Spanish slate installed on a metal insulated barrelled roof slopes. The build up over the metal sheets was counter batten and then permeable underlay and 25 mm x 100 mm boarding. The Tiled Roofing Consultancy was asked to inspect the slate installation and workmanship by the Spanish Slate suppliers.
In general, the workmanship is very good, the setting out of the works has been very carefully undertaken, and they have taken time to set their horizontal lines and vertical lines to give a good appearance. The design of the building and using a natural slate has made the construction of the roof surface difficult, but the roofing contractor has taken a difficult design and made it look good.
There was movement and rise in the slate, because of the curvature of the roof slopes, to get the curve in the slate roof, the nail fixing are not being able to be driven into the timber too deeply, this will not affect the fixing of the slates, as the nail fixing has entered the timber boarding by as much as 25 mm.
The Colour variation in Chinese sand face plain tiles and damaged caused by weathering over a 5 to 6-year period. The tiles are delaminating or shaling this is the face pulling away from the tile in layers, other tile is broken across fault lines. When viewing damaged tiles across the section of the tiles, there is a visible colour differences in the clay.
The tiles lose the sand face and delaminate depending what compass position the roof slope is facing. This could be possibly because the tiles get less sunlight and stay damp longer.