The reliability and durability of the entire structure depends on the quality of the foundation. Mistakes made when creating the foundation are impossible or very difficult to correct in the future. Therefore, this task must be approached with full responsibility right away. How to pour a strip foundation correctly?

Preparing for pouring

Before choosing a location for your home, it is necessary to conduct a geodetic examination of the site. This will make it possible to determine how deep the groundwater lies, what kind of soil is on the site, and how much the soil freezes. Knowing this data, choose the type of foundation.

Important! To develop a foundation project for a house, it is better to contact specialists. Creating a foundation is the most expensive and most important part of the work.

Before pouring the strip foundation with your own hands, clear the area of ​​debris and plants and remove the fertile layer. Then it is marked in accordance with the project.

Professionals do this using special tools, for example, a theodolite; you can mark the area yourself using a right-angled triangle made of cord.

• First, using pegs and rope, mark the outer facade - that part of the building that will face the street.
• Then, side walls perpendicular to it are built from its corners.
• Internal markings are made parallel to the external one. To do this, you need to retreat 40 cm from the outside to the inside of the site.
• The correctness of the construction is checked by comparing the diagonals of the rectangle: they must be equal.
• The marking can be done using stretched cords, or you can apply it directly to the ground with lime mortar.

Trenches are dug along these markings. If the area is uneven, then the depth is calculated from the lowest point. This way the foundation will turn out without distortions. The walls of the trenches must be vertical. It is important to ensure that the entire trench lies in the same plane.

The depth of the trench depends on what type of foundation is intended for the house. If this is a shallow strip foundation, then the depth of the trench can be from 30 cm. Usually they make 40-60 cm, for heavier buildings - 80 cm. If the strip foundation is deep, for example, they plan to make a basement or basement, then the depth of the trenches should be 40 cm below the freezing level.

Then the bottom of the trenches is compacted. This is especially important on heaving soil, since compaction increases the bearing capacity of the soil.

Next, pour a cushion of gravel or coarse sand. Usually sand or small crushed stone is used, or a mixture of them is also used. Often they make a two-layer pillow. First, pour a 20 cm layer of sand, compact it with a vibrating foot or manually, then a layer of crushed stone of the same thickness. It is also compacted. A waterproofing material (roofing felt) is placed on top.

Formwork and reinforcement

To properly fill a strip foundation, high-quality formwork is required. It not only gives the foundation its shape, but also creates its above-ground part. It also strengthens the walls of the trench. Formwork is made from boards or panel materials: plywood, metal tiles.

The most commonly used edged boards are 25*100 mm in size. The boards or boards are fastened together with self-tapping screws. A plastic film is placed inside the formwork and secured to the boards with a stapler. The film prevents the concrete from adhering to the boards and preventing water from flowing into the cracks and being absorbed into the sand cushion.

You can rent ready-made removable formwork. Sometimes permanent formwork made of expanded polystyrene is used, which at the same time plays the role of insulation. The upper edge of the formwork should rise 30 cm above the trench. Inside the formwork, use a cord to mark the level at which the concrete will be poured.

Reinforcement is also an important stage; reinforcement gives strength to a concrete structure. Typically, ribbed rods with a thickness of 10-12 mm are used for longitudinal reinforcement, and thinner, smooth ones for transverse reinforcement.

Pouring concrete

Typically, factory-mixed concrete of grade M200 and higher or hand-mixed concrete from sand, crushed stone, cement and water is used. The ratio of sand, crushed stone and cement should be 3:3:1.

Concrete is poured in layers of 20 cm. Each layer is compacted.

The technology of pouring a strip foundation implies that it is concreted in one stream. You cannot pour in different corners at the same time, this can lead to the foundation being crooked.

After pouring, the concrete is leveled with a trowel or a flat board, and then compacted with a vibrating platform to release air bubbles. It is possible to compact concrete manually by bayoneting with a metal rod, however, this is a labor-intensive process. It is better to rent a vibration platform.

Attention! The vibrator must not be used to distribute concrete inside the formwork. Before compacting, it is necessary to level the concrete so that there are no protrusions larger than 10 cm.

Compact the concrete until laitance appears on the surface. After concreting, it is necessary to tap the formwork - this will get rid of air bubbles stuck to it. For an overview of typical mistakes when building a foundation, watch the video.

