An excellent option for the supporting part for a residential building will be a do-it-yourself strip foundation, step-by-step instruction will help to complete the work without errors. The result of labor will be solid foundation which even a brick building can withstand.

Types of strip foundation

Before you make a strip foundation with your own hands, it is worth studying its design features. Depending on the technology used, the tape is of two types:

• monolithic;
• team.

A - monolithic; b - prefabricated

A monolithic strip foundation will be a more profitable option for frequent construction. Prefabricated technology is more often used for mass development. This is due to the fact that concrete blocks and prefabricated reinforced concrete foundation slabs are used for installation. Such structures on average have a length of 1-2 meters and weigh from a couple of hundred kilograms to a couple of tons.

The device of the strip foundation from the blocks becomes impossible without the rental of lifting equipment: tower or truck crane. This significantly increases the cost of construction. In addition, in a small area there is a problem of placing mechanisms.

Filling the strip foundation avoids additional costs. This option is rational when building a house with your own hands. A few people will be enough to complete the work.

By design, the tape is of three types:

• deep-seated strip foundation;
• shallow;
• not buried.

The first option is suitable for the construction of buildings on any grounds. In this case, it is possible to make a basement or a technical underground for utilities. The device of a strip foundation of a shallow type is considered for small buildings and in case of occurrence on the site it is not heaving soils with good strength (coarse-clastic, medium or coarse sands).

Unburied tape is used only for auxiliary buildings. You can put a gazebo or a canopy on it. Properly selected type of foundation will be the key to the success of all work.

To choose materials for the strip foundation, you need to decide on the technology. When using prefabricated elements, you will need to purchase:

• concrete blocks brand FBS;
• concrete slabs brand FL;
• brick and concrete for sealing holes;
• waterproofing materials;
• thermal insulation materials if necessary.

The sealing of holes made of brick or concrete is used because it is almost impossible to completely lay out an underground wall from standard blocks. Also, concrete and reinforcement will come in handy to make a tape concrete belt along the edge of the supporting part. A reinforced concrete element is necessary to bind the entire structure into a single whole. It allows you to evenly transfer the load from the walls to the underlying parts. If necessary, read the detailed article about foundations from FBS.

The technology of pouring a strip foundation involves the use of:

• liquid concrete of classes B15-B20;
• fittings: working, vertical, transverse;
• boards or polystyrene foam for the manufacture of formwork;
• waterproofing materials;
• thermal insulation if necessary.

Before you properly fill the strip foundation under the house, you will also need to prepare bulk material. Use sand of medium or large fraction, crushed stone, gravel or sand and gravel mixture. Such a pillow simultaneously performs several functions at once:

• aligns the base under the tape;
• performs the function of a drainage layer;
• prevents the negative effect of the forces of frost heaving.

Pros and cons

Before making the final decision to go deep with the help of the type of structures in question, it is worth studying the pros and cons of the types of strip foundation. The foundation tape deep laying has the following advantages:

• the possibility of building a basement;
• simplicity of technology;
• high reliability;
• application for heaving soils.

The recessed strip foundation also has disadvantages:

• large volumes of earthworks;
• high cost and labor intensity;
• the need for a drainage device;
• the complexity of the application at a high level of groundwater.

In some cases, a reasonable solution would be the installation of a shallow strip foundation. The option has the following advantages:

• reduced cost;
• there is no need for large volumes of earthworks;
• the ability to use when the GWL is located longer than 1.5 m from the surface of the earth.

But the construction of a strip foundation of this type is not available in all cases. This reinforced concrete option has several disadvantages:

• not recommended for heaving soils (if there is no other choice, they make reliable waterproofing, drainage, storm sewers and insulation);
• not suitable for buildings with a basement;
• cannot be used when the groundwater level is located above 1.5 m from the surface.

Strip foundation for the house: laying depth

This question should be the most important when designing a structure. The deepened strip foundation is supported so that its sole is 20-30 cm below the freezing mark. This is the only way to protect the building from uneven deformations during frost heaving.

The height of the strip foundation in this case depends on the climatic features of the area. The freezing depth is determined by the formulas. But with a simplified calculation of the dimensions of the supporting part, you can use ready-made tables developed for different cities of the country.

Depth of soil freezing by city

The shallow-depth design of the strip foundation assumes its laying at a distance of 70-100 cm from the surface level. It is important to remember that this option has a lower bearing capacity and is not resistant to the forces of frost heaving.

Before you start concreting under your house, you need to carefully select the depth of support of the sole. At the same time, not only freezing, but also GWL is controlled. General rule: water should not be closer than 20 cm to the base of the building.

The foundations of low-rise buildings usually do not need a detailed calculation. All values ​​are assigned by eye. In this case, there is a high probability of overspending. But if possible, it is better to turn to specialists who will accurately select the laying, width and reinforcement. If this is not possible, use the minimum values:

• height depending on soil freezing;
• width, depending on the width of the wall (the value for the foundation is taken not less, but better a couple of centimeters more);
• working reinforcement with a diameter of 12 mm;
• clamps with a diameter of 6-8 mm.

How to do it right: step by step instructions

Making strip foundations is not such a difficult task. But you will need to carefully study all the nuances and nodes for private houses.

Strip foundation: device diagram

First of all, a strip foundation scheme should be prepared. It lists all sizes. Such a drawing will not only make it easy to make a recessed strip foundation, but also calculate the required amount of materials in advance.

Example of a working drawing with dimensions

There is a certain order of work, according to which the strip foundation is poured, the technology is as follows:

1. preparation and marking of the site;
2. excavation;
3. installation of formwork and its waterproofing;
4. installation of a metal frame;
5. do the pouring of the strip foundation with their own hands;
6. set of strength and care of concrete;
7. stripping works;
8. waterproofing, insulation.

