How and with what to insulate the foundation of a house from the outside with your own hands? How to properly insulate the foundation of a house from the outside. How to insulate the foundation from the outside.

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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 from the ground, 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 serves as a plinth. This design does not bear any 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

The foundation is an important load-bearing part of the building structure. It carries a vertical load - the weight of the entire house, and resists horizontal soil pressure. It also experiences the influence of groundwater and condensate. Moisture is absorbed by the foundation through the pores. In winter, all moisture that has penetrated into the pores of materials freezes. Ice crystals tear apart the material. The nearby soil masses are also in a state of seasonal movement. All these factors can lead to the destruction of the base.

Properly performed waterproofing and thermal insulation for the winter will help reduce these risks to a minimum. Insulation only from the inside is much less effective, because the foundation itself remains subject to temperature changes.

General scheme of foundation insulation

In addition, at the junction of the foundation, floors and walls, a “cold bridge” is formed; heat will flow through it into the external environment.

Thermal insulation of the foundation from the outside helps protect it and prevent heat loss.

Types of foundations and features of their insulation

Tape at the formwork stage

If you take care of thermal insulation in advance, during design, you will get a thoughtful, energy-efficient and economical solution.

After the trench has been dug, it should be filled with sand and formwork made of sheet polystyrene foam. Such formwork must be protected from expansion by poured concrete mortar by installing supports made of boards or thick-walled plywood.

There are also special polystyrene foam blocks with cavities on sale. They are used for masonry, like bricks or foam blocks, joined together with glue. Reinforcement is installed in the cavity of such masonry, concrete is poured and vibration compaction is carried out.

Permanent foundation formwork

Formwork of this kind will be permanent and, remaining on the foundation structures, will serve as excellent thermal insulation for it.

Belt made of concrete or stone

An insulated monolithic strip foundation will last much longer. First, the structure poured or built from foundation blocks should be waterproofed. For this purpose, special bitumen mastics are used. The waterproofing layer must be allowed to dry until the solvents have completely evaporated. This takes from three days to a week.

Foamed foam is glued to concrete using adhesives. Acetone-based glue should be avoided - it dissolves the foam.

Thermal insulation of strip plinth

Protective sheets of asbestos cement can be installed on top of the foam or a layer of plaster can be applied, reinforced with a pre-installed support mesh.

Thermal insulation coated with a layer of plaster

How to insulate a foundation made of rubble stone? Before thermal insulation, it should also be leveled with a layer of mesh plaster.

Columnar

How and why to insulate a columnar foundation? Its thermal insulation is more difficult than tape insulation, since there is no closed loop. Insulating each pillar will have less effect than insulating a closed external contour formed by tape. Most often, the insulated contour begins with joists and a subfloor.

To ensure that the columnar foundation does not act as a conductor of cold into the house, it is necessary to create a thermal break between the top of the column and the floor structures. The material for such a gasket should:

have low thermal conductivity;
be strong enough - through this gasket the weight load of the house will be transferred to the foundation.

Special finely granulated high-strength foams are suitable for this.

Slab

Foundation slabs are the most advanced type of supporting structure. The insulated Swedish stove, as it is popularly called, ensures maximum strength of the structure and its resistance to seasonal soil fluctuations. Thermal insulation is carried out before casting, both from the bottom and from the ends of the slab, in order to prevent the formation of the so-called. "cold bridges"

A layer of rolled waterproofing material is unrolled onto a leveled and compacted sand cushion, then expanded polystyrene slabs are laid out. A reinforcement system is installed on top of them, after which the slab can be poured. Sheets cut to fit the thickness of the slab are secured at the ends, which will serve as permanent formwork. They are secured against expansion with special squares.

Insulation of Swedish stove

Just in case, experienced builders place external supports for the end part of the formwork from boards and thrust beams for insurance.

The thickness of the plates in Russian sources ranges between 60 and 100 mm, Western recommendations say from 200-300 mm.

