When it comes to building small house, the walls of which will be made of lightweight material, for example, foam concrete, cinder block or wooden beams, then to strengthen it, it will be enough to apply new technologies for the use of insulated foundations of small depth. Doing it right is not so difficult, you just need to carefully study shallow foundation and quality indicators of the soil of your site.

Where to use

Shallow strip foundation suitable for installation:

• Houses with an area of ​​up to 100 m 2 and a height of no more than 2 floors;
• Log cabins;
• Commercial and decorative buildings.

This type of laying the foundation of a house is especially interesting when it comes to building in areas with heaving soils.

It is customary to call heaving clay or sandy moist soils, the soil of which is saturated with water. When it freezes, water turns into ice. When the melting process occurs, the water expands and begins to crush everything that comes in its path. Previously, they struggled with heaving soils, burying the structure below the freezing depth of the earth, and this is about 1-2 meters depending on the terrain, for example, in Siberia, this depth goes into the ground by more than 2 meters, in the Moscow region - by 1.5 m.

The use of insulation

At one time, the following statement was taken into account: the greater the depth of the foundation, the closer it is to the warm earth, the less the heaving load acts on it. But with the advent of modern high-quality heaters (whose homeland is Finland, Norway and other countries with a cold climate), they began to lay a shallow strip foundation with their own hands while insulating the base of the building, the so-called blind area. The only rule that should be taken into account: the colder the area, the greater the layer of insulation should be laid under the blind area around the house.

Extruded polystyrene foam or other insulation does not lose its properties when wet. But it is not designed to be walked on, so after laying it should be decorated with tiles or other convenient, beautiful and practical material.

Making a blind area around the house from insulation even wider than required is still cheaper and easier than digging a deep trench, pouring a large amount of concrete, wasting time waiting for shrinkage. Thus, you save time, money and make your work easier.

Another advantage of such a device is durability. Over time, nature will still take its toll, and even the highest quality concrete will begin to collapse under the influence of temperature loads exerted on it. With the above option of installing a house under a base with a large insulated area, the earth remains warm during the entire cold period, and heaving soils do not exert pressure on the soil under the building.

A shallow foundation with a wide insulated blind area is a victory of man over nature: as long as the insulation is alive (and its lifespan is at least 100 years), nothing threatens the house.

The earth has one feature: while the soil is not warmed up, it takes energy into itself, cooling the house, and when warmed up, it becomes a source of heat and turns into a layer of insulation. When a shallow foundation is laid in the presence of a blind area, the temperature situation under the house stabilizes, heat losses are reduced to zero. As soon as a couple of meters of soil under the house warms up, it becomes a heater itself.

Laying process

It is very easy to make a shallow strip foundation with your own hands. The process of laying it does not take much time and materials. It is enough to have an idea of ​​what should be done and for what.

1. Markup and design. At the initial stage, it is necessary to conduct reconnaissance of the area, study the properties of the soil of the site and decide how deep the blocks should be laid for the future building. Having a project of future construction in hand, and having made preliminary measurements on the site, you can proceed to the next stage.
2. Digging trenches. Mark the places of the future corners of the building with pegs driven into the ground. Trenches should be dug around the entire perimeter of the future structure, along the lines of the location of the bearing walls, which will take on the main load. Tape is used to reduce costs and time. The main thing is to correctly distribute the load on the load-bearing walls, and you can even use a monolithic slab into which you can mount a warm floor, thus adding heat and additionally warming up the soil around the house and the soil under a shallow foundation.
3. Trenches should initially be as flat as possible.. To check how smooth your surfaces are, use a spirit level and a tape measure. How you cope with this task will depend on the consumption of materials and the amount of effort that will have to be applied for further work.

The depth of the trench with this option for laying the foundation may not exceed 50 sentiments. The width should exceed the planned wall thickness. You can dig manually if the building is small. If it is possible to use the services of a mini-excavator, then this is ideal, since the bottom of the trench will immediately acquire the necessary degree of evenness.

1. The device of a shallow strip foundation. This type of foundation can be made for one-story log buildings on sandy and clay soils. It consists of:
   • waterproofing;
   • products;
   • concrete grade 250 and above;
   • fittings with a diameter of 12;
   • crushed stone, expanded clay;
   • sand cushion.

Requires the installation of formwork in the process.

1. Laying waterproofing. The bottom of the trench must be insulated. If you do not have the opportunity or need to lay insulation from expensive materials, you can make it from ordinary roofing felt. The task of waterproofing this case– retention of concrete slabs from the impact of underground ground water and preservation of the sand cushion.
2. Pillow making. The pillow under the base is prepared as follows:
   1. At the bottom of the trench, coarse-grained sand is poured with a layer of 15-30 cm;
   2. Filled with water;
   3. Compacted with a special tool;
   4. A layer of crushed stone or expanded clay is poured with a thickness of 20 to 30 cm.

1. Production of reinforced gratings. To give the base rigidity and strength, it is required to lay a reinforcing mesh in its base. Such a mesh is woven by knitting using ordinary wire. Rebar is used with a diameter of 12 mm for longitudinal rows and 20 mm for transverse ones, and is made so that there are from 4 to 6 (ideally 5) twigs in each row. The grid spacing should not be less than 15 cm.

