How to properly insulate a slab foundation. Insulation of the foundation slab: the advantages of technology. Carrying out insulation measures during the construction process

On unstable soils, it is difficult to arrange a solid foundation. In such cases, a slab base is used. It acts as the foundation of a small deepening, drifting around the site, when moving soil masses. Since the entire structure moves, no destructive stresses arise.

For the proper operation of this type of foundation, it must be protected from freezing. Insulation of a monolithic foundation slab:

• prevents the destruction of concrete from temperature differences;
• contributes to the warm floor of the first floor;
• makes it possible to save on building heating;
• reduces the heaving of the soil under the building.

The choice of insulation

Not every, even the most effective material, is suitable for working in the ground or in its vicinity. When choosing a material, you need to be guided by:

• moisture resistance. Being saturated with water from the soil, the product loses its insulating properties. Expanding when freezing, moisture violates the integrity of the coating, reducing all work to nothing;
• strength. Seasonal movements of soil masses create tangible pressure on the material. It is especially noticeable in rocky soils. Sharp edges can push through products, leaving cracks or breaks in it;
• resistance to aggressive environments. Soils are often chemically and biologically active. Groundwater may contain high concentrations of salts. All these factors lead to premature destruction of the insulation.

When installing insulation inside the building, the material must be non-combustible. If there is a possibility of ignition, no harmful substances should be released that can cause suffocation.

With all this, the service life of the insulation should not be less than the service life of the finishing material. In this case, you do not have to change it before the coating becomes obsolete. Otherwise, you will have to dismantle the finishing sheet that still meets the standards.

Often, extruded polystyrene foam is used for zero-cycle work. Insulation of the foundation slab with expanded polystyrene, made in accordance with all the rules, allows you not to worry about the safety of concrete and saving heat.

Characteristics of expanded polystyrene

Expanded polystyrene is used for thermal insulation of the foundation slab:

• outside;
• from within;
• in the body of concrete

External insulation technology

The height of the plate can be from half a meter. Freezing around the perimeter is the most dangerous for the foundation. Therefore, basically, the insulation is attached precisely to the side surfaces.

Before covering the foundation with a layer of insulation, it must be waterproofed. Despite the fact that expanded polystyrene is waterproof, the coating is not seamless. Moisture penetrates into the seams between the plates, which can destroy the plate.

Waterproofing occurs by applying bituminous mastic or melting along the surface and edges of the paraffin slab. The second method is more economical and reliable. With the help of a gas burner, pieces of paraffin are melted. The material is evenly distributed over the surface, soaking into it.

Waxing closes the pores of the concrete, creating a barrier to moisture. Full adhesion contributes to the exclusion of insulation peeling. This means that you can easily attach a heater to it.

Expanded polystyrene plates are mounted on glue or on a cement-sand mortar. The first option allows you to conduct insulation at sub-zero temperatures. The underground part is fixed only by gluing. This is necessary to avoid violation of the hydrobarrier.

The basement part of the insulation of the slab foundation with polystyrene foam is additionally fixed with plastic dowels. To do this, holes are drilled through the glued plates. They go through all the insulation and part of the foundation.

Glue is applied along the perimeter of the plate and in several strips in the center. It is held for 1 minute and the plate is pressed against the surface for a couple of minutes. After gluing, the bottom plates are sprinkled with a layer of sand. This helps secure them in their mounting position.

The second row of insulation is mounted with offset seams. It is desirable to make a dressing and horizontal joints. This helps to avoid cold bridges.

If the thickness of the plates is not enough, the insulation is carried out in two layers. Products with maximum thicknesses are taken to avoid the installation of several layers. Plates of the upper layer must overlap the seams of the lower ones.

Fixation with umbrellas is carried out at five points of the plate. The dowels are mounted after the plates are completely glued, but not later than three days later.

After installation, the seams are sealed with mounting foam. Excess foam is cut off and the surface is plastered over the grid. The mesh is necessary for better adhesion of polystyrene foam and plaster.

Internal insulation technology

When insulating a monolithic foundation slab from the inside, the material is laid in two ways:

• On top of the plate;
• In the body of concrete.

With the first method, the sequence of work is as follows:

• waterproofing is arranged on the foundation slab, with entry to the wall;
• logs are screwed on top of the waterproofing layer;
• a layer of insulation is arranged between the lag;
• a waterproofing film is attached to the lags on top of the insulation;
• a plank base, plywood or OSB boards are mounted on the film;
• a cork, polyethylene foam or needles underlay is laid over the subfloor. A finishing floor is mounted on it.