Pile-screw

The problems of insulating a pile-screw foundation of a house are the same as in the case of a columnar foundation. Theoretically, you can dig up the soil to the freezing depth and make an insulated contour around the external piles.

Insulation of piles

However, in this case, the entire main advantage of screw piles is lost - the almost complete absence of excavation work and installation of the foundation of a wooden house in one day.

Most experts agree that the piles themselves do not need insulation, and it is worth focusing your attention and efforts on insulating the walls, floors and points of contact between the joists and the tops of the piles and framing to prevent the transfer of cold through them. And the piles will have to freeze.

Materials

Traditionally, materials such as:

Expanded clay, sand or slag. The oldest and least effective method.
Sheet foam plastics. Polystyrene foam and expanded polystyrene are much more effective than bulk materials.
Mineral wool. High thermal efficiency and low moisture protection.
Sprayed coatings. Maximum efficiency and very expensive equipment.

Bulk materials

The only advantage of traditional bulk materials is their low cost. They do not place high demands on the qualifications of workers and do not require complex and expensive equipment. Such materials are often used to insulate the foundation inexpensively and with your own hands.

A large volume of backfill is carried out in parallel with the functions of waterproofing the foundation, diverting groundwater from it. This is especially important in loamy and clayey soils with high groundwater levels and low levels of freezing.

Scheme of foundation insulation with expanded clay

Sequence of work:

Select the soil around the foundation deeper than its base. The width is selected from 0.5 to 1.5 meters depending on the freezing depth and groundwater level.
Waterproof the foundation walls.
At the bottom of the resulting trench, lay geotextile waterproofing, cover with a layer of crushed stone about 10 cm and lay out drainage pipes.
Fill the hole with the selected bulk material using layer-by-layer compaction.

A cubic meter of sand costs several hundred rubles, depending on the delivery distance.

Sheet foam plastics

Polystyrene foam is a modern and relatively inexpensive insulating material. It combines low thermal conductivity with high resistance to stress and damage resistance. Its installation is not difficult, does not require expensive equipment and is accessible to home craftsmen.

The disadvantages of the material are the need for additional waterproofing, requirements for surface preparation and low resistance to rodents.

Sequence of work:

Clean the foundation walls up to the base from soil and bitumen and oil contaminants. Dry them.
Lay drainage pipes along the bottom to drain groundwater.
Perform waterproofing with materials that do not contain bitumen and acetone - they react with foam plastic and destroy it.
Thermal insulation boards are glued with polymer glue. Gaps and cracks are filled with polyurethane foam to minimize heat loss.
Thermal insulation is protected from rodents with fine-mesh reinforcement mesh.
Fill the trench with sand.

A sheet of foam plastic measuring 1000*600*50 mm costs 80-100 rubles.

A sheet of polyurethane foam measuring 1200*600*50 mm will cost 120-140 rubles.

Mineral wool

Despite the availability of the material, mineral wool is rarely used for insulating foundations. This is due to the high labor intensity of the associated work, the need for additional waterproofing of the insulation and the installation of a protective screen made of asbestos cement sheets, protecting the material from mechanical damage by the soil. As a result, the cost per square meter of thermal insulation is approaching more modern materials. Mineral wool, or ecowool, is used mainly for insulating the above-ground part of the foundation.

Insulation with mineral wool

Sequence of work:

Clean and dry foundation walls. If necessary, repair defects.
Secure the guides from slats or metal profiles.
Lay mineral wool slabs. Perform steam and waterproofing using special films.
Install a ventilated façade or plaster it.

A square meter of mineral wool 50 mm thick costs 100-110 rubles.

Sprayed insulation materials

This type of material provides extremely effective thermal insulation, since the sprayed layer of foamed plastic has no seams or joints. In addition, it also serves as waterproofing.

However, a significant disadvantage is the need to use expensive specialized equipment for spraying. The cost of professional installation reaches hundreds of thousands of rubles. Household devices are cheaper, but they can only pay for themselves with a large amount of work.

