Brick and mortar are porous, and in a climate as wet as Seattle's that means your chimney is drinking rain all winter. Waterproofing with a breathable, vapor-permeable sealer stops that absorption while still letting the masonry dry out. It's one of the smartest low-cost things you can do here, because it heads off the freeze-thaw cracking and efflorescence that lead to expensive rebuilds. Here's what waterproofing costs across the Puget Sound region and when it's worth doing.
What chimney waterproofing costs in Seattle
Standard waterproofing of a typical single-story chimney runs about $299–$500. A large or two-story chimney, which needs more product and more roof time, runs $500–$800. Height, access, and the amount of surface area set the price. You get a free written quote first, and we price-match plus 10–25%.
Why waterproofing matters in Puget Sound
Untreated brick soaks up our near-constant rain, then the water freezes in winter and cracks the masonry from the inside out. That freeze-thaw cycle is the number-one killer of Seattle chimneys. Waterproofing repels the rain while still letting trapped moisture escape, so the brick stays sound. On shaded, moss-covered north roofs in King, Pierce, and Snohomish counties, where masonry never fully dries, it matters even more.
Signs your chimney needs waterproofing
- White, chalky efflorescence staining the brick.
- Mortar joints that look sandy, soft, or crumbling.
- Damp patches or a musty smell inside the firebox.
- Brick faces flaking or spalling off in thin layers.
- Green moss or dark staining on the masonry.
A cheap treatment that prevents a rebuild
A $299–$800 waterproofing treatment is one of the highest-value repairs you can make, because it stops the water intrusion that turns into cracked crowns, spalled brick, and eventually a rebuild costing many times more. We use a breathable sealer — never a paint-on coating that traps moisture and makes things worse. Free written quote, free second opinion, and a price-match plus 10–25%.
What Chimney Waterproofing Costs in Seattle (2026)
Real 2026 ranges for the Seattle–Tacoma–Everett area, with a free written quote before any work begins.
| Standard waterproofing | $299–$500 |
| Large or two-story chimney | $500–$800 |
Get a free quote
See our full chimney service pricing, or learn more about Chimney Waterproofing. You get a free written quote before any work begins — call 206-453-2045 or request your free quote online.