When solving complex issues of thermal protection of a building, among all the options, contractors and owners most often choose the popular method of insulating the foundation of a house from the outside with polystyrene foam. There are other technologies, but unlike wall insulation, not all “usual” thermal insulation materials are used here - the specific operating conditions and a wider range of tasks impose certain restrictions. Since the foundation has not only an underground part, sometimes it is necessary to use a combination of several technologies. How and with what to cover the foundation from the outside to reduce heat loss, we will consider in this article.

A warm home is the care of the owners Source vikonda.zp.ua

Why insulate the foundation

Thermal losses of the building through the foundation are small - from 5% to 15%. Its position and the peculiarities of the “physics” of heat transfer affect it.

About 15% of losses remain on the foundation and floor, but how much this is in absolute value depends only on the owner of the house Source ps-b.ru

There are only three ways to transfer thermal energy: radiation, convection (for gas and liquid media) and thermal conductivity.

Radiation is clearly not “about the foundation”, but about the heating system devices. They have a higher temperature compared to air and surrounding objects and serve as sources rather than “receivers”. But the walls of a heated room during the cold season emit energy in the infrared spectrum to the street. To see this background, just look at them through a thermal imager. It is especially bright in uninsulated areas and “cold bridges”.

It’s so easy to see how heat escapes through uninsulated walls Source rte-france.com

Natural convection is characterized by an upward flow of warm air and a downward flow of cold air. Of course, the temperature of the foundation cannot affect this process. It is important here to insulate the roof and ceiling so that they do not quickly “cool” the warm air.

Of the above three methods of transferring thermal energy, it is “thanks to” the thermal conductivity of structural materials that a cold foundation affects heat loss and heating costs of the house. And the thermal conductivity of reinforced concrete, from which the foundation is usually made, is quite high, so its low temperature is transferred to the walls and load-bearing partitions.

The air in the room cools due to the enclosing structures, which release heat to the environment. For the underground part of the foundation it is soil, for the base and walls it is air. Insulating the foundation reduces these losses.

Video description

Details about the heat loss of the building and the purposes of insulating the foundation are described in the video

But there is also another function of thermal insulation of the foundation of a house - increasing the service life of the foundation. Building materials have such a criterion as frost resistance. Its numerical expression means how many freezing cycles (assuming water saturation) must pass before signs of destruction appear. Therefore, for regions with cold and long winters, insulation and waterproofing of the foundation is a prerequisite to ensure the strength and durability of the structure.

Technologies and materials

There are only two types of foundations that need to be insulated: slab and strip. For columnar and pile foundations, we can only talk about thermal insulation of the floor of the first floor and the insulation (basement) - a kind of screen that protects the subfloor. But piles and pillars do not directly insulate.

Plate

The technology for insulating a slab foundation is no different from the thermal insulation of concrete floors on the ground:

a solid base of compacted soil;

geomembrane as protection against capillary rise of groundwater;

crushed stone-sand cushion to improve the bearing capacity of the soil and proper load distribution;

roll waterproofing;

sheet insulation (expanded polystyrene or EPS);

Eps is the best material for insulating slab foundations Source rmnt.ru

On our website you can find contacts of construction companies that offer foundation design and repair services. You can communicate directly with representatives by visiting the “Low-Rise Country” exhibition of houses.

The Swedes have slightly improved the technology and already at the stage of pouring the base they install a “warm floor” into the slab. In our country it is often done the old fashioned way - in a screed or under the finishing floor covering. Scandinavians are “boring” people and already know in advance where not only the partitions will be located, but also how the furniture will stand (one of the conditions for the correct operation of the “warm floor”). Our people have a different character - they are not only furniture, but also interior walls are often moved from place to place.

Strip foundation

Insulation of this type of base has a wider selection of materials and technologies:

permanent formwork;

fastening sheets of foam plastic or extruded polystyrene foam;

spraying liquid polyurethane foam;

filling of expanded clay.

Among foundation insulation materials, only one popular thermal insulation material is missing - mineral wool. When saturated with water, any type of water loses its thermal insulation properties. And although it not only easily absorbs, but also easily releases moisture, it is impossible to create conditions for its weathering for the foundation.

Places for foundation insulation Source anticafe-sandbox.ru

Technologies for insulating strip foundations

Each type of insulation has its own characteristics, which dictate the methods of its application.

This is the only method of insulation that is possible only at the stage of construction of a monolithic strip foundation. In fact, this technology can be called “two in one”, when the formwork made of thermal insulating materials remains as part of the structure upon completion of construction. Moreover, permanent formwork solves two problems - how to insulate the foundation of a house from the outside and from the inside.