The minimum non-rechargeable set of equipment for spraying along with materials, containing 0.6 cubic meters of foam, costs from 20 thousand rubles.

Insulation process

The technological process depends on the material used for thermal insulation. Details are given above in the description of materials. The general requirements are:

Cleaning the foundation wall from soil, unevenness and dirt.
Drainage device at a level slightly below the sole
The need for a blind area and its thermal insulation.

Some features of the process in particular situations are given below

Insulation from outside with close groundwater

If groundwater is high, foundation insulation loses its effectiveness. In addition, seasonal movements of freezing and thawing soil can damage or tear off thermal insulation.

Disposal of nearby groundwater

How to properly protect yourself from groundwater? During construction the following operations are performed:

Below the base, a drainage system is laid that drains groundwater from the foundation.
A wedge-shaped filtering sand cushion is poured between the insulation and the ground, which removes moisture from the surface of the thermal insulation to the drainage pipes.

The sand cushion will also play the role of a damper, protecting the insulation from the pressure of the heaving soil.

In order for this method to work, the following conditions must be met:

The foundation surface line should be as smooth as possible, without ledges or depressions.
For backfilling, use large fractions of sand, possibly mixed with slag.
The backfill must be sifted from stones that lead to sharp damage to the thermal insulation during seasonal movements.

Insulated blind area

An insulated blind area significantly increases the efficiency of thermal insulation of the foundation. For its device you should:

Along the perimeter of the foundation, dig a recess about a meter to one and a half meters wide and up to half a meter deep.
Lay drainage pipes along the outer contour, connected to the general drainage system.
Place a cushion of sand 20 cm thick and compact it.
Lay sheets of expanded polystyrene with a thickness of 30, or preferably 50 mm. The slabs are laid with the short side facing the wall, the width of the insulation is thus 120 cm.
Cover the top with a 10-15 cm layer of sand.
Pour the concrete blind area.

Instead of foamed polystyrene, you can use a 20-centimeter layer of slag.

Insulation of the blind area. The formwork was installed and the reinforcing mesh was laid for pouring the mortar.

Biosecurity

Insulation for foundations made of foamed plastics needs protection from a number of biological factors:

Rodents.
Plant roots.
Mold and fungi.

To prevent rodents from accessing the insulation, a layer of sand should be compacted tightly. The dug trench must be thoroughly cleaned of plant roots. Sheets of asbestos cement are installed on the end side to block access to biological objects. Modern heat-insulating materials contain additives that prevent the development of mold and fungi.

Most thermal insulation methods are not complicated and do not require expensive materials and equipment. However, if the work is carried out on a ready-made foundation, all of it is associated with significant volumes of excavation work. In this case, it is better to work with assistants. With the exception of spraying, all work is performed with conventional construction tools.

Everyone who starts building a private house dreams of warmth and comfort. He expects that even in severe frosts he will feel comfortable and under reliable protection. But in order not to suffer from frost and dampness in cold weather, you need to take a responsible approach to solving the problem of preserving heat in the house.

What's the problem here?

While we have long been accustomed to insulating walls, not all builders pay due attention to the issue of insulating the foundation. Not everyone remembers that the foundation is not only an important structural element of any structure. It also performs thermal insulation functions. In winter, the foundation accounts for 20% of heat loss.

Therefore, it is necessary to insulate the foundation. This is a construction technology that has been proven over the years and cannot be neglected. And, of course, the ideal option is to take care of the heat in the house already at the time of laying the foundation. If the house has already been built, it is better to choose the spring-summer season for insulation.

The list of thermal insulation works and their sequence depend on the design of the insulated foundation, the chosen technology and the material used.

Which insulation to choose: inside or outside?

Definitely, it is better to insulate the foundation from the outside. In this matter, builders show enviable solidarity and give weighty arguments in defense of this method.

The outside is most exposed to weather conditions. When moisture gets into the micropores of the foundation material, it freezes, expands and leads to the formation of microcracks.

Repeated processes of freezing and freezing, temperature changes gradually lead to destruction of concrete, and a threat to house construction arises.