Training

How to make a strip foundation? - Answer: make geology and calculation. You will also need to clear the area and remove debris.

Geological surveys are carried out by specialists. In a simplified version, you can make them yourself. In this case, holes are torn off or wells are drilled to a depth that is 50 cm higher than the laying of the tape. The main task at this stage is to determine:

1. type of soil at the level of the base of the underground wall;
2. groundwater level.

After testing, they finally take the mark of occurrence, and also assign a cross section depending on the strength characteristics of the soil. With high accuracy, only an engineer will perform such work.

Plot marking

For marking use a wooden cast-off and a cord. Another option is to draw lines across the ground with lime mortar. How to pour the foundation under the house with high accuracy? You need to try at the markup stage. In advance, it is worth preparing a strip foundation scheme, which subsequently needs to be taken out to the area. The drawing made is needed so that all dimensions are at hand.

To markup, first mark the first corner. After that, a side is built from this point. It is easier if this side is parallel to the fence or road. The next step is to build a right angle. In such a situation, you need to use the Egyptian triangle method.

Cast-off stakes should be placed at a small distance from the outer walls of the building. This will prevent the cord from sagging when developing a trench or pit. After the markup for a square or rectangular building is prepared, it is worth checking the dimensions of the diagonals. They must match. Deviation up to 20 mm is allowed. A house that is complex in plan can be broken down into simple shapes.

To prepare the base for heavy equipment, you will need to mark out separate foundations. The expansion joint between them and the main tape is assumed to be at least 10 cm. After pouring the structures, this space is filled with loose non-combustible material.

Soil development

Technology involves a large amount of work. Most likely, it will be necessary to attract additional equipment: an excavator, dump trucks to transport the soil outside the site. The scope of work depends on whether the building will have a basement:

• if available, dig a pit;
• in the absence - trenches.

When performing earthworks, it is imperative to remember safety precautions. The width of the trench must be such that formwork can be installed in it. The walls are made with a slight slope. To prevent shedding of the soil, temporary supports are installed. Do not work in the trench alone. There should always be another person on the surface who will help in case of danger.

The dimensions of the trench or pit should provide unhindered access for workers to the side surface of the underground wall. This is necessary in order to make future insulation and waterproofing of the basement. The width on each side of the tape increases by about 80 cm.

sand cushion

A sand (crushed stone or gravel cushion) is laid at the bottom of the pit or trench. Its thickness is assigned depending on the strength of the soil from 20 to 50 cm. The weaker the soil, the thicker the backfill is needed. The same rule applies to heaving.

Sand cushion - the lowest layer of the base

The cushion must be level throughout. When laying it, it is compacted in layers (the thickness of the layer for compaction is taken no more than 15-20 cm. Compaction can be done by vibrating or pouring water. The method of pouring is not recommended for use for clay soils, since they have a low filtration coefficient.

On top of the pillow, a concrete preparation is made of lean concrete B 7.5 with a thickness of 5-10 cm.

drainage system

Drainage at the level of the sole of the tape is used not only at high GWL. For the device, drainage pipes with a diameter of 110 to 200 mm are used. The choice of diameter is carried out depending on the geological conditions of the site. Pipes are laid with a slope of 0.003-0.01.

Drainage is mounted in a layer of crushed stone with a fraction size of 20-40 mm. It performs a filtering function and prevents clogging of pipes. To prevent crushed stone from spreading, it is wrapped with geotextile.

Drainage device at high GWL

When installing a drainage system, several rules are taken into account:

• pipes should be 30 cm or more below the foundation foot mark;
• the maximum distance from the outer edge of the house to the drain is 1 m.

The output of the system is carried out in an open area, in a septic tank or sewer.

Formwork

Formwork for reinforced concrete foundations is of two types:

1. removable (from wooden boards);
2. fixed (from expanded polystyrene).

The second option also performs the function of thermal insulation and additional waterproofing. The formwork is set strictly according to the markup. Its height is assigned 10 cm higher than the foundation. Supports are mounted on the outside for stability. Jumpers can also be provided inside the structure. The first mounted node is a corner one. A plastic film or roofing felt is placed in a wooden formwork, which prevents the flow of cement laitance.

The upper edge of the formwork is placed 2-5 cm above the concrete mark. This will allow the mixture to be compacted without problems. She won't splash. The fill mark is drawn on the inner surface of the formwork with a marker.

Reinforcement installation

Reinforcing cages consist of three types of rods:

• working longitudinal diameters from 12 mm;
• horizontal clamps with a diameter of 6 mm;
• vertical clamps with a diameter of 8 mm.

All connections are recommended to be made on a knitting wire. Welding weakens the reinforcement and does not give a high guarantee. Even if the rods are connected along the main length with a welding machine, wire is used at the corners. To reduce labor intensity, a knitting gun is used.

Reinforcing cage placement pattern

in strip foundation

The pitch of the clamps is prescribed on average 20-30 cm. In the places where the walls adjoin each other, the pitch is halved. Before performing work, it is worthwhile to carefully study the methods of reinforcing the foundation at the nodes. Read the rest of the rules and recommendations in the article about the reinforcement of the strip foundation.

Pouring concrete

Before pouring the strip foundation under the house, it is recommended to order the mixture at the factory. This allows you to work without interruption. Also, in the factory, it is easier to observe the proportions of the components, which are very important. By adding a little more crushed stone or sand, you can get weaker concrete than required.

Pouring concrete

It is recommended to use material of classes from B15 to B20 for pouring. The heavier the house (from frame to brick), the more durable concrete will be required. Filling is desirable to perform in one day (without stops). This is the only way to prevent the occurrence concrete joints weakening the structure.