Structurally, there are two types: block and panel. When pouring a strip foundation, shields are used. The blocks have walls and wide transverse bridges, which reduces the strength of the reinforced concrete base.

Ready-made kits have a set of polymer jumpers that can be used to adjust the width of the foundation Source visualizepicture.com

Such formwork is made from different materials, but most often the foundation of the house is insulated from the outside with polystyrene foam (regular or extruded).

In addition to the “clean” technology, there is a combined technology, when the slabs are not “connected” to each other, but are attached to removable formwork.

The combination of removable and permanent formwork provides increased strength for large volumes of concreting Source pobudova.in.ua

After backfilling the cavity near the underground part of the foundation, a “trough” is prepared for the blind area from compacted soil. And then according to the standard scheme: crushed stone, sand, waterproofing film, insulation (expanded polystyrene or EPS boards), formwork, reinforcement and concrete pouring. Instead of concrete, you can use paving slabs or gravel, but insulating the blind area as part of the general work is mandatory.

Insulation of the blind area will reduce the impact of soil heaving on the foundation Source de.decorexpro.com

Unlike the previous method, the existing foundation is insulated. Therefore, only external insulation is present. Work is carried out both during construction and during reconstruction or repair of a house.

Insulation during the construction of a house is much easier than during reconstruction Source volk1.ru

The most difficult work has to be carried out during repairs. Before insulating the foundation of the house from the outside, you need to dig out and clear the soil from the tape up to the heel. The stages then proceed in the following sequence:

• Waterproofing is carried out - first a bitumen primer is applied, then strips of rolled materials are glued (soldered) from bottom to top with overlapping seams.

Note. It is better not to use bitumen mastics in combination with sheet insulation - they are “fluid” and do not provide reliable fastening of the slabs to the adhesive solution.

Prepare an adhesive composition based on cement, and use it to secure the slabs to the foundation. In the above-ground part, additional fixation with dowels is not necessary - only on the base. Direct fastening of slabs using mechanical fasteners without an adhesive solution is unacceptable - the glue also serves as a “gasket” between polystyrene foam and bitumen, which is an aggressive environment for the polymer.

After backfilling and making the blind area, the base is finished: a layer of adhesive is applied, reinforced with fiberglass mesh and plastered or tiled.

Video description

You can get acquainted with the features of polystyrene foam insulation technology in the video:

Insulation with sprayed polyurethane foam

Among all polymer insulation, sprayed polyurethane foam is the most expensive type. Its advantage is that the thermal insulation layer has no seams, and foamed polyurethane has very good adhesion to all types of building materials.

Application of polyurethane foam to a surface cleared of dirt is very quick. There are two types of materials: two-component and one-component.

In the first case, professional equipment is needed, the work of which is to supply both components under pressure to the working head, where they are mixed and foamed.

Single-component polyurethane foam is produced in liter aerosol cans, and even an untrained beginner can handle them correctly. But this technology is good for a small area of ​​work, or when it is necessary to apply a small layer up to 2 cm thick.

Spraying polyurethane foam is similar to painting with a spray gun, so it is better to cover the cladding of the house. Source ppuspb.ru

If the soils are dry, the water level is low and proper drainage work has been carried out, then waterproofing of the foundation and base need not be carried out - there are no seams, and the water absorption of hardened polyurethane foam is small (no more than 2%). When finishing the base with plaster, reinforcement is not necessary - there are no joints, like with foam plastic slabs, and, therefore, there are no prerequisites for cracks to occur.

In addition to the price, polyurethane foam has one more small drawback, which is a consequence of its advantage - good adhesion. When carrying out work on insulating the base, it is necessary to protect walls that already have finishing (or do not require it) - this is easier than cleaning off hardened foam.

Recently, this bulk material is rarely used for foundation insulation. Its use is limited by two factors: quite high, compared to polymer insulation, water absorption and thermal conductivity.

The thickness of bulk thermal insulation can reach 60 cm Source obustroeno.com

The first indicator lies in the range of 8-20% of the volume. Moreover, such water absorption is typical for “fresh” expanded clay - over time it becomes even higher. For comparison, for ordinary polystyrene it is no more than 4%. Therefore, waterproofing of both the foundation and the entire insulation layer is necessary.

It is impossible to ensure complete “tightness” of expanded clay, and it will take a long time to dry underground, wrapped in film - its use is not recommended in conditions of high seasonal rise of groundwater.

Thermal conductivity also does not meet modern requirements for thermal protection of buildings - 0.07–0.18 (W/m*°C) versus 0.02–0.04 for polyurethane foam, 0.03–0.04 for EPS/EPS. Therefore, the recommended thickness of bulk thermal insulation for our middle latitudes lies in the range of 40–60 cm.

