DIY strip foundation. Monolithic strip T-shaped foundation

Strip foundation is the most common and universal type foundations for the construction of a private house. It is a continuous strip - a tape, which is constructed under all load-bearing walls, external and internal, or under supporting columns.

Along its entire length, the structure has the same cross-section and shape. More often, the cross-section of strip foundations has a rectangular shape, but to reduce pressure on weak-bearing and easily deformable soils concrete base can be cast in a trapezoidal or T-shape.

Being a solid structure, it evenly distributes the loads of the structure, therefore its varieties are successfully used for buildings of different weights and configurations, with different types soils and their freezing depths.

Application and types of strip foundations

It is most appropriate in the following cases:

• construction of buildings with recessed rooms - basement, ground floor, underground garage;
• if the house is built from heavy materials (concrete, brick, stone) with massive slab floors;
• the site has uneven soil stratification;
• the construction site has a significant slope;
• groundwater lies quite close to the surface.

Based on their location relative to the surface of the site, there is a division of strip foundations into buried and shallow. The choice of option is determined by the nature of the building loads. When constructing massive stone houses, buried foundations with high load-bearing capacity are used. The forces of frost heaving pressing on the structure from below should not exceed the force of its gravity.

Another argument in favor of using a recessed foundation is the underground premises of the house. They serve as walls. Deepening the foundation is also necessary when there are significant differences in elevation on the site. The foundation is laid at a level below the freezing depth of the soil. Typically this distance is 1.2-2 m.

A shallow foundation (laying depth is 50-70 cm) is suitable for light buildings - wooden, frame houses. It can be used for stone buildings on slightly heaving and stable soils. When installed on heaving soil under the tape, cushions are made of sand, crushed stone, slag, etc., which counteract deformations of the structure and do not freeze.

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How to independently determine the type of soil

The area of ​​the base and the depth of the foundation will depend on the properties of the base, in particular on its load-bearing capacity.

It is advisable to entrust soil investigations at the site to specialists from a specialized organization. But if a building of relatively small size is being designed, then you can rely on a soil analysis carried out independently.

To determine the properties of the soil at the site, it is necessary to dig wells about 2 m deep in the center of the site and in the corners of the proposed foundation. When digging deeper, every 0.5 m, soil samples should be taken for research.

The main task in soil analysis is to determine the concentration of clay in the layers. It is this that contributes to frost heaving of the soil. Quicksand (weak sandy-silty soils) are also undesirable in the soil composition. Soil fragments in dry and moistened form are studied. The mass is rolled into a cord or compressed into a cake to a minimum thickness.

Examining samples under a magnifying glass, we determine the type of soil visually based on its characteristic features.

1. — sand particles are visible; when dry, the sample is free-flowing. When moistened, the soil does not roll into a cylindrical strip.
2. Sandy loam - predominance of large grains of sand, interspersed with clay particles. The soil does not roll into a cord and breaks up into pieces up to 5 mm. When moistened, the soil is not plastic.
3. Silty sandy loam is a crumbly fraction with a predominance of dust, similar to a powdery mass. When wet, “dirt” is formed. It gets crushed into a cake, the cord does not form.
4. Light loam - inclusions of sand and clay are noticeable in the dusty particles. After moisturizing, stickiness occurs. The ductility is insignificant, the long cord does not roll down.
5. Silty loam - powder (dust) is visible against the background of clay and sand particles. Moistened soil is plastic and sticky, the formed cord breaks up into small pieces.
6. Heavy loam - hard lumps are visible among the sand particles that do not crush when pressed. When moistened, the cord is rolled out to a thickness of up to 2 mm. The formed ball cracks at the edges when compressed.
7. Clay soil - no grains of sand, lumps do not crush when pressed. The sample has a homogeneous structure with particles up to 0.3 mm in diameter. The moistened mass is sticky and rolls into a thin cord 1 mm thick. The rolled ball is flexible and does not crack.

