Step flashing, valleys, hips and ridges · Lesson 2 of 4

Step flashing, valleys, hips and ridges: materials, standards and design constraints

The open-valley width and lining rules in a 2018 IRC reproduction, the metal-thickness conflict NRCA describes, older width recommendations, a federal specification's stricter valley details, splash diverters, step flashing metal, and AFS's fabrication limits.

You will be able to: State the valley widths, linings and metal thicknesses the 2018 IRC reproduction and the named recommendations give, keep code, manufacturer, trade and project-specification values apart, and check an order against what AFS can fabricate.

12 min · 11 slides · 8 questions

All lessons in this module

Slide 1 of 11

Which copy of the code

The IRC values in this module are as reproduced in the City of Pacific, Missouri's copy of 2018 IRC Section R905; check the text of the edition your jurisdiction adopts.

Cities adopt different editions and add amendments, so confirm the edition and local changes your jurisdiction enforces before ordering.

Sources

2018 International Residential Code, Section R905 Requirements for Roof Coverings, R905.2.8.2 Valleys (as reproduced by the City of Pacific, Missouri) - City of Pacific, Missouri (reproducing the International Code Council 2018 IRC)

Glossary

Valley lining: The sheet material laid in a valley under or beneath the roof covering; the 2018 IRC permits metal, roll roofing or self-adhering membrane for different valley types.
Splash diverter (center rib): A raised rib down the middle of valley metal, at least 1 inch high in NRCA's 2008 configuration, that stops fast water from one slope crossing to the opposite side.
Cleat: A small metal clip locked into the folded edge of valley flashing and nailed to the deck, so the sheet is held without nails through the exposed metal (UFGS 07 60 00).
Woven valley: A closed valley whose shingles from both roofs are laid alternately across the valley; NRCA does not recommend it with laminated shingles.