The insulation scheme looks like this:

dig a trench of the estimated width (or clear the cavity of the pit) to the heel of the foundation;

lay a waterproofing film over the entire area of ​​the trench - foundation-bottom-wall;

fill and level expanded clay;

cover with film on top;

pour a layer of sand;

make a blind area.

Typical scheme for foundation insulation with expanded clay Source sevparitet.ru

The advantage of expanded clay is environmental friendliness and low price. Although, taking into account waterproofing and a large volume of materials, the cost of work in the end will not be so low. In addition, the base will have to be insulated using one of the above methods.

Conclusion

The choice of a specific material and how to insulate the foundation of a house from the outside depends on many conditions - construction or repair, dry or wet soils, depth of freezing and heaving, volume and budget of work, design and depth of the foundation. Therefore, this problem should be solved by professionals.

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Thermal insulation of the foundation is no less important than the thermal insulation of the walls, especially in areas with a harsh climate. Frozen soil cannot protect the foundation of a house from moisture and cold, and the foundation itself, after repeated freezing, begins to collapse faster. To get rid of these problems and reduce the cost of heating your home, you need to know how to insulate the foundation of a house from the outside, and how you can do it yourself.

The foundation of a house is regularly exposed to moisture, increased load, and temperature changes. After the onset of frost, the accumulated moisture freezes, destroying the material, and through cracks in the concrete the cold penetrates into the home. As a result, the house always has cold floors, dampness emanates from under the baseboards, and condensation or frost appears on the basement walls (in severe frosts). For thermal insulation to be effective, the insulation must have the following characteristics:

• low thermal conductivity;
• waterproof;
• good mechanical strength;
• resistance to temperature changes.

There are no strict requirements for the vapor permeability of the material, but insulation materials with low vapor permeability are usually used, just like the concrete foundation itself. The flammability of the material is not of great importance, because the underground part of the building is least susceptible to fire risks.

Which insulation to choose

Mineral wool insulation for foundations is not the most suitable option: they tend to accumulate moisture, losing their thermal insulation properties, and are not sufficiently resistant to mechanical loads. Soil pressure will lead to shrinkage of the material, and the effectiveness of insulation will decrease to zero.

Prices for mineral wool

But polymer insulation does not have such disadvantages and fully meets the necessary requirements.

Let's take a closer look at their characteristics.

Expanded polystyrene

Expanded polystyrene, or polystyrene foam, is very widely used in thermal insulation. It is lightweight, its sheets have the correct shape, and therefore installation is not a problem even for a novice master. The material is available in various densities and thicknesses, and depending on this has certain areas of application. Only the densest sheets with a thickness of at least 50 mm are suitable for foundations; the rest are best used for insulating walls and partitions.

In terms of thermal conductivity, foam plastic is much more effective than wood, expanded clay, and mineral wool insulation. It almost does not absorb water, is not prone to shrinkage and deformation, and serves as an excellent sound insulator. In addition, polystyrene foam boards fully retain their properties when exposed to salt and chlorinated water, soap solutions, and weak acids. The insulation can come into contact with bitumen mastics, lime, water-soluble adhesive solutions and cement plaster.

For slab foundations, as well as deeply buried foundations, it is necessary to use polystyrene foam marked PSB-S-50, which is able to withstand heavy mechanical loads and provide reliable protection against soil swelling. For columnar and standard strip foundations, PSB-S-35 grade foam is used.

All other varieties are not suitable for foundations due to the low density and fragility of the sheets.

Expanded polystyrene made by extrusion is significantly superior to polystyrene foam in all respects. It is many times stronger, absolutely moisture-proof, and has the lowest vapor permeability and thermal conductivity. Microorganisms also do not develop in it, even under conditions of prolonged exposure to dampness.

Foundation insulation with extruded polystyrene foam - EPS

EPS boards with a smaller thickness have a much greater effect. To thermally insulate the foundation in a temperate climate, an insulation thickness of 40 mm is sufficient, in northern conditions - about 60 mm (a two-layer laying of slabs with a thickness of 30 mm is recommended). For ease of installation and greater packing density, the slabs are equipped with tongue-and-groove joints.

They are attached to the base using an adhesive solution and disc-shaped dowels.

Laying of EPS slabs can be done vertically (when insulating columnar and strip foundations) and horizontally (when installing a slab foundation).

Due to its increased strength, the material perfectly tolerates the load from the concrete layer, does not flatten or shrink, unlike polystyrene foam and polyurethane foam. The most popular brands of extruded polystyrene foam are Penoplex and TechnoNIKOL.