You can do without lag. In this case, the slab foundation is completely insulated with polystyrene foam. The material is laid in a continuous layer. Immediately on top of it, a substrate and a finishing floor covering are laid.

When installing in concrete, the following work is performed:

• the base plate is waterproofed;
• a layer of insulation with a thickness of at least 100 mm is arranged. It is better to use products with a locking system;
• a PVC film with a density of at least 1.42 g / cm3 is laid on the insulation;
• reinforcing mesh is laid. In its role can be a masonry mesh with a cell of 100 * 100 mm;
• the surface is poured with a screed no thinner than 5 cm;
• the finish coating is laid on the screed.

For internal insulation, only self-extinguishing polystyrene foam should be used. For installation under the screed, products of the G4 flammability class can be used.

Insulation of the body of the foundation slab

Warm concrete is used in many areas of construction. It can be purchased in the form of a ready-made mixture or manufactured in the conditions of a construction site. For preparation, granulated polystyrene foam is added to the initial mixture for the formation of the foundation slab.

For the device of structural elements, polystyrene concrete with a density of D1200 is used. When preparing 1 cube, the composition includes:

• 300 kg of cement M400;
• 1.1 m3 of expanded polystyrene granules. It is better to use granulated rather than crushed material. It has the shape of a ball, which leads to a better enveloping of the cement mixture;
• 800 kg of sand;
• PAD. Often, saponified resin is added. Its presence in the composition provides better adhesion and increases heat-shielding properties.

When creating such concrete, you need to remember about shrinkage. It is 1 mm per 1 m of surface. The plate needs to stand for some time after curing. On the surface it is necessary to arrange a leveling screed.

The flammability class of such a product is G1. The concrete itself does not burn, but the insulation granules are exposed to fire. As a result, pores are created in the body of the foundation slab. They reduce the density of the structure and increase its moisture absorption.

The thermal conductivity of such a plate will be approximately 0.105 W / (m * C). The product requires additional insulation of the slab foundation from below. The thickness of the insulating material will be less than plain concrete.

The choice of the type and technology of insulation of the foundation slab depends on the design features of the building and the construction site. Choosing the optimal solution is based on the data of the heat engineering calculation and comparison of the estimated cost.

The slab base withstands significant external influences and is suitable for construction in areas with complex, unstable soils prone to frost heaving, with a high level of groundwater. Insulation of the foundation slab will help to significantly reduce heat loss through the base and reduce the effect of frost heaving of the soil. The building, when the soil moves, rises and falls along with the foundation, which protects the structure of the house from the formation of cracks.

general information

The design of the slab base consists of layers:

• geotextiles are covered with overlapping strips on the sandy layer, the joints are glued with adhesive tape;
• pour gravel, a layer of 15-20 cm;
• pour a leveling layer of cement mortar, 5-10 cm thick;
• be sure to isolate the structure from moisture with the help of roll or coating materials;
• arrange a heat-saving layer;
• cover the plastic film with overlapping strips of 20 cm;
• lay the reinforcing mesh;
• poured with concrete.

Installation and insulation of a slab monolithic foundation is expensive due to the high consumption of building materials. When the soil freezes to a great depth and a significant deepening of the strip foundation is required, the slab installation will be cheaper, and less land work will be required.

Advantages of the slab foundation

The slab base has the following advantages:

• the concrete slab acts as the floor of the first floor, which further reduces the cost of its installation;
• is an excellent option for the foundation of a house, the construction of which is carried out on floating soils, the slab and the whole house with it move simultaneously with the soil;
• you can mount the plate on any type of soil, even on peat bogs and swampy areas;
• the slab is erected above the level of soil freezing; thanks to the sand cushion, frost heaving practically does not affect the structure;
• reinforced concrete slab is not subject to shrinkage;
• suitable for building up to 3 floors.

Insulation of the foundation slab reliably protects it from deformation during seasonal heaving of the soil and prolongs the life of the structure.

Advantages of slab thermal insulation

Expanded polystyrene, polystyrene, polyurethane foam are used as heat-insulating material. Mineral wool is unsuitable due to its low strength and high moisture absorption.

There is a technology for mounting a Swedish plate. The main difference is that the concrete structure is built on a layer of heat-saving material, thanks to which the soil under the house does not freeze and does not heave.

