Roof insulation with expanded polystyrene

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Roof insulation with expanded polystyrene
Roof insulation with expanded polystyrene

Options for insulating a pitched and flat roof with a polystyrene-based coating, the pros and cons of a protective shell from this product, the choice of components for forming an insulating layer. Insulation of the roof with expanded polystyrene is the thermal insulation of the roof with a high-quality product in order to prevent heat leaks and create a serviceable room or open area. Sheathing is created from different materials, which are selected depending on the purpose of the roof and its structure. The article provides basic information about the rules for the formation of a protective coating.

Features of work on thermal insulation of the roof with expanded polystyrene

Extruded polystyrene foam
Extruded polystyrene foam

Any roof is originally designed to shelter from precipitation and keep warm in the house. Problems are quickly solved if it is covered with extruded polystyrene foam - a sheet material, the basis of which is formed by evenly spaced very small closed cells. It is made from polystyrene and copolymers of styrene, carbon dioxide or natural gas.

To quickly distinguish it from outwardly similar products, it is labeled with the letters XPS. There is also a full name in which all the main characteristics of the material are encrypted - dimensions, density, color, etc. Example of Styrofoam product designation: XPS-EN13164-Tl-C5 (10 / y) 250DS (TH) -TR100. For other manufacturers, the full designation of the goods may be different.

The sheets are very dense and capable of withstanding large mechanical loads, therefore they are most often used for insulating flat roofs. Expanded polystyrene can be stacked in two ways:

  • Classic, with a top waterproofing layer. The roof in this case is unexploited.
  • Inverted, where polystyrene foam is placed on top of the waterproof shell and reliably protects it from damage. This option allows you to effectively use the floor area of the upper floors. The material not only insulates the building, but also becomes the basis for parking spaces, green areas, cafes, etc.

When repairing a roof using expanded polystyrene, the "plus roof" scheme is used. In this case, a waterproof coating is created on top of the existing thermal insulation, and then expanded polystyrene, expanded clay and another waterproofing layer are laid.

Also, the material can be used to insulate the attic roof, but in most cases, a cheaper insulator is used for this purpose.

Advantages and disadvantages of roof insulation with expanded polystyrene

Insulation of the roof of the house with expanded polystyrene
Insulation of the roof of the house with expanded polystyrene

The insulating roof covering made of expanded polystyrene and other components has many advantages.

Positive qualities can be formulated as follows:

  1. The material is lightweight and is often used on older buildings that cannot be loaded with heavy weight.
  2. The manufacturers have provided everything possible to shorten the installation time. Plates are made with great precision, there are mills at the edges for quick joining.
  3. Products are capable of functioning in high humidity conditions without loss of thermal insulation qualities. They are moisture-proof, do not deform after getting wet.
  4. The cladding has a very valuable property - it does not change its dimensions with temperature fluctuations, which is typical for roofs.
  5. The material does not have such an unpleasant property as shrinkage.
  6. Plates can be easily processed with any sharp tool.
  7. A flat roof covered with expanded polystyrene can be used as a terrace, flower bed or other high-load area.

Even such a modern product has disadvantages:

  1. It takes a lot of time to insulate the roof with extruded polystyrene foam in a residential building due to the presence of the lathing. Each element has to be finalized individually in size between the rafters. However, if the work is carried out at the initial stage of the construction of the building, the rafters are mounted with a step equal to the width of the expanded polystyrene panel, which excludes its revision.
  2. The insulator burns well, so a house with such a roof does not comply with state fire regulations.
  3. Expanded polystyrene is afraid of sunlight and ultraviolet radiation. After installation, it should be covered with special materials. In addition, you need to make sure that the item is properly stored before purchasing.