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Bearing capacity of natural foundation

If we were able to determine the type of soil at the construction site, we determine the resistance value of the foundation to the loads from the structure. The list indicates the maximum permissible weight (mass) of load per 1 cm² of base.

Values ​​for sandy soils take into account the degree of its density:

• coarse sand - 3.5 kg/cm² (medium density) and 4.5 kg/cm² (high density);
• medium sand - 2.5 and 3.5, respectively;
• fine sand with low moisture content - 2.0 and 3.0;
• fine wet sand - 2.0 and 2.5;
• low-moisture silty sand - 2.5 and 3.0;
• silty wet sand - 1.0 and 1.0.

The resistance of silty clay soils to loads depends on their porosity (looseness, density) and fluidity (stickiness, plasticity):

• dense sandy loam - 3 kg/cm² (non-plastic) and 3.5 kg/cm² (plastic);
• dense loams - 2.5 and 3, respectively;
• porous sandy loam - 2.0 and 2.5;
• porous loams - 1.0 and 2.0;
• medium density clay - 2.5 and 3.0;
• dense clay - 4.0 and 6.0;
• porous clay - 1.0 and 2.5.

Resistance values ​​for gravel, crushed stone, pebbles, and coarse soils are practically independent of other factors and are applicable for loads up to 5-6 kg/cm². These indicators are necessary to determine the permissible pressure of the base of the strip foundation on the foundation soil.

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We determine the load of the building on the foundation

When determining this parameter, the total mass is taken into account:

• building structures - walls, ceilings, roofing elements, finishing and insulating materials;
• operational loads - communications, indoor objects, etc.;
• the weight of the strip foundation itself;
• weight of possible snow cover.

To determine the weight of a building, the area and then the volume of all of it are calculated separately. structural elements. Specific gravity building materials can be found in the tables for estimators, which are publicly available. Knowing this value and the dimensions of the main structural elements of the building, the approximate weight of the house can be calculated by simple arithmetic operations. Operating loads (furniture, equipment) are taken with a margin at the rate of 150-200 kg/m².

Since the parameters of the strip foundation are only being determined, the average value of its weight is taken. The width of a strip foundation should not be less than 30 cm. The height of the structure depends on the depth of the foundation. To deepen the foundation, at a depth of soil freezing of up to 1 m - at least 0.5 m; up to 1.5 m - 0.75 m; up to 2.5 m - from 1 m, respectively.

The snow load is determined by multiplying the roof area by the thickness and density of the snow cover characteristic of the region. For middle zone In Russia, the value is about 100 kg/m², for the northern regions - 190 kg/m², for the southern regions - 50 kg/m².

We sum up all the loads and calculate the required area of ​​the foundation base. In this case, the resulting load of all components of the building should not exceed the calculated resistance of the soil foundation. If the resistance of the soil area under the base of the foundation is not enough for the design load, the area of ​​the base must be increased. When the foundation mass increases, its component in the total load should be recalculated.

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Preparatory work and marking the foundation

The area is cleared of vegetation. The site must be 5-7 m larger than the building outline on each side for the equipment to operate. The fertile layer of soil in the working area is removed. Produced vertical layout. Sites on slopes are equipped with drainage.

The necessary tools are prepared:

• portable or electric concrete mixer (70-90 l);
• welding machine;
• shovels, containers for concrete mortar and water;
• electric rammer, concrete vibrator, rule;
• cutting machine;
• sledgehammer weighing up to 5 kg;
• pliers, crowbar, hammer;
• theodolite or level, marking cord;
• protractor, level, ruler, tape measure;
• wooden wedges of various sizes;
• metal pins (ø1-2 cm).

Marking is carried out along the axes load-bearing walls and in both directions from the axis they recede along half the design width of the foundation. With the planned installation of formwork to the full depth and installation of waterproofing, the width of the trench is increased. If the soil does not crumble when digging a trench and the walls can be used as formwork, markings are made along the inside or outside of the building.

