Where a shingle roof runs up beside a vertical sidewall, the correct flashing is:
- one continuous L-shaped strip under all courses
- a bead of sealant along the wall joint
- roll roofing turned up the wall 2 in.
- step flashing, one piece with each course
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D. step flashing, one piece with each course
Individual step flashings are interleaved with every shingle course so each piece laps the one below and water is stepped back out onto the shingles. A single continuous strip lets water that gets behind it run all the way down under the shingles.
Reference: IRC 2021 R905.2.8.3
Under the IRC, step flashing for asphalt shingles at a sidewall must be at least:
- 4 in. high and 4 in. wide
- 2 in. high and 4 in. wide
- 3 in. high and 3 in. wide
- 6 in. high and 2 in. wide
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A. 4 in. high and 4 in. wide
The code minimum is 4 in. up the wall and 4 in. onto the roof. Smaller legs let wind-driven water get over the top or around the side of the flashing.
Reference: IRC 2021 R905.2.8.3
Under the IRC, a cricket is required on the upslope side of a chimney when the chimney dimension parallel to the ridge is more than:
- 18 in.
- 24 in.
- 30 in.
- 48 in.
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C. 30 in.
Chimneys or penetrations wider than 30 in., measured perpendicular to the slope, need a cricket to split the flow. Narrower chimneys can be handled with a back pan flashing.
Reference: IRC 2021 R903.2.2 and R1003.20