When choosing a foundation structure for a future building, each developer is guided primarily by its cost, reliability and durability. The ideal foundation that combines all of these qualities is the monolithic foundation slabs, which can be constructed on various types of soil. But concrete has a high thermal conductivity, therefore, developers need to take care of the insulation of the supporting structures even in the process of performing construction work.
Warming methods
Insulation of the slab foundation must be carried out in the part that is located in the zone of soil freezing. The developer should lay insulation under the foundation slab, as well as under the outer blind area, which is necessarily created around the building. And also the basement of the building and the upper part of the foundation wall should be covered with a special material. Timely warming of the monolithic foundation slab will protect the soil adjacent to the building and its walls from freezing, thereby preventing frost heaving of the soil and minimizing heat loss at home.
When planning the insulation of a slab foundation, the developer must take into account the type of supporting structure:
- Tape (in-depth). Various materials are used for insulation, which are laid on the vertical surfaces of the supporting structure, above the ground surface.
- Shallow strip foundation. For insulation, tile materials are used, which are laid on the sole and vertical surfaces of the supporting structure.
- Pile. Only the lateral surfaces of piles deepened into the soil are insulated.
- Monolithic tiled construction. The base slab is insulated not only from below, but also on the sides.
Benefits of timely insulation
The insulated slab foundation has a lot of advantages that every developer needs to know about:
- Developers will be able to save concrete mortar, which is used in large volumes when pouring slab foundation structures.
- The insulated foundation allows you to minimize heat loss. This has a positive effect on indoor climate and utility bills, which skyrocket during the winter months.
- The timing of construction work is accelerating.
- The useful life of the supporting structure is maximized, since the harmful effects of moisture and low temperatures cease to be exerted on it.
- The insulated base plate prevents condensation from forming on the interior walls of the premises.
- The service life of waterproofing materials that are used in the construction of slab foundation structures is maximized.
What materials can be used to insulate a slab foundation?
Currently, a huge range of materials is presented on the domestic construction market that developers can use when carrying out insulation measures:
- Polyurethane foam. This material is made of foamed plastic, which has a porous structure filled with air bubbles. This insulating mixture is created directly at the construction site and applied to the foundation structures using special equipment. The components that have entered into a chemical reaction, already on concrete surfaces, form a durable foam that hardens almost instantly. This material helps to minimize heat loss, prevents extraneous noise from the street from entering the premises, does not undergo putrefactive changes in constant contact with a humid environment, and is highly resistant to ignition.
- Styrofoam. This material has been used for decades in the construction industry as insulation. Its main disadvantage is its low mechanical strength, which is why it needs additional cladding.
- Extruded expanded polystyrene. This material has a fine-mesh structure and is supplied to the construction market in the form of rectangular sheets. It possesses excellent technical properties, is able to withstand high loads, without changing either the internal structure or the geometric shape. In recent years, developers, when insulating slab foundation structures, have been using extruded polystyrene foam, since it does not need additional protection and can perform the functions assigned to it for decades.
Why do experts recommend using Penoplex for insulation?
In recent years, many developers prefer to carry out insulation of the foundation with penoplex. The choice of this material is due to the fact that it is highly resistant to moisture, and also has the lowest thermal conductivity. Due to the fact that the slab supporting structure will have to be in contact with a humid environment for many decades, the insulation of the foundation with penoplex will protect the building from its harmful effects.
Extruded polystyrene foam is ideal for thermal insulation of monolithic foundation structures, as it can withstand compressive loads. Polyurethane foam boards and polystyrene foam are cellular materials with a closed structure, so that moisture is not able to penetrate into their cavities. That is why they are used when carrying out insulation measures.
Insulation rules for slab foundation structures
Before insulating the slab foundation, the developer must learn about all the features and nuances, as well as the most effective technologies. If the foundation is insulated with foam from the outside, this will protect not only the slabs, but also the walls from freezing. In the event that the expanded polystyrene panels are laid on the inner sides of the walls, the developer will be able to significantly improve the indoor microclimate, but at the same time, the slabs and walls of the building will not be protected from freezing. It follows from this that external insulation of the foundation with foam-plastic will be an ideal option for any construction projects.