It is difficult to transfer the house plan to the site while maintaining the rectangularity of the contours. The perpendicularity of the axes can be set by constructing an “Egyptian triangle”. If measured from the angle along the 3 and 4 m axes, the distance between the resulting points (hypotenuse) should be 5 m at an angle of 90˚. If the size does not match, the axes are adjusted. Additional control is carried out by comparing the diagonals of the rectangles of the strip foundation contour. If possible, a laser builder is used.

The resulting contours are marked by pulling cords (fishing line) between guide pegs. The markings are placed no closer than 1.5 m from the design edge of the trench. Then, using a level, the depth of the trenches is determined at various points on the tape. Marking the height can be done with a water level, making mutually horizontal marks on the stakes, pulling the cords in one plane and modeling the surface of the foundation. In this case, the depth of the trench is measured with a tape measure from a stretched cord. Before digging a trench, its outline is filled with a strip of sand or lined with grooves.

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Excavation work, installation of formwork and reinforcement

For shallow strip foundations, it is preferable to excavate soil from the trench manually. In this case, the bedding of the natural soil is not disturbed. can be poured directly into the trench without installing formwork. If you plan to build a basement, you will have to prepare a solid foundation pit, and it will be difficult to do without using an excavator.

When constructing strip foundations on soils with a stable bearing capacity that do not require their replacement, they are filled with crushed stone or sand. The layer is made small in height (about 10 cm) and performs only a leveling function. In any case, the pillow made of dry materials must be thoroughly moistened and compacted. To prevent water from escaping from the concrete, the sand cushion is covered on top with polyethylene or roofing felt and folded onto the walls of the formwork.

Formwork can be made from any material that meets the requirements of concrete pouring technology and does not have a chemical effect on it. Used steel, wood, aluminum, plastic, moisture resistant plywood etc. Wood formwork is assembled using nails. To improve the tightness, the prefabricated wooden formwork is covered with polyethylene.

During the installation of formwork, after installing the panels, a reinforcing frame is installed on one side. The diameter of the reinforcement for strip foundations of light (up to 50 tons) houses is taken to be 8-10 mm. For massive buildings, rods ø12-16 mm are used. The heavier the structure of the building, the greater the thickness of the frame elements used. Without welding, the frame can be assembled with a rod diameter of up to 40 mm. For installation, knitting wire is used with a connection at three overlap points of the reinforcement, crimp sleeves or special couplings.

There is no need to say too much about the fact that any structure that is large in size and heavy in weight requires a reliable foundation underneath. After all, a house, terrace, bathhouse or garage should not fall through the ground, which cannot be avoided without a reliable foundation, since the earth and all its constituent soil rocks are loose and unstable under the pressure of large weights, which are characteristic of absolutely all permanent buildings. The best option Of all the possible foundations, a strip foundation is considered.

There are several terms used by professional builders to name the parts of a foundation, such as the lowest part of the foundation, called the footing, and the top area that is visible above the ground, called the edge or foundation surface. The size of the foundation and the difference between the dimensions of the base and the surface, which in some cases may be equal, depend on how heavy the weight of the load exerted on the soil is. This applies, for example, to low-rise private construction. But the sole and edge of the base of a high-rise building should be different.

You can handle its organization yourself and without the involvement of heavy automatic equipment. Acquiring a sufficient amount of knowledge on this topic, building materials and tools will allow you to quickly and efficiently create a strip foundation for a house, garage, bathhouse and others country houses. The base on the tape provides for the installation of a strip of reinforced concrete along the perimeter of the future house, located at a depth that will be sufficient for the object under construction to rest on the foundation for a long time and reliably. In accordance with current construction standards, this tape is laid not only under external walls, but also under those partition walls that will be located according to the design inside the building. Since subsequently the owners of the house may want to add another, or maybe two, floors. In this case, these walls will not become ordinary partitions, but load-bearing walls.

Strip foundation, its types and technology for their creation

Reinforcement of the corners of the strip foundation: a) – reinforcement of the T-shaped connection; b) – reinforcement of the L-shaped connection.

The technology of laying the foundation tape allows us to distinguish several types of this foundation. These include:

• monolithic;
• made.

