Do I have to replace all the flashings when I replace my old slate roof?
February 29, 2024I’m concerned about the underlayment of my slate roof. What should I know about it?
February 29, 2024When using natural slate for historic home roofing, it’s important to use 1-inch wood planks as the deck material. Wood planks are generally the approved historic decking, as this is how slate roofs were historically installed. Planks allow for expansion and contraction (less slate breakage) and allow water to drip off between planks in the event of a broken-slate leak, rather than destroy a large amount of wooden decking. Plywood has less expansion & contraction, so if slates are nailed too tightly the roof may experience broken slates simply due to shifting outdoor temperatures.
However, plywood is a double-edged sword. It will prevent leaks from showing up in the interior for quite some time. But when a slate breaks and water does come in, the plywood decking will already be extensively damaged, and the repair costs will be significant. Additionally, it should be noted that thinner or lower-grade wooden decking will not provide enough support for the weight of the slates.