Curing

In order for concrete to harden well and gain maximum strength, it is necessary to care for it during the hardening process. It is very important for concrete to cure in a damp environment. Therefore, 2 hours after pouring, the concrete strip is covered with sawdust or protected with covering material. In hot weather, concrete must be wetted. The foundation is also covered from rain with plastic film or other waterproof material.

Dismantling formwork and other work

The formwork is removed when the concrete gains 70% strength - after 24 days. After this, the foundation is waterproofed and insulated, the sinuses are filled with soil, compacting it thoroughly.

How to pour a foundation in parts

Experts recommend pouring the entire foundation strip at one time. This actually turns out to be a monolithic structure, without seams that will become cold bridges. However, in practice this is not always possible for various reasons. Is it possible to fill a strip foundation in parts and will this affect the strength of the foundation?

SNiPs state that if certain rules are observed, concrete can be poured in parts without loss of quality.

• In this case, the seams must be made perpendicular to the tape - horizontally or vertically.
• Typically, concrete is poured in layers so as not to make additional partitions in the formwork. 2-3 days should pass between pouring layers, during which time the concrete will have time to harden. Otherwise, the pressure of the new layer will lead to cracks in the weak lower layer.
• Before pouring a new layer, the hardened concrete is cleaned with a brush from dust and dirt, washed to remove the cement film and allowed to dry. Only after this the next layer is made.
• If concrete is poured in one day, then the break between pouring layers should not exceed 3 hours in summer, 4 hours in the off-season and 8 hours in winter.
• The thickness of the layers is 20-50 cm. Each layer is compacted.

If the process of pouring a strip foundation is carried out in parts, high-quality reinforcement is very important. Be sure to install vertical reinforcement.

Pouring the foundation without formwork

Pouring a strip foundation into the ground allows you to save on materials and installation of formwork, however, this method is not always suitable.

It is not recommended for residential buildings. When pouring into the ground, even if polyethylene is placed at the bottom of the trench, there is a possibility that the reinforcement will pierce it and the cement laitance will begin to go into the ground. Then the strength of the foundation will be lower than expected. Therefore, strip foundations without formwork are usually poured for small buildings: outbuildings, sheds, garages, gazebos, temporary buildings or small country houses used seasonally. On the other hand, on heaving soil, too light buildings cannot be placed on such a foundation, since they will simply be squeezed out of the ground by the forces of frost heaving.

This type of foundation is not suitable for loose, sandy soils. It is better to do it on clay and loamy soils.

As when creating a strip foundation with formwork, the area is first marked out. Then they dig a trench 80-100 cm deep. Its width should be approximately 30 cm greater than the width of the future wall. A sand cushion approximately 15 cm thick is poured into the bottom of the trench and compacted.

You can pour a high-quality foundation yourself, but for this it is important to follow the technology. The foundation is the foundation of the house, and mistakes when pouring it will certainly affect the entire building.

A monolithic strip foundation is an integral structure made of steel reinforcement and 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 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 when the groundwater level is low: when it is located below the required foundation depth. Otherwise, it is necessary to organize drainage, and this requires additional (and considerable) funds.

Device and types

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

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

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

With or without formwork

In general, the technology for constructing a monolithic strip foundation involves the installation. These are structures made of panels that give shape to concrete and prevent it from spreading. It is clear that formwork means additional costs for materials, as well as additional time for its assembly and installation.

Formwork is a structure made of boards or plywood that gives the foundation its shape.

Sometimes, in order to save money, on good soils a foundation pit is dug exactly according to the markings - to the required width and depth. And concrete is poured into these pits without formwork. Such technology cannot guarantee the required degree of reliability; the result is impossible to predict. 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 soil, which can affect the quality of the concrete stone itself. In the worst case scenario, it may crumble.

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

A foundation without formwork is a risky undertaking

In some cases, such foundations can last for a certain number of years without problems. But sooner or later, cracks appear or the concrete begins to crumble. The second difficulty of 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: it is very difficult (almost impossible) to glue the film onto uneven, porous concrete interspersed with soil. Whether this approach is justified or not is up to you to decide, but such a foundation can only be recommended for a fence or shed.

