Shallow foundations are used quite often in construction today. There are many varieties of them, each of them has its own characteristics and characteristics. Such structures are most often used in wooden house construction; they are recommended for the construction of buildings that are light in weight. These types of foundations have low cost and fairly good load-bearing capacity. They don't cost much.

Tape monolithic grillage

Such shallow foundations have dimensions ranging from 200 x 300, 300 x 400, and 400 x 500 millimeters. They are lined up on the surface of the earth, which eliminates negative impact with seasonal heaving. The reinforced horizontal contour, which is made in the form of a tape, absorbs all the impacts that occur during soil movements. Such foundations can be built on sand preparation, which is formed by layer-by-layer compaction. The thickness of the pillow should be 20 cm, and such a base can be used for buildings made of laminated veneer lumber, ordinary timber, as well as rounded logs. Quite often houses are built on them using frame-panel technology. This type of foundation is perfect for small baths, barbecues, outbuildings and summer kitchens.

Features of using a monolithic strip grillage

The described shallow foundations are economical and practical. The size of the tape should be 200 x 300 millimeters for light buildings. The parameters 300 x 400 millimeters should be used for light buildings and houses that are built from wood with a cross-section of up to 200 millimeters. The size 400 x 500 millimeters is used for light buildings and buildings made of wood with a cross-section of up to 300 millimeters.

Prefabricated monolithic strip foundation

The dimensions of such a base can be 200 x 600, 200 x 400, 400 x 600 millimeters. The laying depth in this case is 40 centimeters. Work must be carried out on a sand cushion, the thickness of which is 20 centimeters. It must be laid flush with the ground. This indicates that tangential forces will affect the surface minimally.

Shallow columnar foundation is also quite simple to create, it is suitable for light houses and outbuildings, which are built on uneven areas. The basement part, which is located above the ground, must be laid out from concrete blocks; they must have dimensions of 20 x 20 x 40 centimeters. A similar design is suitable for one-story light houses built from laminated veneer lumber or ordinary timber, as well as for buildings made from hand-cut logs. For frame-panel houses, a foundation of this type can also be used. By choosing this type of base, you can count on efficiency and constructiveness.

Monolithic strip foundation

Such shallow foundations can have dimensions of 200 x 500, 300 x 600, 400 x 700, 500 x 700 millimeters. They are laid 40 cm on a sand cushion. Its thickness is 20 cm. Initially, it is necessary to install a frame made of reinforcement, and then you can begin arranging the structure itself. This foundation guarantees resistance to uneven soil deformations in winter. The structure is capable of uniformly transferring loads from the building to the ground. This is recommended shallow foundation, the depth of which must be maintained, for one-story houses, as well as for buildings with an attic made of timber. This base is also perfect for laminated veneer lumber, rounded logs and hand-cut lumber. If you increase the width of the tape, it will be possible to install the heaviest building with an attic, as well as gables made of logs and timber. If you increase the width of the base and tape, the possibility of soil freezing in the underground space will be reduced.

Application of monolithic strip foundation by size

The size of 200 x 500 millimeters is excellent for light buildings, as for the parameters that are equal to 300 x 600 millimeters, they are suitable for light houses. Houses made of timber and logs, the cross-section of which does not exceed 300 millimeters, can be installed on a tape whose size is equivalent to 400 x 700 millimeters. Houses made of timber and logs can be built on structures with dimensions of 500 x 700 millimeters.

Prefabricated monolithic base series 60

It is quite possible to build a shallow foundation with your own hands; for this you can use a prefabricated monolithic structure, which has dimensions of 200 x 1000, 200 x 400, 400 x 1000 mm. This type of base is distinguished by a deeper laying, which varies within 80 cm. The sand cushion has the same thickness as those described above.

A tape is laid in the trench, the base part of which protrudes above the surface of the ground; the latter must be formed from blocks with dimensions of 20 x 20 x 40 cm. The buried part is characterized by more impressive massiveness and rigidity.

To improve resistance to the buoyant force that exists during seasonal heaving, the walls can be covered with waterproofing. This will reduce the impact on the foundation. Such a belt can be equipped by supplementing it with a storm drainage system, a blind area, an insulation system, as well as drainage, thereby reducing the freezing of the soil under the foundation. This shallow foundation, the depth of which must be taken into account before starting construction, is excellent for one-story houses and buildings with an attic. It is often used for buildings erected using frame-panel technology, which are located on areas with a slope exceeding 5 degrees. As distinctive features This type of foundation is characterized by constructiveness and reliability.

Features of the construction of a shallow strip foundation

The cost of a shallow foundation is quite low, which is why such foundations are so popular among private developers. First you will need to dig a trench that compacts well. If the soil is heaving, then you will need to use a vibrating plate. If the area has dusty fine sand, then the cushion is protected with geotextiles, this will prevent siltation of the soil. Among other things, this approach will eliminate the growth of weeds. Gravel is poured onto the surface of the pillow and roofing felt is laid. If there is a need to insulate the bases, it is best to use permanent formwork made of expanded polystyrene.

