How thick is polystyrene foam needed to insulate the foundation? Technology of foundation insulation with polystyrene foam. Types of polystyrene foam materials

Insulating the foundation with polystyrene foam is a popular way to improve thermal insulation performance and prevent freezing of the foundation. Expanded polystyrene is nothing more than polystyrene foam made using more modern technologies. Extruded polystyrene foam has greater strength compared to conventional foam, as well as a more convenient form of plates for installation.

Advantages of insulation using expanded polystyrene:

High thermal insulation characteristics, frost resistance;
Low vapor permeability;
Expanded polystyrene slabs are easy to install and cut to the required size;
Surface does not require additional training, irregularities are allowed;
The price of the material is low.

Disadvantages of polystyrene foam:

The material is flammable, therefore, when installed on the base part of the foundation, it requires finishing with non-combustible materials;
Expanded polystyrene is often damaged by rodents and requires the installation of reinforcing mesh;
Expanded polystyrene absorbs moisture, which contributes to its destruction, therefore, when insulating foundations in damp soil, additional waterproofing is necessary;
The mechanical strength of the material is also low, therefore, when backfilling with soil containing solid inclusions, additional mechanical protection in the form of shields is required.

Technology of foundation insulation with polystyrene foam

Preparing the foundation. Foam insulation is possible both for objects under construction and for those already in operation. The foundation must be completely excavated, cleaned of soil, dust, construction debris, grease stains and rust. Remains of rolled waterproofing from the foundation must also be removed. You can insulate the foundation with polystyrene foam both from the outside and from the inside, but the most effective is external insulation, when the foundation itself is included in the heat-insulated zone.
Selection of polystyrene foam. When choosing, two factors should be taken into account - the density and the calculated thickness of the insulation layer. Expanded polystyrene slabs have a thickness of 30 to 100 mm; if it is necessary to make a thicker layer of insulation, they are attached in two layers. The density of expanded polystyrene for foundation insulation must be selected from 35 kg/m 3, the flammability class for the underground part of the foundation does not matter; for the base it is better to choose expanded polystyrene with fire-retardant additives, or to isolate it from the structural combustible parts of the building with a layer of non-combustible material.
Foundation waterproofing. This important stage will allow you to avoid the foundation getting wet from groundwater if the insulation layer passes through it. under the insulation can be carried out in any way, with the exception of waterproofing bitumen mastic on organic solvents - polystyrene foam in contact with solvents quickly loses its properties and is destroyed. Therefore, when performing coating waterproofing, it is better to choose polymer or water-based mastics.
Fastening polystyrene foam to the underground part of the foundation. Insulation boards are attached to the foundation using contact glue for expanded polystyrene. The glue is applied around the perimeter of the slab and in several stripes in its center, left for 1 minute and pressed firmly to the foundation. Wait a few minutes, then attach the next slab. It is better to fasten the plates level to avoid distortions at the joints. If, according to the calculation results, an insulation layer of greater thickness than the maximum is required standard thickness polystyrene foam, then the insulation is attached in two layers, one on top. In this case, the slabs are positioned so that the second row completely overlaps the joints of the first with the center of the slab. If after the sticker there are still gaps, they are foamed with polyurethane foam.
An important step is protecting the insulation. The disadvantages of expanded polystyrene include its low mechanical strength and the likelihood of damage by rodents. Therefore, to maintain the integrity of the thermal insulation layer, it is necessary to protect it using reinforcing mesh or wooden shields. The mesh or panels are attached along the perimeter of the foundation to the height of the backfill using dowel nails. You can plaster the foundation on top of the mesh cement mortar with the addition of waterproofing components, which will also help to avoid the insulation getting wet and being destroyed when freezing.
Drainage. This stage is mandatory for buildings installed on wet soils With high level groundwater. Drainage is carried out along the entire perimeter of the foundation and leads into a natural depression, reservoir or specially dug drainage well. The drainage is a perforated pipe made of any material, laid on a specially prepared bed of crushed stone and sand. The foundation is backfilled with soft soil or sand, carefully so as not to damage the polystyrene foam slabs.
Basement insulation. The basement part of the foundation is also subject to insulation. The prepared and waterproofed foundation surface is ready for laying insulation boards. The polystyrene foam boards are attached to the same glue, the gluing procedure is similar.
After the glue has dried, that is, after a day or two, the insulation boards are additionally fixed to the base using special fasteners– dowel-nails with a wide head. Each slab must have at least 4 fastening points, and to reduce their total number, dowels can be installed at the joints of the slabs. They pre-drill a hole in the slab and foundation a couple of centimeters deep than the length of the dowels, after which the dowels are carefully hammered in, followed by the nail. Plastic dowels, due to their wide caps, perfectly hold polystyrene foam boards and at the same time do not create cold bridges.
Soil insulation. Effective reception, which allows not only to improve the temperature in the building, but also protects the foundation itself from destruction. Its operating principle is that the soil around the foundation is isolated from subzero temperatures with the help of an insulated blind area, and the frost line moves away from the foundation walls to the distance of insulation. Usually the width of the blind area is no more than a meter. The blind area is insulated with polystyrene foam slabs laid in formwork on a prepared sand bed, after which the blind area is reinforced with rods and filled with concrete. When pouring it is necessary to do slight slope outside so that precipitation does not stagnate on the blind area.
Basement finishing. Finishing is necessary to protect the insulation from mechanical damage and give decorative look the basement part of the foundation. Reinforcing painting mesh is attached to the insulation boards using cement-based glue, after which they wait for the glue to dry and plaster the base. You can attach any type of material to plaster facing material, or paint the base with paint.