When performing work, you should follow the basic rules:

• pouring is done in one day with maximum breaks of 1-2 hours;
• the mixer moves along the perimeter of the building, dispersing the mixture from one point reduces the quality of the material;
• the maximum height from which the solution can be dropped is 2 m;
• concrete must be compacted after laying with a vibrator or bayonet.

Concrete care and stripping

Before you build a house, you need to study the weather forecast. Filling is recommended at an average daily temperature of +20 degrees Celsius. In hotter weather, the quality of the material decreases, in colder weather, the hardening rate. In total, it takes 28 days to set strength.

Immediately after pouring, the structure is covered with polyethylene, tarpaulin or burlap. This will prevent moisture loss too quickly. The formwork can be removed upon reaching 70% of the branded value. With an average daily temperature of +20°, this will take one or two weeks.

The film maintains the required humidity conditions during curing

During the first week after laying the mixture, you need to water it with water at intervals of a couple of hours. This will avoid the appearance of cracks on the surface of the structure. One way to wetting the surface is to spread sand or sawdust over the concrete; these materials are already wetted during care. They will gradually release moisture to the concrete.

Warming and waterproofing

Moisture isolation is a must. It includes:

Insulation is performed if necessary (if a warm basement is planned). For these works it is not allowed to use mineral wool. The best option will be extruded polystyrene foam ("Penoplex").

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

All about how to properly fill a monolithic strip foundation: the pros and cons of technology, instructions for pouring, installing and building a foundation strip

This page provides information about reinforced concrete strip foundations. We will consider the varieties of these bases, their scope, calculation features and construction technology - from marking to concreting the foundation tape.

The strip foundation is a closed reinforced concrete contour, arranged along the supporting structures and contributing to a uniform distribution of the mass of the building over the entire area. There is effective resistance to buckling processes occurring in the soil, which eliminates the possibility of distortions and subsidence.

What is strip foundation

The strip foundation is a monolithic reinforced concrete or prefabricated strip that repeats the perimeter of the walls of the structure. The tape is laid under the internal and external walls of the building, its cross section is identical both in the longitudinal contours and at the intersections.

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In comparison with the technology of mounting slab foundations, the construction of a strip foundation is simpler in execution and requires less material. The operational characteristics of the tape allow you to build on it the following types of buildings:

• Heavy houses with walls made of concrete, brick or stone, weighing more than 1000 kg / cubic meter;
• Buildings with reinforced concrete and metal floors;
• Light houses made of timber, logs and wood panels.

Important: the height of structures erected on a strip foundation varies between 1-5 floors. Such bases are suitable for construction in places where there is a risk of uneven soil shrinkage associated with frost heaving or soil heterogeneity. The reinforced frame of the tape provides a uniform redistribution of the loads acting on the foundation, which protects the walls from deformation.

The operational durability of strip foundations depends on their type:

• Monolithic reinforced concrete tapes - up to 150 years;
• Prefabricated brick strips - up to 50 years;
• Prefabricated tapes from reinforced concrete blocks - up to 75 years.

Strip foundations (deep) are used if necessary ground floor- the contours of the tape (1.5-2 m high) form the walls of the basement. In order to save building materials, deep laying tapes are often equipped with different perimeter configurations - the outer contours of the foundation deepen below the soil freezing limit (by 30-40 cm), and the inner contours are placed at a depth of 50-60 cm.

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In conditions of dry clay and sandy soils, the minimum depth of laying the foundation tape is 60 cm. On heavily heaving soil with a low freezing limit, such foundations are practically not used due to the financial inexpediency of laying the tape to a great depth. An alternative in this case are pile foundations.

Types of strip foundations

Tape bases are of 2 types:

• monolithic
• prefabricated.

Monolithic strip foundations are distinguished by the presence of a reinforcing cage, subsequently poured concrete mortar directly on the construction site. Thanks to this technology, the continuity of the structure is ensured. Prefabricated bases are formed from prefabricated reinforced concrete blocks.

Between themselves block structures fasten together cement mortar and reinforcement method. There are strip foundations according to the degree of deepening: deep-buried, shallow-buried. The depth is determined, depending on the bearing characteristics of the soil and the expected design load.

Strip foundation technology

It is rational to carry out the construction of a strip foundation in the warm season, from April to October. The construction of the tape does not require the involvement of special equipment, it is only necessary to have a concrete mixer and small-scale mechanization - a welding machine, a grinder, an electric drill.

Stage number 1 - preparatory work and marking

Construction begins with the preparation of a building site - the territory is cleared of debris and stones, vegetation and tree roots are removed. It is necessary to remove a layer of fertile soil (sod) to the depth of a shovel bayonet. If the site has a natural slope, the site is leveled at one horizontal level.

Important: marking the axes of the foundation is carried out using cast-off boards and wire or construction cord. The run-down shield consists of two stakes driven into the ground, which are connected by a horizontal belt. The twine on the shield is fixed using a self-tapping screw or a nail screwed into the board.

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When marking the contours, the shields are carried out beyond the axes of the foundation at a distance of 1-2 meters, so that in the process of digging a trench, the structures do not interfere with work. The design outlines of the foundation are transferred to the site - initially the external contours of the building are indicated, then the width of the tape retreats from them and the twine is pulled along the inner contour.

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The marking of the internal walls of the building is carried out upon completion of the breakdown of the external axes. In the process of work, you need to check the right angles of the markup. This is done according to the method of the Egyptian triangle - in one of the corners from the intersection on the first twine, a mark is made at a distance of 3 m, on the second - with an indent of 4 m. Next, the diagonal is measured, with the correct right angle its value is 5 m.