Basement in a house with a strip foundation

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

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

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

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

If the basement is located under the entire area of ​​the house, then all the soil is removed to the required depth. In general, such a project cannot be called a budget project: 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 basement walls will need to resist soil pressure from the outside. Therefore, the thickness of the tape will be much greater and the reinforcement will be more powerful; it will be laid in smaller increments; the number of reinforcement belts will also increase. As a result, the consumption of reinforcement only for the foundation will increase. Secondly, concreting and, possibly, reinforcement of the basement floor over the entire area will be required. And these are the materials again - concrete and reinforcement. Third, effective ventilation will be necessary to remove underground gases. You can no longer design such a structure yourself. The work must be done by a professional, and with extensive experience.

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

Monolithic strip foundation: stages of construction

Even if an organization or team builds the house, the developer needs to know the technology: this is the only way to control the process and be confident in the quality of the work.

In general, the technology is as follows:

• Site marking.
• Land works.
• Base compaction, base filling and compaction.
• Tape marking.
• Waterproofing.
• Assembly and installation of formwork.
• Knitting reinforcement.
• Pouring concrete and vibrating it.
• Curing.

Some clarification is required. Double marking - site and tape - is needed if the house has a basement under the entire area of ​​the house. The first time you mark out the area of ​​the house, taking into account allowances for installing the formwork. There is no way to do without her. Then, after the pit is dug and the bottom is filled and compacted, it will be necessary to mark the tape. The formwork will then be installed using these marks, which will form the “profile” of your home.

Now a little more about each of the stages.

Site marking

Since the soil was examined in a certain area for design, it must be tied firmly. An underground structure is often heterogeneous and a displacement of half a meter can be critical: suddenly there are subsidence rocks or a cavity. It’s hardly worth positioning with centimeter accuracy, but it’s advisable not to miss too much.

Land works

Their volumes and the equipment used depend on whether your house has a basement or without. If not, then you have marked the tape - so you will need to remove the soil. Only with a reserve for installing formwork - and this is sometimes 50*80 cm on each side. Shields need spacers to prevent 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 the same reserve for spacers for formwork.

If the house has a basement, the pit turns out to be large

For large volumes it is better to use special equipment. Renting it costs a lot, but the work of a team of “diggers” for several days will cost no less. The speeds are disproportionate.

The top fertile layer is laid separately, it can be immediately distributed throughout the garden. The rest of the soil is dumped into a heap: partly it will be used for backfilling, partly it will need to be removed.

Compacting 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 need to be corrected: filled and compacted.

Tamping and leveling are needed over the entire area of ​​the pit or trench. Moreover, not with the help of a deck. It can be used if you are building a fence. Even when building a bathhouse or cottage, it is better to use a vibrating plate.

Let's figure out why. This level bears 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 this can be eliminated using a tamper. It’s even better if you add a layer of medium or fine grain sand to 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. This is exactly the layer that needs to be poured at a time. If, according to the project, the layer of sand is 30 cm, then you first need to pour 15 cm, spill it and compact it to a high density. Then pour in the second one and pour it too and compact it.

Often the project requires the creation of sand and gravel bedding. Then another layer of crushed stone of a fraction of 30-60 mm is poured on top of the compacted sand. And it also gets compacted. The thickness of this layer of bedding is 10-15 cm. It also needs to be poured in small layers of about 5 cm and each 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 slab hits the stone with great force, compaction occurs to a depth of 40-50 cm. And this is very good.

Formwork for monolithic strip foundation

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

Shields made of sheet materials are reinforced with transverse and longitudinal bars. The boards are held together with cross members. The assembled panels are aligned according to the tape markings, secured on the outside with bevels, 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 out when pouring concrete: the mass will put considerable pressure on the walls, so 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 needs to be strengthened along the long side. Here they use powerful ribbed reinforcement with a diameter of 10 mm and more. All transverse reinforcement only stabilizes the longitudinal bars in space, so it can be taken smooth and used in 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 construction of a foundation with a basement under the entire house.

The diagram 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. The work goes faster, but the connection is tough. When knitting with wire, the reinforcement remains some freedom. And this helps 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 structure that is too rigid can cause cracks.

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

At this stage, the installation of ventilation ducts and ducts takes place, through which utilities will be brought to the house. If you forget about this, you will have to destroy the monolith, and this is very undesirable: the fewer flaws, the stronger the structure will be.

Pouring strip foundation

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

You can make concrete yourself. But this will require a concrete mixer. It is impossible to ensure the proper degree of homogeneity by manually mixing the components in troughs.