The main advantages of the Swedish plate are:

• the construction of the foundation and the laying of communications are carried out in one technological cycle;
• the heat-saving layer allows you to increase the efficiency of the warm floor;
• installation of the foundation is carried out without involving a large amount of construction equipment.

Around the building, a drainage system is provided, consisting of pipes for draining rain and melt water.

The design of the plate contributes to the transfer of all loads from the building to the layer of heat-saving material, therefore, increased requirements are imposed on the materials used.

Disadvantages of slab foundation

A slab foundation is not always the best option. It is always necessary to carry out all the necessary calculations in advance and select the most suitable type of foundation for the house.

Disadvantages of the plate:

• not suitable for erection in areas with a slope;
• to build a house with a basement on a slab, you need to deepen it to a great depth, it will be very expensive;
• it is difficult to repair communications under the foundation slab;
• during construction in winter, additional costs will be required for heating concrete and maintaining the desired temperature on the site.

A slab foundation is erected only when a strip foundation is not possible.

Materials for insulation

The table shows the materials used to insulate the foundation slab and their characteristics:

Most often, extruded polystyrene foam is used as a heater under the foundation slab.

Installation of an insulated plate

The erection of a monolithic slab base requires the performance of all calculations, taking into account geological, climatic conditions and the mass of housing construction.

Insulation of the slab foundation allows you to save significant funds on heating the premises during operation.

Site preparation

At the design stage, the project must take into account that the area for the foundation slab must be wider than the housing construction by at least 1 m on each side.

Instructions for performing preparatory work:

1. The site where construction is being carried out is cleared of debris, the root system of trees and shrubs.
2. Mark the position of the plate according to the project.
3. They clean and remove the fertile layer of soil. The degree of deepening of the plate depends on the geological and climatic conditions. Most often, the thickness of the plate varies from 20 to 30 cm, less often the base is buried by 50 cm.
4. They dig a pit, manually level its bottom and side walls.
5. Pipes are installed around the perimeter to drain rain and melt water.
6. Lay the geotextile in overlapping stripes. The material should cover the bottom and go to the walls along the entire height.
7. Drive in wooden stakes or metal rods. Stretch the cord strictly horizontally. It will serve as a guide for uniform backfilling of sand and gravel.
8. Sand is poured, 20-30 cm thick. Sand is evenly distributed over the entire area, moistened with water and compacted well.
9. Spread geotextiles.
10. Crushed stone is poured, evenly distributed around the perimeter, carefully rammed.
11. Conduct all necessary communications. They dig trenches under them in rubble a little wider than the section of pipes. The pipeline is laid, a layer of sand is poured on top.
12. The sandy surface is leveled.

If the pipeline is laid before the crushed stone compaction stage, the pipes may crack.

Plate insulation

Step-by-step instructions for insulating a slab of a monolithic foundation:

1. They mount a removable formwork from boards, install props so that the structure does not fall apart under the weight of concrete.
2. A layer of concrete is poured, 50 mm thick.
3. After the cement mortar has completely hardened, foam sheets are laid on it butt against each other and glued. The adhesive composition is applied with dots along the perimeter of the sheet and in the center. A layer thickness of 10-20 cm is sufficient. The joints of the row are placed in a checkerboard pattern, with an offset of 1/3. When laying in two rows, the joints must not intersect.
4. Spread dense polyethylene with overlapping strips. The joints are sealed with adhesive tape.
5. The reinforcing cage is laid, the formwork is poured with concrete.

After the slab has dried, the formwork is dismantled, the side walls are thermally insulated with the same material that was used for laying under the slab.

The insulated plinth helps to increase heat saving inside the room.

When installing insulation on bituminous insulation, you need to wait for it to dry completely. If laying on a wet layer, the materials may be damaged and the effect of thermal insulation and waterproofing will decrease.

Rules for installing heating pipes

When installing the UWB, heating pipes are used. There are such rules for their installation:

• A denser laying of pipes allows you to get higher temperatures for heating the room.
• The distance between the outer walls and pipes should not exceed 150 mm. Closer to the center, the laying step can be increased up to 250 mm.
• To minimize hydraulic losses, the length of one loop should not exceed 100 m.
• Do not lay pipes closer than 100 mm apart.

It is impossible to mount heating pipes at the junctions of monolithic plates. In this case, it is better to lay two circuits. The pipeline crossing the joint is insulated with steel sleeves 30 cm long.

