Chapter 3 of 517% of exam

Low-Slope Roof Projects

Low-slope roofs are continuous membranes that must drain, be flashed at every edge and penetration, and be attached as tested. CSLB weights this section at 17%. For worked examples, named traps and a full practice exam at CSLB's weights, see the PrepPass C-39 Roofing study guide.

Drainage and flashing

Drains go at low points; where a parapet would trap water, overflow drains or scuppers are required above the primary drains. Walls and curbs get base flashing under counterflashing.

Overflows

Overflow drains match the primary size with the inlet 2 inches above the low point; overflow scuppers are three times the drain size and at least 4 inches high.

2025 CRC R903.4.1

Edge metal

Metal edge systems on built-up, modified bitumen and single-ply roofs are tested to ANSI/SPRI ES-1.

2025 CBC 1504.6

The systems

Built-up roofs are assembled on the roof in plies; modified bitumen arrives as factory sheets; single-ply membranes are fastened, adhered or ballasted; spray foam must be coated.

Spray foam coating

Applied not less than 2 hours nor more than 72 hours after the foam.

2025 CRC R905.13.3

Recoating

A protective coating may go over an existing single-ply, built-up, modified bitumen, metal or spray foam roof without tear-off.

2025 CRC R908.4

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