The first option will need to be laid directly on the site where the house will be installed or laid out. To do this, a trench is dug into which a reinforcing mesh is installed, which is necessary to give the foundation greater strength. The grid can be replaced with steel wire, the diameter of which in cross-section can be equal to 3-4 mm, but when laying the foundation for a house of several floors, it is better to insure yourself and further strengthen the base by hammering metal crowbars around the perimeter of the foundation, which reach 8-15 mm in cross-section. Concrete solution is poured into trenches reinforced with formwork.

As for prefabricated foundations, they, on the contrary, are built using concrete blocks, in turn brought from a construction base or factory. They are delivered to the construction site and assembled using heavy machines, among which the main one will be a crane, since the slabs are heavy in weight and large in size. To make the foundation look more durable and stable, it can be laid in several stages. Blocks with larger areas are placed down, and on them are those that correspond to the width of the future walls of the house. These layers must be tied together with reinforcing wire, and then all joints are carefully poured with concrete mortar. Such a foundation will be homogeneous in cross-section.

Less popular is the prefabricated type of strip foundation, which is laid out of brick. Red brick is used for it, since, unlike silicate brick, it removes moisture much faster, which means the strength qualities of the brick strip increase. This type of foundation is quite easy to install, as it is completely reminiscent of the process of laying ordinary brick walls.

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Determining the foundation depth of a house

Strip foundation - structure and dimensions.

It is worth thinking especially carefully about such a characteristic as the depth of the foundation, since the durability of the house under construction will depend on it. The foundation of a shallow recess will be suitable for lung device house, for example frame using Canadian technologies, from wooden material, for bathhouses and garages, verandas. In some cases, it is allowed to install shallow tapes under stone houses on one floor. The maximum depth of this type of foundation is 50 cm. In any case, in order for the foundation to stand for as long as possible without problems, it must be reinforced with wire with a cross-section of up to 5 mm.

When the dimensions of a building under construction do not allow the use of a shallow foundation and at the same time the groundwater level in the area under the house is high, it is recommended to build the building on a deep foundation. It will be possible to more accurately determine the starting point only after a study of the soil and the level at which groundwater is located. It should be remembered that excavation work will need to be carried out at a level lower than the existing result by 20 - 25 cm.

Having selected a specific foundation depth on the tape, you can begin the work process. However, experts recommend laying the foundation in warm seasons, when at least there is no frost. Otherwise, some of the initial quality characteristics of the building material will disappear, thereby reducing the level of strength of the foundation of the house and its service life.

The list of popular building materials for strip foundations consists of 4 points:

• reinforced concrete;
• reinforced concrete blocks or slabs;
• red or sand-lime brick.

You will need to choose the appropriate material option based on how many years you plan to build the foundation, what strength you have (this assumes the presence of heavy equipment) and what your financial situation is.

One of the effective types of foundations suitable for any building is T-shaped strip foundation cost. This base is rigid because it has a T-shaped profile. If there is no water in the nearby soil layers, the T-strip foundation does not need to be deepened too much. If the structure is massive, for example, stone house, then the T-shaped strip foundation must be deepened to the extent of soil freezing. Our company has extensive experience in constructing such foundations throughout the Leningrad region, and quality control of work at each stage allows us to guarantee the quality and exact timing of construction. To calculate the cost of the foundation, you can call us and get advice from an engineer on all issues of interest.

