90% of chimney leaks are flashing, not brick

Chimney flashing spec generator.

Tar and caulk aren't flashing. A correct chimney flashing job has five distinct parts — step, counter, apron, cricket, kickout. Fill in your chimney below and print a code-correct spec sheet to hand any contractor.

Your chimney
Chimney flashing specification

36″ × 24″ brick chimney · shingle, 6:12

  1. 1. Step flashing

    7 pcs · 5" × 7" pre-bent aluminum or 26-ga galvanized, one per shingle course

  2. 2. Front apron

    44" wide × 10" tall front apron, hemmed edge, 4" up chimney face

  3. 3. Cricket / saddle

    Yes — required (chimney ≥30" wide per IRC R1003.20). Frame at 12:12 with 15/32" OSB, ice-and-water shield, then wrap in matching shingle.

  4. 4. Counter flashing

    Cut a 1" deep reglet into the mortar joint 1" above step flashing. Bend counter flashing 90°, insert, and seal with polyurethane sealant (NOT silicone).

  5. 5. Kickout diverter

    Kickout diverter at eave termination — 26-ga, 4" leg, angled 110° to throw water into gutter, not down siding.

  6. 6. Underlayment

    Ice-and-water shield 18" up chimney faces and 24" out onto deck under all flashing. Required in NM per IRC R905.1.2 amendment when >5,000 ft elevation.

  7. 7. Material

    26-ga galvanized or aluminum step + counter; painted to match trim.

Prepared by Roof Doctor NM · independent roof inspector · NM. Hand this to any bidder — a legitimate roofer will match it or explain why they deviate.
Common failures

Why chimneys leak — and what a repair looks like.

Tar smeared over old flashing

3–5 year band-aid. UV cracks tar, and lifting tar traps water against the flashing. Correct fix: strip and re-flash.

Missing cricket on wide chimneys

Any chimney ≥30" wide across the slope pools water uphill. Correct fix: frame a 12:12 cricket and integrate flashing.

Silicone sealant on brick

Silicone doesn't bond to porous brick, and it's not paintable. Correct fix: polyurethane sealant into a chased reglet.

Next step

Chimney still leaking? Free flashing inspection — (505) 595-7203.

Book the free on-site inspection, or send a photo and we'll tell you what to do next. No sales pitch — we don't install roofs.

Book Free Inspection See a sample report