Roof insulation technology with expanded polystyrene

Insulation methods for flat and attic roofs are different. In the first case, the sheets are laid on top, and in the second - from inside the room. To insulate a flat roof with expanded polystyrene, dense products are needed to withstand the weight of a person and other loads. Samples that are less rigid and less expensive are suitable for a pitched roof. The last word is for the owner, who determines the purpose of the attic, the temperature on the upper floor, the structure and composition of the layer. Manufacturers produce several modifications of polystyrene foam, so it is not difficult to find samples for each specific case. For work, you will also need waterproofing materials and glue.

Materials and tools for roof insulation

Extruded polystyrene foam for roof insulation
Extruded polystyrene foam for roof insulation

The product on the roof functions in harsh conditions, so a good result can only be expected from high quality products. In the store, you will not find out the actual characteristics of the proposed building material, but everyone can determine the fake.

To do this, follow the simple procedures:

  • Start with an external examination. The goods must be packed in plastic wrap. Tears in the containment are not allowed.
  • Study etiquette. It should contain all information about the product - dimensions, main characteristics, purpose, manufacturer.
  • If you are unfamiliar with the manufacturer, search the Internet for reviews of its products.
  • Ask the seller for a broken sheet and inspect the place of the break. In a quality product, the granules are so small that they are barely visible to the naked eye. The particles are evenly distributed in the sheet, no compaction is observed. Large granules indicate the presence of pores through which water penetrates into the insulation and deteriorates the heat-insulating properties.
  • Press down with your finger where the leaf breaks. If you hear a crack, this is a fake. The sound appears during the destruction of the thin walls of the material. After installation, the product will crack quickly.
  • A quality product smells slightly of alcohol. There should be no other odors.
  • The main characteristic of the panel is density, it depends on the applicability of the product. It is recommended to lay material with a density of more than 25 kg / m on a flat floor.3, however, please note that a coating over 35 kg is designed for a very heavy weight. On the roof, you can mount sheets with a density of up to 25 kg / m3, they are cheaper than rigid products.
  • The optimal thickness of the slabs can be determined according to SNiPs. The size is mainly influenced by the climate of the area and the purpose of the room. Roughly, it can be assumed that for areas with mild winters, the sheathing thickness is within 100 mm, for severe winters - at least 150 mm.

Adhesives are used to fix the material to concrete floor slabs in the case of a classic flat roof insulation scheme. Less commonly, it is glued from the inside of the attic. All funds are divided into two types - universal and special. The second includes solutions that are used only with expanded polystyrene. All formulations must meet the same requirements:

  1. For a flat roof, glue is used for outdoor use, in the attic for indoor use.
  2. The substance with which the samples are glued in the attic should not emit harmful elements that harm the human body. The degree of toxicity is indicated in the certificate of conformity supplied with the product and kept by the seller.
  3. The glue reliably holds polystyrene foam at any ambient temperature.
  4. The product contains no gasoline, kerosene, ethers and other agents that dissolve the insulation.
  5. The mixtures must be stored indoors, otherwise they will absorb large amounts of water and lose their quality.
  6. Choose a product that does not harden 2-3 hours after application to the surface. You will have time to adjust the position of the panels during installation work.
  7. The glue must not have expired.
  8. Always buy the product with a margin, it will be used up on uneven surfaces.
  9. The most convenient means for fixing the panels is foam glue, which is sold in cylinders and is ready to use immediately after purchase. But you need to remember that the period of its hardening is only 12 minutes.
  10. Universal products include a polymer mixture for indoor and outdoor use ANSERGLOB BCX 30 or a product Ecomix, which is suitable only for indoor use.
  11. The special products include the products of the CEREZIT company - ST 83, ST 85, ST 190.

When insulating an inverted roof, the waterproofing is located at the very bottom of the sheathing. For this purpose, the following products are used:

  • Films and special membranes - they are available in various modifications; for reliable protection, you should choose materials designed for slopes with a low slope.
  • Bituminous mastic - used to cover surfaces of complex shapes or hard-to-reach places. They are very often used in combination with roll insulators. Also popular are acrylic mastics, rubber, silicone.
  • Roll products (roofing felt, roofing felt, brizol, fiberglass roll waterproofing) are the most popular solution for protecting a flat surface.
  • For reinforced concrete slabs, the best option is liquid rubber. It is applied using mechanical devices and reliably protects the overlap for a long time.

