Roof Sailing Roof Flashing and Waterproofing 1 — Questions and Answers
Question 1: What material is most commonly used for roof step flashing in the US?
- Copper
- Galvanized steel or aluminum (Correct answer)
- Lead
- PVC
Correct answer: Galvanized steel or aluminum
Galvanized steel and aluminum are the most commonly used step flashing materials in US residential construction due to their corrosion resistance, affordability, and compatibility with asphalt shingles.
Question 2: How is step flashing correctly installed along a sidewall?
- One continuous piece bent over the entire wall
- Individual L-shaped pieces, one per shingle course, interwoven with shingles (Correct answer)
- Applied only at the bottom of the wall
- Installed only under the first three courses
Correct answer: Individual L-shaped pieces, one per shingle course, interwoven with shingles
Step flashing consists of individual L-shaped metal pieces installed one per shingle course, with each piece overlapping the one below and tucked under the siding above to direct water onto the shingles.
Question 3: What is counter flashing and where is it used?
- Flashing installed under shingles at valleys
- Metal cap flashing embedded in masonry walls that laps over base flashing (Correct answer)
- Flashing applied at ridges
- The bottom layer of valley flashing
Correct answer: Metal cap flashing embedded in masonry walls that laps over base flashing
Counter flashing is a second piece of flashing embedded into mortar joints of masonry walls (like chimneys) that overlaps the base flashing to create a two-part seal that allows independent movement.
Question 4: At what minimum height should flashing extend up a vertical wall adjacent to a roof surface?
- 1 inch
- 2 inches
- 4 inches (Correct answer)
- 8 inches
Correct answer: 4 inches
Roofing codes generally require flashing to extend a minimum of 4 inches up any vertical surface to ensure wind-driven rain cannot force water behind the flashing.
Question 5: What is the purpose of a cricket (saddle) behind a chimney?
- Providing an anchor for the antenna
- Diverting water and debris around the chimney and preventing ponding (Correct answer)
- Adding structural support to the chimney
- Providing ventilation behind the chimney
Correct answer: Diverting water and debris around the chimney and preventing ponding
A cricket (saddle) is a small peaked structure built behind a wide chimney to divert rainwater and debris around both sides of the chimney, preventing ponding and ice dam formation.
Question 6: Which valley flashing method is considered the most watertight?
- Open valley with W-metal (Correct answer)
- Woven valley
- Closed-cut valley
- California valley
Correct answer: Open valley with W-metal
Open valley with W-metal (or W-profile valley flashing) provides the most watertight protection because the raised center rib prevents cross-flow of water and the open design allows full water volume to flow freely.
Roof Sailing Roof Flashing and Waterproofing 1
What material is most commonly used for roof step flashing in the US?