Chimney flashing repair cost

What it costs

A full chimney reflash runs $500 to $2,500. The spread is not about the metal — it is about the chimney. A small stack near the ridge on a walkable roof is at the bottom; a wide chase low on a steep slope, needing a cricket and some repointing, is at the top.

The four pieces of a chimney flashing

Apron across the downhill face, lapped over the shingles below. Step flashing up both sides, one piece per shingle course, woven in as the courses go on. Back pan or cricket on the uphill face. Counter-flashing over all of it, its top edge let into a saw cut in the mortar joint and folded down so water on the masonry cannot get behind.

Four pieces, two trades, one detail. Any of them missing and the chimney leaks; all four present and it does not, for as long as the roof lasts. The wider family of details is on the flashing guide.

When a cricket is required

A cricket is a small ridged structure built behind a chimney to split water around it instead of letting it pile against the uphill face. Codes generally require one where the chimney is 30 inches or wider measured across the slope. Below that, a properly lapped back pan is accepted — but on any chimney wide enough to hold snow behind it, a cricket is the right answer regardless of the minimum.

Why a patch is usually the wrong buy

Tar over old chimney flashing costs a couple of hundred dollars and lasts two or three years, and it makes the eventual proper repair dearer because the tar has to come off everything it touched. If the roof is otherwise sound, buy the reflash. If the roof is near the end of its life, wait and do the chimney with the re-roof — flashing is dramatically cheaper when the shingles are already off, which is the whole argument for insisting on new flashing at replacement time. The repair-or-replace arithmetic is on the repair cost guide.