For better bonding to each other, it is necessary to use special reinforcing corners. To facilitate the process of installing the grating, you can make small coasters from the remnants of plastic pipes by sawing them in the form of rings on a home circular, and placing them under the finished reinforced mesh.

1. Reinforcement is the most important part of laying the foundation. It is the reinforced grating that gives rigidity and strength to the entire structure and forms a monolithic frame.

1. Formwork construction. This step is not always required in a device of this design. Above the ground surface with this method of laying formwork is not installed. But if you decide that it will be more convenient for you, then for more even walls it is advisable to prepare boards from edged boards and, after installing the gratings, equip wooden structures that allow you to pour concrete trenches with a mesh.

Often, instead of formwork, polystyrene foam or other insulation is used, which will forever remain part of the foundation, while performing the important function of preserving heat. You can use reinforced concrete blocks.

1. Columnar way of laying the base. The columnar option involves the installation of the building structure on low columns. After pouring the base with a tape shallow-depth method, brick columns are erected at the corners, on which a monolithic slab is laid.

The columnar method of laying is used in cases of building baths and saunas. The structure looks like it is floating above the ground, which adds to its charm.

1. Pouring concrete. At the final stage of construction, the voids in the trenches are filled with a concrete mixture consisting of sand, cement, fine gravel and water. It is preferable to choose a high grade cement, at least 250. During the pouring process, the concrete should be carefully compacted and air bubbles should be expelled to give the desired strength. This can be done with a stick or a special tool - a vibrator.

Try to level the upper part as much as possible, since it is on it that the structural materials for laying the walls will fall.

Technology options

A shallow foundation can be laid out in three ways:

• Like a monolithic slab;
• Pouring with concrete using reinforcing knitted stacks;
• Separate pre-prepared blocks or brickwork.

All three methods are easy to use. Choose what suits you best or what material you have available.

Advantages of a shallow foundation

Recently, with the use modern technologies it became possible to build small buildings by laying the foundation in a shallow-depth tape method. The advantages of this method are as follows:

• You can make a shallow strip foundation with your own hands;
• Simplicity and ease of execution;
• Low cost and low budget;
• Possibility of laying and preparatory work without the use of construction equipment;
• The possibility of warming the basement and basement;
• The possibility of laying a monolithic slab on the base using the "warm floor" technology;
• Achieving high strength required for durable construction of small outbuildings and individual houses;
• Possibility of replacement: performance of work from those materials that are at hand.

Flaws

Of the shortcomings, only one can be named: insufficient strength for buildings on heaving soils. As noted above, in order to solve this problem, more attention should be paid to the blind area around the building. If necessary, it is possible to carry out a drainage system under the base of the foundation, that is, lay pipes with a large cross section before starting work and fill them with a sand-gravel mixture.

Another important point! Laying a shallow foundation should be carried out only on warm ground and does not require shrinkage. Moreover, a building on such a basis must be erected within a short period of time, no more than 3-5 months.

Now you all know how the process of laying the foundation for small buildings is carried out correctly, and you can get to work!

Usually, when private buildings are erected with a small number of floors from lighter materials (bricks, gas blocks, foam concrete, etc.), a strip foundation is used at a shallow depth. This solution is beneficial in terms of economy and practicality.

For such a foundation, a foundation pit is created under brick house or for a house made of aerated concrete. It deepens below the level of soil freezing. In the Urals and in Siberia, and in other regions with severe cold, it deepens below 150 cm. And in such a section it is necessary to work with heavy equipment. This foundation covers the perimeter of all load-bearing walls. Its device only in exceptional cases is obtained below 150 cm. SNiP for a similar type of foundation is calculated from the load of the walls on the area. The bearing capacity or feature of the soil in a particular area is also taken into account.

Benefits of this foundation:

1. Ease of work.
2. Good cost savings.
3. No need to use special equipment (it is needed only in the indicated regions).
4. Excellent strength if a small building of 1-2 floors is being erected.
5. It makes it possible to insulate the basement.
6. A rich range of materials and technological solutions for its erection.
7. It can be created as a monolithic view where concrete is to be poured.
8. Its other configurations are bricks or concrete blocks.

The design of such a foundation:

1. Weak strength for buildings on heaving soils. The dilemma is solved thanks to the sand filling and drainage system. This reduces the effect of the soil.
2. Impossible to create on frozen ground.
3. You can not leave unloaded for the winter.
4. Points 2 and 3 determine the short time for its filling and the erection of walls: about 4-5 months.

More about monolithic strip foundations and slabs

For MLF, there are several types or subspecies. Let's list everything:

1. Tape belts. Without recesses, suitable for frame houses and lightweight structures. The peculiarity is that the width is always greater than the height. So the supporting surface will be much better.
2. Unrecessed tape. Ideal for timber structures. Feature - the plinth belt is raised.
3. Shallow LF. We will analyze its device in more detail. It is used for any type of construction, both for a log house and for a stone.
4. Recessed is, in fact, a monolithic slab, because it is poured below the freezing level. Suitable for absolutely any building.

For your information! Any type or type of MLF cannot be put into operation without drainage, waterproofing and backfilling with sand.

