Roofing, Thermal and Moisture Protection
This domain tests roofing systems, underlayment, flashing, insulation, vapor retarders, waterproofing, and drainage. Questions often ask where a barrier belongs, which flashing detail is required, and how slope affects material selection.
Core rules and concepts
- Roof slope determines system selection. Low-slope roofs typically use built-up, modified bitumen, or single-ply membranes; steep-slope roofs use shingles, tiles, or metal. Underlayment requirements vary with slope and material.
- Ice-dam protection is commonly required at eaves in cold climates, including Nebraska, and must extend upward from the eave according to code. Drip edge, valley flashing, step flashing, and counterflashing keep water out at edges and penetrations.
- Wall assemblies need a weather-resistive barrier and a drainage plane. Vapor retarders belong on the warm side of the insulation in cold climates, but placement depends on assembly design and code.
- Attic ventilation and insulation must work together to prevent condensation. Waterproofing differs from dampproofing and is used where hydrostatic pressure exists.
Worked example
A plan shows a 30-square roof at 4:12 slope. The slope factor is about 1.054. Roof area = 30 x 1.054 = 31.6 squares. The estimator must not order 30 squares, because sloped area exceeds plan area. Underlayment and ice-barrier quantities should use the sloped area.
Traps that cost marks
Placing a vapor retarder on the wrong side; omitting ice-dam membrane at eaves; confusing waterproofing with dampproofing; using plan area for sloped roof takeoff; and skipping counterflashing at walls.
Key point: moisture control depends on slope, flashing, drainage, and vapor placement.