What goes beneath a roof covering and how to choose the underlay
A layer of underlay is laid beneath the roof covering to take over water that gets under the tiles or metal sheet, as well as condensation. When choosing the underlay, check whether it works with the selected covering, the pitch and the whole roof build-up, not just whether it has good parameters. Continuity of the system at the eaves, chimney and penetrations is also important. The underlay should not be confused with a vapour barrier or insulation. The method of support depends on the product, so verify the intended use of the membrane or rigid underlay and the requirements for vapour flow and ventilation.