Main characteristics

Sprayed thermal insulation, or PPU, is increasingly used to insulate foundations. Polyurethane foam forms a very durable seamless coating that is resistant to adverse influences. At the same time, it simultaneously performs the functions of vapor and waterproofing, which greatly simplifies the work process. Another useful property of this insulation is its high adhesion to the base. It adheres equally firmly to stone, concrete, brickwork, and wooden structures, is easily applied to hard-to-reach areas, and fills the slightest cracks.

Polyurethane foam is applied in two ways - pouring and spraying. The first option is more labor-intensive and expensive, so it is rarely used when insulating private houses. The second method is actively used to insulate the entire building - from the roof to the foundation. Before application, the components are mixed in a foam generating unit with air and the finished mass is sprayed under pressure onto the working surface. Within a few seconds, the composition hardens, and upon completion of the work, you can immediately begin finishing. The only disadvantage of such insulation is that it is impossible to do without installation, and this is an additional cost.

In addition to the described insulation materials, bulk materials, in particular expanded clay, can be used for foundations. It is environmentally friendly, inexpensive, has good thermal insulation characteristics, and is suitable for both vertical and horizontal insulation. But since expanded clay can absorb moisture, losing some of its properties, and the work process requires more effort and time, this insulation is used less and less, giving way to more modern and effective materials.

Prices for expanded polystyrene

Expanded polystyrene

Foundation thermal insulation technology

Insulation of pile, column and strip foundations can be carried out both during the construction process and during the operation of the house. Before installing the insulation, the base must be prepared, which includes cleaning, sealing cracks, and installing waterproofing. The better the preparation, the more effective and durable the result. Slab foundations are insulated directly during construction, because thermal insulation slabs are located horizontally under a layer of reinforced concrete.

Strip foundation

The most labor-intensive stage in insulating such a foundation is excavation work. The foundation must be excavated to its base or to the level of soil freezing. If possible, it is better to hire special equipment, because digging by hand will take a lot of time and require a lot of physical effort. The foundation is dug around the entire perimeter to a width of at least 1 m, then the bottom of the trench is compacted and covered with a layer of sand and crushed stone.

The foundation walls are cleaned of soil with a stiff brush and left open for 10 days to allow the moisture to evaporate. For this reason, work must be carried out in the warm and dry season.

Step 1. The dried walls are carefully inspected for damage, and any identified defects are eliminated. Before sealing, cracks are opened and cleaned of dust; if necessary, the surface is leveled with cement-sand plaster. If unevenness exceeds 20 mm, the plaster is additionally reinforced with metal mesh. After plastering, you must wait until the surface is completely dry.

Step 2. Waterproof the foundation. It is most convenient to use coating waterproofing, for example, polymer, rubber or bitumen water-soluble mastics. Compositions containing organic solvents cannot be used, since polystyrene foam boards are destroyed upon contact with them.

To improve adhesion, the surface is pre-treated with a bitumen primer, applying it in a thin continuous layer. It takes about a day for the primer to dry, after which you can begin applying mastic.

Step 3. Stir the mastic; if the mass is too thick, add a little water.

Prices for bitumen mastic

For application use a wide brush with dense bristles or a roller. The composition is evenly distributed over the walls in a continuous layer, very carefully coating the corners. The layer should not be transparent, but it should not be made too thick, so that streaks do not form. The mixture is rubbed well over the surface, filling the smallest pores of the depression. When the first layer has hardened, apply the second in the same way. Usually two layers are enough, but if the area is often flooded with groundwater, it is recommended to apply 3 layers of mastic.

Step 4. After the waterproofing has dried (after 5-7 days), you can begin installing foam plastic or EPS. To attach the plates, a special adhesive composition is used, for example, ALLFIX, Ceresit CT 83, Titan.

Installation of insulation is carried out from the bottom up, in horizontal rows, with mandatory bandaging of the vertical seams. Apply glue, press the slab to the surface and check its position with a level. When installing the next slab, it is necessary to align the mounting grooves as tightly as possible so that the joints are barely noticeable.

Advice. When laying thermal insulation slabs in two layers, the joints of the lower layer must be completely covered by the slabs of the upper layer. Combining joints will lead to the formation of cold bridges, which means that the effect of insulation will be lower than planned.

Step 5. As a rule, the underground part of the insulation does not need additional fixation, because after backfilling the material is tightly pressed with soil. But in the above-ground part of the slab it is recommended to strengthen it with dowel nails with wide heads. Fastening is carried out after the adhesive solution has completely dried. To do this, through holes are drilled in the slabs (in the center of the slab and in the corners) and buried 40-50 mm into the base. Next, insert the dowels and hammer them in until they stop.

Step 6. To protect the surface of the slabs from accidental damage, plastering is performed with a fiberglass reinforcing mesh. Apply the adhesive solution to the insulation, spread it in an even layer 40-50 mm thick, lay a mesh on top and forcefully smooth it with a spatula, deepening it into the solution. For convenience, it is recommended to cut the mesh into pieces and overlap them by 10 cm.

