Chimney Leak or Ice Dam? Finding the Water in Twin Cities Homes

Twin Cities roofs carry snow for a long time. NOAA's normals for the MSP airport show about 51 inches of snow a year and around 90 days with an inch or more on the ground. That snow melts and refreezes all winter, and when a stain appears near the chimney, homeowners are often unsure whether to call a roofer or a chimney company. Sometimes both are involved.

We start by working out where the water is coming from. A chimney leak comes through the crown, an open cap, failed flashing or porous brick, and it can show in any thaw or rain. An ice-dam leak comes from water backing up under the shingles at the cold eave. The inspection is free. Chimney leak repairs run $150 to $500, crown repairs $200 to $700+ and flashing work $300 to $1,800.

Signs you need this

• A stain on the ceiling or wall right beside the chimney
• Water in the firebox or rust on the damper after rain
• Icicles or a thick ice ridge along the eaves below the chimney
• Damp, crumbling plaster on the chimney breast inside
• A musty smell or efflorescence on the chimney in the attic or basement

How we do it

1. Map the waterWe note where the stain is, when it appears, and whether it follows rain or a thaw.
2. Check the chimneyCrown, cap, flashing, mortar and brick, plus the attic side of the chimney where we can reach.
3. Check for an ice damWe look at the eaves, icicles and the roof around the chimney for signs of heat loss.
4. Price the right fixIf it is the chimney, you get a written price; if it is an ice dam, we tell you what UMN Extension recommends.

How to tell an ice dam from a chimney leak

The University of Minnesota Extension explains that ice dams form when the roof is warmer in some places than others: heat melts the snow higher up and the water refreezes at the cold eave. Water then backs up under the shingles. Extension names frequent fireplace and wood stove use among the ways heat moves from the chimney into the attic.

A practical rule of thumb from our side: if the water shows up near the eave, think ice dam. If it shows on the chimney itself, or appears after a rain with no snow on the roof, think chimney.

• Leak appears only during thaws with heavy roof snow: likely an ice dam
• Leak appears after summer rain: likely the chimney
• Water in the firebox: crown, cap or flue top
• Stain on the ceiling where the chimney passes through: flashing or the attic air gap

What UMN Extension says to fix first

For ice dams, Extension's order is to make the ceiling airtight first, then consider adding insulation. It states that mechanical attic ventilation is not a recommended solution to ice dams in Minnesota. Raking snow off the roof removes one ingredient but can damage shingles. The gap where a chimney passes through the attic floor is a common air leak, and sealing it is work for an insulation contractor using materials rated for chimney clearance.

What a chimney leak repair involves

Most chimney leaks come from one of a few spots, and each has its own repair and price on our list.

• Crown cracks: $200 to $700+; a new crown is $1,000 to $3,000
• Flashing repair or replacement: $300 to $1,800
• An open flue with no cap: a cap at $200 to $850
• General leak repair: $150 to $500