Roofing Materials and Components
Domain 1 tests how well you can identify roof coverings, name their components, and explain why slope, underlayment, and flashing must work as a system. Exam items often pair a material with a minimum slope or show a roof section with a missing component.
Material and slope rules
- Asphalt shingles: fiberglass or organic mat; 3-tab or architectural. Minimum slope 2:12. From 2:12 up to 4:12, use two underlayment layers (or a manufacturer-approved equivalent); at 4:12 and steeper, one layer is typical.
- Wood shingles: 3:12 minimum. Wood shakes: 4:12 minimum.
- Clay or concrete tile: 2.5:12 minimum; heavy, so fasteners and structural support matter.
- Slate: 4:12 minimum; use corrosion-resistant fasteners.
- Low-slope membranes: built-up, modified bitumen, EPDM, TPO, PVC; typically 1/4:12 (2%) minimum.
- Metal: manufacturer governs. Many standing-seam panels are rated to 1:12 or lower; exposed-fastener panels commonly need 3:12 or steeper.
Components
The system includes the deck, underlayment, drip edge, valley flashing, step flashing, counterflashing, ridge and hip coverings, vents and boots, and gutters and downspouts. Step flashing is required where a roof slope meets a sidewall, and counterflashing covers its top edge. Underlayment is not a substitute for flashing.
Worked example
A roof has 3-tab asphalt shingles at 3:12 with a single layer of No. 15 felt. Is it acceptable? The slope is above the 2:12 minimum, but below 4:12 asphalt shingles require a double underlayment layer. The single layer is the defect.
Traps
Do not confuse minimum slope with best practice. Do not assume ice-and-water shield replaces underlayment everywhere. Do not call drip edge optional. Do not forget that tile and slate need special fasteners.