Formwork and reinforcement

When building a shallow foundation for a house, it is necessary to install formwork; it is best to use support posts for this, which will be 10 x 2 cm boards. Support posts in the form of bars with a square section with a side of 50 mm can be used. It is necessary to finish the formwork with glassine. When reinforcing, it is best to place 5 rods in the upper and lower chords. Longitudinal reinforcement of 12 millimeters is best suited for this, as well as transverse reinforcement, the size of which is 20 millimeters. The step between the longitudinal reinforcement must be left within 15 cm. The corners must be reinforced with overlap and tied with wire.

Working with concrete

If you are building a shallow foundation on heaving soils, then the best grade of concrete is B15 F100 P4 M200. For the pouring process, a concrete pump or mixer is most often used, this greatly simplifies the process. If the soil is heaving, then it is recommended to load the finished foundation for the winter. If the conditions in the area are normal, then the base is placed on a leveling bedding, whereas if you have to work with heaving soil, then the bedding should be made of fine crushed stone, sand and boiler slag.

Shallow foundation price

If you decide to install a house on the type of foundation described, then you should be interested in the cost of the foundation. The average market price per linear meter is 2800 rubles. If you decide to determine the cost of the foundation yourself, you will need to calculate the amount of materials used. In order to find out the volume of mortar used, the area of ​​the foundation must be multiplied by the thickness. It is important to take into account the cost of reinforcement, as well as sand. The volume of the latter is calculated using the same technology. The amount of preparation will depend on the thickness.

Thus, if you have to build a foundation whose dimensions are 5 x 6 meters, then using these dimensions you can calculate the volume of sand. The thickness of the cushion is most often 20 cm. This indicates that you need to purchase 6 cubic meters of sand, which is true if you do not make concrete yourself, but order it from a factory.

Conclusion

We looked at the design of a shallow foundation. Now you can begin work on its construction. However, it is necessary to take into account all the nuances and rules of the work. Only then will it be possible to achieve the expected result.

(SPb, 2012).

This article provides information on calculating the depth of a strip foundation into the ground based on the heaving of the soil, the groundwater level and the depth of soil freezing in winter. The continuation of the article talks about choosing the width of the strip foundation based on the size and type of the house.

Shallow strip foundation is one of the most widespread types of foundations for private country house construction. Shallow-buried monolithic strip foundations are more economical and simpler to implement, compared to costly deep-buried strip foundations - “underground walls”, which, for reliability, are buried in the ground to depths exceeding the standard depths of soil freezing in winter in each specific climate zone.

A shallow monolithic strip foundation consists of a continuous strip of reinforced concrete, which is located centrally under the load-bearing walls or structures of the house. A shallow strip foundation absorbs the load from the house and redistributes it to the ground without causing additional compaction. The bearing capacity of the soil must be greater than the loads per unit area transferred by the shallow strip foundation from the building.

A shallow strip foundation is best installed on non-heaving and slightly heaving homogeneous soils, with a low groundwater level, at a distance from large trees equal to their height, in flood-proof areas in radon-safe areas.

Shallow strip foundation It is prohibited to build on biogenic organic soils(peat, saporpel, silt), and It is not recommended to build on heterogeneous soil layers, at the junction of different underlying soils, on extremely heaving soils (plastic clayey water-saturated soil, water-saturated silty sands), on flooded areas and in areas with a very high groundwater level.

The main geometric parameters and configuration of a shallow strip foundation depend on the perceived load from the building, the properties of the soil (bearing capacity, drainage properties, heaving), climatic conditions (freeze depth of the soil) and the materials used for the construction of the foundation. Before calculating the strip foundation, it is recommended to conduct an engineering-geological study of the soil.

Depth of shallow strip foundation

The minimum depth for laying a shallow strip foundation is determined by the depth of soil freezing, the degree of soil heaving and the height of groundwater. The more water in the soil closer to the surface (level of planning) and the greater the depth of freezing of the soil, the stronger will be the heaving forces acting on the shallow foundation from below, tangentially and from the side. These forces will push the shallow foundation towards the surface and will compress the foundation. To reduce the impact of these forces, the strip foundation will have to be deepened. In addition to deepening, the forces of frost heaving can be influenced by insulating the soil, installing permanent insulated foundation formwork, complete or partial replacement of the soil, its compaction, water removal and drainage.