External insulation of the foundation with expanded polystyrene or expanded polystyrene is possible only at the initial stages of construction. If the developers miss this moment, then in the future they will only be able to carry out internal insulation of the foundation with penoplex or polyurethane foam.
Carrying out insulation measures during construction
The procedure for warming the foundation with expanded polystyrene must be carried out at the initial stage of construction work. Developers should strictly follow the technology:
- First of all, a pit is dug, in which a monolithic slab of concrete will be created. Its depth should be 1 meter. Depressions are made at the bottom, into which drainage pipes are laid, the functions of which are to divert surface water into specially created wells. Such measures will protect not only the foundation, but also the walls of the building from getting wet.
- After laying the drainage pipes, the bottom of the trench is leveled and a special material is rolled out on its surface - geotextile. It will prevent the germination of rhizomes of trees and shrubs that can disrupt the integrity of the supporting structure.
- A layer of sand and gravel is laid on top of the geotextile. Thus, at the bottom of the pit, a sand-crushed stone cushion is created (approximately 30-40 cm thick).
- Utilities are being laid, for example, water and sewer pipes. After laying, the surface is sprinkled with sand and leveled.
- Formwork is being constructed along the perimeter of the prepared pit. For these purposes, it is customary to use boards or sheets of moisture-resistant plywood. Outside, the formwork must be supported with jibs or stops so that the wooden structure can withstand the load that the concrete solution will exert on it.
- A small amount of concrete is poured into the bottom of the pit, which will create the first foundation layer. After it has solidified, the developer must proceed with waterproofing and thermal insulation measures.
- Due to the fact that a monolithic concrete slab will constantly be in the ground and in contact with a humid environment, the developer must perform its high-quality waterproofing. For these purposes, in the construction industry, it is customary to use roll material or coating. The concrete base must be thoroughly cleaned of debris and then dedusted. To increase its adhesive properties, it is recommended to carry out treatment with diluted kerosene or solvent. After that, roofing material is rolled out on the prepared concrete base, the canvases of which should overlap. All joints should be treated with mastic, after which experts recommend laying another layer of waterproofing. If the developer decides to use liquid insulation, then he needs to apply it several times to the surface of the concrete base and, after complete drying, continue construction work.
- At the next stage, the slab is insulated. For these purposes, most developers use sheets of extruded polystyrene foam (15 cm thick). Such material is laid, as a rule, in two layers. Make sure that the top sheets overlap the joints of the bottom panels.
- Reinforcement of the foundation structure is carried out, due to which its strength and bearing characteristics will increase.
- The concrete solution is poured in several stages. After pouring the first batch, the developer must use a deep vibrator to remove air and eliminate the resulting voids. After that, the remaining solution is poured out.
After the concrete has set, the developer can continue construction work. In order to maximally protect the building from the harmful effects of harmful environments, he must also carry out internal insulation of the foundation. For this, sheets of extruded polystyrene foam should be used, which are glued to the floor and walls of the premises and are subsequently finished.
Warming a slab of any foundation is one of the most important things when building a house. It is best to do this in the warm season, and you cannot do it in rainy weather. Insulation of a monolithic foundation slab is especially important for cold regions where the soil freezes at great depths. When freezing, heaving soils can increase in volume, which leads to deformations of the entire building. Therefore, it is so important to take care of the external insulation of the foundation. This will help reduce the heat loss of the entire future building and preserve its durability.
What does foundation insulation give?
The better all the work is done, the longer and more reliable the building will stand. And most importantly, the house will keep warm even in severe frosts. Do not forget that most of the cold penetrates into the house through the foundation. And if the building has a basement (billiard room, gym), then you should take care of the internal insulation. This is especially important if the basement is not heated. But the most important thing is the external insulation of any residential building.
The main reasons why insulation is necessary:
- Improving waterproofing properties.
