Did you say "watertightness”?
The kind of roof underlay to choose depends first and foremost on the roof's requirements and its minimum pitch.
The minimum pitch is the pitch below which the covering has to be waterproof. It is usually specified by the covering manufacturer.
Requirements are more stringent for pitches which are lower than the minimum pitch for the covering material or in the following situations:
• long rafters;
• room in the roof applications;
• buildings designed for specific climates;
• buildings designed under strict planning rules.
Besides these aspects, only the highest possible technical specifications can guarantee the sustainability of the investment and contribute to the building’s correct market value. Therefore, we also recommend installing:
• a vapour barrier or vapour control layer;
• protective strips against “electromagnetic smog”.
Building in accordance with good practice in roof construction is guaranteed to provide you with an impeccable roof for decades...