The vapor barrier for a flat roof guarantees the protection of insulating materials, which are very sensitive to humidity and therefore to water vapor. Two types of vapor barrier are particularly used: bituminous felt and aluminum foil.
Which vapor barrier to choose for a terrace?
Before choosing the vapor barrier that will equip your terrace roof, you must consider the humidity level (hygrometry) and the type of heating that is used on the floor below the terrace. These considerations will allow you to choose either a bituminous felt vapor barrier or aluminum felt. It can be made of different materials: PVC, polyester, kraft polyethylene, etc. The coefficient Sd (in meters) will allow you to assess the resistance of the vapor barrier. The higher it is, the less it will let water vapor through. The prices are of course a function of this coefficient, of the material and of the dimensions of the membrane.
Installation of the vapor barrier: precautions and continuity
The vapor barrier must then be installed carefully to avoid being ripped. The slightest cut would allow water to escape, greatly reducing the efficiency of the system. Only the first layer of insulation should be covered by the screen. The entire surface of the terrace must be equipped, and continuously. Use adhesive tapes provided for this use for seals and repairs in case the membrane has been torn.