Chimney Step Flashing and Counter-Flashing Rebuild
Project Overview
Persistent leak at the front-facing wall of a masonry chimney during heavy wind-driven rain. Existing flashing was surface-caulked and showed separation along the brick line.
Analysis
Step flashing was the original single-piece pan flashing caulked into the mortar - a common older detail that fails as sealants age. No counter-flashing was present, and water was entering along the top edge of the pan.
Process
Removal of caulked pan flashing and affected shingles; up-wall ice-and-water shield; new step flashing laced into shingle courses; reglet cut; counter-flashing install; mortar patch; hose-down leak test.
Outcome
Leak fully resolved through a controlled water test. Homeowner reported no moisture during the next wind-driven rain event. Detail now matches modern two-piece flashing standards.
Project Details
Materials Used
Aluminum step flashing (5"x7"), aluminum counter-flashing, lead-free chimney sealant, mortar for reglet cuts, ice-and-water shield up-wall, matching shingles for re-weave.
Methods & Techniques
Shingles re-woven one course at a time with new step flashing laced into each course. A reglet cut into the mortar joint received fresh counter-flashing bent to tuck in and cover each step piece. All terminations sealed.
Key Highlights
Two-piece chimney flashing; step + counter-flashing; reglet cut into mortar; water-tested before cleanup; no reliance on surface caulk.