Insulating the foundation with polystyrene foam is not the best effective method for buildings experiencing large mechanical loads from the ground. Expanded polystyrene has more durable analogues, for example, insulation with polyurethane foam or slabs. To perform thermal insulation of the foundations of buildings built on highly heaving soils, it is more reliable to use these materials.

The key to the longevity of any structure is the reliable foundation on which it is based. " Zero cycle“, that is, the construction of the foundation is one of the most important stages of construction. Errors and shortcomings made during such work, neglect of technological recommendations or unjustified simplification of certain operations can lead to very unpleasant and sometimes even catastrophic consequences.

One of the most common types of foundations is strip. It is quite versatile, suitable for most residential or outbuildings, is characterized by high reliability and stability even on “difficult” soils. But it will show all these qualities only if the concrete strip is reliably protected from negative external influence. Unfortunately, not all novice builders know that the foundation of a house especially needs hydro- and thermal insulation. One of the solutions to this problems - insulation foundation with polystyrene foam, the technology of which is quite accessible to everyone.

Why is the foundation insulated?

At first glance, it even looks paradoxical - to insulate a monolithic concrete belt buried in the ground and slightly rising above the ground in the basement. What's the point if there are no living quarters here? What difference does it make whether the “foundation is warm” or whether it remains open?

Unfortunately, such an amateurish view is not at all uncommon, and many land owners, starting to work for the first time in their lives self-construction own home, ignore the issues of thermal insulation of the foundation and do not even provide for the corresponding costs for these measures. Alas, by doing so they are planting a “time bomb” under their home.

Strip foundations are usually buried in the ground below the freezing level of the soil. It turns out that the temperature of the sole or lower part of the tape is approximately the same throughout the year, but the upper part of the foundation, depending on the season, is subject to either heating or cooling. This unevenness in a single concrete structure creates strong internal stresses - due to the difference in linear expansion of different sections. These internal loads lead to a decrease in the strength qualities of concrete, to its aging, deformation, and the appearance of cracks. The solution is to ensure approximately equal temperature of the entire tape, which is why thermal insulation is necessary.

An uninsulated foundation becomes a powerful bridge for the penetration of cold from outside to the walls and floors of the first floor. Even seemingly reliable thermal insulation of floors and facades will not solve the problem - heat losses will be very large. And this, in turn, not only creates an uncomfortable microclimate in the residential area, but also absolutely unnecessary heating energy costs. Conducted thermal calculations prove that proper insulation foundation provides up to 25 - 30% savings.
Definitely high quality concrete solutions have their own operational “reserve” in terms of frost resistance - this is the calculated number of deep freezing and thawing cycles without loss of strength qualities. But you still need to spend this “reserve” wisely, and it is better to protect the foundation as much as possible from the influence of negative temperatures.
Insulated foundation walls will dampen less, since the thermal insulation layer will bring the “dew point” out. This - more one plus for the insulation of the tape.
In addition to insulating the external walls, conscientious builders also install a horizontal layer of thermal insulation, which will prevent cold penetration through the soil to the base of the foundation. This measure is aimed at reducing the likelihood of soil freezing near the belt, which is dangerous due to swelling and the appearance of strong internal stresses in reinforced concrete structure and its deformation.
And finally, thermal insulation mounted on the walls of the foundation also becomes a good additional protection against soil moisture, and in addition, it becomes a barrier that protects the required waterproofing layer from mechanical damage.

To solve the problem of insulating the foundation, thermal insulation stands are placed on its outer wall - from the base (sole) to the upper edge of the base. There is no need to rely on insulating the foundation from the inside - this will not eliminate external influences in any way, and can only slightly improve the microclimate in the basement.

You need to start with waterproofing!