- Reduced heat loss.
- Reducing heating costs at home.
- Preventing the formation of condensation on the walls.
- Stabilization of the internal temperature of the building.
All this will help not only to always feel comfortable in your home, but also increase its life span.
What kind of insulation to use for the foundation?
The most important part of the work when insulating a slab of a fresh foundation is required is the selection of a suitable material. It should not deform under soil pressure and absorb moisture. These are the most important parameters of any thermal insulation. Soft materials such as rock wool will not work. The best options are polyurethane foam and extruded polystyrene foam. Both of them have excellent thermal insulation characteristics and a fairly low cost, which is also important in construction.
Polyurethane foam
This material is versatile, since it combines not only thermal insulation, but also sound and waterproofing properties. To use this type of insulation, you need special equipment, as it must be sprayed. For full-fledged insulation, 50 mm of insulation thickness, laid in several layers, is enough. All joints after insulation must be sealed.
This material has a number of positive properties:
- low heat permeability;
- good adhesion properties;
- reliability;
- durability.
And most importantly, when using polyurethane foam, there is no need to use additional means for steam, water and waterproofing. He has only one drawback - the need to use special equipment. Therefore, this method of insulation will require either considerable investment or the help of experienced specialists with the appropriate equipment.
Extruded polystyrene foam
This type of insulation is significantly lower than polyurethane foam, it is easier to install. Such material consists of plates that do not pass or absorb moisture. It retains its thermal insulation properties for a long time even in cold regions. Advantages of extruded polystyrene foam:
- high strength;
- long service life;
- reliable thermal insulation properties.
It is most often used when it is necessary to insulate the foundation, since it can be mounted independently, without the use of additional equipment.
Extruded polystyrene foam with grooves
This is a new type of insulation. Milling grooves on the surface of expanded polystyrene plates are excellent for warming the foundation. It is used in conjunction with geotextile fabric, as an attached drainage. Its main properties:
- good thermal insulation;
- protective layer of waterproofing;
- waterproofness.
Insulation of the foundation with expanded polystyrene
To insulate a monolithic slab, you can use both expanded polystyrene and polyurethane foam. But the first option is preferable. Expanded polystyrene is the most effective and less expensive, and most importantly, it is easy to install. Before proceeding with its installation, it is recommended to lay the waterproofing, then you can start laying the extruded polystyrene foam plates.
The most effective method of warming a foundation using this material is to use it in areas of soil freezing. Insulation is mounted to the depth of freezing. This is quite enough. When insulating, special attention should be paid to the corners: in such places, the used polystyrene foam should be thicker than in other areas. It is imperative to insulate the soil around the perimeter of the building. To do this, it is necessary to place a heater under the construction of the blind area.
All rows of extruded polystyrene foam boards should be stacked end-to-end, from bottom to top. Large joints are filled with polyurethane foam. This will provide high tightness, thermal insulation and waterproofing properties. Plates are planted on polymer glue or mastic, and then pressed with a layer of soil. When insulating, it is important to take into account that all plates are of the same width, you cannot use already used material, this can break the tightness. This method is suitable for all types of foundations, including monolithic ones.
Insulation of the foundation with polyurethane foam
When insulation of a monolithic foundation is done using polyurethane foam, it is important that there are no breaks and gaps. The insulation must form a completely closed loop. This will allow you to achieve maximum thermal insulation properties. It is sprayed onto the foundation using special equipment. The material then hardens within 20 seconds. In general, the whole process of installing insulation is quite simple and quick. The application of polyurethane foam is done in several layers, after each of them has dried. One layer should be about 15 mm thick.
At the end of all work, it is done with soil. Equipment for the installation of such insulation can be purchased in specialized stores or rented. But it is easier and faster to use the services of professionals.