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Stage number 2 - digging a trench and backfilling the compacting pad

The trench for the foundation tape can be developed manually or using excavators. When using special equipment, the bottom of the trench must be leveled at one horizontal level.

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Upon completion of the formation of the trench, the compacting pad is backfilled. Its thickness is selected based on the degree of heaving of the soil; under normal conditions, a bedding 20 cm thick is used, consisting of two identical layers of crushed stone and sand. Sand is poured first, which is watered and manually compacted. If necessary, gravel can be replaced with fine gravel.

Stage number 3 - formwork installation

To create formwork, planed boards with a thickness of over 0.5 cm are used. It is acceptable to use boards processed on one side (a smooth surface is installed inside). The boards are knocked down into shields with a height equal to the height of the ground part of the foundation and are installed along the perimeter of the trench.

Important: the formwork must be fixed with the help of side braces and the upper transverse bar, which prevent the deformation of the form under the pressure of concrete. Make sure that the nails and screws that connect the shields do not protrude onto the inner surface of the formwork.

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It is important to achieve the verticality of the formwork walls, which is controlled by the level. The part of the formwork raised above the ground forms the basement part of the foundation tape. Holes are pre-cut in the shields for the placement of sewer and water communications, into which metal pipes are installed to form cavities in reinforced concrete structure.

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The formwork walls and internal surfaces of the trench must be covered with waterproofing material that will prevent leakage from concrete mix water and cement laitance.

Stage number 4 - assembly of the armored carcass

To reinforce the foundation, a double-circuit frame is used, consisting of an upper and lower longitudinal belt connected by vertical bridges. The number of rods in the longitudinal belts is selected based on the width of the tape (3-5 pcs), rods with a diameter of 12 to 16 mm are used. Vertical lintels placed in increments of 20-30 cm.

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For convenience, the frame is assembled outside the trench, after which the finished structure is placed inside the formwork. Each side of the frame should be removed from the contours of the concrete body of the foundation at a distance of 4-5 cm; special mushroom stands are used to raise the frame above the bottom of the trench; it is not recommended to use bricks for this purpose.

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Important: at the junction of the walls and the corner parts of the foundation, the frame is joined using curved reinforcement and is additionally reinforced with L-shaped rods. Cross docking cannot be used, as it reduces the strength of the structure.

Stage number 5 - concreting

For concreting the foundation tape, concrete grade M200 or M300 is used. When self-mixing, the proportions 1:2:4 (cement-sand-aggregate) are used. As a filler, fine-grained crushed stone with a particle size of 40-70 mm is used.

It is important to achieve the optimal consistency of the composition - when stirring with a shovel, it should not flow around a metal surface, but should be mixed with considerable effort. When using excessively liquid concrete, the aggregate may settle at the bottom of the trench, which should not be allowed.

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When pouring the foundation, gutters are used - it is impossible to pour concrete from a height of more than 1 m from the bottom of the trench, this can lead to its delamination. Do not allow intermediate hardening of concrete, layers should be poured before setting of previous layers. After concreting, the tape must be pierced with a reinforcing bar in order to remove air cavities from it.

Dismantling of the formwork is carried out after 5-7 days after pouring the foundation, it takes 25-30 days for the concrete to fully cure.

Frame reinforcement technology

The strength of the foundation is provided by the reinforcing structure, without which it is impossible to form an integral foundation. Reinforcement work includes several stages:

• formwork installation - a plank frame is installed along the perimeter of the future building, the walls of which are lined with parchment on the inside, thanks to which it will be easy to remove it later;
• driving vertically arranged reinforcing bars into the soil - the length of the reinforcement is comparable to the depth of the base. It is necessary to deepen the bars at a distance of 50mm from the walls of the formwork, while they are introduced into the ground in increments of up to 600mm;
• installation of supports on the bottom (height up to 100 mm), on top of which horizontally located reinforcing bars are laid: the function of supports can be performed by halves of bricks installed on the edge;
• horizontal rows connected to vertical rods;
• fixing structural elements at intersections by welding or wire.

Useful materials

One of the traditional, time-tested types of foundations is a monolithic, tape version.DIY strip foundationit is easy to build if you know the whole algorithm of actions. By design, it is a reinforced concrete strip passing under the load-bearing walls of the future building.

Construction stages

A tape monolithic foundation can be shallow, with a depth of 50 to 70 cm (for foam concrete, wooden, frame light houses) and buried - from 70 to 150 cm (for significant design loads from walls). The buried option is more stable, as it is below the freezing level of the soil.

Stage 1: design

Aiming to makedo-it-yourself foundationcompetently, one cannot rely on chance and ignore the phase of engineering and geological surveys. It is carried out by experts design organization, and at this stage determine:

type and main characteristics of the soil;

its bearing capacity;

freezing depth;

occurrence of groundwater.

This analysis will allow developing detailed project with calculations of the action of all loads from the future structure, the selection of the material corresponding to the obtained values ​​​​and the determination of the required safety margin. The project will detail the conditions for the safest location of the future structure for the surrounding landscape.

If the work is planned without developing a project, in any case, you need to know the composition of the soil (sand, sandy loam, loam or clay), the presence of groundwater and the approximate depth of freezing of the soil layer. It should be borne in mind that the buried foundation receives resistance from frost heaving, which is characterized by the fact that water, expanding upon freezing, squeezes it out with force. This phenomenon is most pronounced on clayey and heavy loamy soils.

Stage 2: preparation

At the preparation stage, all construction site. It will be necessary to level the relief with pronounced elevation differences.

Necessary construction material. It is necessary to provide for the arrangement of a canopy as a temporary warehouse.