According to UK building codes, the minimum depth for laying a shallow strip foundation on all types of non-heaving and low-heaving soils (except rocky and clayey) is equal to 45 cm (The Building Regulations 2010, A1/2, 2E4 - British Building Regulations, 2010, A1/2, 2E4). On rocky soil, if deepening is physically impossible, a strip foundation can be built directly on the surface without deepening. The minimum depth for laying a shallow strip foundation on clayey (and other heaving) soils according to British standards is 75 cm(optimal depth 90-100 cm).
In case of excessive softness, possible mobility (sands, sandy loams, water-saturated soils) and low bearing capacity of the surface layers of the soil, the depth of laying a shallow strip foundation can be increased to the depth of reaching soils with good bearing abilities and stable characteristics. The maximum reasonable and economically justified depth of laying a strip foundation is 2.5 meters.

The depth of laying a shallow strip foundation can be set regardless of the calculated freezing depth if the foundation is based on sand with a confirmed lack of heaving. Another possibility to deviate from linking the depth of laying a strip foundation to the depth of soil freezing is “special thermal engineering measures that prevent soil freezing.” (Clause 2.29 SNiP 2.02.01-83 “Foundations of buildings and structures”). That is, horizontal insulation of the soil and vertical insulation of a shallow strip foundation. The following table can serve as a guideline from domestic standards for the depth of laying a shallow foundation:

Estimated freezing depth of conditionally non-heaving soil	Estimated freezing depth of slightly heaving soil of solid and semi-solid consistency	Foundation depth
up to 2 meters	up to 1 meter
up to 3 meters	up to 1.5 meters
More than 3 meters	from 1.5 to 2.5 m
	from 2.5 to 3.5 m

The presence of high groundwater can make adjustments to the depth of the strip foundation. If the groundwater level is high, it is quite possible that a shallow strip foundation will have to be converted into a deep strip foundation. As a guide, you should follow the requirements clause 2.30 SNiP 2.02.01-83 “Foundations of buildings and structures”. We provide below a table with requirements for foundation depth:

Table No. 2. The depth of laying the foundations of buildings with cold basements and technical undergrounds (having negative temperatures in winter) depending on the depth of the level groundwater and depth of seasonal freezing. *

Soils under the base of the foundation, lying to a depth not less than the standard freezing depth	The depth of foundations depending on the depth of the groundwater level and the depth of seasonal freezing
	The groundwater depth level is above the soil freezing depth level + 2 meters	The underground depth level is below the freezing depth level + 2 meters
Rocky, coarse-grained with sand filler, gravelly sands, large and medium-sized		does not depend on the depth of soil freezing
The sands are fine and dusty		does not depend on the depth of soil freezing
	not less than the depth of soil freezing	does not depend on the depth of soil freezing
Loams, clays, as well as coarse clastic soils with silty clay filler	not less than the depth of soil freezing	At least ½ soil freezing depth

* Table adapted based on table No. 2, clause 2.30 of SNiP 2.02.01-83 “Foundations of buildings and structures”

If the soil on your site is heaving and the groundwater is high, then it’s time to think about using another type of foundation: a pile-grillage foundation ( pile foundation with load-bearing beams). Such a foundation is not afraid of either frost heaving or high groundwater. Soil freezing depth in Russia:

Table No. 3 Standard depth of seasonal soil freezing (m)

City	Loams, clays	fine sands	Medium and coarse sands	Rocky ground
Vladimir
Kaluga, Tula
Yaroslavl
Nizhny Novgorod, Samara
Saint Petersburg. Pskov
Novgorod
Izhevsk, Kazan, Ulyanovsk
Tobolsk, Petropavlovsk
Ufa, Orenburg
Rostov-on-Don, Astrakhan
Bryansk, Orel
Ekaterinburg
Novosibirsk

Height of strip foundation

The maximum height of the above-ground part of a monolithic shallow strip foundation when internally filling the space limited by the strip with soil (sand) for the installation of floors (floors) on the ground should be equal to four dimensions of the width of the strip foundation.

Foundation height above ground = 4 x Foundation width

The above-ground part of a monolithic shallow strip foundation cannot be larger than its underground part, but can be arbitrarily smaller than the underground part of the foundation. The most common option is the depth of laying a monolithic shallow strip foundation and its height above the ground of 45-50 cm (if the conditions of the underlying soil allow).

The height of the above-ground part of the foundation is less than or equal to its underground part.
In most cases, if there is a subfloor, the strip foundation requires vents for ventilation of the subfloor.

Length of a building on a strip foundation
Extended buildings should be cut along their entire height into separate compartments, the length of which is taken: for slightly heaving soils up to 30 m, for medium heaving soils - up to 25 and, for highly heaving soils - up to 20 m, for excessively heaving soils - up to 15 m. (VSN 29-85 “Design of shallow foundations of low-rise rural buildings on heaving soils”)

Read more about calculation

The foundation of a house is a solid foundation. It absorbs loads from the building structure and redistributes them to the ground. Acts as a kind of “sole” of any constructed object. The magnitude of the load is the main criterion for choosing the size of the base and its type. Strip foundations are the most popular in private housing construction. A seemingly simple basis, in fact, requires serious calculations using the standards laid down in SNiP and state standards.
Table of contents:

Tape type: advantages

The base in the form of a tape is a structure constructed from a continuous concrete belt, reinforced with reinforcing elements. It runs under all load-bearing walls, is necessarily fixed in the corners, and represents a closed contour along the entire perimeter of the base. Located in the ground, it repeats the exact plan of the building and the dimensions of the walls that will be mounted on the foundation.

