices:

• rubble foundation masonry - 300 UAH / m3 (or 40 USD);
• laying of brick pillars - 250 UAH / m3 (or 33 USD);
• walls - 600 UAH / m3 (or 80 USD).

Overlap device prices:

• installation of a monolithic reinforced concrete floor (formwork, reinforcement, concreting) - 1300-1500 UAH / m3 (or 170-198 US dollars).

The relationship between the contractor and the customer.

It will not be superfluous to remind you that if a construction organization (contractor) will be engaged in the construction of a house, then the relationship between you should be built only on a contractual basis.

The construction contract is the main document of the relationship, which stipulates the terms of cooperation, the cost of work, the timing of the start and end of construction, etc.

The estimate is an integral part of the Construction Contract. All types and costs of work and materials are written in it.

The work schedule must provide for the timing of the work and the timing of payment for the stages of work.

The contract must also provide for project documents: the architectural design of the facility, structural sections of the project and other documents required for construction.

For an overview of the types of foundations for the house, read the article.