Step 7 After a day, a final leveling is carried out, and when this layer dries, the surface is treated with a grater and emery cloth.

Step 8 Fill the trench with soil, leaving a distance of about 30 cm to the top. The soil is compacted well to reduce shrinkage. A layer of sand 10-15 cm thick is poured on top, which is also carefully compacted, and then a waterproofing membrane and a layer of insulation are laid at a slight slope from the wall. The final stage is the arrangement of the blind area by pouring a concrete screed.

If it is decided to insulate the foundation with polyurethane foam, there is no need for leveling and waterproofing. After digging a trench and clearing the base of the earth, it is only necessary to eliminate cracks and also remove peelings, if any. When the foundation walls are dry from moisture, you can begin applying polyurethane foam. You can rent a spraying installation from a construction company or buy it, but if you do not have the skills to work with such equipment, it is better to turn to specialists. After the material has hardened, the trench is filled with soil, and a blind area is made on top, as described above.

Columnar foundation

Thermal insulation of columnar and pile foundations is performed a little differently. To thermally insulate the space between the grillage and the ground, it is necessary to build a fence that acts as a plinth. This design does not carry a load, so there are no special requirements for the mechanical strength of materials.

Step 1. A narrow trench up to half a meter deep is dug between the foundation pillars, and a third of it is covered with a layer of sand and small crushed stone.

Step 2. A frame of metal rods is laid on top and a layer of concrete mortar is poured.

Step 3. After the concrete has hardened, the space is bricked around the entire perimeter, leaving small vents in the opposite walls for ventilation.

Step 4. When the masonry is dry, insulation boards are glued to the outside and then plastered using reinforcing mesh. After the plaster has dried, the trench is filled with soil and compacted.

Finally, decorative finishing of the base is carried out - this can be painting, applying decorative plaster, or facing with artificial stone.

Instead of a brick fence, you can install a frame made of timber or a metal profile between the foundation supports. Before installation, the timber must be treated with antiseptic impregnation and dried well. The beams are fastened using metal corners, bolts 65-80 mm long and self-tapping screws; it is preferable to use welding to assemble a metal frame. After installation, the frame is sheathed with EPS or foam plastic boards, and corrugated sheets or plinth panels are attached on top.

Slab foundation

With horizontal insulation, the slabs can also be laid in one or two layers. Most often, insulation with a thickness of 50 or 100 mm is chosen for slab foundations. Thermal insulation begins after the foundation pit has been prepared and the sand cushion has been backfilled.

Step 1. The sand layer is thoroughly compacted over the entire area and leveled horizontally. The smoother the base, the denser the insulation will lie.

Step 2. Film and heat-insulating boards are laid on the sand cushion, joining the mounting grooves. In each subsequent row, the joints are shifted by the width of half the sheet.

Advice. When laying insulation in two layers, the lower slabs are placed in rows along the long side of the foundation, and the upper slabs are placed in rows along the short side. This will not only eliminate cold bridges, but will also further strengthen the strength of the thermal insulation layer.

Step 3. Along the perimeter of the foundation, close to the slabs, formwork is installed, inside which a reinforcing frame made of steel rods is mounted. Concrete is mixed and poured.

Step 4. After the concrete has hardened, a blind area is made. Carefully level and compact the sand with a slight slope from the foundation. The slabs are laid tightly and covered with a waterproofing membrane on top. The membrane sheets are overlapped by 10-15 cm. Next, they are backfilled with sand, again everything is leveled and compacted.

Prices for thermal insulation materials

Thermal insulation materials

Video - How to insulate the foundation of a house from the outside

Video - Insulating the foundation with polyurethane foam

Video - Insulating a slab foundation

Fluctuations in temperature and soil moisture cause gradual cracking of the foundation of the house and its destruction. Thermal insulation of the foundation solves this problem and reduces heat leakage by a third. This measure, in combination with waterproofing, protects premises and communications from freezing and dampness.

How to insulate the foundation

Insulation of the foundation of a house is carried out with traditional materials that are used for walls or ceilings:

• Glass wool.
• Expanded clay, sand and other bulk building materials.

The most effective insulation of the foundation of a house from the outside is carried out using progressive techniques and materials:

Insulating the foundation with polyurethane foam is considered expensive, but it will pay off in the near future - the costs of insulating a house with such thermal insulation are minimal.

Foundation insulation with extruded polystyrene foam. The material is similar to polystyrene foam, but is stronger and contains air cells that increase its thermal insulation properties. Available in the form of easy-to-install slabs.

