Shallow strip foundation. Design and pouring of a shallow strip foundation Pour a T-shaped foundation

Construction of a house begins with the foundation. Building materials for its construction are often selected taking into account regional availability. In some areas, the cost of a strip foundation is comparable to a reliable foundation structure built from granite. Such a foundation firmly holds a house of any size, even built on black soil and other unstable soil. Taking into account modern construction requirements, the main purpose of the review is to talk about innovative approaches and how to make a strip foundation guaranteed to be reliable.

If there is no possibility of constructing an “airbag” for a house made of high-strength material, craftsmen recommend that novice builders use ready-made foundation blocks. This construction option will help to avoid a number of mistakes, which for a number of reasons are not taken into account in cases where the strip foundation is built with your own hands.

Classic mistakes when building strip foundations

The strip foundation remains the most affordable option for constructing the foundation of a house with your own hands and is recommended for the construction of light houses. Meanwhile, the strength of the foundation depends not only on the conditions of its construction, but also on the territorial features of the area. Let's look at the main mistakes when constructing strip foundations, as well as how to avoid them.

Geological and hydrological works

Before starting work, it is recommended to obtain geological and hydrological survey data, which, when developing a project, will allow making calculations based on the location. Most standard projects, as expected, were made without taking into account the characteristics of the soil, so in some regions one can observe abnormal behavior of the foundation.

Strip foundations installed on black soil are not considered a solid foundation for any residential building. Typically, areas of black soil under the foundation are selected, covered in layers with sand, carefully compacted using water and covered with a bed of crushed granite stone.

Features of Extreme Design

When building a house yourself, you can conduct a soil analysis on your own. To do this, you need to drill the area in 2-3 places and check the depth of the fertile layer, water, clay and sand. It will be useful to ask your neighbors about the features of foundations that have stood for several decades:

to what depth the foundations were buried;
types and materials used for the device;
about the presence of a drainage system near the house;
about cases of soil sliding on slopes.

Errors during work and installation

Construction of foundations in autumn-winter

Foundations are not installed on waterlogged and frozen soil, or on snow. The construction of a concrete foundation in winter is undesirable or must be carried out using strict technology using construction equipment. When concrete is laid in a trench on snow, voids filled with water are formed.

Heaving soils and their features

A standard error is the lack of soil when digging a trench under the foundation to the design level. According to SNiP, in heaving soils it is allowed to deepen the base of the foundation below the calculated freezing depth.

On heaving soils, pile and strip-buried (strip-pile type) foundations are not installed. The piles hold the foundation in place, and heaving forces push it to the surface, as a result of which the concrete strip is very likely to crack or the pile to break off.

Reducing the likelihood of soil heaving on any soil

To prevent heaving, drainage is laid under the base of the foundation, clay is selected and the foundation pit is filled with sand and crushed stone, eliminating the source of heaving. On such soils, the blind area must be insulated, which prevents the foundation from freezing and eliminates the possibility of heaving.

Pasting and thermal insulation of the outer side allows you to shift the dew point beyond the boundaries of the foundation, which eliminates the influence of tangential heaving forces.

Foundation protection includes:

gluing waterproofing film;
installation of XPS polystyrene foam (high density);
cover with 2 layers of dense polyethylene;
Additionally, sheets of polystyrene PSB 25 are pressed to the foundation by backfilling with soil.

Principle: soil heaving forces crush PSB 25, which moves up the polyethylene without damaging the main thermal insulation. After thawing, the structure restores its sandwich structure.

Do-it-yourself strip foundation photo: step-by-step instructions

Basic strip foundation structures: their appearance and design diagrams

Depending on the characteristics of the soil and the type of construction, choose the design of the future concrete foundation of the house. When building houses on black soil, buried and deep-buried modifications are used. When building on black soil, the depth of the foundation depends on the thickness of the black soil layer. In some cases it reaches 2 m.

Trench and sub-concrete waterproofing

Communications

Simultaneously with the removal of soil for the foundation, the preparation of communications that must be connected to the house is carried out. At this stage, special attention should be paid to the house sewer pit and the waste drainage device. If water will be supplied from a well, it is necessary to make simultaneous preparation of communications, since the laying of water supply pipes is carried out at a depth of 1.5-2 m.

