What is shallow foundation

Flat strip foundation. Flat strip foundations: characteristics and subtleties of installation

The strip foundation is the most common type of foundation used to build a house. Therefore, with him everything is clear, but what is the difference between the shallow (MZLF) - the foundation of shallow laying, how to calculate and how to do it?

Properties - a constructive principle of action

The shallow depth of the strip foundation or just the MZLF in terms of the method of laying it is similar to that of its counterpart, but has important differences:

  • foundation laying depth up to 700 mm;
  • located above the freezing zone of the floor;
  • designed for placement on extensive (undulating) floors.

The main feature of the flat strip foundation is that it is possible to level out the frosty pile of earth. This is due to the fact that, despite the general rigidity, the MZLF design moves up and down depending on the season, along with the weight of the entire structure. Since the foundation is not deepened, but shifted evenly, it does not collapse due to such vibrations.

The scheme of the device ribbon foundation

  1. Sand and gravel pillows
  2. Baseband
  3. Waterproofing layer
  4. Vertical (or coated) waterproofing
  5. Anchor (diameter 12)
  6. Anchor (diameter 8)
  7. Cap
  8. Wall

Purpose of use - application

The ribbon foundation is suitable for the construction of low residential buildings and other structures from such materials that do not exert significant pressure on the foundation base. Such structures and materials include:

  • log cabins;
  • cellular concrete - foam concrete, gas silicate blocks;
  • light masonry;
  • frame panel building.

If you arrange a foundation of greater width, you can build heavy houses from a bar or log on to it. However, in this case, the ground will freeze to a shallower depth, and there is a possibility of deformation of the foundation. So, if a monumental building is to be built, then it is better to equip the monolithic strip foundation.

It should be noted that by increasing the width of the tape of the shallow foundation, heavier houses with an attic can be built. The large width of the foundation tape (or base) helps reduce the freezing depth of the ground in the space below the ground.

What should be considered when building a shallow foundation?

Flat foundations are laid on undulating ground.

It is forbidden to fill MLF on biogenic organic soils such as peat, sapropel (deposits of freshwater reservoirs), as well as on clay. The photo shows that her appearance is already not good.

The closer the water is to the surface of the earth, the more unstable the MLF becomes

  • Vertical drop
  • If the terrain is characterized by a significant difference in elevation (a house on a slope), installing a shallow strip foundation will be quite problematic. In this case, an ordinary strip foundation is built or a substantial area under the MLF is leveled. In terms of time and money, both options are equivalent.

    It represents the height from the lower point of the foundation, the so-called sole, to the zero mark (soil surface).

    • Climate (freezing depth of the ground)

    Laying a flat strip foundation at a height calculated according to the formula - freezing depth minus 20% - is quite common among builders. So you can be sure that the foundation will rise along with the building.

    The minimum depth of the shallow strip foundation is regulated by SNiP II-B.1-62.

    The depth of ground freezing for some cities of Russia is given in the table.

    How to calculate the load on a shallow tape foundation

    First of all, you should consider the following:

    • structural design features;
    • building height;
    • planned number of floors;
    • materials from which the walls are built;
    • weight of coatings;

    Tip.
    In general, the total load can be divided into a constant (calculated before construction starts) and a variable. The latter depends on the number of inhabitants, the weight of the furniture, etc.

    • trench depth;
    • cushion thickness;
    • foundation strip parameters;
    • concrete quality.

    You can also use

    Calculation of a shallow strip foundation

    1. The depth is determined by the proximity of the groundwater and the freezing depth.

    2. Height above the floor \ u003d 4x width.

    Good to know. The height above the ground is less than or equal to the depth.

    3. The width is determined by the formula:

    Where D is the width of the base of the foundation;
    q - design load of the foundation, t / m;
    R is the calculated soil resistance, t / m². This indicator for a laying depth of 300 mm is given in the table.

    4. The thickness of the pillow is determined from the conditions of the terrain strength.


    The formula is used for heavily undulating floors:

    Where tn is the thickness of the pillow;
    A, C, W - coefficients;
    A and C are determined by the following tables.
    And W \ u003d 0.1 or 0.06 square meter / t for heated and unheated structures.

    Above the line - for MZLF with a laying depth of 300 mm, below the line - for unfilled foundations.

    Tip.
    Do the MLF calculation with both formulas and prefer a larger value.

    Flat strip foundation cost

    Varies within 4-6 thousand rubles. per running meter. The price depends on the width, height, number of jumpers and sizes. For example, the cost of building the foundation of a 6x6 house is 70-80,000 rubles and 10x10 \ u003d 120-150,000 rubles.

    Types of ribbon foundations (laying flat)

    Depending on the type of MLMF, the technology of the device differs. Therefore, you should briefly familiarize yourself with the most important:

    Flat monolithic tape foundation

    Poured directly on site resulting in a seamless tape

    Flat block tape foundation

    Blocks are bought ready-made or purchased separately and only assembled on site. A cement solution is used as the fastening material.

    Each of them has its own advantages and disadvantages. But in general, the life of the second is three times shorter than that of the first. Hence, in this article, we will go into detail on a shape like a monolithic MLF.

    MZLF technology or how to make a flat foundation tape with your own hands

    Lessons are more easily perceived when all the work is broken down into clear steps. We will not deviate from this scheme. So the device of the shallow tape foundation is as follows:

    Preparatory phase

    1. The place where the foundation is to be filled is freed of all unnecessary.

    Advice root near trees with roots.

    2. All necessary materials and tools are delivered to the workplace. In addition, it is advisable to locate all of these goods immediately so that you do not waste time looking for them later.

    Place under the strip foundation

    The importance of this phase is difficult to overestimate. Therefore, it is necessary not only to find out where to dig a trench, but also to make reference points with a rope (if possible, it is better to use a laser plane).