Insulation of a monolithic slab updated: February 26, 2018 by: zoomfund
Insulation of a monolithic slab, as a technology, has already proven itself positively in Europe and in the countries of the post-Soviet space. Shallow UWB is in demand in those geographic zones where a harsh climate prevails. The monolithic frame is poured on different types of soil bases, including heaving ones, with a weak tolerated load. At the same time, the main danger for a monolithic slab is negative temperatures, when the earth base rises, deforming the slab base. This leads to mechanical defects of the structure, unsuitability and accident rate. To avoid this, the horizontal insulation of the foundation slab will help. We will consider below whether it is necessary to insulate the foundation, and how to do it.
The advantages of insulation
Insulating the foundation slab ensures durability and long-term operation without the need for intermediate repairs. For owners of apartments on the ground floor, houses, cottages, this problem often arises, a project for warming the basement with expanded polystyrene is needed. To avoid heat loss, the base plate is insulated. In what cases is the basement insulation performed:
- provide a level of waterproofing of the foundation;
- reduce the rate of thermal insulation losses;
- reduce waste on heating a living space;
- prevent excessive formation of condensation on the surface of the structural walls of the building. After all, condensation leads to the destruction of buildings, oddly enough it sounds;
- make living conditions comfortable in an insulated building;
- stabilization of the temperature regime inside the premises, residential building.
Classification of materials for insulation
Very often, homeowners have many difficulties in choosing one or another material, basement insulation turns into a problem. People get confused about the names and properties, they mix up the thermal insulation characteristics, which only complicates the process for both parties when buying. In order to provide methodological assistance, we will consider the insulation of the slab foundation, materials and characteristics.
The material is selected depending on the characteristics of thermal insulation, climatic conditions of the region. The second point: the use of special equipment for spraying a chemical reagent - polyurethane on a shallow surface. The third factor is the availability of funds, since insulation is not a cheap procedure.
- Polyurethane foam: Penoplex slabs for the foundation are a popular material among the rest of the line of insulation. Manufactured from oxygen-foamed plastic. The chemical mixture itself is made directly on site during construction. There, the procedure of mixing two reagents for insulation takes place. Foam sheets or polyurethane foam have excellent qualities for preserving thermal energy in a building, reducing noise levels, and increasing sound insulation. Not susceptible to the negative effects of moisture, resistant to inflammation;
- foam - insulation for foundation slabs in the base contains hygroscopic foam. Extruded foam is also used to insulate facades and other parts of structures. Tiled foam has a low strength factor and instability to mechanical damage on a shallow surface;
- EPPS extruded polystyrene foam - insulation for foundation slabs: takes an honorable first place in functionality and application. Manufactured in a standard rectangular shape. The sheets are composed of a honeycomb structure. The material is able to withstand loads, is not subject to changes, is resistant to temperature extremes. It is used for thermal insulation of the foundation with expanded polystyrene, moreover, additional protection is not required. The presence of holes for the drainage of condensate and moisture.
Insulation of the slab
For the purpose of warming the foundations, granular polystyrene foam (polystyrene) is used in shallow concrete. Also called warm concrete. The preparation of insulation for the slab foundation is possible both at the factory and directly at the construction site. It depends on the customer and the possibility of access of construction equipment to the site for insulation of the foundation with expanded polystyrene.
It is recommended to use PPP with a density of at least 1200D in a slab foundation. Project: for one cube of concrete mix: 0.3 tons of M400 cement, one cube of granulated polystyrene foam, 0.8 tons of sand, saponified resin as needed.
When placing concrete, the shrinkage rate is taken into account, one millimeter per meter. The thermal conductivity of the mixture will not be great. You need extruded polystyrene foam under the plate from the bottom, but not from the top. The foam must have a layer thickness of no more than 10.0 cm.
What to be guided by when choosing a material for insulation
Since not every product may be suitable for use as insulation, the choice should be guided by the following factors:
- indicator of water resistance: the less the foam absorbs water, the longer it retains its useful properties, and vice versa. During the period of negative temperatures, water crystallizes, expands, changes the molecular structure of the element, violates the integrity;
- strength factor: data are important when constructing a foundation on mobile soil masses, rocks. The edges are capable of causing deformation, damage to the foundation;
- resistance to various environments: each type of soil has its own characteristics, composition, both chemical and biological. Because of this, the level and concentration of salt increases, which leads to the premature destruction of the shallow insulation.