External insulation can reduce heat loss to a greater extent than internal insulation, the cost of heating the house is reduced, and it also improves the waterproofing of the basement and foundation.

Features of insulation of wooden houses

Owners of wooden houses often complain that the floor freezes in winter. A frozen foundation transmits its low temperature to the entire house, greatly cooling it. Not only can the floor freeze, but heating, sewer and water supply pipes can also be damaged.
Wood, no matter how reliable it may seem, is susceptible to all sorts of natural factors. It needs protection no less than other materials.

Wooden houses are usually lighter than stone ones. They are erected on shallow foundations, and sometimes on poles or piles, which, at first glance, greatly simplifies the work of insulating them.

However, when insulating such houses, it is also important to take into account the depth of soil freezing in a specific geographic area. The insulation circuit and insulation must be made at a depth greater than the freezing depth. Only in this case will there be an effect from the work done.

Does a foundation without a basement need insulation?

If we analyze the regulatory documents on civil engineering and building codes, we will not find specific instructions on the need for this work.

But even if the building does not have a basement, the reinforced concrete structure itself is a source of cold in winter. Heat loss is inevitable both through the foundation and through the walls of the house.

For builders, the answer is obvious. Yes, definitely.

Materials used for insulation

Before you begin insulation work, you need to decide on the material. The quality of insulation and the positive result of the work performed depend on the right choice.

Basic requirements for materials used to insulate the foundation of a house:

resistance to deformation under pressure and swelling of the soil,
high water-repellent properties,
resistance to aggressive action of groundwater,
inaccessibility to the process of decay.

When choosing the type of insulation, you should also consider:

type of soil under the building,
air temperature and humidity in the cold season,
intensity of load on the foundation.

Modern industry offers various types of thermal insulation materials that even a novice builder can easily handle.

Expanded clay

It is a material made from expanded and melted clay. The material is very light, porous and contains a large amount of air. The air in the pores allows you to retain heat. Expanded clay has the following advantages over other insulation materials:

low cost,
low thermal conductivity,
you don't have to be afraid of rodents,
fireproof,
ecologically pure,
resistance to low temperatures and temperature changes,
not susceptible to mold and mildew formation,
moisture resistance.

Expanded clay has only one drawback - fragility. If the granules are damaged, the thermal insulation properties of the material deteriorate sharply. Therefore, when working with expanded clay, care must be taken not to damage the granules.

Styrofoam

Another popular and affordable material for external insulation is polystyrene foam (expanded polystyrene or expanded polystyrene).

The popularity of polystyrene foam is ensured by:

low thermal conductivity,
not afraid of a humid environment, not susceptible to mold,
resistance to chemicals and aggressive substances,
full preservation of operational characteristics in the temperature range from -180° to +80°.

The disadvantage of polystyrene is its low strength. When using it for external insulation, additional protection will be required (laying it with bricks or pouring concrete).

Extruded polystyrene (penoplex)

This additional work can be avoided by using extruded polystyrene. Possessing all the advantages of expanded polystyrene, it is also highly resistant to deformation and mechanical damage.

But this material is not ideal either:

burns very strongly
at temperatures above 75° it releases substances harmful to humans,
destroyed by exposure to ultraviolet radiation.

Polyurethane (PPU)

You can carry out external insulation of the house using polyurethane. This material will achieve an amazing effect.

It is a synthetic polymer material with unique characteristics:

has a minimum thermal conductivity,
excellent adhesion (adhesion between surfaces),
almost not saturated with moisture,
mechanical strength,
durable (the material does not rot or decompose),
resistance to chemical environments.

When insulating polyurethane foam, a continuous continuous contour is created around the foundation without any breaks or gaps.

But polyurethane foam also has disadvantages that are characteristic of this material:

destruction under the influence of ultraviolet radiation,
smoldering at high temperatures,
the material is expensive.

Technologies for foundation insulation work

To carry out insulation work with your own hands, you need to clearly understand what types of foundations exist and what technology to choose correctly.