    To mark the foundation:

    1. make measurements around the perimeter;
    2. hammer fire in the corners;
    3. Check the diagonal between the corners.
    4. move the beacons if necessary.
    5. blind area at least three feet from the beacons;
    6. attach a rope to the blind area boards showing the edges of the foundation.

    The layout process is shown more clearly in the diagram.

    How to dig a trench under the foundation

    The foundation trench is an excavation strip.

    The depth of the trench is determined by the depth of the shallow strip foundation and pillow.

    For example, the most common depth is 300 mm, the thickness of the pillow is about 200 mm, depending on the quality of the soil. Then the depth of the trench is 500 mm.

    consultation
    So that the edges of the trench do not crumble, make small slopes.

    Given the type of soil, it is better to start pouring the foundation immediately. Otherwise, it will crumble and part of the work will have to be repeated.

    A cushion of sand under the foundation is a mixture of sand and gravel. They can be mixed, but are easier to pour in layers. Moisten each layer with water and stuff well. Since the structure of the pillow is quite porous, it is separated from the main foundation by a sealing film.

    In principle, the foundation for the shallow foundation can be natural soil, but its bearing capacity is much less than that of the proposed sand and gravel cushion.

    Install the entire formwork structure vertically. The supports are attached in steps of 500-600 mm. They are needed so that the formwork does not fall apart under the weight of the concrete and does not warp.

    Useful advice.
    Make sure the boards are seated firmly with no sudden changes. Then you will avoid work on leveling the surface of the finished foundation under the cladding.

    Tile foundation filling

    Getting concrete is an individual problem - you can buy (or rather order) and deliver concrete with a mixer, or make it yourself (and the second option is how to make it).

    Pouring concrete is standard in such work - concrete is poured into the finished formwork.

    Advice If the formwork is poured with water, the concrete will lie more evenly on the edges.

    When pouring concrete, try to repel it every 40-50 mm. Heights. This allows you to "kick out" air bubbles that can destroy concrete in the future.

    Flat strip foundation reinforcement

    If no heavy load is expected on the foundation, this step can be skipped. Even so, MZLF will be much stronger with the reinforcement.

    Correct reinforcement of the shallow foundation foundation:

    • Complete the starting shift. This layer should be approximately 30% of the total height of the MLF. The purpose of this action is to create a flat surface to lay metal and protect it from moisture.

    • Knitted reinforcement for strip foundations. To do this, you need to tie it in blocks and put it in a trench.

    • Pour concrete to the desired height.

    An example of a reinforcement cage for a strip foundation

    An example of knitting a reinforcement with wire.

    An example shows that the bundle is made of wire. This is a relatively new approach to joining as contact welding is better known.

    However, the methods of joining the reinforcement by welding have several major drawbacks, including:

    1. need a welding machine and a specialist who can carry out welding work;

    2. due to the high temperature of the welding arc, the strength of the hardened rebar is lost.

    3. welding does not apply to fittings with a diameter of more than 20 mm.

    4. The most important thing is to increase the rigidity of the reinforcement cage. Since the flat band foundation "plays" depending on the season (a kind of flexible foundation, so to speak), increased rigidity leads to its destruction. And as a result, it will be required.

    This is what the installed fittings will look like

    Concrete protection

    In order to avoid overdrying and cracking, the concrete poured into the formwork is covered with a foil and regularly moistened with water.

    Thermal insulation of a flat strip foundation

    • Immediately after the foundation has acquired the necessary strength, construction of the house should begin. Try to do all of the work in one season. Because the ground under the foundation freezes and MZLF, which is not pushed by the weight of the house, is deformed.

    • If you can't start building, cover the MLF and the area near it (200-300mm) with straw or sawdust. To protect the floor from freezing.

    • During the operation of the structure, try to plant perennial plants and shrubs near the shallow strip foundation. They will help reduce soil freezing. They can also hold back a significant amount of snow, which also reduces the depth of freezing.

    Video with flat strip foundation

    Conclusion

    In this article, we figured out how to make a shallow tape foundation with our own hands. When you have gone through each stage in detail, you can avoid annoying mistakes and fill the foundation on which your home will stand for decades. Above all, don't forget that you need to order geological surveys before starting construction. Otherwise, there is a risk that the floor on your site is not intended for the installation of MLF.

    The foundation is the main component of any structure as it acts as the load-bearing structure on which durability and operational safety depend. Recently, for the construction of half-timbered houses, cottages and household furnishings, the installation of a shallow strip foundation has been chosen.

    It is ideal for all types of soil, is characterized by high strength and can easily be laid with your own hands.

    properties

    The shallow depth of the strip foundation is one of the modern types of foundations that are used in the construction of one-story and two-story buildings from foam block, expanded clay and wood. According to the requirements of SNiP, it is not recommended to make such foundations for buildings with a height of more than 2 floors that exceed an area of ​​100 m2.

    Such structures are considered a good option for adobe buildings, but the dimensions of the structure must be taken into account when planning them. GOST also enables shallow strip foundations for unstable ground. Due to their design features, they can move along with the ground, protecting the building from possible shrinkage and destruction. They are inferior to the column foundation.

    To make the foundation reliable and durable, it is installed on bored piles and laid monolithic reinforced concrete slabs, which are deepened into the ground by 40-60 cm. First, the site is carefully leveled, then the formwork is laid around the entire perimeter, the ground is covered with sand, and the reinforcement is laid. For such a foundation, as a rule, a monolithic slab with a thickness of 15-35 cm is made, the dimensions of which depend on the dimensions of the future structure.

    In addition, the flat strip foundation has some features that must be taken into account when building:

    • the base is buried no deeper than 40 cm, and its width is 10 cm greater than the thickness of the walls.
    • It is imperative to create monolithic reinforced concrete structures on a heaving ground, which will help reduce the load from above and balance the heaving forces from below.
    • it should be laid on well-prepared and pre-compacted floors.
    • with a high water table, it is necessary to install high-quality waterproofing and the installation of a drainage system.
    • a shallow foundation must be heated from above, since the thermal insulation layer protects the base from temperature changes and serves as an excellent source of heat.

    advantages and disadvantages

    Nowadays, when building buildings, you can choose any type of foundation. However, an unfilled strip foundation is especially popular with developers, since it is considered the most reliable and has positive reviews in the operation of structures on floating soils and clay. It is also often installed in a sloping area where a buried version of the structure cannot run. The main advantages of such a base are several properties.