To manually pour, you will need at least three people: one mixes the concrete in a concrete mixer, the second distributes the finished portion, and the third vibrates the newly poured area.

Concrete is vibrated using hand-held or portable submersible vibrators. This process removes all voids and distributes the aggregate more evenly. As a result, the strength characteristics of concrete are much improved; it becomes frost-resistant due to the fact that it absorbs much less water. Therefore, do not skip this stage: with the same components in the solution, the result is concrete of a higher grade.

One more point: when pouring from a machine, you need to use special gutters. Firstly, they make it easier 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 work was carried out in hot, dry weather, the tape must be covered with plastic film or any other material that prevents rapid evaporation of moisture. Since the depth of the concrete is large, wetting the surface will not give noticeable 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 remains around +20°C, three days after pouring the concrete will gain about 50% strength. And on the fourth day, the formwork can be removed and further work can begin.

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 to either insulate the formwork or heat the concrete.

The monolithic strip foundation is ready, but there is still work to be done on its insulation and waterproofing. Only after this is it filled up (backfilling).

The future condition of the erected building and the period of its trouble-free operation will depend on the quality of foundation work. When choosing a foundation design for a house, you need to take into account factors such as the number of storeys and weight of the future cottage, the type of soil, and the groundwater level. In private low-rise buildings that are being built with your own hands, in many cases the optimal solution will be a strip foundation.

When arranging the foundation, you must strictly observe all stages of work and their order. First, choose the material to fill. It directly depends on the type of soil on which the house is built. When constructing a building on excessively and heavily heaving soils, only monolithic reinforced concrete is used. On medium and slightly heaving bases, monolithic concrete can be used. A strip foundation on soils with strong heaving should be a rigid frame of intersecting strips that can withstand strong soil pressure.

Compacting the base is especially important when building on heaving soils. It reduces soil heaving and increases the bearing capacity of the foundation. If a house is built on peat and loess soils, then to enhance the load-bearing capacity, a monolithic pad of concrete or reinforced concrete is placed at the bottom of the foundation. On strong foundations (sandy, sandy loam soils), a bed of coarse sand or fine gravel will be sufficient. It is filled in parts, the layers are leveled and compacted with a manual or mechanical tamper.

Installation of formwork

Scheme of arrangement of strip foundation formwork

• the simplest wooden formwork is made from edged pine boards with a thickness of at least 40 mm;
• install the formwork in such a way that the edge of the foundation for the house (its upper part) protrudes above the zero mark (ground level) by 100 mm;
• formwork panels are assembled on the ground;
• then install them in the trench;
• secured to posts driven into the ground.

To make formwork with your own hands, you can also use special moisture-resistant plywood. Such material will cost slightly more than pine moldings, but it provides higher quality foundation work. Due to the almost complete absence of cracks and gaps between the parts of the formwork, water from the solution does not seep into the ground, so the concrete will dry more evenly.

On dense clay and loamy soils, pouring can be done without formwork. But this method of constructing a foundation is only suitable for a traditional stone house that is quite heavy. What is the benefit of constructing a foundation without formwork? The time spent on work is significantly reduced. In addition, part of the money intended for the purchase of lumber for formwork is saved. On the other hand, with this pouring method, concrete consumption increases by 10-15% compared to the standard.

Reinforcement

The technology for pouring strip foundations on heaving soils requires mandatory reinforcement. The reinforcement scheme is developed when designing a house, depending on the individual characteristics of the structure (number of floors and weight of the building, building area, depth of the foundation for the house, etc.).

View of the finished reinforcement cage for the “tape”

To arrange the reinforcement frame, corrugated steel reinforcement is used. But recently, composite materials have become increasingly popular. Fiberglass reinforcement is not inferior to steel in its strength characteristics. At the same time, it has much less weight (which greatly facilitates the work) and is not subject to corrosion.

The rules for installing a reinforcement frame recommend connecting all its elements together using steel wire. It is not recommended to use welding to connect reinforcement. In places where welds are made, the structure of the metal is disrupted, so such joints quickly collapse under the influence of corrosion. At the same time, the strength and load-bearing characteristics of the foundation structure are significantly reduced.

Pouring the foundation

Pouring a strip foundation manually

To pour the foundation for a house, factory-produced concrete M200 or cement mortar prepared with your own hands directly on site is used. The use of industrially produced concrete mortar is preferable. In this case, the developer can be confident in the stable quality of the material and compliance with its stated technical characteristics. In addition, the manufacturer will deliver any amount of concrete needed at the construction site at the moment. This allows you to quickly complete any volume of concreting yourself.

The rules for laying a foundation on a gravel or sand bed in autumn are simple:

1. First, the so-called “starting layer” is poured.
2. A layer of concrete about 10 cm thick is poured into the bottom of the trench. The solution will fill the pores in the base, which will prevent further loss of concrete due to its seepage into the ground. In addition, the starting layer will become a good basis for laying reinforcement.
3. The strip foundation can be poured in parts. The concrete mixture is poured in layers 40-50 cm high at a time.
4. The completed filling must be compacted to remove air bubbles from it as much as possible. Previously, the concrete mixture was “beaten” with a reinforcing rod. This task is long and tedious. To make the work of laying out the foundation with your own hands easier, you should rent a pneumatic vibratory rammer.

But a strip foundation (both shallow and deep) can be poured not in parts, but at one time. If a solution prepared at the construction site with your own hands is used for pouring, then it is advisable to periodically compact the mixture with a vibrating rammer.

Special additives are added to factory-prepared concrete to increase the fluidity of the solution. This prevents the formation of air bubbles during pouring and the delamination of concrete during drying. Therefore, there is no need to compact such a solution.

The final stages of working with the foundation begin after the concrete has hardened. At normal temperature and humidity, concrete gains 70% strength in 24 days. After the structure has reached the required strength, the formwork is dismantled and the foundation is waterproofed with bitumen. Although waterproofing work can be avoided if you order concrete with hydrophobic additives from the manufacturer. Then the foundation sinuses are filled with soil. Backfilling is carried out in parts, each layer is carefully compacted.

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The most common material for building a foundation is reinforced concrete. The optimal structure in terms of labor intensity and cost is a structure made of a monolith. This method avoids the need for lifting equipment, but requires strict adherence to technology. Pouring the foundation with your own hands should begin only after a detailed study of the stages of the process.

The design and construction of the supporting part of a building begins with a study of the soil characteristics. There are two options for performing this task:

• contacting a specialized company that will perform a full geological study with laboratory tests;
• self-study using test pits or hand drilling.

The first option will allow you to determine the strength characteristics of the soil most accurately. Before pouring the foundation of a multi-story building, such an event is mandatory. For buildings with a low degree of responsibility and private buildings, you can study the soil visually using GOST 25100-2011 “Soils. Classification"" determine its type. Based on which group the base belongs to, its approximate strength is assigned. The method does not provide high accuracy, but can be used to save money.

Marking axes and dimensions of the structure

An important stage that affects all other building structures. If you make a mistake in marking the foundation, the distance between the walls will change. This is especially critical if prefabricated elements are used for walls and ceilings. Marking is carried out correctly using the following technology:

1. removal of the fertile soil layer, which is from 30 cm;
2. designation of the first side of the house (most often marked parallel to the front boundary of the site or fence);
3. then mark the points on the first side, which will be the corners of the house;
4. From the marks, right angles are built using the Egyptian triangle method; all walls and corners of the building are marked using the same method.

Marking the foundation using cast-offs.

Marking the foundation can be done using pegs or full cast-offs made of vertical posts and horizontal lintels. The elements are installed at a certain distance from the axes of the building so that they do not interfere with the work when excavating trenches or pits. After completing the excavation work, a thread or cord is attached to the wooden markings, which will mark the contours of the supporting structure of the house.

It is important to control the following points related to geometry:

• compliance of the design lengths of the sides with the actual ones;
• the equality of the diagonals of structures that have a rectangular or square shape in plan (deviation of no more than 20 mm is allowed), the coincidence of the diagonals indicates that all angles of the rectangle are equal to 90°.

Development of the soil and laying of the cushion

The most difficult excavation work is if you fill the foundation yourself using tape technology. To dig a trench or pit yourself (if there is a basement), in this case you will need quite large penetrations into the ground. In this case, the following recommendations should be observed:

• The width of the trench is set to be 0.8-1 meter greater than the width of the foundation to provide access to the structure when performing waterproofing and insulation.
• It is important to correctly brace the walls of a pit or trench. If you miss this moment, filling work can become dangerous to life and health. This is especially true when constructing buried foundations. The maximum height of a trench with vertical walls without reinforcement depends on the type of soil. More detailed information is presented in the table below.
• It is also important to take into account the angle of internal friction of the soil (natural slope). When constructing an angle equal to this value from the bottom of the pit, a minimum distance is obtained at which massive equipment can be installed or materials can be stored.

After excavation of the pit or trenches, the need for backfilling under the base is considered. According to SP 50-101-2004, it can be made of sand (medium or coarse), sand-gravel mixture or gravel. Before pouring the foundation, it is worth laying the bedding in the following cases:

• depth below freezing in heaving soil;
• the presence of a bulk layer (it is replaced with a more durable material).

In other cases, there is no urgent need to lay the substrate. In general, bedding performs two functions:

• leveling the base under the base of the foundation;
• prevents capillary moisture from rising to the structure.

This element is necessary to remove excess moisture from the supporting part of the house. It is carried out even when the groundwater level is low to prevent troubles when liquid rises in the spring or during large amounts of precipitation. Work on laying drainage pipes must be carried out in accordance with the following recommendations:

• depth relative to the base of the foundation by 30-50 cm;
• the distance from the foundation of the house is no more than 1 m;
• the slope of the pipes in one direction is assumed to be 3-4 degrees so that the liquid moves by gravity;
• To prevent silting, the crushed stone laid around the pipes is wrapped in a layer of geotextile with an overlap of 30 cm.

Formwork work

Formwork for pouring concrete according to GOST R 52085-2003 is classified according to the following criteria:

• design;
• materials;
• turnover (possibility of reuse);
• possibility of use at different ambient temperatures;
• impact on the concrete mixture.

In addition, the filling mold can be removable and. One of the most common removable options is wooden; among non-removable ones, polystyrene foam is most often used. It is also possible to manufacture from materials such as metal, plastic, foam concrete, and moisture-resistant plywood.

When installing formwork, you need to control:

• accuracy of geometric dimensions and installation;
• shield stability;
• tightness (seams no more than 2 mm).

The placement of reinforcement is necessary to increase the structure's ability to resist bending loads. Reinforcement of strip and column bases is performed with spatial frames. Meshes are used for the slab. If the structure thickness is more than 150 mm, the mesh is laid in two layers. The following are the main recommendations for reinforcement:

• calculations for a private house can be performed in a simplified form, assigning the total area of ​​the rods depending on the cross-section of the structure; the minimum diameters differ for different types and sizes of foundation, so this issue requires separate consideration;
• for the manufacture of frames and meshes, reinforcement of a strength class not lower than A400 can be used, but the use of rods A500 and higher is not economically justified;
• it is important to observe the protective layers of concrete; in general, it is worth remembering the following numbers: foundations without concrete preparation - 70 mm, with concrete preparation - 40 mm;
• reinforcement should be provided in the corners; usually the pitch of transverse horizontal and vertical reinforcement is halved, and the main reinforcement is also reinforced with U or L shaped clamps.

After installing the formwork and reinforcement cage, they begin filling with concrete mixture. The following are recommendations on how to properly pour a foundation for a house:

• Filling is done in one step. Breaks are allowed only during the setting period of the solution, which depends on the type of binder and weather conditions. On average, a break is allowed for 1-2 hours.
• It is best to carry out work at a temperature of 20°C. At lower values, the period of strength gain by the material increases. When the temperature rises to 30°C, the characteristics of concrete may deteriorate. It is important that there is no dry weather during pouring, since high-quality pouring requires air humidity of approximately 80%. Also, you should not carry out work in the rain, if it started during the work process, use plastic film. It is laid immediately after pouring.
• The formwork is filled so that 2-5 cm remains from the top edge of its panels to the mortar level.
• Liquid concrete is poured by moving the mixer from point to point. Pouring from one point followed by manual movement reduces the quality of the material.
• Concrete mixture cannot be dropped from a height of more than 2 m.
• After pouring, thoroughly compact the solution using deep vibrators. Such a tool provides compaction to a depth equal to 1.25 of the length of the tip. It is recommended to first pour the mixture into the formwork to a height of 60 cm, then compact it and pour another 60 cm. The operation is repeated until the design mark is reached. It is important that all stages occur before the previous layer finishes setting.