Stages of creating a strip foundation at shallow depth (LFMG)

When working on heaving soils, it is required to insulate the soles of the working tape of this foundation. In the conditions of sands and sandy loams, it is fashionable to insulate only the blind area.

Step-by-step instruction:

1. Calculation of the width of the tape and the reinforcing section, the creation of a reinforcement project.
2. Creating a trench if a house is being built without a basement.
3. A foundation pit is digging if a basement is being considered.
4. Laying drains to divert runoff.
5. Sole insulation.
6. Creating an underlay.
7. Formwork installation.
8. Reinforcement fittings.
9. Pouring concrete. Provides for the organization of communications and ventilation ducts.
10. Hydroprotection of all edges of the tape after dismantling the formwork.
11. For a functioning basement, the outer walls of the tape are insulated.

Determination of soil composition

This procedure can be performed without specialists. Just dig holes in different places. Study the ground visually. Here's how to do the test:

1. It is easily formed into a dense ball, does not collapse under finger pressure. These are signs of clay.
2. If it cracked under pressure, it is loam.
3. If partially crumbled - sandy loam.
4. The ball didn’t turn out at all - it’s sand.

Tape Width Calculation

Here the total load is calculated. It includes the weight values ​​of all structures:

• base;
• overlaps;
• walls;
• roof;
• facing;
• warming materials;
• partitions;
• furniture;
• living people;
• wind and snow loads.

Wind and snow data is taken from your local weather report. Usually a width of 40-50 cm is enough to create a strong belt even on difficult soils.

Depth calculation

Here are the rules:

1. A depth of 40 cm is suitable in the presence of protection against heaving.
2. 45 cm - subject to sandy soil; ground water is low.
3. 50 cm - when the clay freezes 100 cm.
4. 75 cm - clay freezes 150 cm.
5. 100 cm - freezing by 250 cm.

To protect against swelling in winter time there are ways:

1. Under the sole, the soil changes to non-metallic material. The minimum layer is 40 cm.
2. Drainage is created around the perimeter.
3. A blind area and a storm drain are arranged on the surface.
4. The sole and blind areas are insulated.

Insulation project:

In the question of how much you need to raise the tape above the ground, the following numbers will help:

• for the base, the tape is buried in place, it rises 170 cm above the surface;
• for a modest technical underground, a height of 40 cm above the ground will do;
• to create floors on the ground, the tape is obtained on the same level with the ground or exceeds it by 20 cm.

Advice! Any of these options allows you to carry out a normal two-layer reinforcement inside the tape. At the same time, it is still possible to arrange a protective layer of 1.5 - 4 cm.

It is advisable to use a calculator when calculating:

markup

On the building site, you need to pull the cords. They are located on the outer and inner perimeter. Here it is not required to take out the axes, as when working on columnar or pile foundations.

Positional criteria for marks and cords.

1. The starting corner of the main facade is positioned 3 m from the plot line, 5 m from the axial boundary of the street.
2. To mark the wall of the main facade, two cords are pulled along the cast-offs. A bar of 60-80 cm is placed between the pegs. Also, these cords reflect the edges of the foundation.
3. A right angle is defined for each wall. Then the side walls are calculated. Here the work follows the triangle method. They also require pulling the cords over the cast-offs.
4. By the same method, the rear facade and internal walls are determined.

To align the contours of all cast-offs in a single plane, a level is used. Correct position of cords: 5-7 cm below the upper side of the formwork.

Also, the trenches of the tape should provide for the location of insulation, drainage, access to the outer walls of the tape. To do this, the width of the trench develops by 50 - 80 cm inside the perimeter of the building, by 80 - 120 cm outward.

For earthworks you can only depict the contours of the trenches. This is done on the soil with a lime mortar. In the presence of a socle, a pit breaks out. Cast-offs in the corners should not interfere with the removal of soil, which is carried out by special equipment.

Substrate of sand or gravel

Usually the substrate is formed from:

• sand, layer 20 cm, it is treated with water or rammed with a vibrating plate;
• crushed stone, the same layer, it is manually bayoneted in layers or similarly rammed.

An example of a sand cushion

A gravel layer covers a layer of sand

At this stage, drainage is arranged around the entire tape perimeter. They should be flush with her sole. Drainages are looped into a single circuit. It turns out one slope to the underground compartment, where drains will accumulate.

With a 40-centimeter immersion of the foundation, it is possible to get rid of heaving. To do this, line the outer side of the tape with polystyrene. The desired layer is 5 cm. Width is 60 cm.

When the foundation lies at 70 - 100 cm, it is necessary to insulate the blind area. Warming is carried out at around 30-40 cm. Heaving impulses are not completely eliminated, but are significantly reduced.

formwork

As a rule, the following materials are used to create shields:

1. Cutting board. The minimum thickness is 5 cm. Its advantages are that it can be reused. The disadvantage is that it takes a long time to assemble.
2. Plywood with many layers. Its advantages: powerful resistance to moisture, strength. Minus - a huge price.
3. OSB. Pros: the ability to use after the elimination of the formwork, powerful moisture resistance, keeps the geometry.

For your information! Crossbars are placed at the level of the formwork, and a cast-off is stretched. So the formwork is smooth, both horizontally and vertically.