    • The simplicity of the device.With minimal skills, it is quite realistic to lay the structure with your own hands, without using lifting mechanisms and special equipment. Construction usually takes several days.

    • Longevity. Taking into account all building technologies and standards, the foundation will have a lifespan of more than 100 years. In this case, special attention should be paid to the choice of the type of concrete and reinforcement.
    • Possibility of designing houses with a basement and a basement.With this arrangement, reinforced concrete tape serves as a load-bearing structure and walls for the basement.
    • The minimum cost of building materials.For work, you only need reinforcement, concrete and prefabricated wooden panels for making the formwork.

    As for the shortcomings, some characteristics can be attributed to them.

    • Labor input. For construction it is necessary to first carry out earthworks, then make an armored mesh and pour everything with concrete. It is therefore advisable to use the help of the wizards to speed up the installation process. However, this causes additional costs.

    • Easy to build. If the laying is carried out in winter, the concrete will later gain strength after 28 days. And that means you have to wait a month because the foundation cannot be loaded.
    • The inability to build tall and tall buildings.Such a foundation is not suitable for houses, the construction of which is planned from heavy material.
    • The need for additional styling Seal.

    calculation

    Before you start laying the foundation, you need to carry out the design and make accurate calculations. The complexity of the calculations for a flat ribbon base is to determine the hydrogeological properties of the soil on the site. Such examinations are mandatory, since not only the depth of the foundation depends on it, but also the height and width of the slabs are determined.

    In addition, in order to make the correct calculations, it is necessary to know the main indicators.

    • The material from which the construction of the building is planned. The strip foundation is suitable both for a house made of aerated concrete and for buildings made of foam blocks or wood, but it differs in its structure. This is due to the different weight of the structure and its load on the base.
    • Sizes and area of ​​the sole. The future foundation must fully correspond to the dimensions of the waterproofing material.
    • The area of ​​the outer and side surface.
    • Diameter dimensions of the longitudinal reinforcement.
    • Marking and volume of the concrete mortar. The mass of concrete depends on the average density of the mortar.

    To calculate the depth of the laying, it is first necessary to determine the bearing capacity of the soil on the construction site and the parameters of the sole of the tape, which can be monolithic or consist of blocks. Then you should calculate the total load of the foundation, taking into account the weight of the ceiling, door structures and finishing material.

    It is also important to study the depth of freezing of the soil. If it is 1 to 1.5 m, then the laying is carried out at a depth of not less than 0.75 m. If it freezes to more than 2.5 m, the base is buried to a depth of more than 1 m.

    material

    Installation of the plinth for construction requires the use of quality building materials, and the shallow strip foundation is no exception. It is erected from a reinforced concrete frame on a cushion of sand, while the calculation can be both monolithic and block.

    To reinforce the base, steel bars are used, which, depending on their characteristics, are divided into classes A-I, A-II, A-III. In addition to bars, reinforcement frames, rods and nets in concrete thickness are also laid. The grid and frame are a structure of transverse and longitudinal bars that are attached to each other.

    The reinforcement scheme is selected according to the design features and depends on the loads on the foundation. Steel bars with a diameter of 10-16 mm are well suited for installing a flat base, they can withstand loads and stretch. The transverse reinforcement is usually done with a smooth wire with a diameter of 4-5 mm.

    Knitting wire is also used as an auxiliary material, it fixes the rods in the manufacture of meshes and frames.

    In order to extend the service life of the foundation, all elements of the reinforcement must be protected from external influences. A gap of 30 mm remains between the edges of the bars and the concrete.

    In addition to the protective layer, the reinforcement is also placed on the supports, so that both commercially available special stands and steel or metal scraps can be useful for construction. During the laying of the foundation stone, the manufacture of formwork is provided, which can be purchased in finished form, as well as knocked down independently of wooden boards.

    To fill the air cushion, medium-sized sand is used and poured with concrete mortar of various qualities. At the same time, concreting is best done with a high-quality solution of class M100 and higher.

    Device steps

    The technology of installing a shallow foundation is not particularly difficult, so it is quite possible to do all of the work yourself. Before you start laying the foundation stone, you need to create a project and an action plan in which all activities “from A to Z” are to be written down. In order for the foundation to function reliably for more than a dozen years, it is important to pay attention to moments such as insulation, waterproofing and the frequency of fastening the reinforcement.

    It is best if the foundation is monolithic.

    It is also important to conduct a geodetic assessment of the soil in advance, which will determine the water table, soil composition and freezing depth. The choice of the basic type and the laying depth depends on these parameters. In the event that an inexpensive construction option is planned, it is enough to simply drill several pits in different places on the site and examine the soil independently.

    The soil, in which there is an admixture of clay, easily rolls up into a ball. However, if it cracks during formation, then the soil is made of clay. Sandy soil cannot be rolled into a ball because it will crumble in your hands.

    After the composition of the soil has been determined, you can proceed to the construction of the foundation. A step-by-step guide usually provides the following steps:

    • calculation of the cross-section of the reinforcement, the width of the tape and creation of a reinforcement scheme
    • the making of a pit for the basement or a trench for buildings without a basement;
    • installation of a drainage system and thermal insulation;
    • installation of formwork and fastening of fittings;
    • concreting and installing the waterproofing after the formwork.

    The completion of the laying of the foundation is the insulation of the blind area, which is lined with a special material that is moisture-resistant. If all the points of the instruction are correctly implemented in accordance with the technologies and building standards, the resulting shallow-deep strip foundation will not only become a reliable foundation for the structure, but also serve for a long time and protect the structure from external influences.