After removing the soil to the design level, sand is poured in layers of 10 cm with water. In some cases, the cushion can reach 40-80 cm; with high groundwater or a desire to make a safety cushion at low cost, the thickness of the backfill is 40-80 cm, of which up to 2/3 of the height can be crushed stone.

Next, formwork is laid 10 cm deep; it should be twice as wide as the base of the tape and filled with “lean” concrete (B7.5 mixture). After the mixture reaches 70 strength, a waterproofing membrane or polyethylene 0.15 mm thick is laid with a margin of 20-30 cm from the edge of the tape - drains.

A reinforcing belt made of reinforcing wire 10-12 mm (on moving soils up to 16 mm, grade A400) is laid on top and bottom of the trench, fastening it with a spatial wire frame (grade A240, 6-8 mm). Laying is done on plastic spacers 2-4 cm wide. The upper level of the frame should be located close to the surface, no deeper than 5 cm, under the fastening layer of concrete.

The reinforcement is usually overlapped with a size of 50 diameters of reinforcing wire according to the new SNiP requirements (with 12 mm wire the overlap is 60 cm, previously the requirements assumed an overlap of 20-30 cm). At the corners, the reinforcement cannot be installed end-to-end; in the corners, L-shaped and U-shaped shapes are used and fastened according to the scheme shown in the photo.

install sleeves in the reinforcing belt to enter communications into the cottage or carry out simultaneous installation of pipes;
40 cm from the blind area in the formwork of houses with beamed floors, it is necessary to provide for the installation of void formers to ensure ventilation of the subfloor, prevent corrosion, rotting and ensure the removal of harmful radon. The dimensions of the ventilation openings should be a total of 1/400 from the basement of the house.

To fill the foundation, use ready-made or home-made formwork. Shields can be made of OSB boards, plywood or boards. The shields are secured using internal ties, as shown in the photo. Ready-made formwork allows you to concrete structures with complex shapes.

Pouring the foundation

It is advisable to use ready-mixed concrete for foundations. In this case, it is possible to carry out winter work, since for these purposes a special brand of solution is used that hardens in the cold. The brand is selected depending on the type of structure:

M100 – for wooden houses and outbuildings;
M150 – for buildings made of foam concrete;
M200 – for one- and two-story cottages with light floors;
M250 and M300 - for buildings up to 5 floors, as well as for monolithic floors;
M400 – for multi-storey buildings (up to 20 floors).

It is not recommended to fill a layer of no more than 60 cm at a time. Deep foundations are poured in several stages, with a break between them of no more than 2 hours. Concrete can be poured after 12 hours, but the surface film must be cleaned off with brushes or removed with water pressure. Concrete must be placed in the trench with a vibratory compactor. Loose concrete does not gain the declared brand strength.

The formwork is removed no earlier than after 3 days. During this period, the upper part of the tape is moistened with sawdust or rags moistened with water, which will provide the required level of strength and also avoid the formation of craters and cracks.

When laying a concrete foundation, it is not advisable to neglect vertical waterproofing (of the base walls), this will help protect it from damage and ensure long-term operation. This is especially important for those areas that are characterized by winter thaws, during which the foundation is moistened and goes through several freezing cycles.

Do not neglect horizontal insulation, the absence of which can lead to the appearance of fungus on the walls and increased humidity, since moisture from a moistened foundation will be absorbed into the walls of the first floor.

DIY strip foundation video

How to make a strip foundation with your own hands video: monolithic slab

In conclusion, we present one of the modern solutions. As you know, one of the types of strip foundation is a monolithic slab. The technology for constructing a monolithic insulated Swedish slab (USP) is an innovative development that is becoming increasingly popular. And it can also be made with your own hands.

The base of the house is a reliable sandwich structure, which provides the necessary strength to the base of the house and its insulation. This technological solution is used for the construction of passive houses, in which the internal heat of the building is retained to reduce energy costs. Above we showed how to make a foundation with your own hands, video, now we offer technology for constructing USP.