With any insulation method, you must first clear the foundation if it is backfilled. This is a labor-intensive, but quite feasible process. First you need to dig around the foundation around the perimeter. The digging depth should be equal to the depth of the foundation into the ground. The width of the digging should be at least a meter.

After release, the foundation should dry well. Usually two weeks are enough for this. When everything is dry, you can move on.

The next stage is waterproofing.

After waterproofing is completed, there are two options:

construction of an additional brick foundation,
covering the bottom of the trench with film and using insulation.

Strip foundation and its insulation

The most common type of foundation. It is made in the form of a closed structure, passing under all the walls of the building. Let's talk about polystyrene insulation.

In addition to polystyrene you will need:

polystyrene glue,
mounting foam and sealant,
reinforcement mesh,
primer for concrete,
coarse sand or gravel,
cement mortar,
roll waterproofing,
finishing materials at the request of the owner.

Experts never use bitumen as waterproofing when insulating with polystyrene. It promotes the destruction of polystyrene.
After the foundation has completely dried, it must be carefully primed. The primer will fill all microcracks and pores.

Now you need to lay the waterproofing. Modern roll waterproofing is made on a self-adhesive basis. We apply it tightly to the foundation, smooth it with a roller, and treat the joints with sealant.

Next, a sand and gravel cushion is formed. The height of the cushion must match the height of the bedding under the foundation.
The main stage is attaching the insulation. The fastening technology depends on the material used, it can be:

heating method,
fastening with glue or mastic.

If the insulation is laid in several rows, you need to make sure that the joints are not located one above the other.

Please note that you cannot attach insulation boards to the foundation with plastic dowels - umbrellas. You risk not only destroying the insulation, but also damaging the waterproofing, and all previous work will be unnecessary. We attach the insulation only with glue or mastic!
It is recommended to lay a durable film over the insulation. It will provide reliable protection against ground movement during temperature changes.

External insulation of foundations on screw piles and foundations on pillars

The columnar foundation consists of pillars dug to a depth of two meters. The frame of the house is installed on these pillars. The use of a columnar foundation is advisable when building houses on slopes.

A screw foundation (pile) differs from a columnar foundation in that the basis of the structure here is piles that are screwed into the ground. These types of foundations are universal. They allow construction to be carried out in any climate zone, on any surface relief, without fear of the influence of groundwater. This is especially advisable when building houses on slopes.

But there is one negative point - the empty space between the ground and the building, open to all winds and frosty winter air.

A house built on screw piles or support pillars must be insulated, although this is not an easy object for such work. The technology here differs from working with a strip foundation. There are two ways to insulate a pile foundation from the outside:

tape structure,
insulation of the profile along the frame.

Which one to use depends on aesthetic wishes, financial capabilities, and even on the qualifications of the builders who will carry out the finishing.

An important point here is the implementation of waterproofing work. After all, if this is not done, the metal elements of the piles will corrode, and the wooden ones will simply rot. The easiest and most reliable way is to use ordinary roofing material. They cover the visible part of the pile before the start of the grillage and the upper part of the grillage, where it comes into contact with the wall.

It is advisable to treat the metal parts of the foundation with a mastic that protects from moisture, and impregnate the wooden parts with a solution that prevents rotting.

The installation of a strip structure is the construction of a lightweight brick structure. A shallow trench is first dug, filled with reinforcement and filled with concrete. When the mortar dries, bricks are laid into the floor. This will help make the basement more comfortable to live in.

The constructed frame is several rows of horizontal profiles connected to each other by the vertical components of the foundation. Using ordinary self-tapping screws, panels of thermal insulation material are attached to horizontal guides. With this insulation option, it is recommended to use penoplex.

No waterproofing materials are needed here. Penoplex can easily cope with high humidity on its own. Now you can carry out the cladding. Any building mortars for fastening, leveling, plastering, etc. can easily be applied to penoplex. The main thing is to securely attach the plaster mesh to the insulation. Some types of facing materials (siding, corrugated board and others) are attached to the insulation boards with self-tapping screws.

