What is chimney flashing?
Metal flashing and counter-flashing installed at the chimney-to-roof joint to prevent water penetration into the structure.
Chimney flashing is the system of overlapping metal pieces installed where a chimney penetrates the roofline. It includes base flashing (typically lead, copper, or galvanized steel) that sits beneath roof shingles and channels water away from the chimney opening, plus counter-flashing that is either mortared into a groove in the chimney or installed as a two-piece system and covers the top edge of the base flashing.
The two-piece counter-flashing setup is common in Connecticut homes because it allows for seasonal movement and can be replaced without removing roof shingles. This is distinct from a one-piece stepped flashing used on sloped roofs, though both serve the same core purpose: preventing water from entering the gap between chimney and roofing material.
Flashing fails when it corrodes, separates from the chimney, or becomes damaged by weather or poor installation. Failed flashing creates the conditions for water leaks into the attic, interior walls, and chimney itself, leading to structural rot and brick deterioration. Proper installation requires careful attention to the chimney width, roof pitch, and the sequence in which flashing components overlap. Homeowners should have flashing inspected during routine chimney and roof maintenance, especially after severe weather. Qualified masonry contractors in Connecticut can assess flashing condition and replace damaged sections as part of chimney repair work.