Price for a T-shaped strip foundation, prices in rubles

tape, m*m	width height 300mm/600mm	width height 300mm/900mm	width height 300mm/1200mm	width height 400mm/1500mm	width height 400mm/1800mm
6x6	67,000 rub.	91,000 rub.	120,000 rub.	RUB 195,000	RUR 224,000
6x8	74,000 rub.	108,000 rub.	RUB 141,000	RUR 247,000	RUR 275,000
8x8	80,000 rub.	RUB 119,000	RUB 161,000	270,000 rub.	330,000 rub.
8x10	90,000 rub.	RUB 127,000	RUB 171,000	RUB 293,000	RUB 371,000
10x10	100,000 rub.	RUB 143,000	200,000 rub.	RUR 322,000	RUB 390,000
10x12	RUB 121,000	RUB 195,000	270,000 rub.	RUB 375,000	450,000 rub.
12x12	RUB 133,000	RUB 181,000	RUR 303,000	408,000 rub.	RUB 507,000
*Provided that the site has electricity, water and living conditions for the crew. Included in the price: Layout and marking of the area for the foundation Excavation work, foundation pit, trenches Installation of a sand cushion under the foundation Installation of formwork from boards Knitting reinforcement Pouring concrete The cost of the foundation includes materials with delivery to your facility (within a radius of the city) We also carry out additional work on the device drainage systems, waterproofing and insulating the foundation, making wells for water supply, installing septic tanks and treatment plants. **You can find out a more accurate cost of a turnkey strip foundation by calling us.

T-shaped strip foundation

A T-shaped strip foundation is laid almost similarly to a regular strip. The only peculiarity is the construction of a kind of formwork so that the concrete mixture does not leak out. It is important to achieve a perfectly even angle between the main foundation and the plane of the superstructure. The foundation structure is strengthened with reinforcement.
T-strip foundations can be constructed for houses, fences, and sheds. The main advantage is the opportunity to save on materials, because the thickness of the above-ground part is less.
To avoid mistakes, it is better to entrust the T-shaped strip foundation to qualified builders. In our company you can find qualified assistance from a team of builders and the necessary high-quality foundation materials.

There is a lot of unknown here; you need to work with the project and soil data. Based on the data presented, the following comments:
1. You should not make walls from solid bricks. He is very heavy. It doesn't make the slightest sense. Everything you save on bricks will be lost on the foundation.

I'm not saving on bricks, I just need a strong, reliable and cold (with high thermal conductivity) wall. My option is much more expensive than foam concrete and ceramics consisting of 70% air. I go for this based on my own considerations. Because I don’t accept aerated concrete in principle. But I have an extremely negative attitude towards warm ceramics. It is acceptable among the locals, but our production is a different story.
If possible, tell me where exactly?
The designers were given the task of designing a foundation that would contain working longitudinal and transverse reinforcement. That is, such a foundation must not only bear the load from the structure, it must absorb uneven multidirectional soil forces.

3. In the “smart guy” version, the cross-sectional height of the tape for mzlf is small. The tape is not T-shaped, but a regular rectangular one, with foundation pads. You won't do this in one go. You'll have to make the pillows first and then the ribbons. Accordingly, there are questions regarding joint work. It will not be 100% like a monolith.

And in the first option, you can’t fill it all at once.

This task was not set. This is my idea of ​​insulation, borrowed from the documentation of the manufacturer EPS Penoplex.
The filling of the trench sinuses will be sand. Will a brick not survive in sand?
What is an option to lay foam blocks in the ground and then continue with bricks?

Geomorphologically, the site is located within the slope of the watershed facing the stream. Danube. The relief is undisturbed, moderately flat, with a general slope towards the east (i=0.05). The absolute surface elevation is 237.3 m.
Modern physical and geological processes unfavorable for construction are not observed on the site.
3. B geological structure Quaternary deluvial sediments (dQ) take part in the study area to a depth of 8.0 m. From the surface, these deposits are covered by a modern soil-vegetation layer (pdQIV) (Appendix 7).
Deluvial deposits are represented by clays. The clay is brown, micaceous, with rare inclusions of carbonates (IGE-2). The exposed thickness of deluvial deposits is 7.5 m.
Soil-vegetative layer of clay composition (IGE-1). Soil thickness 0.5 m.
4. Groundwater was not opened during the period of work (July 2011) to a depth of 8.0 m. According to potential floodability, the territory is classified as non-floodable (Appendix “I” SP 11-105-97, part II).
5. At the base of the designed building lie clay soils. Up to an explored depth of 8.0 m, 2 geotechnical elements (EGE) were identified.

