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Chimney Waterproofing in Seattle, WA
A breathable water repellent that keeps rain out of sound brick and lets moisture escape. Applied after repairs, not instead of them. Free quote.
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- Price match + 10–25% discount
- Same-day service often available
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Chimney waterproofing is a protective treatment, not a leak repair. We apply a breathable siloxane-based water repellent to sound, repaired masonry so the brick and mortar shed rain instead of soaking it up, while water vapor from inside the chimney can still escape. That second part is what separates it from paint or a film-forming sealer, which trap moisture in the brick and make spalling worse. Used correctly, waterproofing is the last step in a masonry job: it protects the repointed joints and replaced bricks you just paid for.
It is not a fix for an active leak. A repellent will not close a cracked crown, seal failed flashing or stop water coming through an open joint. If your chimney is leaking now, start with chimney leak repair so we find the entry point first. Once the chimney is sound and dry, waterproofing keeps it that way through the Puget Sound wet season.
We quote waterproofing free, on its own or bundled with repairs, and we price match any written quote plus 10-25% off.
Symptoms
Signs you need chimney waterproofing
- Brick that darkens and stays dark for days after rain while the rest of the house dries
- White efflorescence blooming on the brick each spring as the chimney dries out
- Early, light spalling on the weather side that has not yet reached the brick core
- Fresh tuckpointing or masonry repair that you want to protect before winter
- Moss and algae getting a foothold on the shaded face of the chimney
- An older sealer that has gone shiny, peeled, or left the brick blotchy
Common causes
- Porous older brick and lime mortar that absorb rain through the face rather than shedding it
- Six months of near-constant wetting in the October to March wet season with little chance to dry
- Freeze-thaw cycling in saturated brick, which the repellent prevents by keeping the water out
- Film-forming sealers or paint from a past job that trapped moisture inside the masonry
- Shade and moss on the north face holding water against the brick
How It Works
Our chimney waterproofing process
Before we recommend waterproofing we make sure the chimney is a candidate for it. We check that the crown, cap and flashing are sound, that there are no open joints or spalled bricks that need repair first, and that the masonry is dry enough to take the treatment. We also check for an old film-forming sealer, which has to be dealt with before a breathable repellent will penetrate. If the chimney needs repairs, we quote those first and the repellent as the final step.
Free quote and readiness check
We confirm the top of the chimney and the joints are sound, note any repairs that must come first, and quote the repellent as its own line.
Repairs and cure time
Any tuckpointing, brick replacement or crown work is done first and allowed to cure, because a repellent applied over fresh mortar or a wet wall does not bond.
Clean the masonry
We remove moss, efflorescence and dirt so the product reaches the brick, and protect the roof, flashing and cap from overspray.
Apply the repellent
A breathable siloxane repellent is applied in flood coats, bottom to top, so it saturates the face and the joints and penetrates rather than sitting on the surface.
Dry and document
We let it cure, photograph the finished chimney, and tell you when it will be ready for the first real rain.
Options
Repair and service options
Waterproofing is simple, but a few choices change the result:
- Breathable siloxane repellent (our standard): penetrates the brick, lets vapor out, leaves no sheen, and does not change the look of the masonry once dry.
- Whole chimney versus weather side: we treat the entire exposed chimney in almost every case, because water finds its way around a half-treated stack.
- Crown included: a sound crown can be coated with a flexible crown sealer on the same visit (crown repair); a crumbling crown needs a rebuild first, starting at $299.
- Bundled with repairs: waterproofing after tuckpointing or masonry repair is scheduled as a return visit once the mortar has cured.
- Reapplication: repellents wear with weather and need renewing periodically; we note the condition at each annual inspection.
We do not apply paint or film-forming sealers to chimney brick. They look waterproof and trap the moisture that causes spalling.