The construction issue is covered in detail in the video.

A shallow strip foundation (hereinafter referred to as MZLF) is one of the types of strip foundations, which is characterized by a shallow depth, significantly less than the depth of soil freezing, and a relatively small consumption of 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 in 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 the winter season 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 is 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 aerated concrete (foam concrete) and 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 walls made of insulated wooden panels (frame houses), logs and timber 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. You can also use other local materials, for example, 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 necessary materials have been delivered to the construction site. 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.

Before, how to make a strip foundation with your own hands for a home, it is necessary to determine the operating conditions. Then it is enough to choose the type, design, dig trenches, pour concrete into the formwork or perform brickwork. At the last stage, the structure partially immersed in the ground should be protected from heaving forces, soil moisture, and groundwater.

Selecting the type of strip foundation

The main task of an individual developer is rational planning of the construction budget. Due to the variety of LF strip foundations, the principle from cheap to more expensive option is usually used. At the same time, a service life of 70–100 years, maintainability, and ease of use must be ensured. Thus, it is enough to consider all existing LFs and choose the option that suits you:

monolithic belt - the width of the belt is greater than the height, there is no depth, suitable exclusively for log houses, outbuildings, half-timbered buildings, frame cottages on stable soils with low groundwater level
non-buried LF - allows you to build a panel, frame, panel, log house on sandy loam, loam only on flat areas, the height of the tape is greater than the width, floors on the ground can be used
shallow-depth MZLF tape - the volume of excavation work increases, there are no restrictions on wall and roofing materials (suitable for brick walls), trenches have a depth of 0.3 - 1 m depending on the soil
T-shaped strip foundation - the strip is widened in the lower part by a slab, but the structure still cannot be built on slopes, swamps, or at a high groundwater level
buried LF - there are no restrictions, this is the only option for a project with an underground floor; with a high groundwater level, a set of measures will be required to collect and drain soil moisture

The load-bearing capacity of almost all strip foundations has a 2-3 fold reserve with a strip width of 40 cm or more. The problem usually lies in heaving forces or is hidden in the soils themselves. On fresh embankments (former landfills, technogenic zones), the tape will have to be widened (T-shaped modification of the LF) or the bulk layers will have to pass through (MZLF 1 m deep or a deep belt 2 - 2.5 m).

If, according to the results of geological surveys, the structure needs to be buried below 3 m, it is worth reconsidering the choice in favor of a floating slab or a pile foundation with a monolithic hanging grillage of lattice or slab type. Since the budget will be approximately the same, labor costs are 50–70% higher.

Design selection

Depending on the prices of building materials and the skills of the individual developer, the strip foundation can be poured into formwork or laid out of brick. In the first case, it is advisable to lay the concrete mixture in one step.

For a deep-laying belt, this is not easy to do, even when ordering several mixers, since filling the formwork is tedious in 60 cm layers and compacting each layer with a deep vibrator. For MZLF such problems usually do not arise; the volumes here are 4–5 times smaller.

In the second option, you can do without special equipment; the strength of the masonry does not depend on the timing of its production. The solution can be mixed into the building spot yourself.

Brick LF is more resistant to swelling of individual areas:

the structure consists of small-format beams
each has two degrees of freedom without rigid pinching
when individual areas are loaded, the forces are redistributed
after the heaving soil thaws, the foundation returns to its original state

The main disadvantage is the complex waterproofing, and the much shorter lifespan of bricks compared to concrete. The calculation of the width of the foundation based on its bearing capacity is the same for all types of LF. For a monolithic tape, the cross-section of the reinforcement is additionally calculated, and a reinforcement diagram is drawn up taking into account the requirements of the joint venture:

The main measures to eliminate heaving forces are:

In addition, it is necessary to protect the underground structure from moisture with volumetric, lining, and coating waterproofing.

To transfer a drawing of a building to a building site while maintaining the scale, you will need a level or a plane builder (can be replaced with a hydraulic level with a laser level), a 12 m cord, cast-offs of two pegs with a crossbar 60 - 80 cm long between them. Before the full-scale removal of the axes of the dwelling, it is necessary to clarify its location in the building area, depending on external communications (power pole, septic tank, water supply wells, sewerage), parking for a car, and boundaries of the site.

