Waterproofing the roof of the house under the metal, how to

Metal roofs are a practical and attractive solution for a private townhouse, holiday cottage or an apartment building. However, each roofing master will confirm that using this material without organizing proper waterproofing will lead to a decrease in the life of the structure, problems with the rafter frame and the roof covering itself. In order to protect the rafters from the ingress of atmospheric moisture and condensate, waterproofing is installed under the metal tile. In this article we will tell you what waterproofing materials exist, how to choose and apply them correctly.

Functions

Metal tile is a material for roofing on the basis of galvanized steel, covered with paint or polymer with a wavy relief. It has a high thermal conductivity, so because of the temperature difference inside and outside the house is covered with condensate, which significantly reduces the life of the roof. If you do not install the waterproofing film, the following unpleasant consequences for the roof arise:

1. The dampness of the truss frame. If condensate gets onto the rafters, the tree absorbs excess moisture, which leads to the spread of mold, fungus and rotting of the frame elements. Ultimately, this ends in irreversible deformation of the roof structure.
2. Moisture on the insulating material. If the insulation does not protect the waterproofing film or membrane, it eventually dampens, which reduces its effectiveness by half. It should be borne in mind that the properties of the insulating material are not restored even after complete drying.
3. Corrosion of roofing material. If you do not install the waterproofing, condensate accumulates on the inner surface of the roof of the metal tile, from contact with which the metal coating begins to rust. The areas most vulnerable to corrosion are the places of fastening the roofing material to wooden rafters. Rust, gradually eroding metal, significantly reduces the durability and reliability of the roof of the house.

Important! Waterproofing under the metal - mandatory conditions of durability, reliability and quality of the roof of this material. If a waterproofing film or membrane is not used to protect the rafters and insulation, the lifetime of the roof covering is reduced by more than half.

Kinds

The modern construction market offers an extensive range of materials for waterproofing, which differ in price, properties and applications. The choice depends on the type of roofing cake at home and the financial capabilities of the buyer. To protect the rafters, insulation and roof covering from condensation, perform the installation:

• Ruberoid Roofing material of the lining type is the most affordable and inexpensive material for waterproofing under the metal tile. It has high water resistance, mechanical strength and inexpensive price. However, it is used if the roofing pie of the roof of the house belongs to the cold type, since the roofing material does not allow steam to pass through. Experienced craftsmen recommend installing roofing fabric under metal tile only in extreme cases when there are no other options.
• Film. They are considered to be a polymer material to protect against moisture. The construction waterproofing film is made from polyethylene by an extrusion method. It is used as a waterproofing for metal roofing most often due to its relatively low price and excellent performance. Waterproofing film for the roof has a low resistance to ultraviolet, so from contact with the sun, it becomes fragile and brittle.
• Membrane. The membrane is a thin film made of more modern polymers (PVC, HDPE, GDL), which does not allow water to pass through, but provides access to steam, due to the special pore structure. It has a complex, multi-layered structure, has a long service life, resistance to water pressure and ultraviolet. The installation of the membrane under the metal tile is carried out if the roofing cake of the house is of a warm type. Membranes with an anti-condensate effect are considered to be the most effective, since they contain special moisture absorbing material.

Note! If the roof construction is of a warm type, then only vapor-permeable materials can be used as waterproofing. In addition, the installation of waterproofing film is performed so that between it and the roofing material was a ventilation gap. Waterproofing under the metal should not come into contact with either the roofing or insulation.

Mounting technology

Waterproofing material is used to protect the rafters and roof insulation from contact with condensate or atmospheric moisture. Installation of waterproofing is carried out after the assembly of the rafter frame, but before the roof covering is laid. Technology laying waterproofing material is as follows:

1. The film or membrane is cut into strips, the length of which corresponds to the length of the ramp plus 10-15%.
2. Waterproofing under the metal tile is performed with sagging, so that in case of a leakage, the water pressure does not lead to rupture of the film or membrane.
3. The film or membrane is laid in strips perpendicular to the truss feet of the roof with an overlap of 10-15 cm.
4. The waterproofing film or membrane is fixed along the roof rafters with the help of a construction stapler with high-quality, stainless brackets.
5. Roofing material is nailed to the rafters with ordinary or galvanized nails.
6. Joints between the strips can be glued using moisture-resistant sealant, building tape or leave as is.
7. After laying the film or membrane along the rafters, the installation of the laths of the contra-grills, creating a ventilation gap, is performed.

Consider that without properly organized waterproofing, the service life of the roof with metal coating is significantly reduced. This simple, inexpensive measure allows you to save the performance of the roofing and insulation longer, which saves a lot of money usually spent on repairs.

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