Example in the photo:

It is important to know! At the joints in the shields, gaps of more than 2 mm are not allowed. The footing is poured without formwork. Its functions are performed by the walls of the trench.

Formwork mounting options:

1. Removable. The upper side of the shields exceeds the design mark by 5-7 cm. The walls inside are insulated with extruded polystyrene foam.
2. Fixed. Polystyrene blocks are used for assembly. The rigidity of the structure is set by jumpers.

The first option is more popular, because after pouring, hydroprotection is arranged on the surface. Then a heater is laid on it.

An example of setting and strengthening the formwork:

Ties are used for vertical fixation of shields. Required step: 50 - 100 cm. Holes are arranged inside the screeds at different heights. Through them will go through the passage of the sleeves. And in the underground side, engineering technologies will be introduced through such pipes. Above ground level, the holes will become ventilation products. Through them, moisture will leave the underground.

Reinforcement and pouring

On foundations arranged on heaving soils, impressive loads are obtained. For this reason, reinforcement is carried out at the edge of the tape from above and near its sole. The rods are protected from corrosion. The protective layer in thickness should reach at least 1.5 - 4 cm.

To reinforce the monolith, bars of 8-16 mm are used. This is a periodic longitudinal section. becomes stiffer if rectangular clamps are attached to it. They are formed from smooth reinforcement with a parameter of 6-8 mm.

One of the popular reinforcement schemes:

Independent calculation of reinforcement is based on the cross section of the tape, taking into account 0.1% of the reinforcement of the total area. Calculation methods:

1. The total cross section is calculated. The height of the tape (H) is multiplied by its width (W) and divided by 100 (the calculation is in mm). Formula: H x W: 100.
2. The cross section of the longitudinal bar is determined by the table of reinforcement schemes.
3. The adjustment is taking into account the 4 cm layer of protection, according to the criteria of SP 52.101. TO is the maximum number of rods in a row - 40.
4. The thickness of the clamps should be a quarter less than the main rods.

Corner reinforcement example

Wire is used to tie the frame. It can be tied by mechanical or manual method.

An example of reinforcement of interface sections

Reinforcement criteria for this foundation:

1. The overlap spreads in adjacent lines of one belt by at least 60 cm.
2. The length of the overlap is equal to 50 rod diameters.
3. Joints of bars are not allowed in the areas where the walls join and at the corners. One rod is bent there and ends up on the adjacent side by 40-60 cm. Then it is overlapped with the next part of the reinforcement.

Criteria for self-creation of concrete composition.

The elements of concrete mortar are classic: crushed stone, sand and cement. Each brand of cement has its own mixing proportions:

M 300: crushed stone - 3.7 shares, sand - 1.9 shares, cement - 1 share.

M 250: 3.9 (crushed stone), 2.1 (sand), 1 (cement).

M200: 4.8 (u), 2.8 (p), 1 (c).

M150: 5.7 (u), 3.5 (p), 1 (c).

M100: 7 (u), 4.6 (sand), 1 (c).

Mixing should be done only in a concrete mixer. The time of this operation is 1.5 minutes. You can add various additives to improve the quality of the composition. Mark M100 should be used only for footings.

An example of laying engineering sleeves in the formwork:

The filling criteria are:

1. The composition is laid down by one vector in layers. Each layer is 40-60 cm. It is rammed with a vibrating tool.
2. The formwork is filled in one session.
3. Permissible pauses - 2 hours, no more.
4. The composition is poured from a height of 50 -200 cm above the formwork.
5. The nozzle of the vibrating tool is placed in the composition for 2-10 seconds. Air bubbles should disappear.

Concrete care and formwork removal

When the composition in the formwork is 50-70% stronger, the concrete needs care. Here you will need the following operations:

1. It is covered with a film that creates a defense against precipitation and excessive moisture.
2. A heat cable is laid in it, a warm formwork or a layer of straw is arranged. This is how the concrete is protected from freezing. This is especially true in winter time.
3. Concrete is covered with a tarpaulin, poured from a watering can. There must be a diffuse stream. The operation is performed in the first three days after pouring. So concrete is protected from active evaporation.

These actions help to eliminate the appearance of cracks, shrinkage, internal stresses. Moisturize concrete in hot weather after 8 hours. Support of constant conditions of a compress is required.

Formwork can be removed according to air temperatures:

At +30, removal 4 days after pouring,

At +20 - after 8 days,

At +10 - after 14 days

At +5 - after 28 days.

After the formwork has been removed, hydroprotection is installed on the sides of the foundation. Photo example:

Monolith waterproofing methods:

1. Application of 2-3 layers of bituminous mastic.
2. Pasting with rolled polymers.
3. Treatment with penetrating compounds.

The outer walls of the foundation should be insulated along the entire height. To attach the insulation, bituminous mastic is used. Then the blind area is insulated around the circumference of the foundation.

If the site has high soil water, drainage is created.

An example of a completed foundation:

What does a private builder say?

Judging by the reviews of the owners, the following are distinguished from the positive:

1. Acceptable cost.
2. Just put it on your own.
3. Reliably.
4. Suitable bearing capacity for popular gas concrete structures.

Here is how the owners respond, understanding the shortcomings:

1. Not designed for heavy immovable objects above two floors.
2. Questionable durability.

Price aspect

To date, the creation of this foundation costs in the range of 100,000 - 250,000 rubles. The amount is determined by its parameters, spending on materials, tools, equipment, work (if workers are hired).

Foundation in four days

The video below is the first part in a series of materials on creating a competent shallow strip foundation in a short time.

One of the simplest foundations for buildings is a shallow strip foundation. Despite the ease in the production of work, there is always the possibility of doing something wrong, therefore, before installing the MZFL, you should familiarize yourself with common technology. Today we will take a step-by-step look at the device of a shallow tape.

Scope of MZLF

Shallow foundations are used for buildings with a low loaded mass. As an example, we can cite houses on a steel or wooden frame, as well as buildings made of lightweight elements (foam concrete, PCB). Usually the number of storeys of buildings on the MZLF does not exceed two.

In the definition of MZLF, shallow - means completely located in the frozen layer of soil, the underground part of the concrete tape rarely exceeds 500-700 mm. The forces of frost heaving with this arrangement do not create tangential (tearing) loads, but the entire building, together with the foundation, dynamically moves following the expansion of the soil. For this and other reasons, it is not recommended to arrange a shallow-depth tape in areas with a general slope of more than 2%. On steeper slopes, a shallow foundation can be built only after the soil has been re-planned to form a horizontal terrace.

The feasibility of using MZLF lies in a much lower consumption of materials and ease of design. If the building is not planned ground floor, a shallow-depth tape will reduce the volume of concrete mix and reinforcement by 2-3 times, while providing an equivalent bearing capacity.

However, it should be noted that a shallow foundation cannot be established on loose peat, silty soils and mudflow sandy loam. Such soils are too low density and high plasticity, therefore, they require the installation of pile-grillage foundations, based on denser soil layers. MZLF should not be arranged on soils with heaving rates of more than 4% or if the groundwater level is above the depth of occurrence, despite the fact that drainage of the site is not planned, so that after that you do not have to deal with the consequences.

Section and configuration calculation

Since the MZLF acts as a beam, and not a stiffener, usually the section of the tape is close to a rectangle or trapezoid in shape. Tape in the form of a brand or more sophisticated sections is almost never cast due to the fact that the material savings seem too small compared to the installation of more complex formwork.

The calculation of the MZLF is carried out in two directions: sufficient bearing capacity of the soil in the plane of occurrence and its own structural strength, which will allow the tape to maintain rigidity at full design load from walls, roofs, snow, etc.

The width of the upper part of the foundation is determined by the maximum possible wall thickness, taking into account the layer of internal and facade finishing. When installing floors along logs, it may be necessary to form a ledge or expand the foundation by about 50 mm.

The width of the tape in the plane of occurrence is determined entirely by the required bearing capacity. It is enough to divide the total mass of the building and calculate the average load per meter of the perimeter of the tape, and then calculate the sufficient cross-sectional area of ​​​​the support in accordance with the characteristics of the soil. To create a sufficiently high safety factor, the thickness of the incompressible bedding is not taken into account.

Scheme of a shallow strip foundation: 1 - parent soil; 2 - adding gravel or gravel-sand mixture; 3 - blind area; 4 - foundation reinforcement; 5 - shallow strip foundation with a wide sole for even load distribution; 6 - wall; 7 - gravel bedding of the internal area of ​​\u200b\u200bthe foundation of the house

The height of the tape is defined as a component of its underground and aboveground parts. With the above-ground part, everything is simple - it must be at least 80 mm and not more than four widths of the upper edge of the tape. In turn, the height of the underground part can be determined taking into account several factors:

• the foundation should not lie on the border of heterogeneous soils;
• the minimum depth of the foundation is 35-40 cm, but, depending on the intensity of heaving and the depth of freezing, the height of the underground part can increase by an additional 60-80%;
• to maintain the required strength characteristics of reinforced concrete products, the ratio of width to height should not be less than 3:5.

Earthworks and preparation

The trench profile for the MZLF device should have a width 2.5 times greater than the estimated width of the tape and a depth greater than the height of the underground part by two widths. This is due to the fact that MZLF is rarely arranged along the ground formwork, using a plank-panel board for reasons of containing cement laitance and the need to give the section a trapezoidal shape. Immediately, we note that the indentation of the walls of the pit from the formwork should be twice as large from the outside than from the inside.

Compensation for the forces of frost heaving is carried out due to incompressible, non-porous and hygroscopic filling, as well as filling the side sinuses with similar material. Sand and gravel mixture with coarse sand and granite or basalt crushed stone of fraction 25-30 is used as a backfill material. To stabilize the foundation, the prepared bottom of the trench is covered with a 30-50 mm preparatory layer of M 100 concrete without reinforcement.

Backfill at the bottom of the trench helps to distribute the load on support layer soil, increase the area of ​​support and involve forces with a horizontal application vector. The recommendation regarding the thickness of the backfill, equal to two values ​​​​of the thickness of the tape, is rarely followed in practice, more often on weakly heaving soils they are limited to preparation of 25-30 cm.