Foundation insulation technology using extruded polystyrene foam

1. The foundation is cleaned of dirt and waterproofed with polymer or bitumen mastic.
2. Prepare glue for polystyrene and apply it to the inner surface of the slabs. If the foundation is uneven, it is enough to apply glue in the places where it comes into contact with the insulation.
3. The slab is pressed against the foundation for a few seconds and, if necessary, leveled.
4. The next plate is mounted, aligning the connecting groove.
5. It is not necessary to fix the penoplex to the underground part of the foundation - the slab will be securely fixed when backfilled with soil.
6. When the glue dries, the material is additionally attached to the foundation using dowels.

How to calculate the required amount of insulation

The consumption of thermal insulation is influenced by several factors: the type and area of ​​the foundation, the climatic conditions of the area, the type of insulation. Knowing the external area of ​​the foundation wall, it is easy to calculate the amount of thermal insulation. It is more difficult to calculate its thickness. It is calculated using the formula: R=p/k, where p is the thickness of the foundation wall in meters, k is the thermal conductivity coefficient of the material, W/m*k. The thermal conductivity of insulation is indicated on the manufacturer's packaging. For each area there are standards for the thermal resistance of foundations, walls and ceilings of residential buildings. Knowing this value for the material from which the foundation is made, the thickness of the insulation, which is necessary to comply with the building code, is calculated.

Is steam and waterproofing necessary for insulation?

Insulating the foundation from moisture is the most important condition when building a house. This measure prevents contact of rain and melt water with the base. Otherwise, dampness of the walls, basement and basement of the building will inevitably occur, as well as associated phenomena - the development of fungus and mold, destruction of concrete. The measure is especially relevant for areas with frequent precipitation, especially if the building is built in a lowland or on soil with a high groundwater level.

There are several types of vapor barrier for foundations:

All of them are effective as long as they remain sealed.

It is better to insulate a shallow strip foundation with foamed polystyrene or polyurethane foam.

External strip foundation insulation technology

1. A trench is dug along the perimeter of the foundation to the level of the pillow. Its width is equal to the freezing thickness of the soil +5 cm.
2. The foundation is waterproofed with mastic or bitumen-based roll insulation.
3. The insulation on top is covered with film or geotextile. This is necessary to prevent damage to the material when the soil swells.
4. Thermal insulation slabs are attached to the foundation using glue or the same bitumen mastic. An alternative option is to use a burner, with which the material is melted in several places and pressed against the surface of the foundation. Final fixation is carried out using dowels.

1. The insulation board is installed at the soil freezing depth. At the corners, the thickness of the material is increased by one and a half times.
2. To protect thermal insulation from liquid mortar during construction work, it is covered with plastic film. The material is protected from welding with a concrete screed made of low grade concrete.
3. Insulation of the foundation base from the outside with polystyrene foam boards is done with glue or by melting bitumen.

To thermally insulate such a foundation, they create a fence - a special type of base in the form of a layer between the soil and the foundation, which protects from moisture and temperature changes. The collection is created in several stages:

1. Dig a trench 20-40 cm deep.
2. The trench is filled with crushed stone or sand to one third.
3. Beams with grooves are attached to the foundation pillars.
4. Special thin boards are inserted into the grooves.
5. The lower part of the structure is filled with expanded clay.

Many people are interested in how to insulate the pile foundation of a wooden house. A feature of buildings with this type of foundation is the presence of an air gap between the base and the soil, which, in the absence of thermal insulation, leads to significant heat loss. Therefore, insulating a pile foundation from the outside is a necessary measure, on which the comfort of the residents of the house depends.

How to insulate a foundation on screw piles

1. Before insulating a pile-screw foundation, waterproof the grillage.
2. Install insulation for the screw foundation.
3. Finish the outer layer of thermal insulation.

Insulation of the base of a pile-screw foundation is carried out mainly with foam plastic. Also, when insulating a pile-screw foundation of a wooden house, much attention is paid to high-quality waterproofing.

For normal operation of the building, it is necessary to insulate the foundation of the house from the outside and lay polystyrene foam under the blind area. The thermal insulation circuit solves several problems - expanding the frost-free zone, eliminating swelling, cold bridges and heat loss. The need for measures to eliminate swelling conditions (freezing + moisture + clay soil) is separately indicated in the standards SP 22.13330 (foundations), departmental VST, territorial TSN (for example, MF-97 for the Moscow region).

In order for an individual developer to insulate the foundation with his own hands without errors, it is necessary to take into account that the owner’s expenses always consist of the construction estimate and the operating budget. Accordingly, by changing any of these points, you can automatically affect the other:

• by refusing to insulate the blind area or foundation, the owner saves on the purchase of expanded polystyrene, but heating and repair costs increase;
• By investing in thermal insulation, the developer increases initial costs, but automatically reduces operating costs.