Before moving on to the technology of foundation insulation, one cannot help but touch upon the issues of its high-quality waterproofing - without this, all the work can be done in vain. Water, in “alliance” with temperature changes, turns into a serious threat to the foundation of a house:

First of all, everyone knows the property of water to expand when it turns into a solid. state of aggregation- when freezing. The penetration of moisture into the pores of concrete at subzero temperatures can lead to a violation of the integrity of the structure, rupture, cracks, etc. This is especially dangerous in the basement part and at a shallow depth of the tape.

There is no need to think that soil moisture is pure water. A huge amount of organic and inorganic compounds are dissolved in it, falling on the ground with car exhausts, industrial emissions, agricultural chemicals, spills of oil products or other liquids, etc. Many of these substances are extremely aggressive towards concrete, causing its chemical decomposition, erosion, crumbling and other destructive processes.
Water itself is a strong oxidizing agent, plus it contains the compounds mentioned above. Penetration of moisture into the thickness of concrete will certainly lead to oxidation of the reinforcement structure - and this is fraught with a decrease in the design strength and the formation of cavities inside the tape, which then turn into cracking and peeling of the outer layers.

And in addition to all that has been said, water also causes a gradual washout of the concrete surface - cavities, sinks and other flaws are formed.

There is no need to rely on the fact that groundwater at the construction site is very deep and does not pose a particular threat to the foundation. The danger lies much closer:

Water that falls with precipitation or gets onto the ground in other ways (spills, melting snow, pipeline accidents, etc.) forms the so-called filtration layer, which, by the way, is the most dangerous in terms of aggressive chemicals. It happens that in the soil at a shallow depth there is a waterproof clay layer, which leads to the creation of even a fairly stable surface water horizon - perched water.

The moisture concentration in the filtration layer is a variable value, depending on the time of year and established weather. The most important role in reducing the negative impact of this layer on the foundation will be played by the organization of proper storm drainage.

The second level is a fairly constant concentration of capillary moisture in the soil. This is a fairly stable value, depending on the time of year and the weather. Such moisture does not have a leaching effect, but its capillary penetration into concrete is quite possible if the foundation is not waterproofed.

If the area is different high humidity, for example, is located in a swampy area, then waterproofing cannot be limited - will need to be protected the foundation also includes the creation of a drainage system.

Underground aquifers are very dangerous for the foundation. True, they are also a fairly stable value in their location, but in terms of filling they depend on the time of year and the amount of precipitation.

If there is a tendency for such layers to lie close together on the construction site, then very high-quality waterproofing and a drainage system will be required - here the impact of water may not be limited to simply penetrating into concrete, but also cause serious hydrodynamic loads.

An approximate diagram of foundation waterproofing is shown in the figure:

1 – sand and gravel cushion on which the foundation strip is based (2). This pillow also plays a role in general scheme waterproofing, performing the functions of a kind of drainage.

The diagram shows a block strip foundation, therefore a layer is provided between the base strip and the laying of blocks (4) horizontal waterproofing(3), eliminating capillary penetration of moisture from below. If the foundation is monolithic, then this layer does not exist.

5 – coating waterproofing, on top of which the rolled lining (6) is laid. Most often, in private residential construction, tar mastic and modern types roofing felt on a polyester fabric base.

7 – a layer of thermal insulation of the foundation, which in the upper plinth part is additionally covered with a decorative layer - plaster or cladding panels (8).

The construction of the walls (9) of the building begins from the foundation. Pay attention to the mandatory horizontal “cut-off” layer of waterproofing between the foundation and the wall.

To carry out waterproofing work, the foundation strip is exposed to the very bottom - this will also be required for its further insulation.

Within the framework of this article, it is impossible to talk about all the nuances of waterproofing work - this is a topic for separate consideration. But it would still be advisable to give recommendations for optimal use waterproofing materials- they are summarized in the table:

Type of waterproofing and materials used	resistance to cracking (on a five-point scale)	degree of protection from groundwater			room class
		"verkhovodka"	soil moisture	ground aquifer	1	2	3	4
Adhesive waterproofing using modern polyester-based bitumen membranes	5	Yes	Yes	Yes	Yes	Yes	Yes	No
Waterproofing using polymer waterproof membranes	4	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Coating waterproofing using polymer or bitumen-polymer mastics	4	Yes	Yes	Yes	Yes	Yes	Yes	No
Plastic coating waterproofing using polymer-cement compositions	3	Yes	No	Yes	Yes	Yes	No	No
Coating rigid waterproofing based on cement compositions	2	Yes	No	Yes	Yes	Yes	No	No
Impregnating waterproofing that increases the water-repellent properties of concrete	1	Yes	Yes	Yes	Yes	Yes	Yes	No

The table shows 4 classes of buildings:

1 – technical buildings, without electrical networks, with a wall thickness of 150 mm. Damp spots and even small leaks are acceptable here.

2 – also technical or auxiliary buildings, but with a ventilation system. Wall thickness – at least 200 mm. Damp spots are no longer acceptable; only minor moisture vapors are possible.