IGE-1. The soil-vegetative layer has a clayey composition; according to the relative deformation of frost heaving during freezing, the soil is highly heaving. The soil density is recommended to be 1.5 t/m3. The soil thickness is 0.5 m.
IGE-2. The clay is deluvial, highly plastic (flow rate 0.35 units). According to laboratory data, clay does not have subsidence properties. The relative subsidence at a load of 0.3 MPa varies from 0.000 to 0.001 dollars. units (Appendix 3). Clay does not have swelling properties (Table B. 1 of Appendix B SP 11-105-97 (Part III). To obtain standard and design characteristics, archival materials were used. When calculating the deformation modulus, the transition coefficient from the compression deformation modulus to the field modulus was used, equal to 3.7 (arch. No. 3777). The deformation modulus is 14 MPa. According to the relative deformation of frost heaving during freezing, the clay is highly heaving. Rf 102 = 1.16 (clause 6.8.3. SP 50-101-2004). Revealed thickness 7.5 m.

Appendix 2 provides data from laboratory determinations, which took into account survey data from previous years, grouped by element. All characteristics necessary for calculations are given in Table 1 of the text of this conclusion.
6. According to table. 4 SNiP 2.03.11-85, the soils on the site are non-aggressive in relation to concrete of all grades in terms of water resistance (Appendix 4).
7. The corrosive aggressiveness of soil in relation to steel, determined in laboratory conditions, is assessed as average, according to table. 1 GOST 9.602-89 (Appendix 4).
8. Appendix 5 provides an assessment of the biocorrosive aggressiveness of soils to metal structures, in accordance with Appendix “B” GOST 9.602-2005. The criteria for biocorrosive aggressiveness of soil are the presence of visual signs of gleying of the soil and the presence of reduced sulfur compounds in the soil. IGE-2 soils are non-aggressive.
9. The standard freezing depth for clay soils is 1.5 m.

This is the first floor plan. Height - 3.00 m. The second floor has a similar plan to the first, only without partitions. Interfloor reinforced concrete slabs. They rest on the axes AB, BV, VG.
The height difference on the second floor is 1.7 m (axis 2.3). 4.2m (axis 2). The roof is gable. 27 degrees

A shallow strip foundation (hereinafter referred to as MZLF) is one of the types of strip foundations, which is characterized by a small depth, significantly less than the depth of soil freezing, and a relatively low consumption concrete mixture. This article discusses the main advantages and disadvantages of MZLF, the most common mistakes in their construction, a simplified calculation method suitable for private developers (not professionals), and recommendations for constructing a foundation with your own hands.

The main advantages of MZLF are:

- economical - concrete consumption is significantly lower than during the construction of a conventional strip foundation. It is this factor that most often determines the choice of this technology when low-rise construction;

- reduced labor costs - less excavation work, less volume of prepared concrete (this is especially important when it is not possible to pour the finished mixture from a mixer);

- smaller tangential forces of frost heaving due to the reduced area of ​​the lateral surface of the foundation.

However, during the construction of the MZLF, it is necessary to strictly adhere to the technology; a frivolous attitude to the process can lead to the appearance of cracks, and then all of the above advantages, as they say, will go down the drain.

The most common mistakes made when installing MZLF:

1) selection of the main working dimensions of the foundation without any (even the most simplified) calculation at all;

2) pouring the foundation directly into the ground without covering it with non-heaving material (sand). According to Fig. 1 (on the right) we can say that in winter time years, the soil will freeze to the concrete and, rising, drag the tape upward, i.e. the tangential forces of frost heaving will act on the foundation. This is especially dangerous if the MZLF is not insulated and a high-quality blind area is not equipped;

3) improper reinforcement of the foundation - choosing the diameter of the reinforcement and the number of rods at your discretion;

4) Leaving the MZLF unloaded for the winter - it is recommended to carry out the entire cycle of work (construction of the foundation, erection of walls, and arrangement of the blind area) one construction season before the onset of severe frosts.

Calculation of a shallow strip foundation.