During installation, sheets of non-standard shapes and sizes are always needed. Wizards solve the problem in a variety of ways. Most often, the following tools are used to cut off excess parts:

  1. Sharp knives regardless of purpose - kitchen, stationery, wallpaper, etc. To facilitate the process, heat the instrument until it becomes red. Another plus of this method is the absence of waste.
  2. Jigsaws are recommended for cutting thick specimens. The work is done very quickly without physical exertion, but the ends of the panels cannot be cut exactly.
  3. To obtain a workpiece with a complex shape, use a heated nichrome wire. There will be no complaints about the ends of the panels, besides, crumbs and other debris do not remain.

Standard thermal insulation of a flat roof with expanded polystyrene

Insulation of a flat roof with expanded polystyrene
Insulation of a flat roof with expanded polystyrene

The option is distinguished by the presence of waterproofing on top of the sheathing. This is usually how concrete floor slabs are covered. You can walk on the roof after rework, but you must use it carefully so as not to damage the protective shell.

The sequence of work is as follows:

  • Remove debris and build-up from concrete slabs.
  • Shoot down the protruding elements. Fill gaps and gaps with cement mortar or putty.
  • Prime the substrate with a deep penetration agent.
  • Fill the surface with a cement-sand screed, providing a slope of 2-5 degrees. Place a ruler on the surface and make sure there are no gaps underneath. Align the screed if necessary.
  • Wait for the layer to dry completely. You can check the base of the surface with a 1x1 m plastic film. Place it on the screed and glue it with tape. If a wet spot appears under it in a day, the surface is not yet ready for further procedures. With this method of insulation, waterproofing of the base is not carried out, a protective layer will be applied on top of the expanded polystyrene. But if you wish, you can treat the screed with coating waterproofing, for example, bituminous mastic.
  • Bond the sheets to the substrate using an adhesive that is compatible with the waterproof layer. Do not smear the sides of the sheets. After laying, press the material firmly against the adjacent panels. Lay the sheets in such a way that there is no solid joining line. Place the cut blocks last.
  • Cover the sheets with geotextiles - a very dense roll material that protects polystyrene foam from ultraviolet radiation and distributes the load over a large area from mechanical stress from above. Geotextiles with the classical method of insulation can be omitted.
  • Fill the base with a concrete screed.
  • Seal the sheathing with roofing felt.

Insulation of an inverted roof

Installation of expanded polystyrene on the roof
Installation of expanded polystyrene on the roof

When insulating an inverted roof, the heat-insulating layer is formed in such a way as to reliably protect the waterproofing from damage and reduce the load on the expanded polystyrene.

According to the standard technology of roof insulation with expanded polystyrene, the work is carried out as follows:

  1. Prepare the surface as in the previous case.
  2. Thoroughly waterproof the slab using the method of your choice.
  3. Glue the sheets with a product that is compatible with the undercoat. The rules for laying slabs do not differ from the standard installation of panels.
  4. Several different layers are placed on top of the expanded polystyrene, the composition of which depends on the plans for the use of the roof.

The roof covering of an unexploited roof has the following composition:

  • Reinforced concrete floor slab;
  • Slope-forming layer of cement-sand mortar;
  • Roll waterproofing;
  • Extruded polystyrene foam sheets;
  • A protective geotextile layer that protects the main component from ultraviolet radiation;
  • A layer of gravel with a thickness of at least 50 mm from fractions of 20-40 mm, with strong winds in a given area, it can be thicker.