The façade closest to the roadway must be at least 5 m from the center of the road. For minimal shading of the neighboring territory, it is enough to retreat 3 m from the fence:

the first wall is laid parallel to the road
the ends of the building extend from it at right angles, which are found using the triangle method
with legs 4 m, 3 m, hypotenuse 5 m, the triangle is guaranteed to have an angle of 90 degrees

The axles are secured in place with cords/strings only after checking the diagonals (they must completely match in size), aligning the cast-offs to a single horizontal level (use a laser or hydraulic level, a plane builder).

To carry out excavation work, it is necessary to take into account the recommendations of specialists and SP standards:

After this, you can begin preparing the base for the foundation tape.

Preparing the base

It is especially important to manufacture a foundation cushion for shallow-depth MZLF belts. Sand (20 cm) laid on geotextiles, compacted in layers, and crushed stone (20 cm) will reduce the forces of frost heaving. Any of these materials can be used separately:

The bottom layer of geotextile prevents silting and mixing of non-metallic material with the soil. On a sand bed, rolled waterproofing material (TechnoNIKOL, Bikrost) is not subject to mechanical stress, allowing you to reduce the construction budget. If the top layer of the cushion is crushed stone, it is necessary to fill in a 5 cm concrete base, which will protect the hydroglass insulation from punctures by sharp stones.

The drains are laid in the lower trench, the bottom of which has a 4–7 degree slope, on top of a 10 cm layer of crushed stone over geotextile. Typically, smooth, corrugated pipes with point and slot perforations are used. They are wrapped with two layers of Dornit by default by the manufacturers.

Drains are laid between wells (vertical pipe with a plugged bottom) and are interrupted in them. This is necessary for normal cleaning from ground level with compressed air or steam. On the sides and on top, the drainage contour is filled with crushed stone and covered with geotextiles. The top filling of the drains and the foundation pad must match.

Self-concreting the foundation strip

The standard technology of monolithic strip foundation does not cause difficulties for individual developers. After preparing the base, all that remains is to mount the formwork panels, place the reinforcement inside, lay and compact the concrete mixture. Depending on the season and weather conditions, it must be cared for in the first three days.

Calculation of parameters

At this stage, you will need V.S. Sazhin’s reference book or SP 22.13330 standards with tables of snow + wind loads and calculated soil resistances. Next, the width of the tape is determined, sufficient for the load-bearing capacity of the prefabricated loads of the home. To do this, the value of the calculated resistance of sandy loam, clay, sand, loam on which the foundation will be built is taken from the tables.

The combined load is obtained by adding the wind and snow loads, the weight of all power structures, furniture, and residents. This figure is divided by the previous one, then by the length of the perimeter of the tape. The obtained result is adjusted according to the thickness of the wall so that timber, brickwork, or logs do not hang more than 10 cm from it. For light buildings, reinforcement of a periodic section of 8 - 14 mm with clamps made of a smooth rod of 6 - 8 mm is used.

Installation of formwork, reinforcement

The main characteristics of the strip foundation depend on the quality of work at this stage. Formwork uses rigid structural materials that can be reused. Most often, boards are made from edged boards (minimum 4 cm thick), multilayer plywood, or oriented strand board.

The shields are fixed vertically with jibs to the edges of the trenches, into the ground, and are tightened with jumpers and pins. It is necessary to leave ventilation ducts in the basement part (1/400 of the total area of the above-ground part), and underground openings for the input of engineering systems.

Reinforcement occurs according to the following scheme:

longitudinal rods (2 rows minimum for a width of 16 cm or more)
90 degree bend in corners, wall junctions
overlap 60 cm when extending
staggered order of joints in adjacent rows

Rods and clamps are immersed in concrete by at least 2–4 cm to provide a protective layer. Polymer cups, stands, and concrete pads are installed under the bottom row. The belts are fastened together with rectangular clamps.

