The main purpose of the roof is to protect the room from a number of climatic factors: precipitation, temperature, wind exposure and humidity. Therefore, the design of a modern roof consists of several layers, which ensure its durability, reliability and high thermal performance. Waterproofing the roof of a house under a metal tile is one of the stages of protecting a residential building from moisture penetration into the insulation and supporting the indoor microclimate.
Elements of a pitched roof
Building a house involves creating an object with a stable, comfortable temperature and relative humidity inside it. And the modern construction of housing is also based on the preservation of expensive heat in it. The temperature difference inside and outside the room leads to the appearance of various thermophysical processes in the roof layers. This leads to the use of different building materials in the structural elements of the roof, each bearing its own function.
The main layers:
- The bearing system of the roof is the rafters.
- Vapor barrier.
- Thermal insulation.
- Lower and upper crates.
- Counter grill.
- Waterproofing.
- Roofing.
If you neglect at least one of the items listed, then you can suffer from the leakage of the roof, the appearance of a good smell and, as a result, the destruction of the rafter system.
Vapor barrier and waterproofing
These two layers in the upper structure of the building have different functions. The vapor barrier is placed under the insulation, thereby protecting the main material from the vapors coming from inside the house. But the waterproofing is mounted on top of the insulation, that is, closer to the roofing material. This is if these measures are carried out during the new construction. If the upper structure of the building is not undergoing reconstruction, and the attic or attic is insulated, then the roof is waterproofed from the inside of the house and the moisture-proof functional layer is placed under the counter-grill.
That is, the main purpose of these layers is to insulate the condensate from the top of the structure, and to remove water vapor from the inside of the living space from the bottom.
Material selection
The choice of material acting as moisture protection depends on the type of roof, pitched or flat, and on the main coating. For example, waterproofing the roof of a house under a metal tile without the use of insulation, the so-called roofs with cold attics, allows the use of roofing material and glassine. They are good protection against moisture, wind and dust, but the operational life is short-lived. Their main advantage is low cost.
The waterproofing of the roof of the house under a soft roof involves the use of materials based on cardboard or fiberglass, with different impregnations, for example: roofing, roofing felt, glass.
On flat upper structures of the building or with a slight slope (up to 3%), mastic sealants can be used as waterproofing: bitumen, polymer or bitumen-polymer.
Materials for waterproofing the roof of a house under a metal tile in warm attics should be more resistant to condensation. Since the temperature difference is significant, because under the roof there is a heated room, respectively, and the likelihood of moisture is higher. Modern construction in this case involves the use of materials based on polypropylene.
What is waterproofing the roof of a house under a metal tile? Types of films
The simplest material in terms of performance and cheap is considered a classic plastic film. As a rule, it is mounted for pitched roofs under slate, corrugated board, metal and ceramic tiles. And used in conjunction with mineral wool and polystyrene foam. Can be reinforced or not. Unreinforced polyethylene in its properties for transverse and longitudinal rupture is three times inferior to the hardened analog.
A more wear-resistant and reliable material with high vapor permeability among film waterproofing is considered a diffusion membrane. This insulating material is similar in properties to human skin: it also does not let moisture in, but it perfectly removes it from the inside.
Anti-condensation film is the best waterproofing of the roof of the house. Metal materials, such as tiles or profiled sheets, have high thermal conductivity, resulting in condensation. Films with moisture protection are endowed with the ability to absorb it. Therefore, when installing it, a requirement is made: the presence of a lower gap between the insulation and the waterproofing, so that moisture from the material can erode.
Diffusion membranes
The advantage of these building materials in high rates of vapor permeability. They are used for the conversion of a cold attic without replacing the roof structure, as well as for roofs in the attic. According to the ability of membranes to pass steam, they are divided into:
- Pseudo-diffusion membranes with a vapor permeability of 20–300 g / m2 per day. Such an indicator is insufficient to neglect the ventilation gap.
- Diffusion films (400–1000 g / m2), ventilation space can be omitted.
- Superdiffusion membranes are capable of passing over 1000 grams of steam through 1 m 2 per day. Therefore, manufacturers of such a waterproofing film allow the absence of a gap between the insulation and the superdiffusion membrane.
Important! Since the membrane is a perforated film and passes through itself the steam coming from the room, its use is prohibited in metal roofs. Therefore, waterproofing the roof of a house under a metal tile eliminates the use of membrane films. The material can be used for composite metal tiles, cement-sand, ceramic tiles.
Ventilation gaps
The waterproofing of the roof of the house under the metal tile provides for small gaps between the layers in the insulation pie. This is necessary to circulate air and remove condensation. The upper ventilation gap is located between the main roofing material and the protective waterproofing film. It does not allow moisture to get on the insulation, which is the lower layer behind the film. As well as waterproofing material passes through itself the vapor coming from the side of the insulation. Therefore, it is important that the material protecting from moisture has a good vapor permeability.
A lower ventilation gap is created between the insulation and the film. This allows the multilayer structure to be ventilated and keep the wooden and heat-insulating elements of the roof within the limits for normal use.
Expert opinions on the arrangement of the lower gap between the membrane and the heater diverge. Some say that the ventilation layer is not needed, since the membrane type of waterproofing is highly vapor permeable and there is no condensation, and second experts still strongly recommend leaving a lower gap between the listed structural elements. In the case of metal tiles and the use of anti-condensation films, both gaps are a mandatory requirement.
In which cases there are no gaps
When waterproofing a flat roof of a house on a concrete base, liquid glass, rubber spraying or rolled, bituminous materials are used. In this case, the layers of the upper structure of the building are laid without gaps.
If rolled materials are used, a primer is applied as a waterproofing before their fusion. In addition, it is possible to protect the roof from moisture with the help of painting materials, which cover the main waterproofing layer.
For mastic roofs, a waterproof carpet is formed using fiberglass impregnated with hot bitumen or rubber-bitumen mastic.
Factors determining the choice of waterproofing material
- The purpose of the upper structure of the building. Cold attic or heated room under the roof.
- Structural type of roof: complex configuration, pitched or flat.
- Roofing material: profiled sheet, metal tile, slate, mastic.
- The presence of insulation.
- Cost and installation methods.
Installation of a waterproofing carpet under a metal tile
When the rafter elements are prepared, the cornice board is mounted, all the structural parts of the roofing system are impregnated with an antiseptic, the stage of laying the waterproofing layer begins. The film rolls in horizontal overlapping stripes, starting from the cornice, gradually rising to the roofing ridge. The material is attached to the rafters with a staple gun. And the joints of the strips are glued with tape. The waterproofing layer is mounted with a sag of 2 cm in order to avoid a break in the temperature difference.
On top of the waterproofing carpet, bars of 50x50 mm are packed along the rafters. The next step is the installation of the battens from boards 32x100 mm with a step equal to the step of the wave of the metal tile. Then the main roofing material is mounted with screws.
Conclusion
The roof is a system whose longevity depends on the reliability of the constituent elements and the correct installation. Therefore, in order to avoid leaks, it is necessary to professionally approach the issue of choosing roofing materials and the nuances of their installation.
The waterproofing of the roof of the house under the corrugated board, the metal tile is a polypropylene sheet with a pile on the inside, due to which the moisture coming from the room is absorbed. Therefore, additional dampness in the elements of the roof does not occur, which prevents corrosion of the metal.
Popular roofing anti-condensation films on the Russian market: Yutakon, Stroizol, Ranka.