The calculation of the MZLF, like any other foundation, is based, firstly, on the value of the load from the weight of the house itself and, secondly, on the calculated soil resistance. Those. the soil must withstand the weight of the house transmitted to it through the foundation. Please note that it is the soil that supports the weight of the house, and not the foundation, as some believe.

If an ordinary private developer can calculate the weight of a house if desired (for example, using our online calculator located), then it is not possible to determine the calculated soil resistance on your site on your own. This characteristic calculated by specialized organizations in specialized laboratories after conducting geological and geodetic surveys. Everyone knows that this procedure is not free. Mostly, architects who design a house resort to it, and then, based on the data received, they calculate the foundation.

In this regard, it makes no sense to provide formulas for calculating the size of the MZLF within the framework of this article. We will consider the case when a developer carries out construction on his own, when he does not conduct geological and geodetic surveys and cannot accurately know the calculated soil resistance on his site. In such a situation, the dimensions and design of the MZLF can be selected according to the tables below.

The characteristics of the foundation are determined depending on the material of the walls and ceilings of the house and its number of storeys, as well as on the degree of heaving of the soil. How you can determine the latter is described

I. MZLF on medium and highly heaving soils.

Table 1: Heated buildings with walls made of lightweight brickwork or from aerated concrete (foam concrete) and with reinforced concrete floors.

Notes:

— the number in brackets indicates the pillow material: 1 — medium-sized sand, 2 — coarse sand, 3 — a mixture of sand (40%) with crushed stone (60%);

— this table can also be used for houses with wooden floors, the safety margin will be even greater;

— see below for foundation design options and reinforcement options.

Table 2: Heated buildings with insulated walls wood panels (frame houses), logs and beams with wooden floors.

Notes:

— the numbers in brackets mean the same as in Table 1;

- above the line value for walls made of insulated wooden panels, below the line - for log and timber walls.

Table 3: Non-buried foundations of unheated log and timber buildings with wooden floors.

Notes:

- above the line values ​​for log walls, below the line - for walls made of timber.

Design options for MZLF on medium- and highly heaving soils, indicated in the tables by letters, are shown in the figures below:

1 — monolithic reinforced concrete foundation; 2 — sand filling of sinuses; 3 — sand (sand-crushed stone) pillow; 4 — reinforcement frame; 5 - blind area; 6 7 — waterproofing; 8 - base; 9 — ground surface; 10 - sand bedding; 11 - turf.

Option a.— the upper plane of the foundation coincides with the surface of the earth, the base is made of brick.

Option b.- the foundation protrudes above the surface by 20-30 cm, forming a low base or being part of the base.

Option c.- the foundation rises 50-70 cm above the ground, while it also serves as a base.

Option d.- non-buried foundation-basement; Table 3 shows that such foundations are used for unheated wooden buildings.

Option d.- used instead of options b. or V. when the width of the base of the foundation significantly exceeds the thickness of the wall (more than 15-20 cm).

Option e.— a shallow strip foundation on a sand backfill is used quite rarely on weak (peaty, silted) soils with a high groundwater level for wooden buildings. Depending on the size of the building, bedding is done either under each strip or under the entire foundation at once.

Reinforcement of a shallow strip foundation.

MZLF reinforcement is made with meshes of working reinforcement and auxiliary reinforcing wire. The working reinforcement is located in the lower and upper parts of the foundation, and it must be immersed in the thickness of the concrete by about 5 cm. The lower mesh works to deflect the foundation tape downward, and the upper mesh works to deflect the tape upward. There is no point in placing the working reinforcement in the middle of the tape (as can sometimes be seen on the Internet).

Table 4: Options for foundation reinforcement.

MZFL reinforcement schemes are shown in the following figure:

A.— a mesh with two working reinforcement rods; b.— a mesh with three working reinforcement rods; V.— T-shaped joint; G.— L-shaped corner joint; d.— additional MZLF reinforcement with a large sole width, when the sole is more than 60 cm wider than the base (the additional mesh is located only in the lower part.