    Earthworks

    Construction of the foundation should begin with the preparatory preparation of the land, it is thoroughly cleaned of dirt, plants and trees, the fertile layer of soil is removed. The marking is then carried out and all dimensions specified in the building design are transferred to the construction site. To do this, use pens and a rope. First, the facade walls of the building are noted, then two more walls are placed perpendicular to them.

    At this stage it is important to control the evenness of the diagonals. At the end of the markup, a rectangle is obtained that compares all diagonals.

    The beacons are clogged in the corners of the future construction, keeping a distance of 1 m between them. The next step is to install a wooden blind area on which the ropes will stretch. Some craftsmen simply mark the dimensions of the foundation on the ground with a mortar. Then the trench digs, its depth should be equal to the thickness of the sand cushion and tape.

    Since the thickness of the sand cushion usually does not exceed 20 cm, a trench 0.6-0.8 m wide and 0.5 m deep is made for a shallow foundation.

    In the event that the project envisages the construction of heavy structures with stairs, a porch and a stove, it is recommended to dig a pit. For the manufacture of pillows with a thickness of 30-50 cm, crushed stone and sand are used. The most common option is a pillow, which consists of two layers: 8 inches of sand and 8 inches of crushed stone. If the soil is dusty, additional geotextiles must be placed in the trench.

    The pillow is covered in layers: first, the sand layer is evenly distributed, well compacted, moistened with water, then gravel is poured and rammed. The pillow should be placed strictly horizontally and covered with a waterproofing in the form of roofing material.

    formwork

    An equally important point when laying the foundation is the assembly of the formwork. Use shield materials such as OSB boards, plywood or boards with a thickness of at least 5 cm for the production. In this case, the panels should be hammered into the panels. The formwork must be dimensioned so that it is a few centimeters above the future concrete level. The height of the tape corresponds to the depth of the foundation or is less than this, as a rule there are 4 widths of the tape.

    Prepared panels are held together with nails or self-tapping screws and then additionally supported with tenons. It should be noted that not all connecting elements protrude into the formwork. If you ignore it, they will be in concrete after pouring and may provoke the appearance of cracks or chips.

    The formwork of the shallow-deep strip foundation is additionally reinforced by struts made from a 5 cm girder, which are attached to the outside at a distance of 0.5 m.

    In addition, holes for communication must be prepared in the formwork and pipes must be inserted. The inner part of the structure is covered with polyethylene, which improves waterproofing and reduces adhesion to concrete.

    Fixed formwork made of extruded polystyrene foam can also be used.

    Reinforcement

    A device of this type of foundation involves mandatory reinforcement. The fittings can either be knitted with wire or welded. However, for connecting metal bars, the latter option is not recommended, as corrosion will appear at the points of attachment over time. A minimum number of rods is required to assemble the frame, at least 4 pieces.

    A material with a rib profile of class AII or AIII is to be used as longitudinal reinforcement. In addition, the longer the rods, the better the frame because the joints reduce structural strength.

    The transverse parts of the frame are composed of smooth and thinner reinforcement with a diameter of 6 to 8 mm. Two reinforcement belts made up of only 4 longitudinal bars are enough to install a flat base. It is important that the edges of the reinforcement are 5 cm from the foundation and that the distance between the vertical fasteners is at least 30-40 cm.

    The crucial moment in the work is the manufacture of the corners of the frame: the bars must be bent so that the approach to another wall is at least 40 mm from the diameter of the bars. In this case, the distance between the corners formed by vertical jumpers should be twice less than the distance in the wall.

    to water

    The foundation assembly is completed by concreting. For this purpose, experts recommend the use of factory concrete with at least M250. If the solution is to be made independently, then a concrete mixer should be prepared in advance, as it will be difficult to do it manually. A solution must be poured over the substrate immediately, for this it is evenly distributed over the entire surface and compacted. Each fill layer should be carefully aligned with the marking on the formwork.

    Skilled craftsmen who have made more than 100 foundations recommend sprinkling the concrete with dry cement at the end of the pouring process. This improves the quality and the top layer hardens faster.

    As a rule, a month is spent on the full consolidation of the foundation, after which construction work can continue.

    Main flaw

    Since the foundation is the main part of any construction, it must be properly laid, especially with a flat base of tape that is laid over loose soils and clay soils. Any mistake made during construction can ruin all construction work. When inexperienced craftsmen make the foundation themselves, they make some common mistakes.

    • You start construction without calculating the basic dimensions and load on the foundation.

    • Immediately pour the base into the ground without sprinkling and make a cushion of sand. In the winter season, the floor freezes into concrete, pulls and lifts the tape to the top, as a result of which, under the influence of frost, the foundation begins to lift and the bottom of the basement cracks. This is especially true when there is no insulation.

    • Choose the number of bars and the diameter of the reinforcement at your discretion. This is not acceptable as the foundation reinforcement is incorrect.
    • Carry out construction in more than one season. The entire cycle of work should be distributed in such a way that the laying of the foundation, the laying of the walls and the insulation of the blind areas are completed before the onset of the cold.

    In addition, protecting a concrete base with a film is considered a big mistake. Don't close it. The poured solution must be aerated.

    See how to make a shallow tape foundation with your own hands in the next video.

    It is wrong to assume that the ribbon foundation (FMZ) does not require any special knowledge and experience in construction. Choosing a type of foundation, as well as its construction, are the most difficult and important stages in the construction of the entire house.

    Incorrect assessments and errors are not permitted, as otherwise the entire construction process can be reduced to zero or additional maintenance investments are required. In order to avoid mistakes, it is necessary to determine the quality of the soil in the plot, calculate the weight of the future structure and determine the groundwater level. It is advisable to use the services of a professional who will calculate the basis and make the necessary recommendations.

    A professional approach to the creation of a TTK (Standard Technology Card) ensures strict compliance with SNiP, which reduces project costs and labor costs. Only in this case can the quality of the manufactured low-rise building (MLF), which corresponds to all parameters of SNiP, be guaranteed.