The technology (project) of warming the foundation with foam-plastic provides for laying also from the inside. But the material must be fire resistant. When ignited, a minimum amount of toxic substances should be released. Often these vapors serve to excite asthma sufferers.
The shelf life of the panel should not be lower than the period of the finishing material. Otherwise, you will be forced to dismantle the layer ahead of time.
It is better to insulate the foundation with extruded polystyrene foam. This will protect the structure and keep it warm.
Classic project of insulated foundation slab
- Compressed soil surface;
- geotextile interlayer;
- a layer of sand cushion with a depth of no more than 20.0 cm;
- crushed stone pillow layer no more than 20.0 cm deep;
- 10 cm level of a shallow concrete slab;
- ball of waterproofing;
- a layer of insulation with a thickness of at least 5.0 cm;
- 35 cm monolithic slab;
- concrete grillage 50 x 50 cm;
- metal rods of the third class with a diameter of at least 1.2 cm;
- a row of aerated concrete 37.5 cm wide;
- from the front, a row of facing bricks covering aerated concrete;
- ventilation gap 3.0 centimeters;
- waterproofing, insulation, lining of the grillage on a polystyrene base.
Characteristics of expanded polystyrene
The average service life of expanded polystyrene is 30 years. Provided service is provided, the house will last forever. The following factors negatively affect the timing:
- the front surface on which the material will be glued is not leveled, there are air gaps, plugs;
- PPS plates are not made according to technology, do not have proper protection against the negative effects of ultraviolet radiation;
- before installation, the material was lying in an open area and exposed to weather conditions.
Insulation materials, regardless of the name and marking, have an increased level of inflammation. They belong to the third and fourth grade. Currently, most manufacturers add a chemical reagent such as antipyrine to the composition. The main feature is damping on ignition. The "C" grade is added to the standard marking.
- Abundant emission of smoke during combustion, during which cyanides and hydrogen bromide are released into the atmosphere;
- minimum water absorption rate;
- increased bending strength;
- insulating function - the minimum heat transfer rate;
- interaction with petroleum products.
Neutral interaction with bitumen, cement, gypsum, lime, asphalt.
Insulation of the foundation is a simple project. It is enough to have a construction site with an entrance for equipment. Otherwise, you need to prepare the concrete mixture yourself, taking into account the proportions and ratios. Maybe the initial stage will seem costly, but these costs will pay off in full during the first year. Is it worth insulating the base plate with expanded polystyrene sheets, definitely yes.
In practice, it has been determined that approximately ten percent of the heat loss of a house occurs due to the fact that there is no effective insulation of the foundation. Therefore, this issue should be given special attention.
Why insulate the foundation? This question may arise for many. In fact, it is one of the most important points in the construction of any building. The thing is that the underground and surface parts of buildings are exposed to constant high-level physical stress from the effects of temperature changes, the influence of subsoil waters and other corrosive factors.
Photo of the insulated base of the building
All this has a negative effect and can lead to the appearance of cracks and the gradual destruction of the base and basements. To prevent this impact, insulation and waterproofing of the base is carried out during construction works at the zero cycle.
Note! Various materials can be used for this. In addition to solid external insulation, such as extruded polystyrene foam, a waterproofing layer is applied.
This provides protection against subsoil water and thus prevents pressure on the foundation of the building. This ensures the absence of "cold bridges", which significantly increases the efficiency and durability of the base.
Materials for thermal insulation of the foundation
Insulation of the foundation is a mandatory measure to protect the base of the building from adverse external influences.
When choosing a heater, it is important to proceed from indicators such as:
- high mechanical strength;
- waterproofness;
- low vapor absorption.
How to insulate the base of the house? There are several suitable materials on the market today for. We will consider each of these materials in more detail.
Extruded polystyrene foam
Extruded polystyrene foam has recently been used as the optimal insulation for the foundation.
