Steep-Slope Roofing Installation (Shingle, Tile, Metal, Slate, Wood)
Shingles
Start with a starter course at eaves and rakes so wind cannot lift tab edges. Set exposure from the shingle: a standard three-tab is 12 in. tall with 5 in. exposure, giving 7 in. of headlap. Use four nails per shingle, six in high-wind areas, placed above the top of the keyway - not through it and not so high the next course covers the head - and about 1 to 1 1/4 in. from each end. Nails must be flush, not overdriven or angled. Choose valleys deliberately: open metal, closed-cut, or woven (woven only at adequate slope).
Tile
Fasten each tile with the manufacturer's screws or nails into battens or sheathing; two fasteners per tile is typical. Battens create the drainage plane, and weep holes or birdstops at eaves keep out pests. Tiles crack when walked on, so plan traffic paths.
Metal
Standing-seam panels need clips or fasteners that allow thermal movement; fasten at the high rib for concealed systems and use gasketed screws on the flat for exposed-fastener panels. Never fasten through a pan where water runs.
Slate and wood
Slate uses at least 3 in. headlap and side lap, set on smooth underlayment and hooked or nailed at the head. Wood shingles run about 5 in. exposure and shakes about 10 in. for a 24 in. shake, with a minimum 4:12 slope for shakes.
Traps
High nailing is the most common shingle failure; also watch for missing starter, exposed fasteners in a valley, and tile laid without battens on a low-slope transition.
Worked example
A 6:12 gable: starter course, 5 in. exposure three-tab, four nails per shingle above the keyway, ice barrier at the eave, open valley with 24 in. metal.