The Self-Drying Concept for Flat Roofs

Moisture in flat roof systems with an insulation layer has been a long-standing issue for the roof industry. It is now realised, that it is unrealistic and too costly to try to completely keep moisture from entering a roof assembly during its service life. The approach, therefore, should be to keep moisture levels low within a roof assembly by providing a path for moisture to periodically escape.

A design strategy that assumes roof assemblies may get wet and permits them to dry, presents a more forgiving and perhaps less costly alternative.Moisture may enter a roof assembly in a number of different ways. From the interior by diffusion and convection. During construction from moist materials or rain.

Later on, rain water may enter through leaks in the roofing.From laboratory experiment, computer calculations and practical experience it is concluded, that the Self-Drying Roof concept works for both cold- and warm deck roof systems in climate zones where a vapor retarder is needed, if the traditional water proof vapor retarder is substituted by a water permeable vapor retarder.