Slate and Tile. These are the two finest roof coverings; if installed properly they can last up to 150 years. The roof deck preparation for slate or tile is very similar to that of a shingle roof. The differences are in the flashing materials.
Instead of using aluminum drip edge the installer will use copper or stainless steel drip edge. Due to the fact that this roof can last a century or more all materials used in the installation must be able to last that long.
Since slate and tile cannot bend the valleys need special treatment. Where two roof planes meet the installer must fabricate a copper “W” valley flashing. The valley flashing will have a “slaters edge” which mean that the edges of the valley are turned up to keep water flowing down the valley center not washing up and into the other side of the roof.
Either copper or stainless steel slating nails should be used to fasten the slate, tile and flashings. Again because this roof will last for a century the nails should be non-corroding and able to last a lifetime. We have seen slate roofs fall apart because the nails holding the slates had rusted away to nothing long before the slate had reached maturity.