1 — working fittings (A-III); 2 — auxiliary reinforcing wire ∅ 4-5 ​​mm (Вр-I); 3 — vertical reinforcement rods ∅ 10 mm (A-III), connecting the upper and lower mesh; 4 — reinforcement for strengthening the corner ∅ 10 mm (A-III); 5 — connection with wire strands (twisting length is at least 30 diameters of the working reinforcement); 6 — additional working fittings ∅ 10 mm (A-III).

II. MZLF on non-heaving and slightly heaving soils.

Shallow strip foundations on non-heaving and slightly heaving soils do not have to be made only from monolithic concrete. Other local materials can be used, e.g. rubble stone, red ceramic brick. MZLF is laid at 0.3-0.4 meters without a sand cushion. Moreover, for wooden buildings and one-story brick (or aerated concrete) foundations, they don’t even need to be reinforced.

For 2- and 3-story houses with walls made of stone materials, MZLF is reinforced. Concrete foundations are reinforced according to the 1st reinforcement option (see Table 4 above). Foundations made of rubble or brick are reinforced with masonry mesh made from BP-I reinforcement ∅ 4-5 ​​mm with a cell size of 100x100 mm. The nets are placed every 15-20 cm.

MZLF structures on non-heaving and slightly heaving soils are shown in the figure below:

1 - foundation; 2 - base; 3 - blind area; 4 — waterproofing; 5 — subfloor (shown conditionally); 6 - mesh made of wire reinforcement, 7 — reinforcement according to option 1 (see table 4)

Options a. and b.- for wooden and one-story brick (aerated concrete) buildings.

Options c. and Mr.— for two- and three-story brick (aerated concrete) buildings.

The width of the sole b is determined depending on the number of storeys of the building and the material of the walls and ceilings.

Table 5: Values ​​of the width of the sole of the MZLF on non-heaving and slightly heaving soils.

Stages of construction of a shallow strip foundation and recommendations.

1) Before starting construction of the foundation, if necessary, it is necessary to ensure high-quality drainage of surface rainwater from neighboring areas from the building site. This is done by cutting out drainage ditches.

2) The foundation is marked and trenches are torn out. It is recommended to begin excavation work only after all materials have been delivered to the construction site. necessary materials. It is advisable to organize the process of cutting out the trench, filling the tape, backfilling the sinuses and constructing the blind area as a continuous process. The less it is extended in time, the better.

3) The dug trenches are covered with geotextiles. This is done so that the sand cushion and sand filling of the sinuses do not become silted over time by the surrounding soil. At the same time, geotextiles allow water to pass through freely and do not allow plant roots to grow.

4) A sand (sand-crushed stone) cushion is poured layer by layer (in layers of 10-15 cm) with careful compaction. They use either manual rammers or area vibrators. Tamping should not be taken lightly. Shallow foundations are not as powerful as foundations poured to the full depth of freezing, and therefore freezing here is fraught with the appearance of cracks.

5) The formwork is laid out and the reinforcement frame is knitted. Do not forget to immediately provide water and sewerage to the house. If the foundation is also a plinth, remember about the vents (does not apply to buildings with floors on the ground).

6) Concrete is poured. Filling of the entire tape must be done continuously, as they say, in one go.

7) After the concrete has set (3-5 days in summer), the formwork is removed and made vertical.

8) The sinuses are backfilled with coarse sand with layer-by-layer compaction.

9) A blind area is being constructed. It is advisable (especially with a small height of the foundation tape) to make the blind area insulated. This measure will further reduce the forces of frost heaving affecting the MZLF in winter. Insulation is made with extruded polystyrene foam.

As already mentioned at the beginning of the article, it is not allowed to leave the MZLF unloaded or underloaded (the building is not fully built) for the winter. If this happens, the foundation itself and the soil around it must be covered with any heat-saving material. You can use sawdust, slag, expanded clay, straw, etc. There is also no need to clear the snow on the construction site.

It is highly not recommended to build a shallow strip foundation in frozen soil in the winter.

In the comments to this article, you can discuss with readers your experience in the construction and operation of MZLF or ask questions that interest you.