How to lay a vapor barrier on the roof
Each new achievement in the field of building technologies allows a person to improve his home. At the same time it becomes more durable and safe, as well as cozy and comfortable. To do this, it is necessary to ensure strict compliance of all installation work with existing building codes. Since the roof is one of the main architectural elements, you should know how to put a vapor barrier on the roof, observing all the rules and the sequence of work.
Special features
In practice, roofing materials prevent the penetration of external moisture. Meanwhile, one should not forget about the destructive properties of steam that forms inside the premises and penetrates into the roofing space. Therefore, it is impossible to get round the issues related to ensuring reliable insulation of the materials of the “roofing pie”. The fact is that any insulation can lose its qualities due to weathering or moisture saturation. It usually penetrates it either from the outside through destruction in the roof, or in the form of steam that forms inside the building.
According to the physical properties of air, saturated with warm vapors, it rises to the ceiling. In the absence of the necessary insulation, the steam through the miniature slots falls into the sub-roofing part. Here in winter there is usually a low temperature. Getting into the layer of cooled insulation, moist air begins to condense and turn into ice. In this case there will be a destruction of the insulating material.
Moreover, with the onset of spring warming, the ice will turn into water, which will begin to drain, penetrating into the layers of interior decoration, destroying their structure.
Note! As for the icy insulation, it will become unusable, having lost its thermal insulation properties. Mineral wool may collapse in one cold season, and foamed polystyrene will last slightly longer, however, after a while it will also become unusable.
In order to prevent such consequences, it is necessary to install a barrier in the form of a vapor-proof material on the inside of the roof. Its main task will be to prevent the penetration of moist air into the insulating layer. Such a barrier will not allow moisture insulation of the insulation, preventing its destruction and the formation of mold. Also, vapor barrier will provide protection from moisture of wooden elements of the roof structure.
Materials
Today, as a vapor barrier material, special films are widely used, which have a complex structure of several layers. They are characterized by their ability to withstand high and low temperatures, as well as unique vapor tightness. Film insulating materials are strong enough and elastic, and their installation does not cause any difficulties. The basis of such barriers is a polyethylene or polypropylene film. It can be reinforced with a special fabric and laminated with reflective foil.
Steam insulation
To provide reliable protection from the internal moisture insulation and structural elements of the roof, you need to know how to properly install the vapor barrier material. The installation of such a barrier is carried out from the inside of the roof after laying the insulating material. There are two options for laying sheets of vapor barrier film - vertical and horizontal. If the horizontal way of laying such a barrier is more suitable for the roof construction, then it should be started from the top.
The canvas of the appropriate size should be stretched along the inner surface of the roof and fixed to the wooden elements of the batten with the help of a furniture stapler. In this case, the smooth side of the film should be turned to the insulation. The next sheet should be laid on the previous one so as to provide an overlap of about 10 cm. After that, the seams should be sealed. To do this, use one-sided and double-sided adhesive tape. With one-sided tape it is necessary to glue the outer overlap, and connect the inner surfaces of the film with double-sided adhesive tape.
Note! Vapor barrier should be laid with a slight tightness, which will eliminate its sagging.
If the barrier is laid along the rafters, and there is no draft filing of insulation, then it is more expedient to overlap the canvas on wooden beams. At all joints of the vapor barrier film it is necessary to ensure the tightness of the connection. If the roof slope is less than 30 degrees, then clamping strips can be fastened at the gluing points.
In places where such a film is adjacent to the manholes, attic windows or other elements passing through the roof, it is necessary to install a vapor barrier apron. This element is usually equipped with a vapor barrier. If ventilation pipes are passed through the roof, the edges of the film should be wrapped around such elements and carefully sealed with adhesive tape. After the vapor barrier has been laid, the bars should be attached on the top with a step of about 0.5 m. This will provide an air gap between the barrier and the inner lining. More detailed information on the installation of vapor barrier and what is included in the roofing pie can be obtained by watching the corresponding video.
Video
A necessary component of the roofing pie is vapor barrier. In this video, you will be told about how to fix the vapor barrier and which side it should be laid: