Chimney Flashing Repair That Keeps Twin Cities Roofs Dry

Where the chimney passes through the roof, water has a corner to get into. Step flashing woven into the shingles and counter-flashing set into the brick are meant to lead it away. Over time, sealant dries out, counter-flashing pulls loose from the mortar, and a roof replacement may leave the flashing patched with caulk. In a place with long-lasting roof snow, about 90 days a year with an inch or more on the ground at MSP in NOAA's normals, a weak spot gets wet for months.

The free leak check tells us whether the flashing is the culprit or whether water is coming from higher up. Flashing repair or replacement typically runs $300 to $1,800. A cricket, the small peaked diverter behind a wide chimney, is priced at the inspection.

Signs you need this

• A ceiling or wall stain where the chimney passes through
• Tar or caulk smeared along the chimney base
• Counter-flashing pulling away from the brick
• Snow and ice piling up behind the chimney on the uphill side
• Rusted or bent metal around the chimney base

How we do it

1. Free leak checkWe find whether water enters at the flashing or higher up.
2. Remove the failed flashingOld step flashing, counter-flashing and caulk patches come off.
3. Install new step flashingEach piece is woven into the shingle courses so water runs down and out.
4. Set counter-flashing into the brickGrooves are cut into the mortar joints and the counter-flashing is set and sealed in them.
5. Add a cricket if neededOn chimneys wider than 30 inches along the ridge, a cricket diverts water and snow.

When a cricket is required

IRC R1003.20, part of the current Minnesota Residential Code, requires a cricket where the chimney's dimension parallel to the ridge is greater than 30 inches. Without one, snow and water pile up behind a wide chimney and work into the flashing. Many older chimneys built before that rule have none. We measure and tell you whether yours needs one.

Caulk is not flashing

Caulk and roof tar make a quick seal, but they dry out in a season or two of sun and cold. A proper fix uses step flashing and counter-flashing, metal that sheds water without depending on a sealant.

• Step flashing woven into the shingles
• Counter-flashing let into the brick joints
• A cricket on wide chimneys
• Sealant only as a backup, never as the main seal

Flashing, roofs and ice dams

When you replace the roof, new flashing around the chimney is worth doing at the same time. And if the stain is near the eaves rather than at the chimney, see our page on chimney leaks and ice dams, which uses University of Minnesota Extension guidance.