How to make a warmed Swedish stove with your own hands can be seen in the video:

The insulated foundation slab reduces heating costs during operation and helps to reduce the level of frost heaving of the soil. Thanks to this, the life of the foundation is extended, and living in the house becomes more comfortable.

Insulation of a monolithic foundation slab is necessary in areas with cold climatic conditions. Such measures are required in order to protect the foundation from the harmful effects of the environment, to preserve heat, coziness and comfortable living conditions in the house. One of the most common materials for insulation are polystyrene foam and polyurethane foam.

Insulation of the foundation of a monolithic type with polystyrene foam

Thermal insulation of base plates in this way is a relatively young type of modification of private houses. It began to be used in the 50s - 60s of the XX century. This type of insulation plate is durable and long service life. According to statistics, the popularity of polystyrene foam is steadily growing every day.

Strengthening monolithic slabs with expanded polystyrene has proven to be a very successful solution in the construction of houses, because their service life is more than 50 years. After carrying out various tests and checks, it became clear that the material does not change in any way over the entire period of operation.

From this it follows that the growing popularity and steady increase in the consumption of expanded polystyrene is a pattern. Over the past 20 years, its use has increased tenfold. The main consumers of this material are Europe and North America.

Extruded polystyrene foam for insulation of a monolithic base slab is a material that has a uniform structure consisting of closed cells. Due to the low density of the material, its thermal insulation properties increase. You should also know that expanded polystyrene has increased strength characteristics and is able to withstand fairly large loads.

Expanded polystyrene practically does not pass water and is not afraid of exposure to chemically aggressive environments. Thermal insulation with this material is made in regions with severe winters and very cold weather. Expanded polystyrene perfectly copes with repeated cycles of freezing and defrosting, while its performance does not change at all. Expanded polystyrene is usually sold in the form of plates.

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Why polystyrene and not another material?

1. A platform for the foundation is marked.
2. The layer of soil is removed from above. The depth depends on the construction project. When taking out the soil, you must try to make the bottom as even as possible. To do this, the last 0.2 - 0.3 m is taken out manually. A layer of sand is poured onto the prepared site and then rammed.
3. Temporary formwork is installed, concrete base is being prepared. The formwork is poured with a small layer of concrete. Base reinforcement is not required.
4. After the concrete has hardened, the laying of polystyrene foam plates begins, while it is necessary to combine the mounting grooves and try not to leave large gaps.
5. A polyethylene film is placed on the laid layer of insulation. The joints are glued with adhesive tape. Polyethylene creates a layer of waterproofing. In addition, the film prevents leakage of concrete between the joints of the insulation boards.
6. The construction of formwork and reinforcement cage is in progress. Concrete is being poured.
7. After complete drying, the formwork is removed.
8. The side walls are additionally insulated with expanded polystyrene.

A few tips:

• work starts from any corner of the foundation;
• slabs must be laid from the bottom up with a shift in the rows, that is, something similar to brickwork should be obtained;
• at a height approximately equal to the width of the plate, pull the rope. The horizontal tension is checked using the building level;
• the first row of the heat-insulating layer is laid. This is done so that subsequent rows of plates do not diverge, otherwise all the insulation will simply become useless.

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How to properly mount polystyrene foam boards on the walls?

The foundation wall is covered with straightened mastic. Then expanded polystyrene is attached to it and tightly pressed. All plates of a row are mounted in a similar way.

When conducting work, it is necessary to carefully monitor the connection of adjacent plates. It should be clear, without cracks and be in the castle.

The joints on the crests of the locks are cut off in the corners. If necessary, the joints are additionally filled with foam.

As the high rows are laid, the underlying ones are covered with soil. Such actions facilitate the work and help to press the material.

Slabs located below ground level are glued only to the mastic.

This is necessary to prevent damage to the waterproofing.

Insulation located above the ground can be further strengthened with dowel-nails (umbrellas). All this can be easily done with your own hands, you just need to be very careful. To fix the base on the walls, holes are drilled with a puncher. Umbrellas are fixed in the center and at the junctions of adjacent plates.

The foundation, insulated with polystyrene foam, is so popular for the following reasons:

• using this technology, you can save up to 40% of money;
• reduction of heat loss reaches 20%;
• the waterproofing layer of the foundation will last 2 times longer;
• expanded polystyrene guarantees quality and long service life;
• the plates reliably protect the waterproofing layer, providing drainage of accumulated groundwater.