3 is the very class that is of interest to private developers - it includes residential buildings, social buildings, etc. Moisture penetration in any form is no longer acceptable. The thickness of the walls is at least 250 mm. Natural or forced ventilation is required.

4 – objects with a special microclimate, where a strictly controlled level of humidity is required. You won't encounter this in private buildings.

You should not draw a conclusion from the table about the sufficiency of any one layer from those indicated. The optimal solution for the foundation, we repeat, would be a combination of coating and adhesive waterproofing - this will create a reliable barrier against moisture penetration.

After the foundation has received reliable waterproofing, you can proceed to its insulation.

Expanded polystyrene as insulation for the foundation

Of all the diversity thermal insulation materials it is polystyrene foam that is optimal choice for use specifically in foundation work conditions - with inevitable contact with moisture, with load soil, etc. There are other technologies, but if we look at them in terms of self-execution work, without the involvement of craftsmen and special equipment, then, in fact, there is no reasonable alternative.

One of the best representatives of the class of extruded polystyrene foam is “Penoplex”

It should be noted right away that we will not be talking about foamed polystyrene, which is more often called polystyrene foam (it is unsuitable for such use), but about extrusion varieties of expanded polystyrene. Most often, “penoplex” is chosen for foundation insulation - slabs of a certain size and configuration, which are very convenient to work with.

Penoplex prices

penoplex

The advantages of "Penoplex" are as follows:

The density of this material ranges from 30 to 45 kg/m³. It is not difficult to install, but this does not mean the low strength of such expanded polystyrene. Thus, the force for deformation by just 10% reaches from 20 to 50 t/m². Such insulation will not only easily cope with soil pressure on the walls of the foundation strip - it is even laid under the sole or used as an insulating base when pouring a monolithic slab foundation.
The material has a closed cellular structure, which becomes a very good additional waterproofing barrier. The water absorption of Penoplex does not exceed 0.5% during the first month, and subsequently does not change regardless of the duration of operation.
Extruded polystyrene foam has one of the lowest thermal conductivity values - a coefficient value of about 0.03 W/m²×°C.
"Penoplex" does not lose its outstanding performance characteristics in a very wide temperature range – from - 50 to + 75 ° C .
The material is not subject to decomposition (except for exposure to organic solvents, which is very unlikely in soil). It does not emit substances harmful to humans or the environment. Its service life in such conditions can be 30 years or more.

"Penoplex" can be of several modifications designed to insulate certain elements of the building. For example, some types contain fire retardant additives that increase the fire resistance of the material. This is not required for foundation work. For insulation, Penoplex brand “35C” or “45C” is usually purchased. The numbers in the marking indicate the density of the material.

Release form - panels, most often orange color. The size of such slabs, 1200 × 600 mm, makes them very convenient for installation. The thickness of the panels is from 20 to 60 mm in increments of 10 mm, as well as 80 or 100 mm.

Plates of real “penoplex” are equipped with a locking part - lamellas. This is very convenient when laying a single insulating surface - the lamellas, overlapping one another, cover the cold bridges at the joints.

"Penoplex" - optimal solution for insulating the foundation!

This insulation is produced in several modifications, each of which is designed for thermal insulation of certain elements of the building. This line also includes Penoplex-Foundation.

Read more about it in a special publication on our portal.

How to correctly calculate foundation insulation expanded polystyrene

In order for the insulation of the foundation to be truly high-quality, it must first be calculated - for a specific building and for the region in which it is being built.

It has already been said that full thermal insulation of the foundation should consist of at least two sections - vertical and horizontal.

The vertical section consists of expanded polystyrene slabs fixed directly to the outer walls of the foundation strip - from the base to the upper end of the base part.

The horizontal section should form a continuous belt around the perimeter of the building. It can be located in different ways - at the level of the sole with shallowly buried tapes, or at another level above the freezing point of the soil. Most often it is located just below ground level - it becomes a kind of foundation for pouring a concrete blind area.

The diagram shows:

— Green dotted line – ground level;

— The blue dotted line is the level of soil freezing characteristic of a specific area;

1 – sand and gravel cushion under the foundation strip. Its thickness (hp) is about 200 mm;

2 – foundation strip. The depth of occurrence (hз) can be from 1000 to 15000 mm;

3 – sand backfill in the basement of the building. It will subsequently become the basis for laying the insulated floor;

4 – layer of vertical waterproofing of the foundation;

5 – laid layer of thermal insulation – “Penoplex” boards;

6 – horizontal section of foundation insulation;

7 – concrete blind area along the perimeter of the building;

8 – finishing of the basement part of the foundation;

9 – vertical “cut-off” layer of basement waterproofing.

10 – location of the drainage pipe (if her necessary).