To date, penoplex manufacturers have specified the names of the material. They began to produce slabs, not just penoplex, but penoplex foundation, penoplex wall. This greatly simplified the choice for the consumer.

Slab foundation

Another common type of shallow foundation is. A flat reinforced base is made along the entire plane of the surface on which the building structure will be located. This is an excellent option for protection against soil heaving and an ideal surface for further work.

There are also options for insulating a slab foundation. It is possible to perform sub-foundation insulation, with the slab placed on a heat insulator. But for residential buildings, it is preferable to place the insulating layer not under the foundation, but under the screed.
Any material from simple polystyrene foam to extruded polystyrene is suitable as insulation here. A layer of thermal insulation 50-100 mm thick must be applied to the ends of the slab.

It is possible to insulate a slab foundation from the outside only at the first stages of construction work. If builders miss this point, the situation can only be corrected by internal insulation.

A logical continuation would be to lay insulation under the blind area, which is created around the building and will create a barrier to freezing of the walls and protect against frost heaving of the soil.

Do-it-yourself insulation of the blind area of a house

For additional protection from melt and waste water, experienced builders insist on installing a drainage system and constructing a blind area. By creatively choosing a blind area, you can find interesting design solutions for decorating the exterior of your home.

What is a blind area?

This is a perimeter strip around the house with a width of at least 60 cm. It simultaneously performs a decorative function on the site and is designed to protect the foundation. The blind area can be constructed at any stage of house construction. But the least costly in terms of time and finances will be the creation of a blind area after the completion of the installation of walls, foundation and roof.

Often the owners of small old houses and cottages neglected the insulation of the blind area. Experience has shown that it is necessary. After all, even in small areas the soil freezes and thaws unevenly. During these processes, the volume of soil, its density changes, and, as a result, the destruction of the foundation. Well, in terms of heat conservation there should be no doubt at all!

The most effective (and also the most expensive) method is to insulate the blind area with extruded polystyrene. Most often, polystyrene boards with a thickness of 50 mm are used. They are laid on the underlying layer of the blind area and covered on top with dense waterproofing material to isolate the joints.

If you use regular polystyrene, to achieve the same effect, you will need to gain a thickness of 80 - 100 mm.
For foam plastic, this layer should be even larger than 100 - 150 mm. The joints between polystyrene foam boards are sealed with polyurethane foam. It is better to use roofing felt as waterproofing.

Conclusion

So, thermal insulation of any foundation is necessary. And you cannot neglect it, despite the financial costs. Moreover, they are not as large as for the entire construction process.
These small investments will definitely bring dividends in the future, both materially and morally.

Thermal insulation of the foundation is an important and critical stage in the construction and renovation of a house. An uninsulated foundation means not only serious heat loss, but also the danger of freezing and subsequent destruction of the building’s underground structures. Insulating the foundation from the outside allows you to reduce heat loss several times, in addition, it reliably protects the foundation of the house from the effects of groundwater and low temperatures.

Why is insulating the foundation from the outside more effective?

To understand this issue, you need to imagine the operating conditions of the foundation. The foundation takes on both the load from the building and soil pressure. Its underground part is constantly exposed to groundwater and atmospheric waters, while the porous foundation material can become wet, absorbing moisture. When the ground temperature drops below zero, not only the soil freezes, but also the wet foundation. At the same time, cracks and chips form in porous concrete. In addition, seasonal movements of heaving soils also have a destructive effect. These factors gradually lead to partial destruction of the foundation, followed by damage to the walls of the building.

To avoid the harmful effects of the environment on the foundation, they resort to a set of measures, and the two main protective measures are its insulation. In this case, insulation is most often carried out from the outside, since with external insulation, not only the premises of the house are protected, but also the foundation itself. In some cases, they resort to insulating the foundation from the inside, most often when external insulation is impossible.

Materials and methods of foundation insulation

There are several ways to insulate the foundation from the outside:

Backfilling with sand or expanded clay. The oldest and most ineffective method, based on the property of these materials to remove moisture and create an air gap near the foundation walls.
Insulation using polystyrene foam boards and its modern analogues: penoplex, polystyrene.
Insulation using mineral mats followed by covering the foundation with a protective screen;
Spraying polyurethane foam onto the surface using a special installation. The result is a seamless layer that is resistant to mechanical damage and has high thermal insulation properties.

Backfilling the foundation with sand and expanded clay

The advantages of the method include the low cost of the material and the ability to perform thermal insulation yourself, without the use of professional help. In addition, the backfill layer simultaneously acts as waterproofing and compensates for soil pressure during heaving, which makes it possible to effectively use this method on wet clay soils with a high frost heaving coefficient.

Execution technology:

A pit is prepared along the perimeter of the foundation from the outside. Its depth should be slightly lower than the depth of the foundation, and its width depends on the region and soil moisture. The lower the temperature in the winter months and the higher the groundwater level, the wider the pit should be.
Drainage is performed at the bottom of the pit: geotextiles are laid, covered with crushed stone, a perforated pipe is placed on the crushed stone, and again a layer of crushed stone. The pipes are connected into a single system and drained into the well.
The foundation is cleaned and dried, after which it is performed. The choice of type of waterproofing depends on the operating conditions of the foundation, but it should be taken into account: when backfilling with expanded clay, coating waterproofing with bitumen or polymer compounds cannot be used due to the possibility of damage to the waterproofing film.
The prepared trench is backfilled with sand or expanded clay, compacting it in layers.

Insulation of the foundation with polystyrene foam and its analogues

A modern and highly effective method that allows high-quality thermal insulation of foundation walls. The advantages of the method are high thermal insulation characteristics of the material, ease of thermal insulation, resistance of the material to mechanical loads and damage, ease of finishing. Disadvantages - it requires preparation of the foundation surface, protection of the insulation layer from rodents, as well as waterproofing suitable for this method.

Execution technology:

The surface of the foundation is dug out to its full depth, cleaned, and dried. Remains of bitumen waterproofing, fats, and oils must be removed from the surface—foam plastic and its analogues are destroyed upon contact with these substances.
The foundation is waterproofed in one of the following ways: using polymer-based mastics; or .
Plates of thermal insulation material are laid on a special glue - it is sold in the form of a dry mixture. The slabs usually have grooves that facilitate their joining and prevent the appearance of cracks, gaps and cold bridges.
The surface of the foundation is protected from damage by rodents with reinforcing mesh, laying it on the same glue. After the glue has dried, the underground part of the foundation is backfilled with sand, and the above-ground part is additionally secured using special dowels with a wide head.

Insulation of the foundation using mineral insulation (Mineral wool)

This method is used quite rarely, since, along with good thermal insulation, it has a number of disadvantages: its implementation requires the construction of a frame, good protection of the insulation from getting wet, as well as the construction of a protective wall made of brick or other finishing materials. It is usually used to construct the above-ground part of the foundation and the basement as a continuation of the thermal insulation of the walls of the house.

Execution technology:

The surface of the foundation is cleaned and dried, defects are eliminated.
A frame for heat-insulating mats from a metal profile is made on it.
Place thermal insulation mats on the frame and secure them. The surface of the insulation is protected from external moisture with a vapor-permeable wind- and waterproof film.
A protective brick wall or a ventilated frame is erected.

One of the most effective ways to insulate the foundation both outside and inside. To carry it out, special equipment is required - a spraying installation, with the help of which insulation components are supplied to the surface of the foundation under high pressure. The result is a seamless layer of foam with high thermal and waterproofing properties. To perform such waterproofing, it is better to contact specialists, since the quality of the coating largely depends on the correctly chosen mode and the installation itself.

Thermal insulation of the foundation from the outside allows you to reduce the heat loss of the building by 20-25%, while increasing its service life. Thermal insulation of the foundation can be carried out both on a facility under construction and on a building in use.