Attention! A shallow strip foundation is erected in order to prevent first deformation and then destruction of the erected building as a result of changes in the standing of the soil, as well as its heterogeneous structure.

Among the main points in favor of the shallow type of foundation are:

• efficiency, minimal labor costs: the tape is laid only in those places where the maximum load is placed on the ground;
• service life 25 years (average): whether it is a lot or a little is a relative concept;
• ideal for light one-story construction (country houses, Finnish houses, frame buildings, etc.), the most structural wall materials are wood, foam concrete;
• minimum construction time.

There are also restrictions:

• It is necessary to carry out extremely accurate calculations in accordance with SNiP 2.02.01-83 and comply with the requirements for non-heaving soils. Take into account the resistance coefficient to the expected load. Design standards are also used for the construction of the building itself, taking into account wind, snow loads, and the weight of the foundation itself. So, with a belt weight of more than 12 tf/m.p. It is not advisable to build a strip, because Its width turns out to be large; it is better to make the base piled or in the form of a slab.
• Strip-type foundations are calculated using special reference books, which take into account tolerances and coefficients, which only a specialist can do. The task can be simplified by calculating special program, which can be found on the Internet.
• It is forbidden to erect buildings with a load per 1 linear meter of more than 5 tons.
• There are restrictions on the type of soil: it is prohibited to build a shallow foundation on clay and loamy soils. When the clay is heavily moistened, it becomes wet and its resistance to stress weakens. For the same reason, construction on deep black soil is problematic. Foundations cannot be built on heaving soils made of fine sand.
• In regions where there is a significant temperature difference (within 100 degrees), the risk of sole destruction increases. So, in the northern regions, where in summer the outside air temperature can reach +30 degrees or more. Partial defrosting of the soil occurs. The cold weather that follows freezes the thawed soil and increases the freezing layer. Cavities form in the soil into which the foundation can fall.

Laying depth: an important criterion for choosing the type of foundation

The depth of the trench is determined by calculation - you can’t make a mistake in this matter

Foundation depth in individual construction depends on a number of factors: type of soil, climate of the building area, type and design features the building itself (including weight, volume), as well as its purpose. The minimum depth level is 0.5 m (this is when the soil freezes to 2 m). But the most accurate indicators should be taken from SNiP. 2.02.01-83. The type of burial must be specified at the design stage of the house. It should be taken into account that the top layer (fertile) soil, usually about 1 meter thick, is not suitable for arranging the foundation for a house. The soil underneath is much more attractive. It is also important to know the heaving depth (freezing depth) of the soil in a particular region.

Reference. For the Moscow region and the capital itself, the average is in the range of 1.40 - 1.70 m. It must be taken into account when determining the laying depth. Arrangement of the base above this value is fraught with the risk of pushing it out of the soil when it becomes icy. In the case of non-heaving soils, when the soil freezes to 3 m, the foundation must be buried at least 0.75 m.

Algorithm for constructing a foundation strip for construction

After carrying out calculations that meet the requirements of SNiP, you can begin to build a shallow strip foundation with your own hands.

• At the construction site, the fertile soil layer is removed to the depth of the trench and 1.5 m on both sides of its boundaries.
• Trees, bushes and stumps are uprooted. Other vegetation is removed.
• Construction and other debris and wood remains are removed.
• The resulting potholes are filled up. The top layer of soil is leveled.
• Strictly observing the development plan, the dimensions of the trenches are marked.
• Using a level, pegs are placed at the extreme significant points, and the corners are necessarily covered. The twine is pulled.
• Manually or mechanized way a trench is dug. Be sure to check the distance between its parallel walls. Levels if necessary.
• The bottom of the resulting pit under the tape is covered with coarse sand. A “cushion” is formed, which should resist freezing of the trench filling.
• Waterproofing is being carried out. You can use a liquid solution for this. concrete mixture. When hardened, it forms a hard coating that prevents the penetration of cement laitance from the base concrete composition into the soil.
• The formwork is installed using the chosen method (removable, non-removable).
• With a removable structure, the boards knocked together into panels are strengthened from the inside with spacers, clamps, and from the outside - with supports. In this case, the nails are driven in from the inside without bending from the outside. This must be done so that the mixture being laid does not deform the walls under its weight and destroy the formwork.
• A frame is formed from reinforcement either in the trench itself or near it, and then, finished, it is inserted into the formwork.
• The concrete solution is gradually laid into the reinforced structure in layers. After each filling, it is pierced with a reinforcing rod (to remove trapped air and eliminate cavities).
• The mixture is compacted using a tamper or vibrator.
• The formed foundation is covered with a plastic film (roofing felt, roofing felt) to prevent the top layer of concrete from drying out and harden it evenly. At high temperature air, the foundation under the shelter is periodically wetted.
• After 2-3 weeks, when the base has hardened, the formwork is dismantled. During this time, the foundation gains strength by only 70%.
• A layer of sand is first poured into the formed “pockets” between the trench wall and the base, moistened, and compacted.
• Then the soil is backfilled to the entire remaining depth. The pockets are completely removable.
• Walls and other façade elements are being erected. At the same time, under the weight of the structure, the reinforced concrete strip will strengthen for another half a month or even a month.