Pricing
What affects the price
- Square footage of exposed chimney face to be treated
- Cleaning required to remove moss, efflorescence or an old sealer
- Whether repairs must be completed and cured before application
- Whether the crown is coated on the same visit
- Chimney height, roof pitch and access
- Travel for outlying Pierce, Snohomish and Kitsap addresses
Every chimney is different, so you get a written quote after we look at the system. Ask about our price match and free second-opinion quote.
Safety & Seattle Conditions
Safety considerations
Applying a repellent is roof work with a sprayer, and we do it from staging with fall protection while protecting your roof, gutters and plantings from overspray. Please do not try to apply a sealer from a ladder yourself; apart from the fall risk, the wrong product does real damage to brick. We inspect for free and tell you what the chimney needs.
NFPA 211 still recommends an annual chimney inspection; we check the repellent at the same time.
Seattle & Puget Sound conditions
Building science on brick comes down to one rule: damage risk depends on saturation plus freezing, so keeping masonry dry is the controlling factor, not keeping it warm. That is the whole case for waterproofing in Seattle. Sea-Tac's normal annual rainfall is 40.34 inches, about 73% of it between October and March, and Seattle averages roughly 150 to 156 days a year with measurable precipitation. A chimney face in that climate rarely dries out for six months at a stretch.
Add the freeze: about 60 days a year touch 32F while winter lows average around 37F, so saturated brick freezes and thaws repeatedly. A breathable repellent keeps water out of the pores so there is nothing to expand, and makes the surface harder for moss, which spreads fastest October through April on shaded surfaces, to hold onto.
Our Work
Chimney Waterproofing in action
Protect the repair. Get a free waterproofing quote.
Call 206-453-2045. Free quote, free second opinion, price match plus 10-25% off on any chimney work in Seattle, Tacoma or Everett.
☎ 206-453-2045 Request a QuoteQuestions
Chimney Waterproofing FAQ
Will waterproofing stop my chimney from leaking?
No, and anyone who tells you it will is selling the wrong product. A repellent keeps rain from soaking into sound brick; it cannot bridge a crack in the crown, seal failed flashing or fill an open joint. If water is getting in, we find and repair the entry point first, then apply the repellent to protect the repaired chimney.
What is the difference between a breathable repellent and a sealer?
A breathable siloxane repellent soaks into the brick and lines the pores so liquid water beads off, while water vapor can still pass out. A film-forming sealer or paint sits on the surface and blocks both directions. Chimneys always carry moisture, and if it cannot get out it freezes behind the film and pushes the brick face off. We only use breathable products on chimney masonry.
Why do repairs have to come first?
Because the repellent bonds to clean, cured, sound masonry. Sprayed over fresh mortar it interferes with curing; sprayed over open joints and spalled brick it leaves the real problem underneath. The right order is repair, cure, clean, then waterproof, so we schedule the treatment as a return visit after masonry work.
Will it change how my chimney looks?
Once dry, a breathable siloxane repellent is invisible: no sheen, no darkening, no blotches. The brick looks the way it looks on a dry day. During the first few rains you will see water beading on the surface instead of darkening the brick, which is how you know it is working.
How long does chimney waterproofing last?
Repellents wear with exposure, and the weather side of a Seattle chimney gets a lot of it, so the treatment needs renewing periodically rather than once forever. We look at the condition of the repellent during each annual inspection and tell you when it is time. Reapplication is quicker than the first treatment because cleaning and repairs are usually not needed.
Can you waterproof a chimney in the rain?
No. The masonry has to be dry enough for the product to penetrate, and it needs a rain-free window afterward to cure. We schedule waterproofing in the drier months when possible, which also means it is ready before the October rains. Summer here averages only about 3 inches of rain across June, July and August, so there is plenty of opportunity.
Is waterproofing worth it on a recently repaired chimney?
It is the best time to do it. Fresh mortar and new brick are sound and dry, and the repellent keeps them that way, so you are not paying for the same joint work again in a few years. We quote it alongside masonry and tuckpointing work so you can decide with the full picture.
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