How to correctly calculate how thick the insulation layer should be? The method for calculating thermal parameters is quite complex, but two simple methods can be given that will give the required values with a sufficient level of accuracy.

A. For the vertical section, you can use the formula for the total heat transfer resistance.

R=df/λb + dу/λп

df– thickness of the walls of the foundation tape;

dу– required insulation thickness;

λb– coefficient of thermal conductivity of concrete (if the foundation is made of a different material, the value for it is taken accordingly);

λп– coefficient of thermal conductivity of the insulation;

Because λ – tabular values, foundation thickness df we also know, we need to know the meaning R. A this is also a table parameter, which is calculated for various climatic regions of the country.

Region or city of Russia	R - required heat transfer resistance m²×°K/W
Black Sea coast near Sochi	1.79
Krasnodar region	2.44
Rostov-on-Don	2.75
Astrakhan region, Kalmykia	2.76
Volgograd	2.91
Central Black Earth Region - Voronezh, Lipetsk, Kursk regions.	3.12
St. Petersburg, northwestern part of the Russian Federation	3.23
Vladivostok	3.25
Moscow, central part of the European part	3.28
Tver, Vologda, Kostroma regions.	3.31
Central Volga region – Samara, Saratov, Ulyanovsk	3.33
Nizhny Novgorod	3.36
Tataria	3.45
Bashkiria	3.48
Southern Urals - Chelyabinsk region.	3.64
Permian	3.64
Ekaterinburg	3.65
Omsk region	3.82
Novosibirsk	3.93
Irkutsk region	4.05
Magadan, Kamchatka	4.33
Krasnoyarsk region	4.84
Yakutsk	5.28

Now count T t the required thickness of insulation will not be difficult. For example, it is necessary to calculate the thickness of "penoplex" for insulating a concrete foundation 400 mm thick for Central Black Earth district (Voronezh).

From the table we get R = 3,12.

λb for concrete – 1.69 W/m²×° WITH

λп for penoplex of the selected brand – 0.032 W/m²×° WITH (this parameter must be indicated in the technical documentation of the material)

Substitute into the formula and calculate:

3,12 = 0,4/1,69 + dу/0.032

dу = (3.12 – 0.4/1.69) × 0.032 =0.0912 m ≈ 100 mm

The result is rounded up in relation to the available sizes of insulation boards. In this case, it would be more rational to use two layers of 50 mm each - the panels laid “in a dressing” will completely block the paths of penetration of cold.

The monolithic slab foundation has proven itself well when used in weak and heaving soils. Annual soil freezing in winter period leads to uneven rise and settlement of the slab base, which contributes to the occurrence of mechanical deformations that can cause destruction of the slab itself and the building built on it.

A layer of horizontal insulation can reliably isolate the foundation slab from the zone of frost heaving, contact with soil moisture and prevent freezing.

Advantages of insulating a slab base

Horizontal slab insulation

High-quality insulation of a monolithic foundation slab guarantees the durability of the building and long-term operation without the need for unplanned repair work. Insulation is especially important foundation slab under residential buildings, when it is possible to avoid significant heat loss on the first floors of the house.

Insulation of the foundation slab must be performed for the following reasons:

Providing increased waterproofing of the foundation.
Significant reduction in heat loss.
Saving money on heating a residential building, real heat saving mode.
Preventing the formation of condensation that can destroy the building structures.
Improving living comfort.
Temperature stabilization interior spaces exploited residential building.

Materials for insulating a monolithic slab foundation

The choice of materials for insulating a slab base depends on a number of certain conditions, first of all, on the possibility of using special equipment (polyurethane insulation must be performed using a special polyurethane foam installation for spraying insulation), and the availability of sufficient free funds to purchase insulating materials.

Typically, insulation of foundation structures is carried out using the following materials:

One of the best insulation materials- Styrofoam

Polyurethane foam is a type of foamed plastic that is riddled with pores containing air bubbles. The composition for insulation of polyurethane foam is made directly on construction site, for which two compositions are mixed, which as a result chemical reaction form a strong hardened foam. Different ratios when mixing the starting materials make it possible to obtain insulating compositions with different qualities, suitable for insulating bases made of different materials(including reinforced concrete). Polyurethane foam has unique qualities: it helps retain heat in the room; reduces noise; improves sound insulation; does not decompose under the influence of excessive moisture; Resistant to a number of chemical liquids. The material is highly resistant to ignition (some brands of polyurethane foam are not flammable and belong to the group of low-combustible materials).
Foam plastic - the structure of the material consists of a foamed substance containing pores filled with air. Foam plastic is used to insulate building structures, including foundations, but the surface of such insulation requires additional surface protection due to its low mechanical strength material.
Extruded polystyrene foam - produced in the form of rectangular sheets with a fine-cell structure. The material has unique properties - the ability to withstand high loads to compression without change geometric dimensions and internal structure. Extruded polystyrene foam is widely used for thermal insulation of foundation slabs without additional protection. When using material to insulate foundation slabs, it is very important to provide special openings for the free exit of soil moisture.