Accurate calculations, preparation of high-quality consumables and the help of friends will allow you to build a shallow shallow foundation on your own.

This type of strip foundation is widely used in low-rise construction, in the construction of one-story bathhouses, houses made of both wood and various types concrete. Its main difference from a strip foundation is its depth, namely slightly above the depth of soil freezing.

Construction of a shallow strip foundation

The design of this type of strip foundation is different and depends on the variety. So, they distinguish:

• prefabricated foundation;

Made a type of shallow strip foundation is a structure made of ready-made reinforced concrete block structures that are strengthened and connected to each other, which allows the foundation to be installed in any type of soil and in any natural and climatic conditions. For installation, it is enough to purchase ready-made blocks and install them during shrinkage in the place where the foundation is laid.

Monolithic a shallow strip foundation is made directly at the construction site. Its main difference from a prefabricated one is that it is coated with reinforcing paint, which ensures the continuity of the entire structure, and, consequently, the strength and durability of the entire building.

The main components of a monolithic strip foundation are:

• upper plane - edge;
• lower plane - sole;
• base;
• up or “armrest”;
• “glass” or area for mounting poles;
• waterproofing;
• blind areas;
• slopes.

SNiP shallow strip foundation

Features of installing a strip foundation have been regulated building codes and rules, the application of which is compulsory when carrying out this type of work.

Trench dimensions for installation of the foundation depends on the type of soil and structural conditions, however, the depth should not exceed 70 cm, while in mandatory A cushion made of sand or gravel is installed under the base of the foundation. The width of the trench is determined based on the force of soil heaving, but it is mandatory that the sinuses of the trench be filled with soil or sand at the end of the work.

When preparing the trench it is necessary to measure the permissible load and if the pressure for highly swelling soils exceeds the norm, the depth of the trench must be expanded or the base of the shallow strip foundation must be increased. However, subject to the proportion of the width and depth of the trench, strip foundations provide a stable and 2-3 times more economically profitable structure, and therefore, even with heaving soil, they can and should be used for the construction of low-rise buildings.

When reinforcing the reinforcement should extend outward 6-10 cm from the top edge of the concrete pouring. It is necessary to connect the reinforcing rods with tying wire and weld only the letter C of the reinforcement. In addition to the above, individual SNiPs impose requirements for the distance between the reinforcement bars and the pitch of transverse reinforcement in the manufacture of a monolithic strip foundation.

See also:

How to insulate a shallow strip foundation

There are external and internal insulation of strip foundations. External insulation includes both the installation of heat-insulating concrete tape and soil waterproofing. Preparatory work deserves special attention. For example, to prevent foundation destruction or soil heaving, it is necessary to organize a drainage system. Sod allows you to hold the load on the foundation, in the form of snow or water. Planting, loosening and other works can be used as drainage.

No less effective way is thermal insulation, namely insulation of the outer part of the foundation with a special material, which allows concrete structures do not come into contact with the ground and do not freeze. To do this, expanded polystyrene is mounted on special glue or dowels, then 2 m wide penoplex is laid, and in the corners the foundation is additionally reinforced with a layer of penoplex. Insulation of a shallow foundation from the outside is ensured by insulating the floor with penoplex.

Calculation of a shallow foundation Let's consider calculating the cost of a foundation using the example of building a house measuring 6*8 m.

Option 1. Dimensions:

• tape section: 250x1000(h),
• sand cushion: 150 mm,
• cost per 1 linear meter – 4000 rubles.

Total:(8+8+6+6+6+6+2) x 4000 = 168,000 rubles.

Option 2. Dimensions:

• tape section: 350x1000(h),
• sand cushion: 200 mm,
• cost per 1 linear meter – 4500 rubles.

Total:(8+8+6+6+6+6+2) x 4500 = 189,000 rubles.