    Advantages and disadvantages of a shallow foundation

    Each construction has its advantages and disadvantages, and building a flat surface is no exception. Building a house on a flat, shallow foundation has the following advantages:

    • can install ribbon foundation do-it-yourself from "A" to "I" with your own hands;
    • can not applyconstruction equipment - no need to dig deep into the foundation;
    • the possibility of heating strips base, as well as devices of the technology "warm floor";
    • high strength construction;
    • low costthe project, even if the work is carried out under an agreement - a construction company.

    Of the disadvantages, it should first be mentioned - this is the construction of structures on floating floors. In order for the building to have sufficient strength, a blind area is created around the entire structure. According to all norms and rules (SNiP), you can create a drainage system under the floor of the building.

    Another nuance is pouring concrete on heated ground. In addition, according to the instructions of the TTK (Typical Technology Map), the construction of a house on this basis is carried out in a short time - this is up to 5 months.

    labour costs

    The cost of a shallow depth of the tape foundation can be calculated in cubic meters, on average, it is 15 thousand rubles per cubic meter or 3 thousand rubles per linear meter. The cost of building a ribbon foundation includes:

    • earthworks - digging a tape;
    • sand cushion laying - 200 mm;
    • formwork installation;
    • installation of a reinforcement cage;
    • pouring concrete;
    • drainage for a shallow foundation - on heaving soils;
    • dismantling the formwork.

    This is calculated when ordering a ribbon foundation from a professional organization. The calculations should include the cost of the reinforcement - with a diameter of 12 mm, the cost of sand and material delivery. Reinforced glass insulation with hot bitumen mastic is used for high-quality sealing of flat substrates.

    For which buildings is the foundation suitable?

    Flat tape foundation for the house made of aerated concrete, also suitable for two-story buildings made of light material:

    • Wood;
    • expanded clay;
    • foam concrete.

    In SNiP (Foundation of Buildings and Structures) it is not recommended to erect buildings with more than two floors and an area of ​​more than 100 m2. A shallowly indented foundation is laid on clay, but it should be noted that the typical dimensions of structures on clay and clay soil should not exceed 6 x 6 m.

    Features of the ribbon foundation

    In order to save time and money in private housing, they use the foundation of shallow depth. The main advantages of this structure are high reliability and low cost. The use of the ribbon foundation is carried out in buildings with different walls: logs, gas blocks, shields. Unlike other types of foundations, building a buried foundation can save up to 70% in material and up to 80% in labor costs.

    Due to the influence of lifting forces (lifting floors) directed on the walls of the structure on the side and on the floor of the sub-floor, the area of ​​the walls decreases and the tension on the side is significantly reduced, the mass of the building regulates the lifting forces from below.

    There are basic technological rules for building a structure:

    • Laying the foundation stone must not be deeper than 30-40 cm;
    • grounds should be 10 cm wider than the wall thickness;
    • On lifting floors, the subsurface should be designed as a monolithic reinforced concrete structure that is able to compensate for the lifting forces from below and the uneven pressure from above.
    • lay the foundation stone Flat laying on prepared compacted soil with sufficient water drainage coefficient. Coarse sand or gravel is used for this. In this case, the load during subsidence is balanced during the thawing of the soil;
    • a high groundwater level ensures water tightness. In this case, artificial drainage is carried out from above.
    • shallow foundation.It is necessary to insulate from above. Blind areas with a width of up to 1 m are to be built around the basement, for this purpose a thermal insulation layer (extruded polystyrene foam or other insulation) is placed on the floor.

    Is it necessary to isolate? The thermal insulation layer protects the substrate from frost and the effects of temperature loads. The blind area around the house is insulated so that the floor below does not freeze, but on the contrary itself becomes a source of heat and stabilizes the temperature situation under the house.

    Unfilled laying of the foundation

    An unfinished base can be made in three ways: monolithically, using a reinforcing knitted mesh, laid in separate blocks or stones. All methods are practical and equally easy to implement. You can choose any option based on the material available. To begin construction, you need to have an idea of ​​where to begin and the sequence of the next stages of construction.

    First of all, markings and designs are carried out, for this purpose site surveys are carried out, the properties of the soil are studied to decide how deep to lay the foundation for the future structure. After creating a project - sectional drawings of a future building, one can proceed with further steps in the construction of a house.

    Step by step instructions:

    • Markup. A cast of wooden sticks is installed, nailed to the pins at a distance of 1.5-2 meters from the outer edge of the intended corners of the base. Nails are pounded on the poles, on which a tape or rope is pulled - to mark the lines of the future trench.
    • Earthworks. Trenches should be attempted to dig straight at first. Use a spirit level, spirit level and measuring tape to check. The quality of the work in this phase largely determines the later material, time and effort required.
    • Lay pillows. Coarse-grained sand is poured into the bottom of the trench (20 cm) to compact the sand pillow. It is poured with water and rammed with a pounder. A layer of crushed stone, pebbles or expanded clay is laid on top - up to 20 cm.
    • Reinforcement. Making a shallow foundation without reinforcement is not recommended. Use a rod with a cross section of 12 mm for reinforcement. The frame consists of 2-3 rows of reinforcement, horizontal bars are tied to the driven ends of the bar. A step of 15-20 cm must be maintained between the bars, the elements are connected to one another with a knitting wire.
    • Installation of formwork. Formwork is made up of formwork boards or planks. The formwork should be 30 cm above the ground and, after installation, be pressed against the walls of the trench with spacers. "Sanitary" openings are made - sewage, water supply.
    • Pouring concrete. The solution is made in the ratio of cement sand 1: 3. The metal frame should be poured with a layer of solution of at least 3 cm. To prevent the accumulation of air and add strength, the solution is compacted, air bubbles are expelled with a probe or pen.
    • Disassembly of the formwork. Disassemble the shields after the concrete is fully set.

