Roof Sailing Roof Flashing and Waterproofing 2 — Questions and Answers
Question 1: What sealant should NOT be used as the sole waterproofing for roof pipe boot flashings?
- Butyl rubber tape
- EPDM pipe boot collar
- Roofing cement caulk only (Correct answer)
- Lead pipe boot
Correct answer: Roofing cement caulk only
Roofing cement or caulk alone will crack and fail within a few years when used as the sole seal around pipe penetrations; proper pipe boots with flexible collars are required for long-term waterproofing.
Question 2: What is the recommended minimum distance that base flashing should extend up a chimney face?
- 2 inches
- 4 inches
- 6 inches (Correct answer)
- 12 inches
Correct answer: 6 inches
Base flashing at chimney faces should extend at least 6 inches up the face of the chimney to provide adequate protection against wind-driven rain, per most building code requirements.
Question 3: When must a two-piece (two-part) pipe boot be used instead of a one-piece boot?
- On all installations
- When pipe diameter exceeds 6 inches
- When the pipe is already installed and cannot be removed (Correct answer)
- On roofs with a pitch greater than 8:12
Correct answer: When the pipe is already installed and cannot be removed
A two-piece (split) pipe boot is used when the pipe or stack is already permanently installed and cannot have a one-piece boot slid over it; the split boot wraps around the existing pipe.
Question 4: What is the correct overlap for W-metal valley flashing sections when multiple pieces are needed?
- 1 inch
- 3 inches
- 6 inches (Correct answer)
- 12 inches
Correct answer: 6 inches
W-metal valley sections must overlap by a minimum of 6 inches, with the upper piece lapping over the lower piece to ensure water is directed outward rather than into the joint.
Question 5: What material is NOT compatible with copper flashing and can cause rapid corrosion?
- Cedar shake
- Pressure-treated lumber with ACQ (copper-based preservative) (Correct answer)
- Clay tile
- Concrete board
Correct answer: Pressure-treated lumber with ACQ (copper-based preservative)
ACQ (Alkaline Copper Quaternary) pressure-treated lumber contains high levels of copper, which creates a galvanic reaction with additional copper flashing — zinc or stainless fasteners and separating barriers must be used.
Question 6: What is the maximum allowable gap between pieces of step flashing at a sidewall junction?
- 1/4 inch
- 1/2 inch
- There should be no gap — pieces must overlap (Correct answer)
- 1 inch
Correct answer: There should be no gap — pieces must overlap
Step flashing pieces must overlap each other with no gap; each piece overlaps the piece below by at least 2 inches to ensure water is continuously directed outward rather than into any joint.
Roof Sailing Roof Flashing and Waterproofing 2
What sealant should NOT be used as the sole waterproofing for roof pipe boot flashings?