It has the following properties:
- resistance to biological influences;
- complete safety for human health;
- high moisture resistance;
- frost resistance.
Note! Extruded polystyrene foam is produced by molding expanded polystyrene into molds under high pressure. In this case, the structure of the bubbles is closed, and the bubbles themselves have a size from 0.2 to 0.5 mm. This determines its waterproofing qualities and low vapor permeability. The density of the material is usually over 30kg / m3.
Water absorption during prolonged wetting is practically zero. Basement insulation - expanded polystyrene has standard dimensions and high mechanical strength. This determines its use as an insulating material for floors, walls, roofs and concrete foundations of buildings.
Thermal insulation of the base with extruded polystyrene foam
Installation instructions for extruded polystyrene foam:
- Insulation of foundations with extruded polystyrene foam should be carried out at a height of at least 50 cm above ground level.
- It is advisable to carry out installation after applying a waterproofing layer. To do this, you can use a water-based bitumen solution.
- If waterproof cement-based mortars are used as waterproofing, the material can be glued to the base with a special adhesive for thermal insulation.
- After the slab foundation has been insulated, the thermal insulation is covered with a protective geotextile fabric.
- Then the drainage pipes are laid, and the base from the outside is covered with rubble or other material.
Note! This material is used as a monolithic insulation and as a strip foundation insulation.
Polyurethane foam
Another effective material used as foundation insulation is polyurethane foam. It has the following properties:
- retains its qualities in soil saturated with moisture;
- thanks to spraying, it adheres tightly to the foundation, has no seams and "cold bridges";
- some types of this material have waterproofing properties;
- resistant to chemicals.
Polyurethane foam is not only a thermal insulation material. It also protects against moisture and absorbs noise. Installation of this material is carried out by spraying on the foundation in layers, using special equipment.
Thus, it is possible to insulate the foundation slab, as well as other types of bases.
Note! A layer of polyurethane foam, the density of which is 36 kg / m3, only 5 cm is enough to insulate a monolithic plate.The thickness of the expanded polystyrene should be at least 12 cm.
Another advantage of the polyurethane foam coating is its solidity. With uniform spraying, no seams or gaps are formed, that is, no cold bridges are formed.
Plain Styrofoam
Do I need to insulate the base? Of course, yes, because due to the possible formation of numerous cold bridges when connecting the foundation with the walls, optimal thermal insulation is required.
Some homeowners, when deciding how to insulate the foundation for the winter, traditionally opt for ordinary foam. This material can be used only if there is no danger of flooding.
People are attracted by the price of this option. But in the matter of thermal insulation of the foundation, it is better not to save. It is wiser to choose a more practical, moisture resistant, homogeneous, strong material that will last for many years.
Regular foam is more suitable for internal insulation, for example, as insulation of a loggia or a glazed balcony.
Insulation of various types of foundations
When constructing buildings, various base options can be used, for example:
- columnar foundation;
- tape;
- on piles;
- monolithic.
The technology and materials for thermal insulation of the foundation may differ depending on the type of foundation. The main task is to choose the most effective option for your conditions.
- The columnar foundation is insulated to the depth of freezing of the soil layer together with a previously prepared pick-up. To do this, around the perimeter of the finished trench, foam plates are attached, which is considered the best option for isolating a columnar foundation.
- It is also advisable to carry out waterproofing, for better protection from moisture in the space under the floor. Installation of this base can be done by hand. For this, the foam plates are attached to the outside of the foundation.
You can mount it with special glue. When installing, the sheets must be tightly fitted to each other so that there are no gaps. At the final stage, the trench is covered with expanded clay or soil to ground level, and a blind area is made.
You can visually familiarize yourself with the insulation of a columnar foundation by watching the video in this article.
- Many people have a question, how to insulate the elements of the pile foundation? Thermal insulation of a pile-screw base consists of several steps. First, the grillage is waterproofed.