Do-it-yourself shallow strip foundation

Shallow strip foundation, in comparison with slab foundations and deep foundations, is characterized by ease of arrangement. Its creation requires an order of magnitude less financial costs and time.

To build a shallow strip foundation with your own hands, you will need the following materials:

• Sand and crushed stone - for the compaction pad;
• Planed boards, timber, slats, nails or screws - to create formwork;
• Waterproofing material: glassine, geotextile, PVC membrane - for covering the walls of the formwork;
• Reinforcing bars, knitting wire and “fungi” stands - to create a reinforced frame;
• Ready-made concrete or, if prepared by hand, M300 cement, sand and crushed stone - for pouring the tape;
• Rags, oilcloth - for covering concrete while it is maturing.

Also make sure you have the required construction tools:

• Bayonet and shovel shovels, buckets and a wheelbarrow for transporting earth - will be required when digging a trench;
• Hacksaw, hammer, screwdriver - for working with formwork boards;
• Grinder and metal circles - for cutting reinforcing bars;
• Construction stapler - for installing waterproofing on formwork;
• Concrete mixer;
• A variety of small tools - tape measure, level, hook for tying reinforcement, wire.

Building a shallow strip foundation with your own hands - if you know the technology for performing the work, the process is not complicated, but labor-intensive, so get ready for the fact that it will take quite a bit of time to lay out the foundation for the house (about 2 weeks) and roll up your sleeves and get to work.

Stages of creating a shallow strip foundation

The arrangement of a shallow strip foundation begins with the preparation of the work site - all vegetation and construction debris must be removed from the territory. Then the soil is leveled - you need to smooth out all the slopes and irregularities so that the place on which the foundation will be built has a flat surface.

Rice.

Direct foundation work is carried out in the following sequence:

• Marking

First of all, it is necessary to carry out the design marking of the foundation on the territory allocated for construction. You need to mark both the inner and outer contour of the tape. To do this you will need scraps of reinforcing bars, twine, a square and a plumb line.

To begin with, the marking guide point is determined - this can be any outer corner of the foundation strip. A reinforcing peg is driven into the guide point, the distance to the second corner of the wall is measured, and the second peg is mounted. Then string is stretched between the reinforcement and as a result you get the first marked wall of the building.

Using a square and a plumb line, the extreme point of the wall is determined, perpendicular to the one already marked. We measure its duration, drive in a peg and check the correctness of the right angle.

Rice.

Similarly, we mark the remaining walls of the house and create a second marking contour along the inner perimeter of the foundation strip.

• Digging a trench

Upon completion of the marking, digging of a trench for the foundation begins. The depth of the trench should be 20 centimeters deeper than the design depth of the foundation; additional deepening is necessary for the subsequent arrangement of the compacting cushion.

Important: when digging, carefully monitor the verticality of the trench walls, since even the slightest deviations from the vertical will not allow you to install the formwork under the concrete perfectly level, as a result of which you will not get a uniform thickness of the base.

Rice.

If work is carried out in conditions of high flowability of soil and the walls of the trench are constantly collapsing, it is necessary to install supports from boards or sheets of plywood.

• Compaction bedding

Backfill under the foundation is necessary in order to reduce the buoyant effect of soil heaving forces on the concrete strip; it also prevents shrinkage of the foundation as a result of decompaction of the load-bearing soil layer.

The bedding consists of two layers of equal thickness: the first is sand, which is poured with water from a hose and carefully compacted with a hand tamper, the second layer is crushed stone or gravel of medium fractions.

Rice.

The thickness of the compacting bedding in normal soil conditions is 20 centimeters (10 - sand, 10 - crushed stone), however, when building on problem soils, it can be increased to 30-40 cm.

• Formwork installation

Formwork for pouring concrete is made from planed boards 2-3 centimeters thick or moisture-resistant plywood. The formwork is installed on top of the dug trench to a height equal to the required height of the strip foundation base.

Rice.

The boards are fastened together using wooden blocks and supported with side struts for stability.

Important: when creating the formwork panel, make sure that the nails do not protrude from the boards, because if the protruding nails get into the concrete, dismantling the formwork in the future will be very problematic.

After installation, the internal walls of the formwork and the trench space are covered with waterproofing material, which will prevent the concrete from losing moisture during hardening.

• Installation of reinforced frame

To reinforce a shallow strip foundation, a frame is created consisting of two vertical reinforcing bars on the upper and lower contours and horizontal jumpers connecting them.

To create the frame, corrugated reinforcement with a diameter of 10-12 centimeters is used, which is connected into a single structure using knitting wire.

Rice.

The frame must be monolithic along the entire length of the base, special attention must be paid to the joints of the reinforcement in the corners of the foundation strip.

After creation, the frame is laid in the formwork, it must be raised above the bottom of the trench by 5 centimeters (special mushroom stands are used) and at a similar distance from the walls of the formwork.