    In the event of dense occurrence of groundwater, waterproofing should be considered. The use of bitumen is a cost-effective way of producing high-quality seals.

    A shallow ribbon foundation (hereinafter MZLF) is one of the types of ribbon foundations that is characterized by a small depression, which is much less than the freezing depth of the soil, and a relatively low consumption of concrete mix. This article will discuss the main advantages and disadvantages of the MLF, the most common design mistakes, a simplified method of calculation for private builders (not professionals) and recommendations for making a foundation with your own hands.

    The main advantages of the MLF are:

    - Profitability - Concrete consumption is much less than when building a traditional tape foundation. This factor most often determines the choice of this technology for low-rise buildings.

    - lower labor costs - less earthworks, less concrete preparation (this is especially important when the finished mixture cannot be filled with a mixer);

    - Lower tangential frost forces due to the reduced area of ​​the side face of the foundation.

    However, during the construction of the MLF it is necessary to closely monitor the technology. A careless attitude towards the process can lead to cracks, and then all of the above benefits, as they say, fly into the pipe.

    The most common mistakes when installing MZLF:

    1) the choice of the basic working dimensions of the foundation without (even the simplest) calculation;

    2) Pour the foundation directly into the ground, without sprinkling with non-porous material (sand). According to Fig. 1 (right) we can say that in the winter season the ground freezes to concrete and the tape pulls upwards when climbing, i.e. H. Tangential frost forces act on the foundation. This is particularly dangerous if the MZLF is not isolated and there is no quality-assured blind area.

    3) incorrect reinforcement of the foundation - the choice of the diameter of reinforcement and the number of bars at your discretion;

    4) For the winter, leave the MLF unloaded - it is recommended that the entire cycle of work (building the foundation, building the wall and arranging the blind area) be carried out one construction season before the onset of the severe frost.

    Calculation of a ribbon foundation.

    The calculation of the MLF as well as all other foundations is based on the one hand on the value of the load from the dead weight of the house and on the other hand on the calculated soil resistance. That is, the floor must support the weight of the house that is transferred to it through the foundation. Please note that it is the soil that holds the bulk of the house on it, and not the foundation as some believe.

    If you can still calculate the weight of a house if you wish, an ordinary private property developer (e.g. with the help of our online calculator) will not be able to independently determine the estimated soil resistance on your location. This feature is calculated by specialist organizations in specialist laboratories after geological and geodetic investigations have been carried out. Everyone knows that this procedure is not free. Basically, architects who initiate the project of the house resort to it and then calculate the foundation based on the data received.

    In this context, it does not make sense to provide formulas for calculating the MLF size in the context of this article. We will consider the case when the contractor builds independently, does not conduct geological and geodetic studies and does not know the calculated soil resistance in his area. In such a situation, the dimensions and design of the MLF can be selected according to the tables below.

    The characteristics of the foundation are determined depending on the material of the walls and floors of the house and the number of floors, as well as the degree of loosening of the soil. How can I determine the last described

    I. MZLF on medium-heavy and heavy soils.

    Table 1: Heated buildings with walls made of masonry or aerated concrete (foam concrete) and with reinforced concrete ceilings.

    Remarks:

    - The number in brackets indicates the material of the pillow: 1 - medium-sized sand, 2 - coarse sand, 3 - a mixture of sand (40%) with crushed stone (60%);

    - this table can also be used for houses with wooden floors, the safety margin will be even greater;

    - See foundation designs and reinforcement options below.

    Table 2: Heated buildings with walls made of insulated wooden panels (half-timbered houses), tree trunks and wood with wooden floors.

    Remarks:

    - The numbers in brackets correspond to those in Table 1.

    - above the dashed line for walls made of insulated wooden panels, below the dashed line for block and wooden walls.

    Table 3: Unfinished foundations of unheated log and beam buildings with wooden floors.

    Remarks:

    - above the value line for log walls, below the line - for wooden walls.

    The design options for MZLF on medium-grain and high-grain floors, which are identified by letters in the tables, are shown in the following figures:

    1 - monolithic reinforced concrete foundation; 2 - sand filling of the sinuses; 3 - sand cushions (sand gravel); 4 - reinforcement cage; 5 - blind area; 6 7 - Seal; 8 - Basement, cellar; 9 - soil surface; 10 - sand bedding; 11 - Race.

    Option a. - The upper level of the foundation coincides with the surface of the earth, the basement is made of bricks.

    Option b. - The foundation protrudes 20-30 cm above the surface and forms a low base or is part of the base.

    Option c. - The foundation rises 50-70 cm above the ground and is at the same time a foundation.

    Option g - an unfinished basement underside; Table 3 shows that such foundations are used for unheated wooden buildings.

    Option d. - used in place of options b. or c. if the width of the foundation base significantly exceeds the wall thickness (more than 15-20 cm).

    Option e. - On weak (peaty, muddy) soils with a high groundwater content, a shallow-deep strip foundation on a sandy subsoil is rarely used for wooden structures. Depending on the size of the building, backfilling takes place either under each band or all at once under the entire foundation.

    Reinforcement of a shallow tape foundation.

    MZLF reinforcement is made by grids of working reinforcement and auxiliary reinforcing wire. The working reinforcement is located in the lower and upper part of the foundation, while it should be immersed about 5 cm into the thickness of the concrete. The lower net is used to deflect the foundation tape and the upper net is used to bend the tape. There is no point in placing the work fittings in the middle of the belt (as can sometimes be seen on the internet).

    Table 4: Foundation reinforcement options.

    MZFL reinforcement schemes are shown in the figure below:

    a. - a grid with two bars of work fittings; b. - a grid with three bars of work fittings; c. - T-piece; G. - L-shaped corner joint; d. - additional reinforcement of the MLF with a large sole width, if the sole is more than 60 cm wider than the ground (additional net is only in the lower part).