Foundation slab insulation technology

When insulating a foundation slab, horizontal and vertical insulation is used, in which a layer of insulation is laid under the slab base or along the side walls of the foundation structure. Expanded polystyrene or polystyrene foam is most often used as an insulating material. Watch the video on how to insulate a foundation slab with polystyrene foam.

The insulation is laid during the installation of the foundation along next technology performing insulation (consider the option of insulating the foundation with polystyrene foam):

To begin with, the location of the foundation for the building is marked on the building site.
The top layer of continental soil must be removed to the depth of laying the foundation slab, the bottom of the excavation must be as smooth as possible.
The prepared area is filled with coarse sand, which must be compacted using vibrating rammers. A small layer of concrete is poured over the sand layer, for which temporary formwork is installed.
After hardening concrete screed, lay out the insulation from polystyrene foam boards, making sure that the mounting grooves coincide as much as possible. Large gaps should not be allowed between the insulation boards.
A layer is laid on top of the laid polystyrene slabs polyethylene film, which is glued together using special tape.
Construction formwork is erected for pouring a slab base, into which a spatial frame made of reinforcement with a diameter of 10 mm is mounted. Concrete is poured from the corner of the slab foundation, evenly leveled and compacted using a vibrator.
The foundation slab gains strength in about 28 days, the formwork can be dismantled two weeks after the structure is poured - by this time the foundation has gained up to 70% strength.
The side walls of the foundation slab are additionally insulated with expanded polystyrene slabs.

Insulated monolithic slab will last long years without structural damage from exposure to unfavorable factors.

One of the most widely known thermal insulation materials, used today, is polystyrene foam. Usage of this material It’s also attractive because you can do all the work around the house yourself, even without help.

The durability of the building depends on how the foundation was built.

Two types of expanded polystyrene are mainly used as thermal insulation: foamed and extruded. They differ not only in production technology, but also in thermal qualities. To insulate the foundation, it is advisable to use extruded. In comparison, foamed polystyrene foam is less effective as a thermal insulation material, less durable, and hygroscopic.

Expanded polystyrene is easy to install, and the surface insulated with it can later be easily plastered and covered with various finishing materials.

Advantages of thermal insulation with polystyrene foam:

fairly cheap insulation - 1 m² usually costs no more than 30-60 rubles (it all depends on the manufacturer, thickness and manufacturing technology);
is produced in a convenient form - mainly 0.5x1 m slabs. The thickness of the slabs can be different - from 1 to 10 cm. Some manufacturers also offer polystyrene foam slabs with special “locks”, which significantly simplify the installation process;
low weight (20-50 kg/m³) also simplifies the process;
durability of the material (up to 50 years!);
good environmental friendliness;
expanded polystyrene is resistant to many chemical compounds;
low moisture absorption: in the first 28 days after installation - no more than 0.6% of the total volume. And subsequently it is completely insignificant.

Tools and materials required for carrying out:

polystyrene foam boards;
hammer drill with drill, drill diameter 10 cm, length at least 15 cm;
roll self-adhesive polymer-based waterproofing;
primer for concrete;
glue for installing polystyrene foam boards to the foundation;
polyurethane foam;
dowels with a disc head for fastening polystyrene foam boards;
reinforcing mesh;
hammer;
sealant;
facing materials and suitable adhesive;
cement-sand mortar;
buckets;
sand, gravel, geotextiles.

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Technology of foundation insulation with polystyrene foam

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Preparation for fastening sheets

The technology for insulating houses and buildings with polystyrene foam is quite simple and understandable. The operating procedure is as follows.

Dig the foundation to its full depth, the bottom of the trench should be at the level of the base, and its width should be large for comfortable work (1-1.5 m), with a small margin.
It is necessary to thoroughly clean the entire surface of the foundation from substandard concrete and soil, and, if possible, bring it to the same level, without strongly protruding parts and deep depressions. It may be necessary to spend several buckets of solution on redecorating. Then the foundation walls should be dried.
Select the correct insulation thickness. As a rule, this is at least 10 cm; the required layer can be more accurately calculated based on climatic conditions and the purpose of the building. Practice shows that it is best to lay extruded polystyrene foam in 2-3 layers of 5 cm slabs.
If on the site where the house is located there are close groundwater, drainage is made at the bottom of the trench: a layer of sand and a geotextile sheet are placed. A layer of gravel and a perforated pipe with a diameter of 10 cm are laid on the geotextile, then the pipe is covered with gravel, wrapped in geotextile and covered with sand on top. This drainage removes moisture well from the foundation walls. The pipes need to be led into a collector well located near the house.
Lay self-adhesive waterproofing, smoothing it over the entire surface with a hard roller. To do this, use as roll materials, and various penetrating mastics. The joints are additionally sealed with sealant.
If it is below the freezing zone of the soil, then the lower part is covered with sand to the freezing level. There is no need to insulate it, waterproofing is enough.