However, you must remember that the more pronounced heaving, the more responsibility lies with the bedding. Sometimes it is advisable to replace the soil up to the freezing depth and expand the external sinuses to the shape of an inverted wedge, the base of which corresponds to the width of the blind area.

Reinforcement and anchoring

For MZLF, the total content of steel reinforcement without prestressing is set at least 0.1%, a more realistic figure of 0.17-0.2% will provide proper reinforcement without excessive strength, but with a significant margin of safety.

The minimum value of the protective layer for the underground part of the foundation is 60 mm, the maximum is no more than half the width of the tape. The working reinforcement is made with rods with a periodic profile of such a diameter that the total cross section of the reinforcement can be divided into 4 rods for the upper and lower reinforcement lines.

If in the MZLF the vertical distance between the reinforcement lines exceeds 450 mm, another row with rods is added, the thickness of which is at least 60% of the thickness of the main lines.

Structural reinforcement is carried out with clamps or wire for knitting in increments of 2-2.5 values ​​of the average width of the foundation. The diameter of the rods used for the manufacture of structural reinforcement should not be less than 50% of the diameter of the working reinforcement.

In addition, the reinforcement of the MZLF is accompanied by a number of anchorings. At bends and T-shaped joints of the tape, each row of reinforcement in intersecting directions should be connected with bent mortgages of the same section, the overlap of which with the main reinforcement is determined as 25 nominal reinforcement diameters. Anchoring with embedded studs may be required to connect to the base of the frame or masonry walls.

Concrete works

Before concrete work it is recommended to cover the inner cavity of the panel formwork with a polyethylene film, which prevents the concrete mass from losing liquid until it sets. After that, the reinforcement segments are installed, they are linked and distanced using plastic plugs.

Most often, bituminous mastics are used to protect against moisture, on top of which fiberglass-based insulation or cheaper roofing material is rolled out. If the foundation does not require continuous waterproofing, the hydrobarrier film remaining after pouring is sufficient.

The sinuses around the foundation fall asleep with ASG immediately after the waterproofing has dried. Backfilling is carried out in layers of 30-40 cm with careful tamping. After that, it remains only to make a blind area around the house, and the MZLF will be ready for further long-term operation.

The beginning of the construction of any building is laying the foundation. When choosing the type of foundation, various factors should be taken into account, ranging from soil characteristics to design features main building. Lately shallow strip foundation is popular, this is due to its versatility, low cost for construction works and the ability to erect a structure without the use of heavy construction equipment.

When is a shallow foundation used?

Such a foundation can be safely erected under light suburban buildings of a small number of storeys. These can be houses made of wood and its varieties, from gas silicate and foam concrete blocks, frame-panel structures. It is possible to use a shallow foundation under brick houses provided that the walls will have a slight thickness.

The height of buildings erected on a shallow foundation should not exceed three floors.

In addition, a shallow base is suitable for construction on soils prone to heaving, since a small depth protects the structure from the effects of heaving soil.

Features of the construction of a shallow foundation

When choosing a shallow foundation for a house, some features of its construction should be taken into account:

• Such a foundation requires mandatory protection from precipitation. Therefore, it is very important to provide for the organization of a drainage and drainage system. This will move more water away from the foundation line. Our previous articles have detailed information About, .
• One of the ways to protect a shallow foundation from precipitation and surface water is a blind area. Most professional builders insist on its arrangement. Learn more from our article:.
• With the independent manufacture of such a foundation, it is best to involve a large number of people to ensure quick preparation of concrete and its one-time pouring.
• In the process of building a shallow foundation, only high-quality concrete should be used. Read a detailed article about.
• Main Feature of this type of foundation is the need to complete the main construction before the onset of frost, since such a foundation cannot be left for the winter.

What should be taken into account when building an MZLF

Very an important factor is the type of soil on the site. The fact is that on soils of organic origin and on clay, the construction of a shallow strip foundation is prohibited.

The level of groundwater is of no less importance. Their very close location can cause rapid destruction of the shallow concrete tape.

Rules for performing load calculations on a shallow strip foundation

When performing load calculations on a shallow foundation, it is important to take into account all parameters. The total load on the foundation of the house can be constant and variable. In the first case, this is:

• The structure of the building and its features.
• The number of storeys of the building and its total height.
• The material that is planned to be used for the construction of walls and partitions of the building.
• The load from the roof structure, including the weight of the roofing material.

In addition, seasonal loads from precipitation should be taken into account, especially in winter. It is in winter that the snow mass on the roof of the house exerts great pressure.

Variable loads include the number of occupants, the weight of the furniture, and similar factors.

MZLF construction technology

A shallow concrete base tape is erected quite simply, so all work is available for self-fulfillment. In addition, this process will require several assistants, but you can do without heavy construction equipment.

A set of tools for work

The construction of a tape shallow base requires a set of the simplest tools:

• Shovel, you can cook a shovel and a bayonet shovel.
• Hammer and sledgehammer.
• Electric drill, grinder with discs, screwdriver.
• Roulette and building level.
• Regular rope or construction cord.

Trench

When determining the width of the trench, the width of the wall and the thickness of the formwork structure are taken into account. Directly, the foundation monolith should turn out flush with the wall, but taking into account the formwork, the width of the trench should be slightly larger. If construction is carried out on loose or heaving soil, then this trench parameter should be slightly increased.