Preparation and laying of concrete

The recommended mixture proportions for obtaining grades B25, B15 are 30/15 l or 42/25 l (crushed stone/sand), respectively, for a bucket of cement. For the footing, grade B7.5 is sufficient (61/41 liters of crushed stone, sand, respectively). When mixing manually, the characteristics of concrete are reduced by 20 - 30%.

The best option is to lay and vibrate the entire volume in one day. If the interval of 2 hours is exceeded, the concrete that has begun to harden is destroyed when the fresh portion is compacted with a vibrator. Filling is done in layers 60 cm deep along the ring. If it is unrealistic to fill the entire volume, partitions are installed inside the formwork. They cannot be tilted or moved after laying concrete. It is prohibited to cut reinforcement in these areas.

The time it takes for concrete to gain strength depends on the outside temperature. At + 5, +10, +20, +30 degrees, stripping can be done on days 29, 15, 8, 4, respectively. In the first three days, concrete requires care:

Used formwork is usually used in roofing and rafter systems. It is better to waterproof slightly damp concrete, so stripping can be done a day earlier, being careful.

Do-it-yourself LF brickwork technology

Marking, excavation work, bottom waterproofing, drainage are completely similar to the previous case. Instead of formwork, an individual developer lowers bricks into the trench, stacking them in periodic stacks. After that, all that remains is to prepare a reinforcement or wire mesh with a cell size of 3 x 3 cm or 5 x 5 cm, and mix the solution (the volume must be calculated to produce within an hour). The main nuances of brickwork are:

the height of the corners for tensioning the cord - must correspond to the frequency of reinforcement, otherwise they will remain unconnected (usually 3 - 5 rows)
dressing - classic (poke/spoon vertically + displacement of seams in adjacent rows by ¼ - ½ the length of the stone)
seams - 1 - 2 cm, in reinforced rows they are thicker, filled completely in the underground part, partially in the basement part if plastering is planned

The vertical of the corners and the horizontal of the rows are controlled in each row. Experts recommend wetting the brick before laying to increase the correction time in the rows. Adding liquid soap (2 - 3 drops of Fairy per 100 liters of batch) will increase the plasticity of the solution without an expensive Superplasticizer, reducing the strength of the masonry.

Waterproofing

The main requirement for the protective layer of waterproofing is its continuity. The untreated area will become a source of corrosion of the reinforcement inside the tape, allowing the concrete to become saturated with moisture, which, when frozen, will lead to the formation of cracks in the structure of the structure. The following foundation waterproofing technologies exist:

The first two options are usually used in combination, providing a 50-80 year service life of structures. Penetron has an unlimited resource, since even a piece of foundation broken off after processing will retain water-repellent properties until complete destruction.

Regardless of the depth of the tape, it is recommended to insulate the foundation to solve several problems:

If you use the measures in a complex, the MZLF is guaranteed to last 80 - 120 years; non-buried foundations will increase the service life to 70 years.

The above selection, calculation, and construction scheme allows you to independently produce a strip foundation with a minimum construction budget. At the same time, a high service life and maintainability of individual structural fragments are maintained. The quality of additional measures to protect concrete structures from moisture and heaving forces depends on the comfort of use.

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 for walls 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. Quaternary deluvial sediments (dQ) take part in the geological structure of 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 the 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

The strip type foundation is quite often used by individual developers for the construction of houses, bathhouses, outbuildings, cottages and other structures. Its prevalence is associated with sufficient strength, reliability, and availability of technology for independent work. Among the varieties of strip foundations, the T-shaped foundation has a special place. It is used for various buildings. It is characterized by increased rigidity due to the fact that it has the shape of the letter “T”. This version of the supporting structure is made recessed or shallow. This is determined by the load on it, as well as the hydrogeological characteristics of the construction site soil.

A strip foundation is a closed structure, which is erected from different materials of your choice: reinforced concrete, prefabricated elements, stone or brick. Its parameters depend on the following factors:

soil on the site;
location of groundwater;
expected load on the base;
climatic features of the region.

The weight of the constructed structure is distributed along the entire perimeter of the supporting structure.

One-story or more buildings are erected on strip foundations from the following materials:

cinder block;
wood;
bricks;
foam concrete and others.