By investing money in their own home, a young family receives an advantage during retirement in the form of significantly lower utility bills due to energy savings and no foundation repairs.

Heat distribution diagram near the foundation. It can be seen that the freezing boundary is moving away from the foundation.

Depending on the operating mode of the building, the developer’s budget and the type of soil, horizontal and vertical insulation contours solve different problems:

• blind area - an EPS tape laid under it moves the freezing zone outward from the house, swelling is impossible in the soil layers adjacent to the foundation;
• outer vertical surface of the tape - protection of waterproofing, elimination of cold bridges, reduction of heat loss through the floor/floor of the house, shifting the dew point outward for normal operation of the underground floor;
• horizontal layer under the base of the MZLF - if the building does not have heating or is heated during periodic visits, to eliminate freezing of the soil underneath it is necessary to retain the heat of the subsoil with a continuous layer of polystyrene foam.

Important! A set of works to eliminate swelling must be carried out only on clay soils. However, heat loss in a complex base assembly with multilayer cladding and the adjoining of different structures made of different materials can only be prevented by external thermal insulation of the vertical surfaces of the foundation.

Materials and technology for foundation insulation

Given the existing variety of thermal insulation materials, do-it-yourself foundation insulation is most often done with high-density extruded polystyrene foam EPS, XPS, Carbon SP from TechnoNIKOL, Penoplex Foundation. Unlike mineral, glass and ecowool, polystyrene foam retains its heat-insulating properties, even when completely immersed in water. For comparison, basalt wool loses 30% of its properties when wet and begins to slide off vertical surfaces under its weight. It is prohibited to rest concrete structures on soft insulation materials.

Insulation materials

To protect the foundation of a private cottage, the following thermal insulation materials are most effective:

• polyurethane foam - marked PPU, sprayed onto the surface, also available in the form of slabs, density 50 - 60 kg/m3, thermal conductivity corresponds to 0.028 units, costs twice as much as expanded polystyrene;
• extruded polystyrene foam - different designations from manufacturers, slabs of different sizes, density 35 - 45 kg/m3, thermal conductivity 0.03, cheaper than the previous option.

Insulation of the foundation with extruded polystyrene foam.

The polyurethane foam used to fill the seams of insulation is made of polyurethane foam. Therefore, when using Penoplex, EPS, the quality of the joints is higher than that of the main surface.

The main disadvantage of expanded polystyrene is its low chemical resistance - the material is dissolved by petroleum products. Therefore, it is not recommended to paste over concrete surfaces treated with bitumen mastics, fused with roll materials having a bitumen layer. It is better to use polymer mastics, membranes or polyethylene films. Polyurethane foam is inert to petroleum products, acids, alkalis and salt solutions.

Budget foam plastic PSB-S has a density of 15 - 25 kg/m3, thermal conductivity of 0.04 units, and vapor permeability of 0.05. This insulation is used in the following cases:

• outer layer of vertical crushable insulation;
• permanent formwork for a low grillage (lower horizontal deck).

In the first case, insulation is necessary to protect the main layer of heat insulation. In the second option, the foam plastic remains after the grillage is poured under the reinforced concrete structure, and is crushed by the soil during swelling, so that heaving forces cannot tear the grillage beams away from the pillars or piles, the heads of which are embedded in the structure.

Technology overview

Do-it-yourself foundation insulation is carried out according to different schemes depending on the operating mode and design. Protection against swelling is necessary for columnar, strip and slab foundations. Heaving forces have practically no effect on the piles, however, with a low grillage on bored or screw piles, the beams must be positioned at least 10 cm above the ground.

Scheme for insulating the foundation and outside blind area for a house with constant heating.

There are three main operating modes at home:

• constant heating - insulation reduces heat loss, expands the zone of non-freezing soil around the building and protects the foundation from the effects of negative temperatures;
• heating is completely absent - eliminating heat loss in this case is pointless, however, it is necessary to preserve geothermal heat under the building to prevent soil freezing, so the blind area + the entire perimeter of the garden house under the sole is insulated;
• heating is turned on periodically (baths and cottages) - since episodic heating is present, it is necessary to reduce heat loss in the ceilings and floors, the outer surface of the grillage, strip, slab and blind area is insulated; when there is no heating, there is a need to preserve the heat of the subsoil, so the entire perimeter of the house under the sole is insulated foundation.

In garden houses without heating, laying polystyrene foam at the level of the base of the foundation is not always economically profitable:

If the depth of the pillars or MZLF is within 40 cm, it makes sense to make a pit, since the fertile layer will still have to be completely removed in order to make floors on the ground.