Before you start digging a trench, you need to mark the site using wooden pegs and a building cord or rope. The pegs are driven in at the corners of the future foundation, and the cord is pulled between them around the perimeter. In this case, both the internal and external perimeters should be noted.

If construction does not require accurate calculations of a shallow-depth concrete tape, then the depth of laying is determined by the location of the layer of hard clay. In this case, the bottom of the trench should be lowered 25-30 cm below the top level of the clay layer.

For general reference, it should be said that the soil most often represents the following structure:

• The top 10 cm is a layer of fertile soil.
• The next 10-20 cm is occupied by a mixture of sand and clay.
• Below this layer is hard clay, which is quite difficult to dig.

The bottom of the trench should be deepened by about 30 cm in order to build a foundation and a pillow for it. Thus, the total depth of the shallow foundation is about 0.7 meters. This parameter fully complies with the requirements for the construction of frame, panel and other structures of low weight.

Creating a pillow

In order for seasonal soil movements and other changes in the soil to be evenly distributed over the entire area of ​​\u200b\u200bthe sole of the foundation, it is necessary to create a kind of pillow of sand and gravel. The sand layer should be about 5 cm thick. The sand is poured into the trench, leveled, watered and carefully compacted. Crushed stone is poured with a layer of the same height, well leveled, compacted and poured with liquid cement mortar. As a result of the actions performed, the sole of the foundation is obtained.

Reinforcement

The strength and reliability of any foundation is provided by a frame of reinforcing bars. It is not recommended to neglect the creation of a reinforcing belt, as it takes on the main load. For the same reason, you should not save on fittings or use low-quality elements.

To create a reinforcing belt, it is necessary to take reinforcement bars with a cross section of 10-12 mm and tie them, creating two levels of two bars each. The width and height of the reinforcing frame is determined by the parameters of the foundation, the reinforcement should recede by 5 cm from each edge of the foundation. The main bars of the frame must be connected with each other by vertical and transverse bars. For knitting, it is best to use a special soft wire. If it is necessary to connect the rods along the length, it is important to overlap the ends of the reinforcement by 10-15 cm.

Formwork construction

The formwork can be erected before assembling the reinforcing belt, but for convenience, this stage is slightly pushed back. The fact is that it is much more difficult to knit a frame in a finished formwork structure.

The main purpose of the formwork is the formation of even walls of the concrete tape, therefore, for its manufacture, it is necessary to use shields knocked together from boards or plywood. The inside of the shields should be as smooth as possible, so the boards are well processed (find out). In order for the structure to be able to hold the heavy concrete mass inside, it is recommended to make supports and lintels. Supports are installed on the outer side of the structure at a distance of 50-60 cm, jumpers are fixed along the upper edge of the panels so that the formwork does not disperse under the pressure of concrete.

Pouring concrete

A high-quality foundation can only be obtained using well-prepared concrete. Therefore, a factory-prepared solution is considered an ideal option. Most experienced craftsmen advise using this option whenever possible. However, with a small construction budget, savings are required at every stage, including the preparation of concrete. An excellent solution to the problem can be a mobile concrete mixer, it can be rented, which will significantly save money.

The quality of concrete also depends on the components used and their quantity, therefore, proportions and quality ingredients will help to make a solid and reliable foundation for a house or other building.

It is recommended to pour concrete in one step, while the thickness of one layer should not exceed 20-25 cm. After pouring one portion, it is necessary to compact the concrete mass, for this purpose a vibrator or an ordinary metal rod is used. In the latter case, the concrete is carefully pierced in several places, removing air bubbles. The compaction of the concrete solution helps to increase the strength of the entire base.

Warming and waterproofing

To avoid freezing of a shallow foundation, do not neglect the insulation and waterproofing of the base. In this case, the protection must capture both vertical and horizontal walls.

You can make a shallow strip foundation with your own hands. At the same time, it is necessary to take into account the main factors that affect the quality of the foundation, take into account the features of the construction of this type of foundation and observe the technology of its construction.

With a depth of the sole of the underground supporting structure of 0.2 - 0.7 m, it is called shallow foundation(MZF) and has a minimum construction budget. There are shallow slabs, poles, tapes. Piles are always sunk below freezing, so they fall into the category of buried foundations by default.

Varieties of MZF

The main problem of the load-bearing structures of buildings operated underground is the frosty swelling of the soil, which occurs when the following conditions are present:

• high percentage of clay
• an abundance of moisture to saturate these grains
• freezing of the soil, leading to an uneven increase in volumes in different areas

Several solutions were used to solve the problem:

To reduce labor intensity, deadlines for the completion of facilities, and the construction budget, a set of measures was created to reduce or completely eliminate swelling in frost:

• insulation - blind areas and various foundation elements to preserve geothermal heat under all load-bearing structures and adjacent soils

Attention: Subject to these measures, it is possible to lay in the project a shallow foundation of a slab, strip or column type, which is indicated in the regulation SP 22.13330 for the foundations of dwellings.

It is customary to call prefabricated and monolithic structures shallow-depth, the sole of which lies at around 0.2 - 0.7 m. Therefore, on soils with a low clay content, drainage and insulation may not be required at all.

