How should shingles be installed around chimneys to prevent leaks?

• A. Use step flashing with counter-flashing, seal joints with compatible sealant, and integrate chimney flashing with the surrounding shingle field.
• B. Seal joints with only caulk.
• C. Install shingles flush against chimney without flashing.
• D. Remove shingles near chimney.

Answer: (A)

Water leaks around chimneys are best prevented by a proper flashing system that directs water away from the chimney and into the shingle field. Start with step flashing along the sides of the chimney, installing each piece as you lay shingles so water runs down the slope in a stair-step pattern. The top of this flashing is then sealed with counter-flashing to keep wind-driven rain from lifting or wicking under the joints. Use a compatible sealant to seal joints where the flashing meets the shingles, but rely on the flashing system as the primary waterproofing. Integrating the flashing with the surrounding shingle field means the shingles tuck over and around the flashing so water sheds off the roof rather than seeping into gaps around the chimney.

Sealing joints with only caulk isn’t enough because caulk can deteriorate and won’t provide a durable, long-term water barrier. Installing shingles flush against the chimney without flashing creates a direct leak path, and removing shingles near the chimney eliminates the necessary overlap and protection the flashing provides.