Marking is carried out in strict accordance with the drawings, for which a rope or wire is used (the latter is preferable, since it stretches less) and stakes. For pegs, it is advisable to take reinforcement. First, the central axes are marked along the perimeter of the future structure. A peg is driven into the first point of the corner of the house and a wire is pulled from it strictly at a right angle in two perpendicular directions. Having noted the desired length, two fixing pegs are driven in, having received two more vertices of the rectangle, from which two more wires are also pulled at a right angle, which is calibrated with a square. At their intersection, a fourth vertex is formed. Subject to all markings, the angle at the fourth vertex is automatically straight (a control measurement is required).

It is necessary to check the correctness of the geometric figure by measuring the two diagonals, which should be equal. Errors are not allowed. If they are detected, an additional refinement of the entire markup is performed.

Then the axes of the internal load-bearing walls are marked in compliance with all the requirements for perpendicularity at the intersection.

When all the center lines are accurately marked on the surface, mark the contour of the future trench, setting aside half of its estimated width on both sides of the axis, equal to the width of the foundation, taking into account the laying of the formwork.

The calculated width of the foundation is equal to the width of the walls. This adds the next exterior finish, if it is included in the project, with insulation, which also rest on the foundation.

Stage 3: markup

This type of work is necessary in areas with slopes. A cast-off in the form of dug-in columns 1.0–1.3 m high with boards nailed from the outside is installed at a distance of about two meters from the marking of the building. The upper even cut of the boards should be in the same horizontal plane, which will serve as a guide when marking the bottomtrenches. Such control will ensure that the sole of the foundation will be in the same plane without distortions.

Stage 4: digging a trench

can be erected faster if this laborious process for manual digging is carried out using an excavator. After it, the bottom and slopes must be manually leveled. The depth of the trench varies depending on the soil: sandy - 1 m, sandy loamy and light loamy - 1.25 m, heavy loamy and clayey - 1.5 m.

The walls of the moat are made vertical by controlling these areas with a plumb line. To ensure cushioning during seasonal swelling of the soil, a sand and gravel cushion is arranged on a leveled bottom (about 10 cm of sand, which is moistened and compacted, and 10 cm of gravel or crushed stone) of the same thickness throughout. It is unacceptable to mask the uneven bottom of the trench with a pillow.

Stage 5: formwork installation

Formwork scheme

For formwork, a collapsible panel board is used. metal structure or use edged boards in cm. of minimum thickness, having a standardized width and a smooth edge. The assembly of shields from such boards, which are planed for the inner surface on one side, is carried out on the ground. After that, supports are installed along the edges of the trench, to which the downed shields are attached.

The formwork walls are made higher than the level of the future foundation so that the mixture does not spill over the top. The entire installation process is constantly controlled by a plumb line to achieve a strict vertical wall. Holes are immediately made for future sewer and engineering networks. The wooden structure is pressed against the walls of the trench with spacers and is abundantly wetted with water.

To mark the fill level, a cord is pulled inside, expecting that it rises at least 30 cm above the ground, subsequently forming the basement of the building.

Stage 6: reinforcement

The strength and reliability of the foundation depends on the reinforcement, which determines the necessary fixation of concrete. The smallest cross-sectional area of ​​the reinforcement is 8 mm. The installation of the reinforcing cage in accordance with the project is carried out in parallel with the installation of the formwork.

The rods are installed in two rows vertically in increments of 10 to 25 cm. Horizontally, reinforcement is attached to them with a wire. Reinforcing meshes with almost square cells rigidly fastened together by transverse horizontal bars are formed. A frame is made to the height of the foundation, a gap is maintained between the formwork wall to the central axis of the rod from 40 to 70 mm, so that it is completely inside the structure.

It is possible to make a frame by welding, performing separate sections outside the trench according to the design parameters. Then they are installed in place and welded into a single structure.

Stage 7: installation of basement ventilation

To ensure natural ventilation of the basement and subsequently the house, an asbestos-cement or plastic pipe with a diameter of about 100 mm is attached to the reinforcement with a wire flush with the formwork.

Stage 8: foundation drainage

To avoid destructionhandmade foundationfrom closely occurring groundwater, it is advisable to arrange a drainage closed channel with a slope to remove water at a distance of one and a half to three meters along the entire perimeter. Its depth is half a meter greater than that of the foundation, and a perforated drainage pipe is laid along the bottom.

Stage 9: pouring concrete

Before pouring, wax paper is laid along the walls of the formwork, which will greatly facilitate its subsequent dismantling.

Concrete (the grade is chosen not less than M200) is poured into the frame in layers. At the same time, each layer is pierced to release air, and rammed until “milk” appears on the surface to eliminate voids and obtain the design strength of the foundation. For this, wooden rammers are used with simultaneous tapping of the formwork walls or, if possible, a more efficient concrete vibrator is used.

At this stage, it is necessary to control the quality of the concrete, which must have a uniform consistency and not be excessively fluid. It is necessary to use additional devices in the form of a gutter when pouring from concrete mixers with a height of more than one and a half meters, since there is a risk of mixture separation when it is poured from such a distance.

With self-preparation of M-200 concrete, you will need cement (M-400 grades), sand and crushed stone (fine grain) in a ratio of 1: 3: 5. The amount of water is determined from the ratio: 0.68 = cement / water, from which water = cement / 0.68.

The topmost layer after tamping is additionally leveled with a construction trowel. After three hours, the entire structure is covered with burlap. For even drying in hot weather, the surface is moistened. If it rains, then it is covered with plastic wrap. After a week, in order to achieve maximum shrinkage, several rows of ordinary brick can be laid on the upper cut.

Stage 10: waterproofing

Foundation and basement waterproofing

Two or three weeks after the completion of pouring concrete, having removed the formwork, waterproofing work begins. To do this, the outer walls are coated with bituminous mastic and roofing material is glued. After a few days, quality control is carried out for the strength of the fit of the material over the entire surface without peeling. Identified shortcomings are eliminated.

