The brick and mortar of a chimney take more weather than almost any other part of a Boston home, standing exposed at the highest, windiest point of the house through every freeze and thaw of a New England winter. Over time the mortar joints wash out, the brick faces spall and crumble, and the crown that caps it all cracks, and once that happens water has free run of the structure. Boston Chimney Sweep repairs chimney masonry across the city with tuckpointing and repointing, spalled-brick replacement, crown rebuilding, and waterproofing, all matched to the existing chimney so the repair restores the structure rather than patching over it. We do the masonry that keeps an old chimney standing and watertight.
- Tuckpointing and repointing of weathered joints
- Spalled and cracked brick cut out and replaced
- Cracked or thin crowns rebuilt and sealed
- Mortar and brick color-matched to the chimney
- Breathable waterproofing where the masonry warrants it
- Repairs that restore the structure, not cosmetic patches
How freeze and thaw take a Boston chimney apart
Chimney masonry fails from the top down and the outside in, and in Boston the engine of that failure is water meeting cold. Brick and mortar are porous, so they drink in rain and snowmelt, and a chimney is the most exposed masonry on the house, with weather hitting it from every side and no roof overhead to shelter it. When the temperature drops below freezing, the water held inside the brick and the joints expands as it turns to ice, and that expansion pushes the masonry apart from within. One cycle does little. A Boston winter delivers that cycle over and over, and across enough winters the mortar joints open, the faces pop off the brick in flakes and chunks, and the structure loses both its weather seal and its strength.
The crown, the sloped concrete or mortar cap on top of the chimney, is usually the first casualty and the most consequential, because it is the chimney's umbrella. When the crown cracks, water runs straight down into the body of the chimney and into the gap between the liner and the brick, where it freezes and accelerates the damage on every front at once. A great many Boston chimneys were finished with a thin, unreinforced mortar wash for a crown rather than a proper cast crown, and those wear through quickly. Reading whether you are looking at a few open joints that need repointing or a crown and upper section that need rebuilding is the first job of an honest masonry assessment.
Repointing, rebuilding, and matching the old brick
Our masonry work scales to what the chimney needs, and the most common job is repointing. We rake out the failed, washed-out mortar from the joints to a sound depth and pack in fresh mortar, restoring the weather seal and the strength of the bond without disturbing brick that is still good. On older Boston masonry, matching the new mortar to the old in color and, importantly, in hardness matters more than it looks, because mortar that is too hard will not flex with the brick through the freeze-and-thaw cycle and can damage the very brick it is meant to protect. We mix and match to the existing work so the repair blends in and behaves like the original.
Where individual bricks have spalled, cracked, or lost their faces, we cut them out and replace them with brick matched to the chimney as closely as the materials allow, so the repair disappears into the surrounding masonry rather than standing out as a patch. Where the crown has failed, we repair or rebuild it as a proper sloped cap that sheds water clear of the joint between the masonry and the liner. And where the structure has deteriorated past the point of spot repair, with whole courses of brick failing together, we will tell you honestly that a partial or full rebuild is the sound path rather than chasing the damage with patch after patch.
Sealing the masonry against the next winter
Once the joints are repointed, the brick replaced, and the crown made sound, the final step on many chimneys is to keep water from soaking back into the masonry in the first place, and that is where breathable waterproofing earns its place. A masonry water repellent applied to a sound, repaired chimney slows the absorption of rain and snowmelt, which is the root cause of the freeze-and-thaw damage, while still letting any moisture already in the brick escape rather than trapping it inside. The breathable part is essential, because a sealer that locks moisture in does more harm than the water it was meant to keep out. We use the right product on the right chimney, after the repairs, not as a substitute for them.
Timing matters with chimney masonry, because the repairs need a stretch of dry, above-freezing weather to cure properly, which makes the milder months the right window to get this work done before another Boston winter goes to work on the structure. Catching the masonry while the damage is still open joints and a few spalled bricks, rather than waiting until the crown has failed and water is reaching the flue, is the difference between an afternoon of repointing and a full rebuild. We will look at your chimney honestly, tell you whether it needs a little repointing or a larger restoration, and put the real scope in writing before any work begins.
Every part of the chimney, handled
A chimney is a system, so masonry & tuckpointing rarely stands alone, it connects to creosote removal, chimney condition assessment, chimney repair, a new chimney cap, chimney liner replacement, and our crew handles all of it under one roof. We bring the same service to Cambridge masonry & tuckpointing, Somerville masonry & tuckpointing, Masonry & Tuckpointing in Brookline, Masonry & Tuckpointing in Quincy and everywhere else across the Boston area.
If you searched for local chimney service, you have reached a local crew, call 508-296-8030 any time. For background, read Chimney Leaks and Water Damage in Boston, MA: Finding the Source on our blog, or head back to our Boston home page to see everything we do.