Brick drinks water. Once it does, the freeze and thaw of winter starts breaking it apart from the inside. We seal the masonry with a breathable waterproofer that keeps rain out while still letting the chimney dry, so the brick lasts.
Sun and time do little to good brick. Water does the damage. It soaks into the masonry, expands when it cools, and breaks the brick apart bit by bit. Keep the water out and a brick chimney can outlast the house. Let it in and the clock starts.
Chimney waterproofing is the job of sealing the brick and mortar of a chimney with a breathable water repellent, so rain runs off instead of soaking in, while any moisture already in the masonry can still dry out through the surface.
Brick and mortar are porous. Left bare they act like a sponge, pulling rain into the wall of the chimney every time it storms. On a warm day that water dries back out and does little harm. The trouble is what happens in between.
Water sitting inside the brick expands as it cools on a cold night and contracts again by day. Repeated enough times, that push and pull cracks the brick from the inside and pops the face off, the flaking called spalling. The same water opens joints, feeds efflorescence, and works its way toward the flue and the framing.
A good waterproofer stops that at the source. It lets the masonry shed rain rather than absorb it, so the freeze and thaw has nothing to work on. The key word is breathable. A proper sealer repels liquid water from outside but still lets vapor escape, which is what keeps the brick dry instead of trapping moisture inside.
That last part is why the right product matters. The wrong coating seals water in as well as out, and a chimney that cannot dry spalls faster than a bare one. We use a breathable masonry repellent made for the job, not a film-forming paint or a hardware-store sealant.
These are the tells that the masonry is drinking rain. Sealing it now is far cheaper than repairing what the water breaks.
Sound, sealed brick sheds a shower and dries fast. If your chimney turns dark and blotchy in the rain and takes days to lighten back up, the masonry is holding water instead of shedding it.
That is exactly what waterproofing fixes. A breathable repellent makes the rain bead and run off, so the brick stops soaking and starts drying between storms.
When the odd brick face begins to blister or shed a thin layer, water and temperature swings are starting to break it apart. It spreads, because pitted brick holds even more water than smooth brick.
We replace any brick that has already gone, then seal the sound masonry so the damage stops there instead of walking across the whole chimney.
That powdery white haze, efflorescence, is mineral salt carried out of the masonry by water and left on the surface as it dries. It is a clear sign water is moving through the brick regularly.
Once any active leak is dealt with, sealing the brick cuts off the water that carries those salts, so the bloom stops coming back after every wet spell.
When we have just repointed joints, replaced brick or recast a crown, that fresh work is worth protecting. Sealing it is the cheap insurance that keeps the water you just shut out from finding its way back in.
We often finish a repair or a rebuild with a coat of breathable repellent, which is the single best way to make that work last as long as it should.
If water is already coming in, showing as ceiling stains, a damp firebox or drips down the flue, waterproofing alone is not the answer. Something is broken, usually the crown, the flashing or the cap.
We find and fix the leak first, then seal. A repellent is there to keep sound masonry sound, not to paper over a hole that needs a real repair.
The instinct with a leaky-looking chimney is to coat it in whatever seals best, often a glossy waterproof paint or a hardware-store sealer. It looks like the safe move. On brick it is the opposite.
Brick has to breathe. A film-forming paint or a non-breathable sealer locks the surface, and any water already in the masonry, or that sneaks in through the crown, is now stuck. It cannot dry out through the face anymore, so it sits in the brick and freezes there. A sealed-but-trapped chimney spalls faster than one left bare.
We use a breathable masonry repellent, the kind that soaks in and repels liquid water while still letting vapor pass out. We also seal water in, not out, if the prep is skipped, so we clean the masonry, deal with any active leak, and let it dry before sealing. That order is what makes waterproofing help instead of hurt.
Done right, a coat of breathable repellent is one of the cheapest things that meaningfully extends a chimney. Done wrong, it speeds up the damage.
The sealer goes on fast. The value is in the checking and prep that happens before it.
Crown, cap, flashing and brick. Sealing only helps a chimney that is not already letting water in, so anything broken gets flagged before we reach for the repellent.
What needs fixing before we seal, if anything, and the cost to waterproof. Nothing starts until you have said yes to it.
Dirt, efflorescence and loose material come off, and the brick is left to dry. A repellent bonds to clean, dry masonry, not to a dusty or damp surface.
The waterproofer is worked into the brick and joints across the whole stack, enough to soak in and repel water while still letting the masonry breathe. It works its way into the brick instead of coating the surface like a paint or film.
We confirm water beads and runs off the treated surface, tidy the roof and grounds, and let you know roughly when it is worth refreshing down the road.
Bare brick and mortar absorb water, and water is the main thing that wears a chimney out. Sealing it with a breathable repellent is one of the cheapest ways to slow that down, especially on an older chimney or one that has just been repaired. It is not always urgent, but it is close to the best value on the list.
Only if the leak is the brick itself soaking up rain. If water is getting in through a cracked crown, bad flashing or a missing cap, a repellent will not fix that, and sealing over an active leak can make it worse. We check for those first and fix them, then seal. Waterproofing keeps sound masonry sound, it does not patch holes.
Because brick has to breathe. A film-forming paint or a non-breathable sealer traps any moisture inside the masonry, and trapped water freezes and spalls the brick faster than leaving it bare. We use a breathable repellent made for chimneys, which repels rain from outside while still letting the brick dry out.
A quality breathable repellent typically holds for several years before it is worth refreshing, depending on exposure and how weathered the brick was to start. We will give you a rough sense of the interval for your chimney, and it is an easy thing to redo when the time comes.
We replace the brick that has already failed first, because sealing over crumbling brick just locks in the damage. Once the bad units are out and the masonry is sound and dry, sealing the rest is exactly what stops the spalling from spreading to the good brick.
Yes, that is one of the best times to do it. Fresh masonry is sound masonry, and a coat of breathable repellent protects the joints and brick you just paid to fix, so that work lasts as long as it should instead of weathering again straight away.
On its own it is one of the more affordable things we do, priced mostly by the size of the stack and access. If the chimney needs a leak fixed or brick replaced first, that is quoted separately. We look, give you the number before we start, and tell you what actually needs doing versus what can wait.
Tell us what the chimney is doing and we will tell you whether it needs a repair first or just a good seal. We check before we coat, use a breathable repellent, and keep the water where it belongs.
