For the foundation, heaving soils are especially dangerous. During winter freezing, this structure can increase in size up to 35 centimeters. The heaving force is so great that it can easily deform the strip foundation and lead to the destruction of the building structure. In regions with unstable soils, a monolithic reinforced concrete base is sometimes used for the entire house. Insulation of the foundation slab allows you to reduce freezing and heaving of the soil under it.
Criteria for choosing a material for warming the base
Insulation applied to a monolithic slab is part of a responsible structure, therefore there is a certain list of requirements for this product:
- High thermal insulation properties must be ensured with a relatively small thickness. It is important that the dew point in winter is not in the middle of reinforced concrete and does not perform destructive work, but is shifted into an insulator.
- The density of the heat barrier must be sufficient to withstand the load not only of a multi-ton screed, but of the entire building as a whole. At the same time, the homogeneity of the structure plays an important role here - shrinkage should occur evenly.
- Not suitable for thermal insulation under the base is a hygroscopic structure that freely passes moisture through itself. In this case, the concrete will become damp, fungal formations will begin to develop in it.
The world practice of building buildings using Swedish technology has shown that it is best to insulate a monolith from below with polymer structures - industrially manufactured foam polystyrene sheets or polyurethane foam. For similar tasks, a special type of this product was developed, called penoplex.
Why is it necessary to insulate the slab foundation
There are several aspects of the positive effect of warming the base of the house on its design and operation. The first and most important thing is to protect the load-bearing parts of the building from mechanical damage. It consists in the fact that under the area of the insulated box the freezing of the soil does not occur so intensively, therefore its deformation is minimal, since the soil is more dried and the building area itself does not allow frost to penetrate deeply or spread under the entire plane.
The second question concerns the freezing and soaking of the foundation. If concrete freezes, this leads to disastrous consequences: it begins to crack, burst and flake off under the action of the forces of expansion of water, because it is still present in its thickness. When wet, a negative corrosive effect is added, which has moisture on the frame from the reinforcement, and the formation of mold and fungi, which feel great in a humid environment. The thermal insulator eliminates this by shifting the dew point outside the supporting structure and creating an additional waterproofing barrier.
Another important point concerns the heat loss of the building. Any surface of the building conducts heat in one way or another, including the floor. The better the insulation of the monolithic slab, outer walls, roof is organized, the less energy is required to heat the space to the desired temperature.The concrete floor of a one-story building without additional measures for its insulation will take on 15% of the total heat loss.
Extruded polystyrene is a structure that has some elasticity, therefore, it will act as a buffer in case of possible swelling of the earth under it.
Pros and cons of thermal insulation
The use of polyurethane foam as an insulator provides the homeowner with the following benefits:
- low thermal conductivity of the layer, the thickness of which may not exceed 5 cm;
- exceptional adhesion properties to any type of surface - there is no need to use adhesives, since the polymer itself adheres well at the initial moment;
- a continuous layer of insulation, since there is a continuous spraying of polymer - the possibility of the appearance of cold bridges is excluded;
- there is no need for additional waterproofing.
One of the important disadvantages of this method of warming the foundation slab is the need to use specialized equipment that must be delivered to the site. That's right, only a qualified specialist can evenly spray the polymer onto the surface. In a liquid state, the material is hazardous to health, therefore, the requirements for the use of personal protective equipment during the operation are increasing.
When installing warm polystyrene foam soles, you can get the following benefits:
- Laying the polymer is not particularly difficult and the involvement of special equipment. This speeds up the process of forming an insulator many times over.
- The sheets are lightweight, easy to deliver to the site, unload and carry.
- The insulation under the foundation slab is ideally uniform over the entire plane.
- The material itself has a high density and is absolutely non-hygroscopic.
- In terms of thermal insulation properties, it is one of the best polymers.
Among the shortcomings, one can single out the need for an additional waterproofing device under polystyrene foam from eroding groundwater, since they can still penetrate into the cracks between the joints. The heat barrier must be glued to the waterproofing base and to each other in order to avoid sheet creep when pouring concrete or moving the soil. The polymer is classified as an expensive coating.
Work technology
When installing a shallow Swedish slab, its base is insulated with a heat barrier using the following technology:
- A non-woven geotextile is laid on the surface of a leveled pit, poured and rammed with a layer of sand, so that when the ground moves, the laid rectangles do not diverge, they do not vomit and cold bridges do not form.
- A waterproofing layer is made of a special polymer membrane.
- Sheets of expanded polystyrene 10 cm thick are laid in the first layer under the entire area of the foundation. Be sure to glue the joints with mounting glue-foam.
- Around the perimeter of the resulting layer, they arrange formwork from the same insulation to the height of the future screed. It is reinforced with external timber formwork.
- Having retreated from the formwork by 40-50 cm along the entire perimeter, drive the second layer of the insulator from expanded polystyrene. It is important that the joints of the first and second layers do not intersect in any way. Here you also need to glue each sheet with the previous and underlying.
The last step is laying the waterproofing base on top of the heat insulator. Its main role is to prevent the ingress of moisture from the concrete into the gaps between the joints, which can significantly worsen the thermal insulation properties of the equipped heat insulator.
You can use insulation with special locks at the end of each sheet.Milled grooves greatly simplify installation, and also contribute to better joining and smaller clearances.
When laying polymer sheets on bituminous waterproofers, various solvents may be present on the latter, which can corrode the material. Therefore, after installing such waterproofing, you need to wait some time for them to evaporate.
Famous brands of thermal insulation products
URSA is a well-known trade mark in Europe. The manufacturer specializes in the production of polystyrene, expanded polystyrene and extrusion products. The products are of high quality in terms of homogeneity and thermal insulation characteristics.
TechnoNikol is an industrial giant of insulation in the domestic market. The plant produces expanded polystyrene and a wide range of other insulation products. The production facilities have their own laboratories, where new types of insulators are being developed.
Elite Plast is a manufacturer of Ukrainian origin. Produces decent polymer heaters that meet all environmental international standards.