The types of strip foundations according to different classification criteria are presented in the table below.

The main task during construction is to choose an option that is suitable economically and in terms of operational characteristics.

Belt-type foundations have a service life of approximately 70 years (subject to technology), they are quite easy to repair. The scope of application of the various options is as follows:

a non-buried foundation is suitable for the construction of panel, panel, frame structures and log buildings on flat areas with loamy or sandy loam soils, on which floors can be laid;
a shallow foundation with a depth of 0 to 1 m is suitable for the construction of buildings from various materials on non-heaving soils;
the T-shaped base is expanded from below and is used for any buildings on different soils, if the site is not located on slopes or in swampy areas, and the groundwater is deep;
recessed support structures are designed for the construction of buildings with basements on various types of soil, even with high humidity;
a monolith belt is a strip whose width is greater than its height, and it is used only if the soil has good load-bearing characteristics, for the construction of frame or yard structures, log houses.

Among the various types of strip foundations, you can choose the appropriate option for different soils. The main problem is the action of heaving forces. If the estimated burial depth is more than 3 m, then it is recommended to give preference to a pile or slab-based support structure, which will reduce the labor intensity of the work.

Technology for constructing a T-shaped monolithic foundation with your own hands

The technology for constructing a monolithic strip T-shaped foundation is similar to the construction of a strip. The only difference is in the design of the extended lower part. The formwork also has a unique design to prevent the solution from leaking out. To strengthen the base, reinforcement is also carried out.

The advantages of a T-shaped base are:

ease of construction;
sufficient strength;
All work can be carried out without the use of special equipment;
requires lower financial and labor costs compared to buried and slab foundations, as well as shorter construction time;
For construction, concrete is used, which is poured into a reinforcement frame, or ready-made blocks, which speeds up the process.

They build support structures for sheds, fences, and houses from different materials. Due to the reduced thickness of the above-ground part, you can save on concrete. In this case, the area of distribution of the load from the building exceeds more than twice the corresponding parameter of the strip base.

The construction of a strip foundation occurs in 2 ways:

with the installation of formwork in an excavated recess, its width exceeding that of the base;
by pouring directly into a trench dug in the shape of the letter “T”.

Experts do not recommend using the latter option, because the buried part remains without a waterproofing coating, and this reduces the operating time by almost a third (by about 20-40%).

The technology of work involves their implementation in 1 or 2 stages. In the latter case, the construction of the lower part (sole) occurs first, and then the construction of the tape.

The general algorithm of actions when working in stage 1 is as follows:

determine the design of the foundation;
calculate the dimensions of the sole and tape based on the load-bearing characteristics of the construction site soil, as well as depending on the depth of freezing and existing loads;
carry out marking of the building site;
carry out excavation work;
cover the bottom of the trenches with a sand cushion;
install formwork;
carry out reinforcement;
concrete is poured;
a waterproofing coating is applied, and if necessary, insulated, a drainage system is installed.

Calculations of foundation parameters are carried out based on SNiP 2.02.01-83, which regulates the construction of building foundations, and using reference books (for example, V. S. Sazhina). They provide snow and wind loads for the region.

Sole device

Work begins with marking. The sequence of actions is as follows:

they make cast-offs, which are perpendicular beams fixed on racks, with a height exceeding the same parameter of the base;
place them in the corners according to the developed plan;
to mark the outer planes of the walls, cords (ropes) are pulled along the upper beams along the perimeter;
check the equality of the internal diagonals to make a square or rectangle.

After marking the territory, excavation work begins:

dig trenches taking into account the width reserve for installation of formwork and soles;
make slopes;
Level the bottom of the excavation;
cover the trench with a sand cushion.

Excavation work should be carried out taking into account the following recommendations:

the width of the trench in the presence of a ground floor or basement should take into account the space for installing the formwork and provide free access for builders: the margin inside is from 0.5 to 0.8 m, and outside - 1.2 m;
to avoid crumbling, at a excavation depth of 1.5 m, the steepness of the slopes is made 1/1, and at 3 m it will be 1/0.67;
around the foundation trench it is necessary to dig a 40x40 recess for the drainage system;
The depth of the recesses must be made taking into account the thickness of the pillow, which ranges from 40 to 60 cm.