Concrete maintenance and formwork removal

Recommendations on how to properly pour the foundation for a house are not limited to laying the mixture. The process of gaining brand strength will take an average of 28 days. During the first weeks, the structure will require maintenance to prevent cracks from appearing on the surface. Its first stage is covering it with plastic film, tarpaulin or burlap, which will not allow moisture to evaporate too quickly.

• in the daytime, moisturizing is carried out every 2-3 hours;
• During the night it is enough to perform the operation 1-2 times.

Formwork according to SP 70.13330 can be removed only after the concrete has gained 70% strength. When justified, it is allowed to perform work at 50% of the brand value. The time spent on this process depends on the outside temperature. Concrete using a normally hardening binder gains the required strength at a temperature of 20°C in 5-7 days, at 10°C in 28 days, and at lower temperatures the process slows down significantly.

Read more about stripping.

backfilling

When making a strip or columnar foundation, or less often a slab foundation, it is necessary to backfill the cavities of the pit or trench after removing the formwork. It is important to observe the following principles:

• work begins only after the soil reaches optimal moisture content;
• for backfilling, soil that is denser and has better strength characteristics is used compared to the extracted soil (coarse sand is often used);
• the work is performed in layers, the maximum thickness of the material at each stage is 30 cm;
• each layer must be compacted before laying the next one;
• The backfill material should not contain foreign components or organic inclusions.

Compliance with technology at all stages of concrete pouring will allow you to obtain a reliable and durable structure that will last for many years.

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The strip foundation is the oldest and at the same time the most common to this day. It is great for buildings with basements, subfloors and basements. You can’t do without it when building massive brick or stone fences. Pouring a strip foundation does not require any special skills or serious financial costs, so anyone can do it with their own hands.

Scheme of the strip base device

It is important to approach work at each stage with special care and attention in order to avoid mistakes. Construction consists of several stages:

• markings;
• earthworks – digging and preparing a trench or foundation pit;
• production of formwork;
• waterproofing;
• ventilation and communication supply devices;
• fills;
• drying.

Before construction begins, you need to realize that there are no unimportant stages in construction. Mistakes made at such simple stages as marking or drying can lead to misalignment, uneven settlement and cracks in supporting structures, even if the concreting was done perfectly.

Tape can be of varying degrees of depth. For brick and stone fences, a depth of 30-40 cm into the ground is sufficient; a one-story house without a basement and small buildings will require a depth of 50-70 cm. Such foundations are called shallow foundations. Their costs are low and amount to 15-18% of the construction budget.

A house with a basement or garage or a house with heavy floors will require a more durable buried foundation, which is buried 20-30 cm below the soil freezing depth (the soil freezing depth must be indicated in the land documents). Both the cost and labor intensity of its construction are much higher, therefore, when designing such a house, it is worth considering the possibility of building a shallow one under the internal walls. The foundation is laid in the warm season.

Scheme of the device of a strip monolithic foundation.

For construction you will need the following tools and materials:

• concrete mixer;
• screwdriver or drill;
• hammer;
• trough;
• buckets;
• shovel;
• trowel;
• hammer-pick;
• jointing;
• plumb line;
• cord or thick fishing line;
• level;
• square;
• roulette;
• gloves (hands will require protection);
• fittings;
• cement;
• sand;
• crushed stone

Before starting marking, you need to level the construction site 2.5 m higher than the proposed structure. Then, using a tape measure, a square and stakes from cut reinforcement, you should mark the outer part of the main elements of the foundation of the building according to the drawing or project (in addition to the width in the drawing or project, the margin for formwork must be taken into account).

After this, you need to check the correctness of the angles by measuring the diagonals of all rectangles. If the diagonals of each of the rectangles coincide in length, then there is no error in the markings and you can stretch a fishing line or cord between the stakes. It is more convenient to mark with fishing line because it does not sag. Having departed from the marking of the outer boundary a distance equal to the width according to the project or drawing, you need to mark and check the inner boundary in the same way.

Trench or pit

You can dig a trench with your own hands or with the help of an excavator. It is more difficult to manually dig a pit for a buried foundation, so it is more convenient to hire an excavator for such excavation work.

