Roofing & flashing

Coverings in tile, slate, shingle, standing seam, built-up and single-ply; underlayment, ice-dam protection and cover board; flashing at every interruption — chimneys, curbs, skylights, hatches, balconies; drainage from scupper to gutter to downspout; tapered insulation and crickets; and the loads a roof is checked for, including snow drift and uplift zones.

Slope, first. A low-slope roof is a membrane problem — laps, terminations, tapered falls, drainage rate — and a steep-slope roof is a coursing problem — exposure, headlap, course count. The same building can have both, and a calculator built for one gives a wrong answer for the other rather than an approximate one.

The structure carrying it, which is framing or steel; the rafters and trusses under the deck; and a green roof's growing medium, which appears here only for its saturated load.