Chimney masonry repair and tuckpointing
Freeze-thaw winters wear out chimney mortar first. Here's how masonry repair works and what to ask before it starts.
Mortar joints are meant to be the weak link. On a sound chimney, the joints wear slowly and get repointed every few decades, and the brick stays intact. On a chimney that's been left too long, water gets through the open joints, freezes inside the stack, and starts breaking the brick itself. Catching it at the mortar stage is far less work than rebuilding.
What is tuckpointing?
Tuckpointing, or repointing, means grinding or raking out deteriorated mortar to a sound depth and packing new mortar into the joints in layers. Done well, it closes the paths water uses to get into the chimney and restores the look of the brickwork.
Why does the mortar matter on old Duluth brick?
Many chimneys here were built with soft brick and lime-rich mortar. The National Park Service's guidance on repointing historic masonry says new mortar should be softer and more vapor-permeable than the brick around it. Hard, straight portland cement mortar traps moisture and forces stress into the brick, which leads to cracking and spalling. Ask your mason what mortar they plan to use and why it suits your brick.
When does a chimney need a partial rebuild?
- Brick above the roofline is loose, cracked through or falling
- The stack leans or has separated from the house
- Spalling is widespread rather than a few isolated bricks
- The crown and top courses have been soaked for years
Rebuilding is usually done from the roofline up, matched to the existing brick as closely as possible. A rebuild is also a chance to add a proper crown, a cap and new flashing in one job. In Duluth, ask whether the work needs a permit from Construction Services and Inspections.
Should I seal my chimney?
Only with a breathable masonry water repellent made for chimneys, and only after repairs are done. Paint and film-forming sealers can trap moisture inside the brick, which is the problem you were trying to fix.
What affects the price?
- How much of the chimney needs repointing, and how high it is
- Roof pitch, access and staging
- Brick replacement or rebuild above the roofline
- Matching older brick and mortar color
The chimney company prices the job after seeing the chimney, usually from the roof and inside the flue. We don't quote prices, and any figure given over the phone before an inspection is only a rough starting point.
Where we connect you with help
Common questions
Can tuckpointing be done in winter in Duluth?
Mortar needs to cure without freezing, so most exterior masonry is scheduled for the warmer months. Emergency stabilization may still be possible in winter. Ask the contractor.
Do I need a state license for chimney masonry in Minnesota?
A contractor who does only masonry can be exempt from Minnesota's residential contractor license as a single-specialty contractor. A company selling several kinds of work needs a license. Ask which applies.
Related services
- Chimney crowns and caps
- Chimney liners and relining
- Chimney leak repair
- Chimney inspection and sweeping
More background: Duluth chimney guide.
Loose brick, a leaking chimney or a stove you haven't had checked?
Call now and a local chimney company will look at it and quote the work.