Tape MZLF

A strip foundation of small depth is economically justified for especially heavy wall materials. The restrictions for MZLF are:

• soils with low design resistance (silt, peat, dusty sand)
• high groundwater level (less than 1 m from the sole of the tape)
• height difference of more than 1.5 m (between opposite walls of the building)

There are prefabricated tapes from one row of FBS blocks and an armored belt on top of them, monolithic structures with maximum performance by default. The manufacturing technology of monolithic MZLF is as follows:

Attention: On the inner surface of the panels, polyethylene should be fixed to prevent leakage of cement laitance and facilitate stripping. It is better to insulate MZLF from the outside after waterproofing, since only in this case a continuous film layer is created.

Stove floating

In 90% of cottage projects, a shallow slab foundation is used. The technology is considered the most expensive, but provides the maximum bearing capacity of the underground structure.

Despite the high strength of a concrete slab with two layers of reinforcing mesh, serious loads from frost heaving occur on heaving soils. Therefore, modernized versions of the floating slab are popular with individual developers:

Attention: Minimum laying depth slab foundations regulated 40 cm. This top layer is rich in humus, so it is forbidden to lean on it bearing structures. Organics rot without access to oxygen for 12 - 36 months, after which, soil subsidence is inevitable.

Columnar MZF

Shallow columnar foundation it is allowed to equip only on dry soils with a groundwater level below 1.5 m from the sole. It is forbidden to erect on slopes, heaving soils. In addition, the poles have low resistance to tipping over, so they must be connected with a grillage:

Attention: For columnar foundations with a deepening above the freezing mark, a set of measures is required to prevent swelling - ring or wall drainage, underlying layer + backfilling with crushed stone / sand of the sinuses of the pits.

Construction technology

shallow foundation constructed much faster than a deep foundation. The construction budget is reduced, but conservation in the winter without load is not desirable.

Marking and excavation

Depending on the type shallow foundation marked in different ways:

• the floating slab is contoured with one cord along the outer perimeter of the formwork
• for MZLF poles and tapes, two strings are pulled on the cast-offs for the inner / outer formwork shield

The pit comes off only for the slab, the trench is more rational for the tape, pillars with a rare spacing. If the prefabricated loads from the weight of the building are small, separate pits are torn off for the pillars.

Attention: In any case, access to the surfaces of concrete structures for waterproofing is necessary. Therefore earthen formwork technology is wrong

Drainage and underlayment

A sand/gravel foundation pad replaces the layer of fertile soil excavated at the previous stage. The thickness of the underlying layer is 40 - 80 cm, depending on the geology of the site, the magnitude of the prefabricated loads from the dwelling.

Drainage is built into this layer along the outer perimeter of the blind area at the level of the base of the foundation. To do this, vertical wells are attached to the corners of the cottage, pipes perforated in the upper part (180 - 270 degrees) are laid between them.

Attention: Non-metallic material is laid in 10 - 15 cm layers, each of which is rammed with a vibrating plate. It is not recommended to spill sand with water, as this can lead to erosion of the lower layers of soil, the formation of perched water already in the process of construction.

The width of the foundation cushion made of inert materials should be twice as large as the size of the tape, pillar. Under the floating slabs, the underlying layer is released to the outside by 40 - 60 cm.

Underlayment with waterproofing

A screed made of lean concrete with a thickness of 5 - 10 cm is necessary only for monolithic structures. If a shallow tape, a columnar foundation is constructed from prefabricated reinforced concrete elements, the footing is not used. The screed makes it possible to provide sealed joints of the waterproofing material, to exclude the absorption of cement laitance by the non-metallic material of the underlying layer.

Attention: The width of the footing is equal to the size of the underlying layer, that is, twice the tape, the section of the column.

As a waterproofing, a polyethylene film (minimum 15 microns) is usually used, glued to the footing, or rolled materials (TechnoNIKOL, hydrostekloizol), welded onto the concrete surface. The edges are released to be later launched onto the vertical surfaces of the concrete structures.

Formwork and reinforcement

Due to the variety of structures of shallow foundations, several formwork modifications are used:

• floating slab - boards along the outer perimeter or polystyrene L-shaped blocks
• tape MZLF - outer + inner deck
• pillars - a square of shields for the widening plate and vertical shields for the pillar

For each specified option, different reinforcement schemes are used:

Attention: Reinforcement is located inside concrete structures in compliance with the protective layer. The rods are recessed by 2 - 7 cm, the bottom row is laid on the footing with plastic spacers.

Concreting and waterproofing

Concrete should be laid in layers of 40 - 60 cm at intervals of 2 hours. Therefore, it is desirable to concrete any type of shallow foundations in one step. Waterproofing of accessible concrete surfaces is carried out with penetrating, coating, pasting materials after 70% curing.

Attention: individual elements inside one foundation (porch, tape on which the veranda will rest) are separated by a technological seam. Different operational loads will not lead to the destruction of walls, foundations, if the roof of the extension is independent of the roof of the main dwelling.

Thus, shallow foundations are not difficult for an individual developer. However, it is necessary to take into account the above recommendations to ensure the maximum possible resource of the building with a minimum construction budget.