We’ve talked about attaching shingle and clay or concrete tiles, now let’s look at metal panels and slate. For metal panels, clips or cleats are preferred over exposed fasteners because they won’t be exposed to weather. Clips and cleats also allow the metal to expand and contract, reducing the risk of buckling. Fasteners should be corrosion resistant and penetrate the sheathing (plywood). Attach slate with flat-head copper-wire slating nails. In high-wind areas, a dab of roof cement or polyurethane sealant should be applied under the exposed part of the slate, which is then installed using four nails per slate. Remember, whatever roof covering you choose to install, always follow the manufacturer’s recommendations as a minimum requirement—more is better when it comes to roofs! Also remember that fasteners should be long enough to penetrate the sheathing (plywood) or penetrate 3/4 –inch into the wood or plank decks.
Credit: Federal Alliance for Safe Homes, Inc. – FLASH