While there are only 3 layers necessary to proper installation of a slate roof, the cost of the material make it a more expensive investment initially, but will last a much longer time than a shingle roof.
1. Starter Course – This is the first layer in a proper installation or repair of a slate roof. Unlike shingles roofs which use plywood as the base layer, slate roofs use board deck which needs to be at least 3/4 inch thick, and slater’s felt. The felt will slowly disintegrate over time allowing the roof to breathe through the slates.
2. Slates – slate tiles need to overlap at least 3 inches on each side in order to perform best. Larger slates are recommended because it will require less numbers of them, less labor and fewer fasteners.