Step 11: backfill

Layers of the finished strip foundation

Do-it-yourself tape foundationalmost ready, as this is the last stage of construction. It consists in manually filling the sinuses of the foundation with sand of medium fraction, which is moistened and compacted in layers. A variant of protecting waterproofing from damage during a layer of geotextile is used.

Strip foundations are the most common, but not applicable on all soils. To begin the construction of such a foundation, it is necessary to carefully examine the soils and decide how thick and how high the tape should be.

In this article, we will describe in detail all the stages of the construction of a strip foundation, starting from digging a trench, reinforcing, formwork and ending with pouring concrete.

Geology of the soil under the foundation

This is the most important stage by which the following data are determined:

1. Soil type and its design resistance.
2. Freezing depth.
3. Ground water level.
4. The degree of heaving of the soil and its uniformity.

After geology, you can proceed to the design of the foundation itself.

Depending on the architectural solution, that is, the initially planned building, the weight of the house is determined, including the weight of the foundation, snow, wind and payload. The type of foundation, in our case, tape, can be buried and shallow.

The next step is to determine the parameters of the foundation itself, namely:

1. Foundation width.
2. The height of the recessed part.
3. Above ground height.
4. Is drainage required?

To determine the width of the foundation, it is necessary to divide the weight of the house by the area of ​​\u200b\u200bthe foundation support, and the resulting value should be less than the calculated soil resistance by 20%.

To increase the area of ​​​​the foundation support, a broadening (heel) is made, which distributes the load over a larger area.

We wrote about this in more detail in our previous article - how to calculate the weight of the house.

For a deep foundation, the laying depth should be 20 cm below the freezing depth. For a shallow foundation, it all depends on the soil, or rather on heaving, freezing depth and groundwater level.

For an approximate determination of the depth of a shallow foundation, see the table.

1. The maximum height of the above-ground part of the strip foundation should not exceed four widths of the foundation strip.
2. The above-ground part should be smaller than the underground part.
3. The optimal height of the aerial part is 40-50 cm.

Performing site markings

By finished project it is necessary to carefully measure all the corners of the future foundation and set the pegs. The stakes are placed along the outer and inner perimeter of the foundation, a cord is stretched between the stakes, defining the contours for digging the foundation trench.

At this stage, a trench is being dug, the depth of which should be under the foundation project, taking into account the sand cushion and formwork. There are two ways to dig a trench: with a tractor using a narrow bucket, and manually (with shovels). The tractor will cope much faster, but with shovels it turns out smoother and more accurate.

The sand cushion is made about 20 cm thick, wetted with water and well compacted.

In some cases, it will be much more convenient to first tie the frame in the trench, and only then expose the wooden formwork.

Frame reinforcement steps:

1. Stones or bricks 5-6 cm high are laid at the bottom of the trench, the task of which is to raise the reinforcing cage in order to create a protective layer of concrete from below.
2. Further, longitudinal reinforcements are laid out on the bottom, not rods, previously bent at the corners.
3. Next, pre-made clamps are put on the bottom row of reinforcement, they are also frames, they are also transverse reinforcement.
4. Clamps and a row of lower reinforcement are connected with knitting wire.
5. If the height of the tape is more than 80 cm, then structural rows of reinforcement are added, one row or more.
6. Further, the upper longitudinal reinforcement bars, L-shaped clamps at the corners are added to the frame and are connected with wire.
7. To provide a protective layer of concrete on the sides of the foundation, special plastic rings are used to help hold the frame in position.

We strongly advise you to read our article about the calculation of the reinforcement of a strip foundation, in which all the nuances for the selection of reinforcement and the scheme for reinforcing corners are described in detail.

The formwork is knocked down from wooden boards, and reinforced with many bars, which additionally rest against the ground on pegs. Also, to strengthen the formwork, metal wire ties are used, or studs are tightened in plastic tubes.

The installation of the formwork must be approached very responsibly, since liquid concrete has a large bursting force, especially if the height and width of the formwork are large. Quite often, formwork bursts for inexperienced builders, and concrete flows to the ground. To avoid this situation, reinforce the formwork as much as possible. And remember that more concrete pressure is created at the bottom.

Do not forget about the installation of sleeves for communications (water, sewerage).

It is very important that the foundation be monolithic, and in order to achieve this state, it is necessary to pour concrete into the trench in one go. Manually, with a concrete mixer, this is unlikely to be achieved, therefore it is better to order the delivery of ready-made concrete in mixers.

1. The time between delivery of concrete trucks should not exceed two hours.
2. Pouring is best done in layers, pulling the concrete around the entire perimeter.
3. For a more plastic (liquid) concrete mix, ask to add a plasticizer to the mixer.
4. Excess water in concrete reduces grade strength, increases the number of shrinkage cracks and increases the number of pores in concrete, making it less moisture resistant. Avoid excess water during the kneading process.
5. During pouring, you need to use a deep vibrator, which compacts the concrete and expels air.
6. Try to level the plane of the foundation tape as much as possible.
7. During the week, it is necessary to shed the surface of the foundation with water, this will avoid shrinkage cracks and help the concrete gain brand strength. We also recommend covering the tape with foil.

The foundation is ready. It remains to perform vertical and horizontal waterproofing, as well as an insulated blind area, which reduces the depth of freezing and removes excess water from the foundation.

About how long the foundation should stand, we wrote a separate article, which discusses options for settling from 10 days to six months.

A monolithic strip foundation is a one-piece structure made of steel reinforcement and a concrete strip. It is located along the perimeter of the building and under all load-bearing walls and elements. If the technology is followed, the structure becomes a single whole - a monolith - and has a very high reliability and strength characteristics. For this reason, it is popular both in the construction of multi-storey buildings and private cottages.

