01
The substrate must suit the fastening method
Slate nails or other specified fasteners need adequate embedment in a compatible substrate. Existing boards can sometimes remain useful when they are sound and properly spaced, while damaged, heavily split or unsuitable materials may require repair or replacement.
02
Flat does not mean perfectly smooth
Natural slate has texture and thickness variation, but abrupt deck irregularities can create high points and stressed pieces. Inspect sheathing transitions, patched areas, deteriorated eaves and previous penetrations before layout begins.
03
Plan repair before covering the deck
Deck repairs affect labor, fastening and the finished plane of the roof. A written scope should describe how concealed deterioration will be documented and priced. Covering uncertain substrate with underlayment does not restore its structural or fastening capacity.