The undercloak is a strip of material that goes underneath the verge to hold the mortar in place. Since the verge of the roof will overlap the wall of the house on a pitched roof, something is needed to go under the verge to cover the excess mortar. At ERoofing, we sell undercloaks made of fibrous cement.
Only roofs that are being constructed using “wet” methods (i.e. with the tiles actually mortared in place) will need an undercloak. Roofs that are constructed using totally dry fix methods have no mortar and will therefore not need a mortar.
Autoclaving is a steaming and heating process. Our undercloaks have been autoclaved in order to maximise their moisture resistance. The fibrous cement makeup of the undercloaks means they meet all official, professional standards required for fire safety.