Covered membranes in roof constructions are generally referred to as ballasted roofs.
These membranes are protected against the direct effects of the climate and temperature changes, rips, punctures and other mechanical damage.
The ballast material may be concrete slabs, pebbles or soil. Soil can form the substrate for vegetation.
The membrane is laid as a loose covering so does not require any mechanical attachment on the roof surface, which means the vapour control layer is not punctured.
Extra ballast material on the corners and edges may be necessary in harsh weather environments. In such cases, pebbles should be replaced with concrete slabs and in extreme cases, poured concrete is recommended. It is important that the load-bearing construction is engineered for the purpose of bearing the weight of the ballast.
The recommended product for pebble ballasted roofs is Protan G. The membrane is root resistant, stabilised to tolerate UV radiation, heat and microbes. For roof constructions that are extra vulnerable to stress, Protan GG, which is thicker than Protan G, is recommended.