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Fastening polystyrene foam sheets

Polystyrene sheets are attached to the waterproofing. Fastening polystyrene foam boards is best done with adhesive mixtures. Do not use mixtures containing organic solvents, dowels or hot mixtures. This can change the properties of the insulation, damage the waterproofing or accelerate its destruction.
The adhesive mixture should be applied pointwise to the slab. So, to securely fix a 0.5 x 1 m slab, about 5-7 strokes 1 cm thick and 10 cm in diameter are needed. After the glue is applied, the slab must be pressed to the foundation and held under slight pressure for about half a minute, exact time usually indicated on the packaging of the mixture.
It is advisable to take the lower corner of any side of the foundation as the starting point, passing along the entire base in stripes. The second layer of slabs must be applied in a checkerboard pattern to avoid the formation of “cold bridges”.
After installation, all gaps are foamed, filled with sealant or puttied with glue.
When the first layer is glued, you can partially fill the trench with sand, approximately to the middle of the first row of slabs. This will simplify further work. You can add gravel over the top layer. The gravel cushion creates a base for insulating the soil layer.
If there is an L-shaped recess or, in other words, a “lock” along the perimeter of the slab, you can coat it with mastic, cold bitumen or an adhesive mixture. This simple procedure can help to better insulate a building.
Corners are the weak point of the foundation. It is advisable to insulate them with an additional layer of slabs, with an interval of at least a meter from the corner in each direction.
Final processing of polystyrene foam is generally not required; it is enough just to evenly fill the trench with sand and soil, compacting it thoroughly. If sheets of polystyrene foam are displaced in some area, you should excavate problem area, including adjacent sheets, if necessary, replace damaged sheets, secure them again and carefully cover everything with soil.
The basement part of the foundation also needs insulation. The principle of laying the slabs will be the same, but here it is possible to use special disc dowels that will securely fix the slabs. Usually 3-5 umbrellas are enough for one stove. It is recommended to use only plastic fasteners, as they conduct heat much worse. To fasten with a drill, you need to drill holes in the insulation so that its depth extends into the concrete by 5-7 cm. The dowels are driven in with a hammer.

Building a house “to last forever” requires the installation of a proper foundation.

On the one hand, the foundation is the support of the house and neutralizes the harmful effects resulting from heaving of the soil and high groundwater levels. On the other hand, it is a source of heat loss. After all, up to 20% of the heat escapes through the foundation. To avoid heating environment, care should be taken to insulate the foundation.

Traditionally, expanded clay was used for thermal insulation of the foundation, which was poured into concrete at the construction stage. Currently, energy saving requirements have increased. And, therefore, insulation with expanded clay can no longer be considered effective.

Foundation insulation with expanded polystyrene - advantages of the technique

Today, among professionals and owners of private houses, foundation insulation with extruded polystyrene foam has gained the greatest popularity. This material appeared on the market relatively recently, but has already become the undisputed leader among thermal insulation materials used for external insulation.

For reference, we note that extruded polystyrene foam is a new generation of time-tested foam plastic. Which is better, polystyrene foam or polystyrene foam, which is warmer, what is the difference and what is the difference? Tests provide an independent answer.

A comparison of expanded polystyrene and polystyrene foam according to their characteristics is given in the table.

The improvement in the main indicators of expanded polystyrene is obvious.

Another thing worth adding is changing the geometry of the sheet. The tongue-and-groove installation system eliminates the possibility of cold bridges and reduces the cost of purchasing foam for blowing out cracks.

At the same time, the technology of foundation insulation with polystyrene foam has not undergone significant changes. And even beginners can do everything.

Insulating the foundation with polystyrene foam - instructions

When insulating the foundation from the outside with polystyrene foam, you must perform the same steps as when insulating with polystyrene foam.

Dig a trench.

Place a sand cushion under the polystyrene foam, and ideally along the bottom of the entire surface. At the same time, the sand flooring should have a slope of about 5o, so that water does not accumulate at the foot of the insulation. If the soil is too saturated with water, care should be taken to provide foundation drainage. To do this, the bottom of the trench is covered with crushed stone, geotextiles are laid on it, and then a perforated pipe. Water seeping through the soil will enter the pipe, and geotextiles will protect it from clogging.

Dry the surface for several days.

Prepare the foundation. To do this, you need to knock down everything that peels off from it and level it out. Leveling is not a mandatory procedure, but it will reduce the consumption of the adhesive mixture and eliminate the possibility of an air gap between the insulation and the wall. The danger of the layer is that when water gets into it, it will freeze and thaw, thereby causing damage to the foundation material.

