Roofing, Waterproofing and Exterior Finishes
Water is patient. Roofing questions test whether you understand the drainage plane and the layering. The assembly runs: structure, sheathing, underlayment, ice-dam membrane at the eaves, drip edge, then covering. In Massachusetts the ice-dam membrane is standard along the eaves, extending from the edge to at least 3 ft inside the exterior wall line, and in valleys. Underlayment covers the whole deck. Shingles generally need a minimum 2/12 slope with special underlayment; below 4/12 expect a double layer or a membrane system. Fastening counts matter in coastal wind zones - follow the manufacturer's high-wind pattern.
Details that fail first: valleys, sidewalls and step flashing, chimneys, skylights, and the deck ledger transition. Flashing is layered shingle-fashion - upper courses over lower, always shedding onto the surface below. Ventilation keeps the deck cold: about 1/150 of attic floor area in net free vent area (1/300 with balanced intake and exhaust plus a good vapor retarder), split between soffit intake and ridge exhaust. Never let insulation block the intake.
Exterior finishes: install the weather-resistive barrier shingle-fashion, integrate pan flashing at windows and doors, and hold siding clearances - 6 in above grade and at least 1 in off roof surfaces, with the barrier lapped over the flashing. Caulk is maintenance, not waterproofing.
Worked example: 1,500 sq ft of attic floor needs about 10 sq ft of net free vent area at 1/150 - roughly 5 sq ft intake and 5 sq ft exhaust.