Chapter 4 of 526% of exam

Steep-Slope Roof Projects

The largest section of the C-39 examination at 26%: underlayment by slope, flashing at every interruption, attic ventilation, and the installation rules for shingles, metal, tile, slate and wood. For worked examples, named traps and a full practice exam at CSLB's weights, see the PrepPass C-39 Roofing study guide.

Underlayment, flashing and ventilation

Below 4:12, shingle and tile roofs need two underlayment layers. Drip edge goes under the underlayment at eaves and over it at rakes. Walls get step flashing and a kickout where an eave meets a wall.

Single layer
At 4:12 and steeper, one layer applied shingle fashion and lapped 2 inches; end laps 4 inches offset 6 feet.
2025 CRC Table R905.1.1(2)
Sidewall flashing
At least 4 inches high and 4 inches wide, vertical leg under the siding.
2025 CRC R905.2.8.3
Kickout
Divert water where the eave of a sloped roof meets a vertical sidewall.
2025 CRC R903.2.1

The coverings

Each covering has its own deck, fastener and valley rules. Nails, laps and valley widths are the numbers that separate one system from another.

Shingle nails
12-gage shank, 3/8-inch head, 3/4 inch into the sheathing or through it.
2025 CRC R905.2.5
Tile nails
11-gage, 5/16-inch head.
2025 CRC R905.3.7
Slate
Two fasteners per slate; headlap 4, 3 or 2 inches depending on slope.
2025 CRC R905.6.6

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