It is advisable to use a monolithic strip foundation at a low level of groundwater: when they are located below the required depth of the foundation. Otherwise, it is necessary to organize drainage, and these are additional (and considerable) funds.

Device and types

According to the depth of occurrence, strip foundations are shallow and deep occurrence. Shallow ones can be used on calm, non-fluffy soils with good bearing capacity for buildings of small mass - made of wood and erected using frame technology.

In this case, the tape should go 10-15 cm into the hard layer, which is located under the fertile one. At the same time, according to the standards, it cannot be less than 60 cm.

Deep monolithic strip foundations are made for heavy, massive houses. In the general case, they are lowered 10-15 cm below the level of soil freezing for a given region. In this case, the sole must rest on a layer with good bearing capacity. If this is not the case, you have to go deeper. For example, if the level of soil freezing is 1.2 m, and the fertile layer ends at 1.4 m, then you have to fall below 1.4 m.

With or without formwork

In general, the technology for erecting a monolithic strip foundation provides for installation. These are structures made of shields that give shape to concrete and prevent it from spreading. It is clear that the formwork is an additional cost for materials, as well as additional time for its assembly and installation.

Formwork - a structure made of boards or plywood that gives the foundation a shape

Sometimes, in order to save money, on good soils, a foundation pit is dug exactly according to the markup - to the desired width and depth. And concrete is poured into these pits without formwork. Such a technology cannot guarantee the required degree of reliability, and it is impossible to predict the result. The fact is that concrete needs a certain amount of water to gain normal strength. Without formwork, water, although a little, is absorbed into the ground, which can affect the quality of the concrete stone itself. In the worst case, it may crumble.

They get out of the situation by spreading a plastic film in the trench. But then they walk along it - reinforcement needs to be done. Both rods and boots damage the film more than once. As a result, moisture still leaves.

Foundation without formwork - a risky undertaking

In some cases, such foundations can stand for a certain number of years without problems. But sooner or later, cracks appear or concrete begins to crumble. The second difficulty in working with such a foundation is its far from ideal geometry. In order to reduce heat loss, the foundation is insulated, most often with foam boards or extruded polystyrene foam. Try sticking them on an uneven surface. The situation is the same with vapor barrier: the film is very difficult (almost impossible) to stick on uneven, porous concrete with soil inclusions. Whether or not this approach is justified is up to you, but such a foundation can only be recommended for a fence or a barn.

Basement in a house with a strip foundation

The basement can be the same area as the house, or it can occupy only part of the space. And you need to decide on its dimensions before the design stage.

If the basement occupies only a certain part of the space, it will be possible not to take out all the soil, but to dig only trenches under the tape. They also dig the basement according to certain rules. Its placement and arrangement can also be developed at the design stage.

A tape monolithic foundation with a basement is a difficult task to design (to increase the size of the picture, right-click on it)

If it was decided to make the basement later, then you need to choose a place and determine the depth so that when you draw lines from the base of the house at an angle of 45 °, they do not pass through the voids (shown in the photo on the right).

If the basement is located under the entire area of ​​​​the house, then the entire soil is removed to the required depth. In general, such a project cannot be called a budget one: there is much more work and expenses. Firstly, reinforced reinforcement of the walls and their greater thickness are required. Since there will be no soil inside, the walls of the basement will need to resist the pressure of the soil from the outside. Therefore, the thickness of the tape will be much larger and the reinforcement is needed more powerful, it fits with a smaller step, and the number of reinforcement belts will also increase. As a result, only the consumption of reinforcement for the foundation will increase. Secondly, concreting and, possibly, reinforcement of the basement floor over the entire area will be required. And these are again materials - concrete and reinforcement. Thirdly, effective ventilation will be needed to remove underground gases. Such a structure can no longer be designed independently. The job must be done by a professional with extensive experience.

One of the options for building a foundation for a house with a basement (to enlarge the image, right-click on it)

Monolithic strip foundation: construction stages

Even if an organization or a team will build a house, the developer needs to know the technology: this is the only way to control the process and be sure of the quality of the work.

In general, the technology is as follows:

• Site marking.
• Land works.
• Consolidation of the base, basic bedding and tamping.
• Ribbon layout.
• Waterproofing.
• Assembly and installation of formwork.
• Knitting reinforcement.
• Concrete pouring and vibrating.
• Curing.

Some explanation is required. Double marking - a plot and a tape - is needed if the house will have a basement under the entire area of ​​\u200b\u200bthe house. The first time you mark out the area of ​​\u200b\u200bthe house, taking into account allowances for the installation of formwork. There is no way to do without it. Then, after the pit is dug and the bottom is poured and rammed, it will be necessary to mark the tape. According to these marks, formwork will then be installed, which will form the “profile” of your house.

Now a little more about each of the stages.

Plot marking

Since for the design the soil was examined in a certain area, it is necessary to bind rigidly. The underground structure is often heterogeneous and a shift of half a meter can be critical: suddenly there are subsidence rocks or a cavity. It is hardly worth positioning with an accuracy of up to a centimeter, but it is advisable not to miss much.

earthworks

Their volumes and the equipment used depend on whether you have a house with or without a basement. If not, then you marked the tape - and you will need to remove the soil. Only with a margin for the installation of formwork - and this is sometimes 50 * 80 cm on each side. Shields need spacers to keep them from falling apart.

If the house has a basement, all the soil will need to be removed. The dimensions of the pit are 2-5 m larger than the dimensions of the foundation. This is all the same stock for formwork spacers.

If the house has a basement - the pit turns out to be big

For large volumes, it is better to use special equipment. Renting it costs a lot, but the work of a brigade of "diggers" for several days will not be cheaper. The speeds are incommensurate.