For this, roofing material is most often used. It is placed between the top of the grillage and the bottom of the walls. As well as between the grillage and the end of the pile. The exposed parts of the piles and grillage are also waterproofed.
Thermal insulation material, in this case, mainly extruded polystyrene foam is used, it is laid, starting from the bottom of the grillage, and ending with the first floor of the house.
Some experts believe that the best way of thermal insulation is to insulate the floor on a pile foundation, which is carried out inside the house.
In addition to thermal insulation of the foundation, walls and other things, do not forget about the insulation of plastic windows. After all, it is known that about 25% of the heat goes through windows and doors.
Conclusion
In conclusion, I would like to say, if you are faced with the question of whether it is necessary to insulate the base of the house, the answer will be unequivocal - it is necessary.
The slab type of foundation has a different name - floating, since the slab can be erected on bulk, eroded, weak soils and with a high rise of groundwater. acts as a raft on which the house "floats".
This type of foundation is ideal for small buildings. Its functions are similar to those of other types of foundations: thanks to the slabs (their rigidity) located under the entire area of the building being erected, it is a deterrent to the movement of soil and protects the house from destruction.
Slab foundation refers to one of the types of shallow strip foundation. Its main difference is that it uses a solid slab made of reinforced concrete and rigidly reinforced over the entire bearing surface of the slab.
Shallow foundation slab:
- makes it possible to reduce concrete consumption by 30%;
- labor costs for installation up to 40%;
- the cost of the foundation as a whole is up to 50%;
- applicable for almost all types of soil;
- short construction time.
Back to the table of contents
Slab foundation construction technology
To build a slab foundation, they begin with the fact that only a fertile soil layer is removed in a previously prepared and marked area. At the bottom of the dug pit, a sand cushion is laid with the addition of sand, which is well tamped. A layer of waterproofing material is placed on the pillow, then a layer of insulation. After that, the slab foundation is carefully reinforced. For slabs, reinforcement d = 12 mm is applicable. And the last stage is the construction of the formwork and pouring concrete into it.
Back to the table of contents
Foundation slab: insulation
It will help to reduce heat loss through the slab, and, accordingly, prevent soil subsidence under the slab by warming the slab. For this, a 10- or 15-centimeter layer of heat-insulating material is laid. The slab foundation will be protected from freezing by insulating it between the slab and the ground.
The issue should be given special attention to residents of regions with harsh climatic conditions and deep freezing soil.
The zone makes up about 80% of the entire territory of Russia. When freezing, heaving soils increase in volume and rise, which causes the destruction of the foundation structure.
Back to the table of contents
Benefits of base plate thermal insulation
- relieves (or significantly reduces) the influence of frost heaving forces on the foundation;
- reduces heat loss through the foundation and reduces heating costs;
- creates the necessary conditions for the establishment of a constant required temperature inside the room;
- protects against the appearance of condensation on surfaces inside the building;
- serves as protection for waterproofing from mechanical damage;
- prolongs the life of the waterproofing material.
Back to the table of contents
How can you insulate a slab foundation?
Thermal insulation materials for absorbing moisture should not, as well as shrink under soil pressure. High rates of water absorption and compressibility when backfilled with soil make mineral wool not quite a suitable material as a heater. Only foam glass and expanded polystyrene meet these requirements. The first option will cost several times more.
Can regular foam be used? Can. Only it must be placed on a waterproof layer (waterproofing), which serves as protection for structural elements from soil moisture. Otherwise, within a few years from the moment of installation, the foam can be expected to turn into a shapeless pile of balls. The accumulated moisture in the insulation during freezing will increase the foam in volume, while destroying its structure.
Extruded polystyrene foam is considered the most optimal heat-insulating material for conditions of increased loads and humidity.
Due to the characteristics of the feedstock and the closed cellular structure that prevents water penetration into it, expanded polystyrene plates have excellent technical characteristics, a long service life, which makes it possible to use it in the insulation of foundation slabs.