If you dig a trench with your own hands, you can immediately make sure that its bottom is level (this is very important) by checking it for level. If a trench or pit is dug with an excavator, then the bottom must be leveled and cleaned manually using a tamper and level. All angles must be 90 degrees so that there are no distortions later.

Drainage laying diagram

On the leveled bottom, you need to pour a drainage layer of sand or gravel with 10-15 cm of sand, pour it with water and compact it thoroughly using a tamper and a level. It is convenient to pour a drainage layer by stretching the fishing line between the stakes at a pre-measured height.

Place a layer of polyethylene film or roofing felt (or other waterproofing material) on the compacted and leveled drainage layer and fill it with a 10cm thick layer of M400 concrete. This must be done so that during the main pouring, water from the concrete solution is not absorbed into the soil, because this will upset the proportions of the solution and deteriorate its quality.

Installation of formwork

For formwork, you can use both edged boards and plywood sheets. If you staple a plastic film to the inside of the finished formwork with a stapler, the materials will remain clean and after removing the formwork they can be used for lathing under the roof. Therefore, there is no need to buy material specifically for formwork.

DIY formwork diagram for a strip foundation.

It is convenient to assemble the formwork with your own hands directly on the site using screws and a screwdriver (or drill). If you assemble it with nails and a hammer, then dismantling such formwork will be much more difficult. It is necessary to screw in screws or drive nails only from the inside of the formwork, so that it can be easily removed when the foundation dries.

The formwork should be made higher than the planned height, and the pouring level should be marked with a stretched cord or fishing line. When making a foundation for a house, it is worth placing spacers around the formwork along the entire perimeter, both on the outside and on the inside, in increments of at least 1 m, so that the weight of the concrete does not damage the formwork with its weight.

Structural reinforcement

The reinforcement grid can be made by welding, or you can tie the reinforcement bars with special wire. Contrary to popular belief that welding is more reliable and stronger, the reinforcement grid for the foundation will be more reliable if it is tied with wire. During earthquakes and ground movements, a flexible structure will be more reliable and durable.

Scheme of strip foundation reinforcement.

If there is a project, then it indicates the cross-section of the reinforcing bars, their number and location. If there is no project, then you need to use reinforcement with a cross section of 12 mm. The reinforcement frame consists of two or three vertical rows of reinforcement, fastened to horizontal rods so that the cross-section of each cell is from 15 to 25 cm.

When calculating the size of the reinforcement grid, you need to take into account that the distance from it to the surface of the future foundation should be at least 5 cm on each side. The finished reinforcement is installed in the trench on a layer of concrete 10 cm thick.

Ventilation and communications

To ensure ventilation and supply of communications to the house, holes are required in the foundation. To ensure ventilation, pieces of plastic or asbestos-cement pipes cut to size above ground level are tied with wire to the installed fittings, one on each side (if the house is small). To avoid filling the pipes with solution, they are filled with sand.

Holes for the output of communications are also made using pipes, but they are located in pre-planned places below ground level, taking into account the depth of soil freezing. With shallow foundations, communications are carried out under the foundation.

Waterproofing and filling

The importance of waterproofing cannot be overestimated. If the foundation is not waterproofed, the room will be damp and its inhabitants will get sick.

Scheme of waterproofing strip foundation.

The most reliable and least labor-intensive way to make high-quality waterproofing with your own hands is to add a penetrating waterproofing additive to the solution used to fill the strip foundation. It will make the entire thickness of concrete waterproof for its entire service life.

Waterproofing by coating with resin and roofing felt (or other waterproofing materials) is less reliable and durable. The foundation for the fence can be poured with M200 concrete, which is prepared from 1 part (kg) of M400 cement, 2.8 parts (kg) of sand and 4.8 parts (kg) of crushed stone. To fill the foundation for a house, you should use M400 cement, which is prepared from 0.4 parts water, 1 part M500 Portland cement, 1.65 parts sand, 2.92 parts crushed stone and 0.006 parts plasticizer.

Saving on solution is a big mistake. The foundation must be poured in layers of 20 cm, piercing each layer with a reinforcement rod (the more often, the better) and tapping the outside of the formwork with a hammer so that air comes out and there are no voids in the fill. After pouring, it is imperative to level the foundation with a rule or a trowel and dry it for three weeks, periodically watering it with water in hot weather (to prevent cracks) and covering it in the rain (to prevent the cement from being washed out).