The upper fertile layer is laid separately, it can be immediately distributed throughout the garden. The rest of the soil is piled up: it will partially go to backfill, part of it will need to be taken out.

Sealing the bottom of the pit and backfilling

After the bulk of the soil has been removed, the bottom must be leveled and compacted. When working with an excavator, it often happens that some areas are 20-30 cm deeper than necessary. All these irregularities must be corrected: fall asleep and tamp.

Ramming and leveling are needed over the entire area of ​​​​the pit or trench. And not with a deck. It can be used if you are building a fence. Even during the construction of a bath or cottage, it is better to use a vibrating plate.

Let's see why. This level accounts for the entire load of the building. Even small voids and irregularities can cause uneven shrinkage and cracking. And the bottom after excavation of the earth is uneven. And you can eliminate this with a rammer. It is even better if a layer of sand with medium or fine grain is poured onto the bottom. Due to its smaller size, it aligns better. But for better and faster compaction, it needs to be moistened (pour water to wet its entire volume). The vibrating plate creates a force that compacts the sand by 15-20 cm. It is this layer that needs to be poured at a time. If according to the project, a layer of sand is 30 cm, then it is first necessary to pour 15 cm, shed and compact it to a high density. Then pour the second one and spill and tamp it too.

Often the project requires the creation of sand and gravel bedding. Then another layer of crushed stone with a fraction of 30-60 mm is poured over the compacted sand. And he, too, rambles. The thickness of this layer of backfill is 10-15 cm. It also needs to be poured in small layers of about 5 cm each and compacted.

In this case, the soil is not only leveled, it also becomes more dense: crushed stone is driven into the underlying rock, increasing its bearing capacity. Since the plate hits the pebble with great force, the compaction occurs to a depth of 40-50 cm. And this is very good.

Formwork for a monolithic strip foundation

The formwork is made of boards with a thickness of at least 40 mm, low-grade plywood or OSB. Plywood is inexpensive, special - formwork. It has a lamination on one side - there is a protective film. Therefore, it can be used several times.

Shields made of sheet materials are reinforced with transverse and longitudinal bars. From the boards are fastened with crossbars. The assembled shields are exposed according to the marking of the tape, fixed on the outside with slopes, and spacers are installed inside. All these fasteners must give the formwork the specified dimensions. They will not allow the shields to fall apart or bulge when pouring concrete: the mass will put considerable pressure on the walls, therefore the fasteners must be reliable.

- an inapplicable attribute of a quality foundation

Reinforcement

Due to the structural features - large length and small width - the strip foundation is mainly affected by forces that try to break the strip across. Therefore, it must be strengthened along the long side. Here they use powerful ribbed reinforcement from 10 mm in diameter and more. All transverse reinforcement only stabilizes the longitudinal bars in space, therefore it can be taken smooth and used with a small thickness - 6-8 mm.

Moreover, in most cases, regardless of the depth, two reinforcing belts are sufficient: at the top and bottom of the tape. The exception is the foundation device with a basement under the whole house.

The scheme is shown in the photo. At each connection point, the reinforcement is tied with a special wire. This is done manually using hooks or automatic devices - knitting guns.

There is another way: welding. But its use is not always justified. Work in progress faster, but at the same time the connection is rigid. When knitting with wire, the reinforcement has some freedom. And it helps to compensate for some deformations without destroying the concrete. When welding, the joints are rigid, which on the one hand is not bad, but on the other hand, a too rigid structure can cause cracks.

Another point: the welding site always begins to collapse first. Although the reinforcement is located in the thickness of the concrete, and therefore does not corrode (oxygen does not penetrate to it), but in case of any violations and the supply of oxygen, the welded joints are destroyed first.

At this stage, ventilation products and ducts are laid, through which they will be brought to the house engineering Communication. If you forget about it, you will have to destroy the monolith, and this is very undesirable: the fewer flaws, the stronger the structure will be.

Filling the strip foundation

When building a more or less large house, it is easier and better to order the delivery of ready-made concrete to the site in a mixer. Then the filling can be done in one day.

You can make your own concrete. But this requires a concrete mixer. Manually, mixing the components in troughs, it is impossible to ensure the proper degree of uniformity.

For manual pouring, at least three people will be needed: one kneads the concrete in a concrete mixer, the second distributes the finished portion, and the third vibrates the newly poured area.

Vibration of concrete is carried out using manual or portable submersible vibrators. This process allows you to remove all voids, more evenly distribute the aggregate. As a result, the strength characteristics of concrete are much improved, it acquires frost resistance due to the fact that it absorbs water much less. Therefore, do not skip this stage: with the same components in the solution, we get a higher grade concrete as a result.

Another point: when pouring from a machine, you need to use special gutters. Firstly, it is easier for them to deliver concrete to the desired point, and secondly, the solution should not fall from a great height. If the fall height exceeds 150 cm, it delaminates. The result is low strength.

Curing

If the work was carried out in hot, dry weather, the tape must be covered with plastic wrap or any other material that prevents the rapid evaporation of moisture. Since the depth of the concrete is large, wetting the surface will not give tangible results. The main thing is not to let the top dry out and the film copes with this task perfectly.

If the temperature during and after pouring is kept around + 20 ° C, three days after pouring, the concrete will gain a strength of about 50%. And on the fourth day, the formwork can be removed and proceed to further work.

At lower temperatures, you need to wait longer: at +10°C it is already 10-14 days, and at +5°C the setting process practically stops. In such conditions, it is necessary either to insulate the formwork or to heat the concrete.

The monolithic strip foundation is ready, but there is still work to be done on its insulation and waterproofing. Only after that it is covered (backfill).