• Pouring concrete

If it is not possible to pour concrete at once, it is necessary to ensure that the work is carried out in such a way that each new layer of concrete is poured before the previous one hardens.

The pouring is carried out to the level of the required height of the foundation strip (the appropriate markings must be made on the formwork first), after which the concrete is compacted using a vibration compactor or, if it is not available, it is bayoneted with reinforcement to remove air voids.

Rice.

After this, the formwork is covered with a damp rag and a vapor-proof material (oilcloth) and the time required for the concrete to completely harden is waited (28-30 days).

Important: if the maturation of concrete occurs in the hot season, the foundation must be regularly moistened by pouring water on the concrete from a hose with a sprayer.

The foundation is designed to transfer the load from the structure to the ground and serves as the base of any stationary object built on the ground. Depending on the load, the foundation has certain dimensions and structure. Most often used. It is calculated in accordance with SNiP and GOST.

The design of the sole in the form of a tape assumes that under each load-bearing wall there is a structure in which a solid concrete tape with iron reinforcement runs along the entire wall and is connected to other tapes in the corners. The result is a contour in the ground that follows the outlines of the walls of the building that will be installed on it. The purpose of the foundation is to prevent deformation of the building as a result of uneven soil structure. But before installing the sole, you will need to create a project, a definition. Only calculations based on soil geology will justify the selected type of foundation.

Strip foundations by their design can be:

• monolithic (MN);
• teams (SL, SLU, SLT);
• shallow (MZ);
• deep-seated (GZ).

Regulatory documents for calculations

To calculate the foundation, surveys are first carried out, with the help of which the main characteristics of the soil are determined. construction site. At the same time, the groundwater level and freezing depth in a given location are determined from the maps. Such research will allow calculations to be made of the soil and its degree of resistance to the load received. They are carried out in accordance with SNiP 2.02.01-83, which sets out the requirements for foundations. At the same time, SNiP for the design of the building itself and other standards that will be required when drawing up the project are applied.

The calculation is carried out using reference literature, which indicates tolerances and coefficients. Tables and graphs are compiled based on the calculations.

Abbreviations are used for brevity. When designing, the depth of freezing and the type of soil matter. Calculation of the foundation with the involvement of road specialists. Therefore, you can use the GeoPlate program, which is available on the construction portal.

SNiP for the design of the building itself and other standards that will be required when drawing up the project are applied.

Shallow foundation

Shallow foundations are used for light buildings. With a weight load of less than 5 tons per linear meter, the structure is considered light. In this case, the calculation includes not only the weight of the structure itself, but the weight of the foundation and the operating wind loads. Only after assessing all the risks is a conclusion made about the chosen type of foundation.

Month		Month	Temperature in degrees Celsius
January	-11,6	July	17,2
February	-10,7	August	15,3
March	-5,4	September	9,4
April	2,4	October	3,2
May	10,0	November	-2,9
June	15,0	December	-7,9

In residential construction of a one-story wooden or foam concrete building, it is often enough to build a shallow foundation. However, if such a house is located on a slope or with a high standard, a reinforced one will be required. As a result of summing up all loads and risks, the reduced weight of the building is calculated.

A shallow foundation can carry different loads, so there are belt options:

• with thermal barrier;
• in a rectangular trench;
• trapezoidal.

A shallow-depth tape thermal barrier is built only for non-residential light structures, for example, under a greenhouse. Rectangular trenches for strip foundations are used on non-heaving soils. It can be gravel or rock. In accordance with SNiP, on other rocks a trapezoid profile with an enlarged lower base is used. In this case, the slope of the side faces is calculated in accordance with the coefficients of the SNiP reference book.

When choosing a site for construction, you should not choose fine sand soil. They are heavies. You cannot install a building on oily clay, since when it gets wet it loses its ability to provide the necessary resistance. Deep chernozems and loams are not suitable. The sole made of construction concrete waste, pebbles, and rocky clastic soil will be stable.

Criterias of choice

A strip shallow foundation is chosen primarily due to its cost-effectiveness. Labor costs during its construction are much lower. It is known that a third of the costs during the construction of a building are the work on preparing the foundation. Therefore, the developer goes to reduce costs by choosing this type of foundation.

The disadvantages of such a foundation include the fact that there is a high risk of destruction of the sole in the event of alternating first a cold summer, when the soil under the sole does not have time to melt, then an abnormally cold winter with an increase in the freezing layer, followed by an abnormally hot summer. In this case, the house will simply fall into the resulting cavity.

Shallow strip foundations are not designed for long-term use. Its service life is no more than 25 years. It can be installed under light buildings such as Finnish houses. Such a tape perceives soil movements and therefore the calculation of the foundation must be entrusted to specialists so that, taking into account the realities and SNiP, the optimal option for laying depth and profile is selected. In this case, you can use standard calculations for non-heaving soils and select the broadening coefficient for the actual rock on which the house will stand.