From the above, it becomes clear that, insulated with polystyrene foam, it will serve for a long time, and the house will be cozy, comfortable and warm. In addition, the material is absolutely safe from an environmental point of view and has a low cost, which clearly inclines the choice in its direction when long-term construction is ahead.

Almost 80% of the territory of our country falls on the zone of heaving soils, which are dangerous for the foundation slab and other types of foundations for buildings and structures. Such soils, when frozen, can significantly increase in volume, which leads to a rise in its surface - frost heaving.

How to insulate the base plate?

Insulation of the foundation slab allows you to cut off the zone of frost heaving, which means avoiding its cracking. In addition, heating bills are reduced. Another plus can be considered the fact that condensation does not form on the walls, which means that mold does not appear. Carrying out work on thermal insulation has a beneficial effect on the operational properties of the entire building, increases its durability.

When choosing a material for insulating a foundation slab, the following performance characteristics should be taken into account:

• high level of mechanical compressive strength;
• minimum rate of water absorption;
• low thermal conductivity.

Such familiar insulation as mineral wool is not suitable for these purposes, since it absorbs water well and shrinks when backfilled with soil. Meets all requirements and is very easy to use expanded polystyrene. Another insulation under the foundation slab, which has the necessary performance, is foam glass, but its use will cost much more.

Warming of the foundation slab can occur not only from the outside, but also from the inside. Experts believe that external thermal insulation is much more effective and allows solving many problems to improve the indoor climate and increase the durability of the building. However, insulation from the outside is not always possible, mainly due to the high labor intensity, so these works are best done at the construction stage.

However, internal thermal insulation also gives its results: the room becomes warmer, the microclimate normalizes, heat does not leak out. It should also be noted the simplicity of such work.

Insulation of the foundation slab with expanded polystyrene

Extruded polystyrene foam is considered to be a fairly effective and simple way to insulate foundation slabs. This material has a closed-cell structure, which is different from ordinary foam plastic, in which, after 2-3 years of operation, the structure will be destroyed and it will turn into a pile of balls.

Extruded polystyrene has the following properties:

• resistance to moisture and aggressive chemical compounds;
• does not age and does not change operational properties;
• ecological cleanliness;
• affordable price, etc.

For thermal insulation, expanded polystyrene is used in the form of special plates. They must have a compressive strength of at least 200 kPa for private buildings, 250 kPa for industrial facilities and high-rise residential construction.

To insulate the vertical part of the foundation slab from the outside, it is necessary to perform preparatory operations:

• if the foundation was covered with soil, then it is necessary to remove all the earth along the side surface to the depth of soil freezing;
• apply a layer of insulation to the entire work surface.

Installation of insulation boards

When bituminous roll material is used as waterproofing, it is enough to heat it up at several points and press the polystyrene plate. It is very important to calculate the pressing force, since it is possible to push through the surface of the insulation and the product will become unusable.

If other types of bitumen or bitumen-polymer materials are used, then a special mastic is applied to the expanded polystyrene under the foundation slab in the form of stripes or dots and applied in the right place. For competent thermal insulation, the plates are staggered. Metal fasteners can disrupt waterproofing, so experts do not recommend using them when insulating foundation slabs.

It is rather difficult and time-consuming to carry out sufficiently large volumes of work that require not only skill, but also knowledge, as well as experience in their implementation. If you live in Moscow or the Moscow region, then by contacting the construction company "Proekt", you can save yourself from this monotonous and effort-consuming work, and get high-quality and quickly performed insulation of foundation slabs at a low price.

Base insulation

It is possible to carry out insulation under the foundation slab only in the process of its installation, which means it needs to be planned at the stage of project development. Thermal insulation products made of extruded polystyrene foam are laid on the insulation layer.

To protect the insulation under the foundation slab from the ingress of liquid components of concrete, a polyethylene film is laid on it in one layer, which should have a thickness of 150-200 microns. Such protection will be enough if it is done by knitting. If welding is used, then it is necessary to create a protective screed, which can be made of low-grade concrete, or a solution of sand and cement. In this case, polyethylene is laid using double-sided tape with an overlap of 150 mm.