Treat the foundation surface with mastic or primer deep penetration. This will improve the adhesion of the surface to the adhesive.

Fastening polystyrene foam to the foundation. Installation of the sheet starts from the corner and proceeds from bottom to top.

How and with what to glue polystyrene foam?

You can glue it using an adhesive solution, which is sold in bags. For example, Knauf, Ceresit, Polimin. Complicit glue mixture applied in separate blots along the perimeter of the sheet or with a notched trowel over its entire area. The advantage of the adhesive solution is that it is relatively cheap, but the disadvantage is that the process is labor-intensive.

More modern way– adhesive foam for polystyrene foam in a container. For example, Ceresit, Tytan Styro 753. Ease of application and minimal consumption compensate for the high cost of the product.

If it is necessary to create a thicker layer of insulation, preference should be given to gluing sheets in two layers. In this case, the seams should not intersect.

Protection of expanded polystyrene with reinforcing polymer or metal mesh. This is done to avoid mechanical damage when backfilling and to protect yourself from rodents.

Cover the mesh with adhesive mixture.

Fill the trench with expanded clay. You can just use soil. But expanded clay will create additional insulation, plus it will provide foundation drainage.

The unit for insulating the foundation with polystyrene foam is shown in the diagram.

The described technology reflects the sequence of work in the event that it is necessary to insulate a strip foundation with polystyrene foam. And other types of insulation differ in some features.

Insulation of various types of foundations with polystyrene foam

1. Insulation of a shallow strip foundation

The main elements of a shallow foundation are shown in the figure.

The peculiarity of the design is that the freezing limit is much lower than the foundation laid. Thus, insulation of a strip foundation with polystyrene foam should be carried out over the foundation area outside the building, and over the floor area inside. This is the only way to achieve high-quality insulation and a significant reduction in heat loss.

To insulate a shallow foundation, you do not need to dig a deep trench. It is enough to “dig out” the foundation. After all, there is no point in digging to the point where the soil freezes. And the width may be smaller, sufficient for installing polystyrene foam boards.

A slab-type foundation is called floating because a house built on it seems to float on it, like on a raft. It is used where eroded, weak or bulk soils predominate.

The insulation of a slab foundation with polystyrene foam is similar in technology to the insulation of a shallow strip foundation. That is, you need to perform vertical insulation of the slab with polystyrene foam. To do this, install several layers of expanded polystyrene with a total thickness of 100-150 mm. along the perimeter of the slab. It should be noted that the depth of the slab rarely exceeds 200 mm. This is due to the fact that as the thickness of the slab increases, the load on the soil increases, thus the house sags. But the main advantage of this type of foundation is reduced to nothing. Next, horizontal insulation is performed. This is due to the fact that the main direction of heat loss is the horizontal surface of the slab, the place where it meets the ground.

The sequence of layers is shown in the diagram.

It is worth noting that high-quality insulation slab foundation with polystyrene foam is possible only at the stage of its construction. Otherwise, you will have to perform insulation from the inside, and this approach to insulation has several disadvantages, which will be discussed below.

Peculiarity pile foundation in the use of piles that go deep into the ground to a depth of more than 1 m. A grillage made of reinforced concrete, wood or metal is placed on the piles. Consequently, insulation of a pile-screw foundation with polystyrene foam is carried out by insulating the grillage. The principle of the device: polystyrene foam is laid starting from the lower level of the grillage to the first row of bricks or timber.

Technology of insulating the foundation with polystyrene foam from the inside

Insulating the foundation from the inside with polystyrene foam is more preferable than insulating with polystyrene foam. This is due to the fact that the sufficient thickness of polystyrene foam to insulate the foundation from the inside is 30 mm. And, therefore, its presence does not take up much useful space.

However, carrying out work inside the basement has a significant drawback: due to the shift in the dew point, the foundation is still exposed to temperature changes, which means that the possibility of its deformation cannot be ruled out.

The procedure for internal insulation of the foundation:

all defects on the surface are eliminated;

the cracks widen to a V-shape. Then they are treated with a primer and sealed with sand-cement mortar;

the entire surface is treated with a primer.

Installation of polystyrene foam is carried out using an adhesive mixture or adhesive foam. The sheet must be fixed with an “umbrella” (if glued to foam, then umbrellas are also attached while it hardens, after which they are removed, this is done in order to prevent deformation of the polystyrene foam boards during the foam swelling process).

the sheet is protected with a metal mesh from rodents;

carry out finishing.

When installing insulation from inside the room, you need to ensure high-quality ventilation to avoid condensation.

Enough simple technology and relatively inexpensive materials will allow you to take the first step towards the implementation of energy-saving technologies.