In this case, the width of the foundation strip can be 300 - 500 mm, which ensures the rigidity and elasticity of the unit. But if the freezing depth is more than 1.5 meters, choosing a shallow foundation for residential buildings is not recommended.

City	M	√M	Soil freezing depth according to SNiP, m
			loams and clays	fine sand, sandy loam	coarse sand, gravelly
Arkhangelsk	46,1	6,79	1,56	1,90	2,04
Vologda	38,5	6,20	1,43	1,74	1,86
Ekaterinburg	46,3	6,80	1,57	1,91	2,04
Kazan	38,9	6,24	1,43	1,75	1,87
Kursk	21,3	4,62	1,06	1,29	1,38
Moscow	22,9	4,79	1,10	1,34	1,44
Nizhny Novgorod	39,6	6,29	1,45	1,76	1,89
Novosibirsk	63,3	7,96	1,83	2,23	2,39
Eagle	23,0	4,80	1,10	1,34	1,44
Permian	47,6	6,90	1,59	1,93	2,07
Pskov	17,9	4,23	0,97	1,18	1,27
Rostov-on-Don	8,2	2,86	0,66	0,80	0,86
Ryazan	34,9	5,91	1,36	1,65	1,77
Samara	44,9	6,70	1,54	1,88	2,01
Saint Petersburg	18,3	4,28	0,98	1,20	1,28
Saratov	26,6	5,16	1,19	1,44	1,55
Surgut	93,3	9,66	2,22	2,70	2,90
Tyumen	56,5	7,52	1,73	2,10	2,25
Chelyabinsk	56,6	7,52	1,73	2,11	2,26
Yaroslavl	38,5	6,20	1,43	1,74	1,86

Pile-tape

Which can be used during construction and costs a little more than shallow-buried one. However, its design allows it to carry a load of up to 12 tons per linear meter. But this type of foundation is suitable if the groundwater is low and freezing does not exceed 1.8 meters. In such conditions, the pile can break due to forces acting in the thickness of the earth.

For medium-hard soils and for loads not exceeding 8 t/p. m, such a foundation is considered universal. It is allowed by SNiP and this is confirmed by the calculation. Such prefabricated foundation designs can have heavy and reinforced versions. In these cases, piles driven below the freezing depth and reinforced tape are used. Depending on the load, the thickness of the piles, its reinforcement and installation diagram are selected according to SNiP.

The main obstacle to installing a pile-strip foundation may be the lack of M300 concrete for pouring a foundation with piles. The sand should not be river sand, it should be of a coarse fraction. It is impossible to produce concrete of this grade without the appropriate equipment.

Block foundation

A prefabricated strip foundation is built when groundwater does not allow the use of cheaper options. However, such a base carries a load of up to 7 tons per linear meter, that is, it is suitable for low-rise construction. The tape is prefabricated, and its transverse rigidity does not withstand heavy loads. This design is also applicable for shallow foundations. One of the varieties is shaped blocks. This is one of best options for brick two-story house, which is confirmed by the calculation and the SNiP standard.

The procedure for constructing the foundation

The strip foundation, after the calculation has been made and complies with SNiP, is installed in a certain sequence.

1. The construction site is cleared of the humus layer, which is carried out at least 1.5 meters beyond the perimeter of the contour. The site is being leveled.
2. The trench is marked with the installation of pegs using a level or using improvised means.
3. A trench is made, and an anti-heaving cushion of coarse sand is placed below.
4. A layer of waterproofing is poured from low-grade concrete so that cement laitance does not go deeper in the future.
5. The formwork is installed as required by the calculation. At the same time, the walls of the knocked down panels are strengthened and tightened from the inside so that the walls do not burst with concrete when pouring.
6. A pre-prepared reinforcement frame is installed.
7. Concrete is poured and hardens for two weeks.
8. The formwork is dismantled and all the spaces between the monolith and the soil are filled with soil.

When arranging the foundation, all work on installing formwork must take into account that during pouring, concrete pushes the walls and can destroy a poorly reinforced structure.

Two weeks are needed for the foundation to gain 70% of the declared strength. In the future, you can begin the construction of the facade, knowing that as the walls grow, the foundation will be strengthened for another two weeks.

Manufacturing of formwork

The board used for formwork is edged, 40 mm thick. Parts for strengthening are called clamps, spacers, supports. The guides are installed at the bottom of the trench. The need for building material is included in the design calculations. The formwork is assembled in accordance with SNiP using nails 150 mm long, which are driven in from the inside and not bent from the outside. This allows valuable material to be used later for wooden rafters or gable cladding. Permanent formwork used for shallow groundwater.

Laying depth of strip and shallow foundations updated: February 26, 2018 by: zoomfund

Read on topic