Warm base plate

The construction of a warm foundation slab begins with the digging of a pit, on the bottom of which sand is first laid, which must be compacted and communication pipes laid in it. Then lay a layer of gravel and thermal insulation in two layers. Fittings are installed on the insulation, on which pipes heating the floor are placed, and they should not intersect with each other. It remains only to fill this multilayer structure with concrete, the thickness of which will be 10 cm.

By analogy, our specialists have developed their own concept of a warm foundation slab. In this case, extruded polystyrene foam is laid on a sand bed. At the same time, the method of placing the insulation depends on the design of the building and the tasks of heat saving. Next, reinforcement is laid and pipes for a water-heated floor are laid right inside the reinforcing mesh. Then they fill everything with concrete.

Cope with any of the above options for the construction of a warm foundation slab, only specialists with sufficient qualifications, experience and sound knowledge can cope. All these criteria are met by our employees. Contact us and you will be able to become the owner of the foundation, the parameters of which will meet all state standards, we will definitely take into account all the wishes of customers.

The purpose of this article is to go beyond the scope of this project and tell on behalf of specialists the basic rules for working with material that can be useful to everyone.

When erecting this type of foundation, extruded polystyrene foam (EPS) was used. In the master class format, professional builders will tell you how to choose and how to work with extruded polystyrene foam when insulating various types of foundations. Namely:

• Why you need to insulate the foundation.
• What to look for when choosing a material for insulation of the foundation.
• How to properly fix extruded polystyrene foam on the foundation.
• What tool is needed for the job.

Why is it necessary to insulate the foundation

The foundation is the underground part of the structure, which transfers the load from the overlying structures to the prepared soil base. Foundations are of the following types:

• Slab, shallow, with spatial reinforcement. This gives the structure rigidity and allows it, without internal deformation, to perceive the loads that occur during uneven movement of the soil.

• Tape - laid below the freezing depth, etc. MZLF - shallow strip foundation, with the depth of the sole above the estimated mark of seasonal freezing of the soil.

• . Insulated Swedish Plate. This foundation is a monolithic concrete slab mounted on a base insulated with extruded polystyrene foam. The system of water underfloor heating and all engineering communications are integrated into the foundation.

This type of foundation is considered the most technologically advanced and energy efficient. In one system, the foundation and the low-temperature heating system are combined, which excludes the formation of local overheated zones and provides comfortable radiant heat. In addition, the foundation is not affected by the forces of frost heaving, because. countermeasures have been taken. Namely, heaving soil was excavated and replaced with non-heaving soil (sand or crushed stone), a drainage system was installed, the blind area and the base of the slab were insulated.

Up to 20% of heat loss from the total heat loss of the building occurs through the foundation.

Kogut Andrey Technical specialist of TechnoNIKOL company

To achieve maximum energy efficiency of the building, it is necessary to create a closed insulated circuit. This means that, in addition to the main structures, such as: walls, roof and plinth, it is necessary to insulate the foundation as well.

In some cases, it is enough to insulate the floor and basement, but when organizing an operated basement thermal insulation of the foundation walls is a prerequisite to achieve the required level of comfort and reduce heat loss.

In shallow strip and slab foundations, thermal insulation can reduce the effect of frost heaving. Soil swelling is formed due to the freezing of water in the soil and its subsequent expansion. Different soils have different degrees of heaving. For example, sands pass water well through themselves, and it does not linger in them. Clay, on the contrary, does not allow water to escape, and due to the presence of a large number of small pores, it has a high capillary suction of moisture. Improper design on heaving soils can lead to serious consequences, up to the destruction of the foundation. If the foundation is left uninsulated, the heat flow will go down and warm the soil, protecting it from freezing. However, the house may not be heated all the time, in which case the soil will heave. Thermal insulation of the foundation and blind area is one of the measures to combat frost heaving.

Basic principles for choosing thermal insulation for foundation insulation

So, summing up all the above, we conclude: foundation needs to be insulated. Not every insulation is suitable for this, but only a material that can work in aggressive environmental conditions. Those. thermal insulation laid on "non-removable" must be moisture resistant, have a long service life, during which it will not lose its thermal insulation properties, and have strength sufficient to withstand the load from overlying structures.

Kogut Andrey

Extruded polystyrene foam (EPS) has a low thermal conductivity of 0.028 W/(m*°C) and a minimum water absorption coefficient of 0.2% by volume. The insulation does not absorb water, is chemically resistant and does not rot. Compressive strength at 2% linear deformation - not less than 150 kPa (~ 15 t / sq. M) and higher. Service life in soils is at least 50 years.