Extruded polystyrene foam has water absorption close to zero (no more than 0.5% by volume for 672 hours and for the entire next period of operation). This prevents soil moisture from accumulating in the thickness of the insulation, expanding in volume under the influence of temperature changes and destroying the structure of the material during the entire period of service.
To insulate the slab foundation for vertical thermal insulation of civil and industrial facilities, polystyrene is used with a compressive strength of at least 250 kPa (linear deformation - 10%). For private low-rise construction, slabs with a strength of at least 200 kPa can be used, since in this case the depth of the foundation will be less, and the pressure of underground and groundwater on the insulation is lower. For structures that require increased strength indicators (loaded floors), plates with a compressive strength of 500 kPa must be selected.
Advantages of expanded polystyrene:
- stability of thermal insulation properties during the entire service life;
- validity period - 40 years;
- compressive strength indicator - 20-50 t / m²;
- is not a nutrient medium for rodents.
Back to the table of contents
How to insulate a slab foundation with expanded polystyrene?
Insulating the vertical part of the foundation, polystyrene foam is installed at the depth of soil freezing, which is determined individually for each region. If you install the insulation deeper, the effectiveness of this will sharply decrease.
The thickness of the thermal insulation layer in the corners should be increased by one and a half times with an indent in both directions of at least 1.5 m.
Insulating outside is a more rational way, since this way the level of heat loss will be lower.
Thermal insulation boards are placed on the waterproofing layer. If you plan to use knitted reinforcement for reinforcing a monolithic reinforced concrete foundation slab or load-bearing floor, then for expanded polystyrene slabs it is necessary to arrange protection from liquid concrete components. To do this, use a polyethylene film (150-200 microns), which is laid in one layer. If the reinforcement work involves the use of welding, then a screed of low-grade concrete or cement mortar must be made over the film to protect it. Polyethylene is laid with an overlap of 100-150 mm on double-sided tape.
Back to the table of contents
External insulation of the foundation
To reduce the depth of freezing of the walls and, to keep the border of freezing in the thickness of non-porous soil - a sand-gravel cushion and backfilling will help warming the soil around the entire perimeter of the house under the blind area structure.
When laying polystyrene foam, it is important to take into account the given slope of the blind area - about 2% from the house. The width of the extruded polystyrene foam insulation along the perimeter should be no less than the depth of seasonal soil freezing.
The horizontal thickness of the insulation must be no less than the vertical thickness of the foundation insulation.
Back to the table of contents
Internal insulation of the foundation
If it is not possible from the outside, thermal insulation is allowed from the inside of the walls of the foundation.
Laying of thermal insulation from the side of the walls of the room is carried out either by gluing extruded polystyrene foam to the surface of the walls with solvent-free compositions (it is possible on a cement basis), or by mechanically fixing the insulation plates with a subsequent finishing device.
Back to the table of contents
How to fix expanded polystyrene sheets to the foundation?
The insulation is placed on the leveled surface of the walls outside the insulated structure with waterproofing already made on it.
It is not allowed to mechanically fix the polystyrene foam plates from the outside when insulating the foundation plates. Since in this case, the integrity of the continuous waterproofing coating can be violated.
To a surface on which there is already a waterproofing layer, polystyrene foam plates can be attached in two ways:
- glue;
- by melting bitumen on waterproofing.
The adhesive is applied at 5-6 points, then the boards are firmly pressed to the surface.
The gluing of the slabs must be carried out from below, laying the slabs in a horizontal row. The second and next rows of slabs are attached end-to-end to the previous row already glued. Reinstallation of the glued boards is not allowed, as well as changing the position of the boards after a few minutes after gluing.
The insulation boards must be of the same thickness and touch each other and the base tightly. In this case, you need to arrange them by shifting the joints (in a checkerboard pattern). If the distance between the joints between the boards is more than 5 mm, they must be filled with polyurethane foam. It is better to use the plate with a stepped edge. The slab is laid close to the adjacent one so that their adjacent parts of the edges overlap each other. With this installation, cold bridges do not appear. Arranging a two-layer (or from more layers) thermal insulation, the seams between the plates are spaced apart.