If the strip or columnar foundation lies deeper, excavation work can be avoided by laying insulation according to a different scheme:

• under the blind area - the perimeter of soil freezing moves away;
• under the base of the foundation – protection against swelling;
• on the inner surface of the tape + under the floor along the ground - preservation of geothermal heat under the entire foundation structure.

If for some reason it is impossible to fill the pit openings with non-metallic material that does not contain clay and, accordingly, frost swelling, instead of the standard insulation of the outer surfaces of the strip foundation, a crush-sliding thermal insulation scheme should be used:

• pasting external concrete vertical surfaces with high-density polystyrene foam;
• covering it with polyethylene (attached only in the base part);
• installation of low-density polystyrene foam PSB-S close to the film without fastening (pressed with backfill material).

This option is especially relevant for deep-laying belts. The contact area of ​​the side surfaces of the belt with clay soils is enormous, and the pull-out loads are very significant. When heaving forces occur, the soil crushes the foam and moves it upward along the slippery film. The main layer of insulation is not harmed; after the spring thawing of the soil, the outer layer moves down again.

Important! Insulation is only one method of eliminating swelling in a set of measures. Therefore, drainage and nonmetallic materials in the underlying layer and backfilling of sinuses cannot be canceled.

In classical technologies of monolithic foundations (slab, strip, pillars), a concrete screed is used to reduce the lower protective layer of concrete, level the base, and eliminate leaks of cement laitance from the concrete at the time of pouring.

If a building for seasonal, periodic operation is insulated with a layer of expanded polystyrene around the entire perimeter of the pit, then there is no need to make a concrete footing. This allows us to slightly reduce the construction budget.

Errors in foundation insulation

Due to lack of experience, individual developers often make mistakes when insulating foundations:

• cold bridges - the thermal insulation contour must be continuous, the seams must be foamed, the joints of the slabs must be displaced in the case of a multilayer contour in adjacent layers;
• the use of low-density materials - PSB-S is allowed only for the lower deck of the grillage, the outer layer of crushable thermal insulation;
• violation of thermal insulation schemes - for basements, MZLF buildings with constant heating, it is necessary to insulate the tape from the outside, without heating and when the heating is periodically turned on - from the inside;

Cold bridges, which negate the effectiveness of insulation work, usually occur at the junction points of the base elements:

• lack of lateral vertical thermal insulation along the perimeter of the floor screed on the ground;
• uninsulated concrete preparation;
• absence of polystyrene foam on the upper horizontal edge of the protruding base;
• incorrect combination of basement insulation and façade insulation.

Errors in pairing the insulation of the base and façade.

Important! It is impossible to correct the cold bridge created as a result of facing the facade with brick, the bottom row of which is installed directly on the protruding plinth.

Thus, despite the fact that it is recommended to mount the insulation on the outer surfaces of the foundation, this scheme is correct only for dwellings with a constant heating mode. In garden houses, thermal insulation is made along the inner edges of the tape. The blind area is always insulated; crushable thermal insulation is usually necessary for deep-lying tapes.

People at all times have strived to build their houses with a good margin of safety, because it is normal for a person to create something that will last forever. But, as is already known, the durability of the structure primarily depends on the quality of the foundation, and even if sufficiently strong concrete is poured into the foundation of the house and deep enough, there is still a risk of negative and destructive effects on the structure of the house.

The bottom of the trench is filled with sand 10 cm thick, and on top of the sand to the level of the lower part of the blind area the trench is filled with expanded clay or other soil with low thermal conductivity. Upon completion of the insulation work on the outside of the building walls, a blind area with a slight slope away from the house is made to a width of 50-80 cm.
If a pile foundation is being insulated, when the grillage can be about 50-80 cm in height, many people fill the entire internal area of ​​a private house with expanded clay; in most cases this is very convenient and cheap.

Use of polystyrene foam

When it comes to insulating the foundation from the outside in a professional and most effective way, then, of course, we cannot help but mention materials based on polystyrene foam. Until the technologies were sufficiently developed, many used foam sheets for thermal insulation work, which showed many shortcomings in their work. Among them are the high flammability of the material, water permeability and toxicity.

Now it is gaining popularity and is rightfully becoming the market leader in thermal insulation materials penoplex.

In essence, penopolex is the same expanded polystyrene, only obtained by foaming it under certain thermal conditions.

Thanks to some technological features of production, the output is a fairly high-quality and dense product, consisting of granules measuring only 0.1 mm.

An example of an insulated foundation with foam plastic

Taking into account the characteristics of the material, it is clear why foundation insulation with penoplex has become so popular:

Penoplex can be used for insulation of facades, walls, foundations and plinths, thermal insulation of floor and roof coverings, as well as for insulation of blind areas.