    1 - work fittings (A-III); 2 - Auxiliary reinforcement wire Ø 4-5 mm (VR-I); 3 - bars with vertical reinforcement mm 10 mm (A-III) connecting the upper and lower lattice; 4 - Reinforcement to reinforce the ∅ 10 mm angle (A-III); 5 - Connection by wire wires (twist length at least 30 diameter of the working anchor); 6 - Additional work fittings Ø 10 mm (A-III).

    II. MLF on non-porous and slightly porous floors.

    Flat ribbon foundations on non-porous and slightly porous soils do not only have to consist of monolithic concrete. Other local materials can be used such as crushed stone, red ceramic tile. MZLF laid to 0.3 to 0.4 m without sand cushions. In addition, for wooden buildings and single-story brick (or aerated concrete) foundations, you can not even do reinforcement.

    The MZLF is reinforced in 2- and 3-story houses with stone walls. Concrete foundations are reinforced according to the 1st reinforcement option (see Table 4 above). Foundations made of buta or brick are reinforced with masonry nets made of BP-I reinforcement Ø 4-5 mm with a mesh size of 100x100 mm. The nets are laid every 15-20 cm.

    Designs of MZLF on non-porous and slightly porous floors are shown in the figure below:

    1 - Founding; 2 - Basement, cellar; 3 - blind area; 4 - Seal; 5 - rough ground (shown conditionally); 6 - wire mesh 7 - Reinforcement according to the 1st option (see Tab. 4)

    Options a. and b. - for buildings made of wood and one-story brick (aerated concrete).

    Options c. and G. - for two- and three-story brick buildings (ventilated).

    The sole width b is determined depending on the number of floors of the building and the material of the walls and floors.

    Table 5: The values ​​of the width of the MLF soles on non-porous and weakly porous floors.

    Construction stages of a ribbon foundation and recommendations.

    1) Before proceeding with the construction of the foundation, it must be ensured, if necessary, that surface rainwater from neighboring areas flows off of the construction site in high quality. This is done by pulling out drainage ditches.

    2) The foundation has been laid and trenches are loosening. It is recommended that excavation work only begin after all the necessary materials have been delivered to the construction site. The act of digging out the trench, backfilling the ligament, backfilling the sinuses, and building the blind area is desirable for continuous organization. The shorter it is, the better.

    3) Excavated trenches are covered with geotextiles. This is done so that the sand cushion and the sand filling of the sinuses do not silt up with the surrounding soil. At the same time, geotextile lets the water free and does not allow the roots of the plants to germinate.

    4) Layer by layer (in layers of 10-15 cm), sandy (sandy-gravelly) pillow is poured with a thorough compaction. They use either manual rammers or platform vibrators. Do not take the manipulation lightly. Shallow foundations are not as strong as foundations that are poured over the entire depth of freezing, and therefore a giveaway here is fraught with the appearance of cracks.

    5) The formwork is exposed and the reinforcement frame is knitted. Do not forget to supply the house with water and sewage immediately. If the foundation is also an underlay, pay attention to the air ducts (does not apply to buildings with floors on the ground).

    6) Concrete is poured. The entire belt should be filled continuously in one go.

    7) After the concrete has set (3-5 days in summer), the formwork is removed and placed vertically.

    8) The sinuses are filled in layers with coarse sand.

    9) The blind area is being built. It is advisable (especially if the foundation tape is low) to isolate the blind area. This measure also reduces the frost resistance that affects MLF in winter. The heating is done with extruded polystyrene foam.

    As mentioned at the beginning of the article, it is not allowed to leave the MZLF unloaded or underloaded for the winter (the building was not fully completed). Should this happen anyway, the foundation itself and the ground around it must be covered with heat-retaining material. You can use sawdust, slag, expanded clay, straw, etc. Snow cleaning on a construction site is also not necessary.

    It is highly recommended not to make shallow strip foundations in frozen ground during the winter season.

    In the comments on this article, you can have a chat with your readers about your experience building and operating the MLF or ask questions that interest you.

    If it is a question of building a small house, the walls of which are made of lightweight material, e.g. B. foam concrete, cinder block or wooden beam, for reinforcement, it is enough to apply new technologies for the use of insulated foundations of shallow depth. Getting it right is not that difficult, you just need to carefully study the shallow foundation and quality indicators of the soil of your site.

    Where to use

    Flat ribbon foundation suitable for assembly:

    • Houses with an area of ​​up to 100 m 2 and a height of no more than 2 floors;
    • Srubov baths;
    • Households and Decorative Buildings.

    This way of laying the foundation stone is particularly interesting in cases where construction is being carried out in an area with undulating floors.

    Clay or sandy moist soils, the soil of which is saturated with water, are usually called corky. When freezing, water turns into ice. When the process of melting takes place, the water expands and begins to crush everything that occurs on its way. They used to struggle with heaving soils and bury the structure under the freezing depth of the earth. That is about 1-2 meters, depending on the terrain. In Siberia this depth goes into the ground by more than 2 meters, in the Moscow region by 1.5 meters.

    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 warming of the earth, the less the load will act on the foundation. However, with the advent of modern, high-quality insulation (the homeland is Finland, Norway and other countries with a cold climate), they began to lay a shallow strip foundation with their own hands, while warming the base of the building, the so-called blind area. The only rule that should be considered: the colder the terrain, the greater the layer of insulation that you need to lay under the blind area around the house.

    Extruded polystyrene foam or other insulation do not lose their properties when wet. However, it is not intended to be walked on, so after laying it should be decorated with tiles or other suitable, beautiful and practical material.

    Even cheaper and easier than digging a deep trench, pouring a large amount of concrete and waiting for it to shrink, is to make the blind area around the house of the insulation even wider than necessary. This saves you time and money and makes your work easier.

    Another advantage of such a device is durability. In the course of time, nature will take its toll anyway, and even the highest quality concrete will begin to collapse under the influence of the temperature loads acting on it. In the variant described above of installing a house under a plinth with a large insulated area, the earth remains warm throughout the cold period, and the pressure under the building is not exerted by floating floors.