When the trenches are ready, then proceed to the installation of formwork and reinforcement:

Every 70 cm, vertical posts are driven into the ground along the lines marked with cast-off cords;
boards are secured to the stakes with self-tapping screws or nails until the full height of the sole is reached;
strengthen the structure with planks, nailing them to the top row;
install vertical reinforcing bars, the height of which is taken with a margin for connection with the overlying tape;
fix horizontal rods using welding or wire;
fill the base with concrete;
compact it with a vibrator or manually;
wait several days for the concrete to partially harden.

Reinforcement rods are laid in at least two layers. The overlaps should be approximately 60 cm, and located offset from each other in the vertical and horizontal planes. The cross-section of the rods used, depending on the design load, ranges from 8 to 16 mm. A tying wire with a diameter of 1.2-1.6 mm is suitable for connecting the rods.

Construction of the strip part of the base

After the base has been poured and the concrete has partially hardened, formwork is installed under the upper part. Initially, according to the height of the tape, panels are made from boards or plywood (or other materials). Their length is determined by the ease of handling them when performing work, and their thickness is determined by the level of future load created by the concrete.

Subsequent steps for constructing the foundation are carried out in the following sequence:

install the panels, resting their lower boards on the formwork structure of the lower part and combining them with the help of long beams (at the top and bottom);
with the help of stretched cast-off ropes, as well as a level, the formwork is aligned in the required planes;
boards located opposite each other are connected with horizontal ties;
using inclined struts, fix the formwork from the sides;
a reinforcement frame is laid in several rows inside the assembled structure, and it is connected to the rods of the sole;
moisten the shields with water;
fill the form with concrete in even layers, compacting it every 40-60 cm;
to ensure the solidification process proceeds evenly, the base is covered with roofing material or plastic film;
Periodically, the upper part of the monolith is moistened with water (about a week or two, depending on climatic conditions).

When installing formwork, special attention must be paid to the corners, connecting the panels there securely so that they do not come apart.

Concrete gains more than half its strength in about 7 days. Complete hardening takes about a month, which is determined by temperature and humidity.

Removal of formwork can be done at least 3 days after pouring concrete. When it hardens, it is recommended to protect the base and underground part with a waterproofing coating. For these purposes, mastics, roofing felt and other materials are used. Reliable protection from the destructive effects of water will extend the life of the building being built.

You can install the formwork and reinforcement cage of the entire T-shaped base at once. You will still need to fill it in parts: first the sole, and only then the tape. This is due to the fact that the concrete of the lower part, if it does not harden enough, will be forced out. For the same reason, compaction of poured layers of tape will need to be carried out carefully.

Installation of prefabricated foundation

The construction of a T-shaped strip foundation can be done using reinforced concrete blocks. The technology for their installation is as follows:

dig trenches below the depth of soil freezing in the region;
their bottom is covered with a cushion of sand, which is then compacted;
lay blocks;
connect them together with reinforcement;
the joints are filled with concrete, having previously installed formwork in these places;
The surface of the base is plastered, and after the applied coating has dried, it is waterproofed and insulated.

The first row of the foundation is laid out with wider blocks (or trapezoidal) compared to those located above.

The use of blocks significantly speeds up the construction process, but requires the use of lifting equipment. Due to the presence of a large number of joints, the service life of the foundation is reduced by approximately 3 times compared to monolithic analogues. The standard dimensions of the blocks determine the choice of belt parameters.

The process of constructing a T-shaped strip foundation is shown in the video below.

With fairly frequent heavy rainfall, the possibility of floods or rising groundwater, a drainage system must be installed. Its type is determined by the abundance of moisture, as well as its source. To reduce heat loss, the basement or T-shaped base is insulated in various ways.

A T-shaped foundation is a reliable foundation that you can build yourself. The choice of concrete grade is determined by the future load on the base: for the construction of lightweight structures, material marked M100 and M150 is suitable, and for heavier ones - from M200 to M400. Waterproofing the sole and tape will help extend the life of the entire building.