Penetrations, curbs, skylights and equipment · Lesson 1 of 4

Penetrations, curbs, skylights and equipment: principles and terminology

The vocabulary of roof penetrations and equipment curbs, the code duty to flash roof openings, when a cricket is required, and why a skylight is a fall hazard before it is a flashing job.

You will be able to: Define curb, base flashing, counterflashing, cap flashing, rain collar, pitch pocket and cricket, say where each belongs, and state the fall-protection duty at a skylight or roof opening.

7 min · 7 slides · 5 questions

All lessons in this module

Slide 1 of 7

What counts as a penetration

The 2021 Seattle Residential Code requires flashings around roof openings (section R903.2.1).

Pipes, vents, skylights and equipment curbs all pass through or stand on the roof plane, and each one interrupts the roof covering.

Sources

2021 Seattle Residential Code, Chapter 9 Roof Assemblies (International Residential Code 2021 with Seattle amendments) - City of Seattle, SDCI
NRCA Roofing Guidelines glossary: Curb - NRCA

Videos for this lesson

What this video shows: Oregon OSHA explains the difference between a hole and an opening and how to protect workers from both; the title names skylights. Oregon is a state-plan agency; the federal rule cited in this lesson is 29 CFR 1926.501.

Video: Protecting Holes and Openings - Skylights, Vents, Windows, Fall Protection by Oregon Occupational Safety & Health (Oregon OSHA), on YouTube. AFS checked its description against this lesson.

Glossary

Curb: A raised member used to support roof and waterproofing penetrations such as skylights and mechanical equipment, so the flashing can stand up above the roof surface.
Base flashing: The membrane flashing that covers the edge of the field membrane and extends up the vertical surface of a curb, wall or pipe.
Counterflashing: Formed metal or sheeting that covers and protects the upper edge of a base flashing, so water cannot get behind it.
Cricket: A construction that diverts water around or away from a chimney, wall, curb or other penetration on the upslope side.
Pitch pocket: A flanged, open-bottomed enclosure, usually sheet metal, set around a penetration and filled with grout and pourable sealer; also called a pitch pan.