    Laying a foundation shallowly with a wide, isolated blind area is a person's victory over nature: as long as the insulation is alive (and its lifespan is at least 100 years), nothing threatens the house.

    The earth has a peculiarity: while the floor is not heated, it absorbs energy, cools the house and, when heated, becomes a heat source and an insulating layer itself. If a shallow foundation is laid in the presence of a blind area, the temperature situation under the house will stabilize and heat loss will be reduced to zero. As soon as a few meters of earth warms up under the house, it becomes a heater itself.

    Styling process

    Doing the self-made ribbon foundation with your own hands is very simple. Laying saves time and materials. It is enough to have an idea of ​​what to do and what to do.

    1. Markup and design. At the initial stage, you need to conduct an exploration of the site, study the characteristics of the soil of the site and decide how deep to lay the blocks for the future building. If you have a project in stock for future construction and you are doing preliminary measurements on site, you can move on to the next phase.
    2. Dig trenches. Mark the places of future building corners with pegs. Trenches should be dug along the entire perimeter of the future structure along the lines of the load-bearing walls that will take the brunt of the load. Use duct tape to save money and time. The main thing is to properly distribute the load on the load-bearing walls, and you can even use a monolithic slab in which it is possible to mount a warm floor, which adds a high temperature and the floor around the house and the floor under a flat foundation is additionally heated.
    3. The trenches should initially be as shallow as possible. Use the level and tape measure to check how smooth your surfaces are. The consumption of materials and the effort that will have to be expended on further work depend on how much you cope with this task.

    With this possibility of laying the foundation, the depth of the trench must not exceed 50 atmospheric images. 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 immediately reaches the required level of evenness.

    1. The device ribbon foundation. This type of foundation can be used for single-story log structures on sandy and loamy soils. It consists of:
      • seal;
      • Products;
      • concrete quality 250 and higher;
      • reinforcing bars with a diameter of 12;
      • gravel, expanded clay;
      • sand pillow.

    Requires the installation of formwork.

    1. We install waterproofing. The bottom of the trench must be insulated. If you do not have the opportunity or the need to lay insulation from expensive materials, you can make them from a regular roofing material. In this case, the waterproofing has the task of protecting concrete slabs from the influences of the groundwater and protecting the sand cushion.
    2. Making pillows. The pillow under the base is prepared as follows:
      1. At the bottom of the trench, coarse sand is poured with a layer of 15-30 cm.
      2. It is filled with water;
      3. Stamped with a special tool;
      4. A layer of rubble or expanded clay falls asleep with a thickness of 20 to 30 cm.
    1. The manufacture of reinforced grilles. In order to give strength and strength to the base, it is necessary to lay a reinforcing mesh. Such a net is braided by knitting with ordinary wire. The reinforcement with a diameter of 12 mm for longitudinal rows and 20 mm for transverse rows is used and manufactured in such a way that there are 4 to 6 (ideally 5) bars in each row. The grid dimension should not be less than 15 cm.

    The use of special reinforcement corners is required for better bonding. To simplify the installation of the grid, you can make small brackets from the remnants of plastic pipes by sawing them in the form of rings on a circular ring and placing them under a finished reinforced grid.

    1. Reinforcement is the most important part of laying the foundation stone. It is the reinforced lattice that gives rigidity and strength to the entire structure, creating a monolithic frame.
    1. Formwork construction. This step is not always necessary with a device of this type. With this laying method, no formwork is installed above the floor surface. But if you choose a more convenient solution, then it is best to prepare the boards for more even walls from the trimmed panel, and after installing the grids, equip the wooden structures that will allow the concrete trenches to be filled with mesh.

    Instead of formwork, polystyrene foam or other insulation is often used, which remains part of the foundation forever and at the same time performs an important function of maintaining heat. You can use reinforced concrete blocks.

    1. Laying in columns. With the column option, the building structure is installed on low columns. After pouring the base with a flat tape method in the corners, brick pillars are erected, on which a monolithic slab is placed.

    The columnar laying is used in the construction of baths and saunas. The structure rises above the ground which adds to its charm.

    1. Pouring concrete. In the final construction phase, the cavities in the trenches are filled with a concrete mixture of sand, cement, small gravel and water. It is preferable to choose high quality cement, not less than 250. During the pouring process, concrete should be carefully packed and air bubbles should be expelled to achieve the desired strength. This can be done with a stick or a special tool - a vibrator.

    Try to level the top as much as possible, as it is on it that the construction materials for laying the walls will be.

    Technology options

    Shallow foundations can be laid in three ways:

    • Like a monolithic slab;
    • Pouring concrete using reinforcing knitted stacks;
    • Separate prepared blocks or masonry.

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

    The advantages of a shallow foundation

    Recently, with the use of modern technologies, it has become possible to build small buildings by laying the foundation with a flat tape method. The advantages of this method are as follows:

    • You can make a shallow tape foundation with your own hands.
    • Simplicity and ease of execution;
    • Low cost and budget;
    • Possibility of relocation and preparatory work without the use of construction machinery;
    • The possibility of warming the basement and the basement;
    • The possibility of laying on the basis of a monolithic slab using the "warm floor" technology;
    • Achieving the high strength required for the long-term construction of small farm buildings and individual houses;
    • Alternative option: Execution of the work from the available materials.

    disadvantage

    There is only one shortcoming: insufficient strength for buildings on floating floors. As mentioned above, in order to solve this problem, more attention should be paid to the construction of the blind area around the building. If necessary, drainage can be carried out under the foundation, that is, lay pipes with a large cross-section before starting work and fill them with sand and gravel.

    Another important point! Laying a shallow foundation should only be done on warm ground and does not require shrinking. In addition, on this basis, the building must be erected in a short time, no more than 3-5 months.

    Now that you all know how to properly lay the foundation stone for small buildings and you can get to work!