High compressive strength allows the use of XPS in loaded structures (foundations) and ensures the stability of the thermal insulation thickness under load.

The thickness of the thermal insulation layer must be taken on the basis of calculations based on several conditions:

• The purpose of the building (residential, administrative, industrial, etc.).
• The insulation must provide the required heat transfer resistance for this type of building.
• There should be no seasonal moisture accumulation in the structure.

Calculation thickness of thermal insulation for the foundation is made according to the methodology set out in SP50.13330.2012 "Thermal protection of buildings". For different regions, the thickness of the thermal insulation may vary, depending on climatic conditions. It should also be taken into account that increasing the thickness of the thermal insulation increases the energy efficiency of the building and, consequently, leads to a reduction in heating costs.

Choosing the technical characteristics of thermal insulation, we are guided by the following principles:

1. When insulating a strip foundation, when only a vertical wall is insulated, increased strength of the material is not required, because. in this case, the EPS takes loads only from the backfill soil. Therefore, for shallow foundations, grades of extruded polystyrene foam with a compressive strength (at 10% linear deformation) of 150-250 kPa are suitable.
2. When laying XPS boards under the base of the foundation or under the slab, the loads on it increase significantly, respectively, the requirements for its strength increase. In this case, it is recommended to use heat-insulating boards with a compressive strength of 250 - 400 kPa.
3. Especially for UWB, a material has been developed with a compressive strength at 10% deformation of 400 kPa and increased plate sizes to increase the installation speed. In addition, the increased dimensions of the slabs make it possible to reduce the number of joints and, consequently, increase the uniformity of the layer.

The nuances of installing extruded polystyrene foam when insulating the foundation

The insulation of the EPPS foundation, depending on its design, should be divided into a number of successive steps:

• Foundation preparation. When insulating the EPPS of the strip foundation, the walls must be smooth, cleaned of dirt and concrete layers. If necessary, we remove irregularities and cover up sinks, chips, etc. cement-sand mortar.

• The choice of the method of fastening the EPS. To fix the insulation, we use polymer-cement mixtures or, to speed up installation, special polyurethane adhesive foam.

• Adhesive foam is applied in a strip, about 3 cm thick around the entire perimeter of the plate, as well as one strip in the center of the insulation.

• The indentation of the adhesive foam strip from the edge of the plate is at least 2 cm.

• Before installing the plate, wait 5-10 minutes and only then glue it to the foundation wall.

• The gaps between the plates (if they exceed 2 mm) are foamed.

• If mechanical fixation of thermal insulation is provided, then we calculate the number of dowels as follows - for fixing 1 sq. m of thermal insulation on the central part of the foundation requires 5 pcs. fasteners. We fix EPPS on the corner parts of the foundation at the rate of: 6-8 dowels per 1 sq. m.

• When insulating the soles of a strip foundation or a monolithic slab, EPS is laid freely on a prepared base (usually on a compacted sand cushion). In this case, it is enough to foam the seams with glue-foam and, if necessary, fasten adjacent thermal insulation boards together. To do this, you can use a nail plate.

In this case, special fasteners can be used, which are a spike with teeth for fixing in the material and a flat area with an adhesive layer.

Together with such fasteners, gluing is carried out on an adhesive foam for polystyrene foam or on a special adhesive mastic that does not contain solvents. If necessary, the seams are sealed with mounting or adhesive foam.

The layout of the XPS plates during the construction of the UWB is as follows. The first layer is laid on a prepared base - a compacted sand cushion - with a gap between the seams relative to neighboring plates. The side elements are "L" - blocks, which are two XPS plates connected perpendicular to each other.

As a rule, such elements are made by setting the formwork, but ready-made elements that do not require the use of formwork can be used. Such "L" - blocks can be manufactured in the factory, or you can assemble it yourself at the work site. For this, a special corner fastener has been developed, which consists of corners and screws, and which is mounted at a distance of 300 mm from each other. All elements of corner fasteners are made of high-strength polyamide, which eliminates the formation of cold bridges.

Summarizing

In addition to increasing the energy efficiency of the foundation, EPPS insulation increases its service life, because waterproofing is reliably protected by durable material from various mechanical influences. By choosing the option of fixed formwork made of extruded polystyrene foam, you can significantly speed up and simplify all work on the construction of the foundation, because. there will be no need to assemble and further dismantle the wooden formwork, which means that the time and money of the developer are saved.