The brick and mortar of a chimney take more weather than nearly any other part of a Cambridge home, standing exposed at the highest, windiest point of the house through every freeze and thaw of a New England winter. Over the years the mortar joints wash out, the brick faces spall and crumble, and the crown capping it all cracks, and once that happens water has the run of the whole structure. Cambridge 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 instead of simply hiding the damage. We do the brickwork 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 cover-ups
How freeze and thaw dismantles a Cambridge chimney
Chimney masonry fails from the top down and from the outside in, and in Cambridge 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 entire house, taking weather from every side with no roof overhead to shelter it. When the temperature falls below freezing, the water held inside the brick and the joints expands as it turns to ice, and that expansion forces the masonry apart from within. A single cycle does little. A Cambridge winter delivers it again and again, 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 to go 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 Cambridge chimneys were topped with nothing more than a thin, unreinforced mortar wash in place of a proper cast crown, and those wear through quickly. Reading whether you are looking at a handful of 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 the failed, washed-out mortar out of 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 Cambridge masonry, matching the new mortar to the old in color and, just as importantly, in hardness matters more than it appears, because mortar mixed too hard will not flex with the brick through the freeze-and-thaw cycle and can crack the very brick it was 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 going at once, we will tell you honestly that a partial or full rebuild is the sound path rather than chasing the damage with one patch after another.
Sealing the masonry against the winter ahead
Once the joints are repointed, the brick replaced, and the crown made sound, the final step on many chimneys is keeping 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, the root cause of the freeze-and-thaw damage, while still letting any moisture already in the brick escape rather than sealing it inside. The breathable part is essential, because a sealer that traps moisture does more harm than the water it was meant to shut out. We use the right product on the right chimney, after the repairs, never as a substitute for them.
Timing matters with chimney masonry, because the repairs need a run of dry, above-freezing weather to cure properly, which makes the milder months the right window to get this work done before another Cambridge 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 wants a little repointing or a larger restoration, and put the real scope in writing before any work begins.
Your whole chimney, one accountable crew
A chimney is a system, so masonry & tuckpointing rarely stands alone, it connects to flue cleaning, chimney camera scan, chimney patching, chimney cap installation, flue relining, and our crew handles all of it under one roof. We bring the same service to Masonry & Tuckpointing in Somerville, Masonry & Tuckpointing in Arlington, Belmont masonry & tuckpointing, Watertown masonry & tuckpointing and everywhere else across the Cambridge area.
If you searched for a local chimney crew near you, you have reached a local crew, call 617-221-4253 any time. For background, read Connecting a Modern Furnace to an Old Cambridge, MA Chimney: Why Sizing Matters on our blog, or head back to our Cambridge home page to see everything we do.