An insulated roof with walkways is formed as follows:

  1. Reinforced concrete floor slab;
  2. Slope-forming layer of cement-sand mortar;
  3. Roll waterproofing;
  4. Extruded polystyrene foam sheets;
  5. Geotextile;
  6. A layer of gravel with a thickness of at least 50 mm from fractions of 10-20 mm, mixed with sand;
  7. Sidewalk slabs;

If you plan to create a green area on the roof, the cover should be as follows:

  • Slope-forming layer of cement-sand mortar;
  • Roll waterproofing;
  • Extruded polystyrene foam sheets;
  • Geotextile;
  • Drainage cover made of gravel with a thickness of at least 50 mm from fractions of 10-20 mm;
  • Anti-root layer of soil substrate;
  • Vegetable layer.

Thermal insulation of the roof space

Insulation of the roof with expanded polystyrene from the attic side
Insulation of the roof with expanded polystyrene from the attic side

When insulating the under-roof space, polystyrene foam can be laid in two ways - by placing it between the rafters or over the beams (from below or from above, at the request of the owner). The second option is preferable, because in this case there are no cold bridges, but it can be done only at the initial stage of building a house. Consider the most popular way to insulate a pitched roof with expanded polystyrene, in which it is attached inside the frame. Perform some test steps before starting:

  1. Make sure that the drainage system is installed correctly, taking into account the angle of inclination of the slope.
  2. In the insulating cake, it is possible to leave a gap of 40-50 mm between the outer membrane and the roof cladding.
  3. The height of the upper floor allows you to close the roof beams from the inside with a waterproofing film.
  4. It will be easier to insulate the ceiling if the lathing under the roof cladding has not yet been mounted.

The sequence of operations when installing polystyrene foam is as follows:

  • Place a waterproofing film on the beams of the attic from the street side and fix with a stapler to the rafters. The film should hang freely, without tension. Lay the cloth with an overlap of 15-20 cm on adjacent cuts and on the walls. Seal the joints with reinforced tape.
  • The membrane will trap moisture that can get inside the attic from the outside and cause lumber to rot. It is removed by an air stream passing through the left gap. For proper functioning of ventilation in the area of the roof ridge and near the ceiling, special holes are made. If necessary, the roof space can be blown through forcibly using fans. At the same time, humid air from the inside of the attic can freely escape to the outside through the pores of the membrane.
  • If the roof is covered with a soft roof, for example, bituminous tiles, it is not necessary to lay waterproofing under the entire area, only corners and cornices are protected, because such material does not allow moisture to pass through.
  • If the covering is made of metal sheets, it is recommended to include a sound-insulating layer in the composition of the "cake" so that the rain cannot be heard.
  • If desired, lay the membrane directly under the cladding, it is possible without a gap.
  • Install the battens on the rafters and cover the roof with cladding material.
  • Check if there is a ventilation gap.
  • When working in the attic of an operated house, the panel can be laid from the inside, placing it at a distance of 40-50 mm to the roof cladding.
  • Cut out blanks from expanded polystyrene sheets, with dimensions that allow them to fit tightly between the rafters.
  • Fill the space between the joists with insulator. Fill all gaps with scraps of material.
  • Check for gaps of 10-15 mm between the insulation and the membrane. It is left so that the pores of the canvas do not overlap.
  • Fix the insulation in this position. The way the panels are attached to the roof depends on its design. It is allowed to use disc dowels, special corners or thin strips.
  • Cover the roof from the inside with a vapor barrier film that will protect the rafters and battens from damp fumes from warm living quarters. Lay the cloth with an overlap of 15-20 cm on adjacent pieces and on the walls. Seal the joints securely with reinforced adhesive tape. Do not stretch the film, there should be a sagging of 10 mm in the middle. It is not necessary to cover the roof from the inside with hard material after insulation.
  • For vapor barrier from inside the room, experts recommend using a three-layer membrane with a reinforced frame or models with foil.

How to insulate the roof with expanded polystyrene - watch the video:

Regardless of the design of the roof, the composition of the coating based on expanded polystyrene necessarily includes waterproofing and a material that protects the main element from damage. Before work, be sure to understand the rules for forming a warming cake. Only by arranging the components in a certain sequence, you can achieve the desired result.

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