Chimney Waterproofing — Breathable Sealer, Done in the Right Order
A siloxane sealer that stops liquid water entering while letting the masonry breathe. We fix the crown and joints first, because sealing a cracked chimney traps water inside it. Book October or November.
Chimney waterproofing with a vapour-permeable siloxane sealer is from $299. A flexible crown coat over a sound crown is from $249, and the two bundled are from $449. We will not seal a chimney that needs masonry repair first — the repair has to come before the sealer or you trap water inside. Call Dans Hollywood Chimney & Air Duct Cleaning at (818) 536-7759.
Siloxane sealer, breathable, 8 to 10 years
Seals a sound crown against hairline cracking
The combination most chimneys actually need
Removing salt staining before sealing
The other main water path, done properly
Credited against whatever work you approve
Why a Chimney in a Dry Climate Still Needs Waterproofing
Los Angeles gets its rain in concentrated bursts rather than steady drizzle, and that is harder on masonry rather than easier. A chimney that has baked dry through a long summer has open pores and micro-cracks, and when the first serious storm arrives it absorbs water fast and deep. Then the sun comes out, the surface dries while the interior stays wet, and the resulting stress is what pops brick faces off. This cycle — long dry spell, sudden soaking, rapid surface drying — is the specific pattern that damages Southern California masonry.
Brick and mortar are porous by design. A masonry chimney is supposed to absorb some water and then release it as vapour; that is how it stays sound. The problem is quantity. A chimney with a cracked crown, recessed mortar joints or a missing cap takes on far more water than it can shed, and then the water does three things: it carries dissolved salts out to the surface as white efflorescence staining, it softens and washes out mortar from the inside of joints, and on cold nights it freezes and widens every crack it occupies.
Waterproofing addresses the absorption rate rather than the cracks. The right product is a vapour-permeable siloxane or silane-based sealer, which penetrates the masonry and lines its pores so liquid water cannot enter, while leaving the pores open enough for water vapour to escape outward. That distinction is the entire technology, and getting it wrong is worse than doing nothing.
Which is why the most important thing on this page is a warning rather than a sale. Do not paint a chimney, and do not let anyone apply a film-forming sealer to it. Call (818) 536-7759 if you are unsure what is already on yours — we can usually tell from a photograph.
The Right Product, the Wrong Product, and What Has to Happen First
Waterproofing is cheap and effective when it is done in the right order with the right material. It is money thrown away, or worse, when it is not.
Vapour-Permeable Siloxane Sealer — The Right Product
Siloxane and silane-based masonry sealers penetrate into the brick and mortar and line the pore walls, so liquid water is repelled while water vapour can still pass outward. The masonry continues to breathe and dry itself, which is exactly what it needs to do. Properly applied to clean, repaired masonry, this is good for roughly eight to ten years in our climate before it wants renewing. It goes on clear and does not change the appearance of the brick, which matters on historic and architecturally significant houses where a coating would be unacceptable.
Paint and Film-Forming Sealers — The Wrong Product
Paint, elastomeric coatings and acrylic film sealers form a skin on the surface. They do stop water getting in, and they also stop water vapour getting out. Masonry always has some moisture in it, rising from the base or driven in at an unsealed edge, and once it cannot escape as vapour it accumulates behind the film. The result is accelerated mortar decay you cannot see, brick faces spalling off behind the coating, and the coating itself blistering and peeling. We see this most often on recently flipped houses, where a painted chimney looks like finished work and is actively rotting.
Repairs Come First — Always
Sealer is not a repair and it will not bridge a gap. Applying it over a cracked crown, recessed mortar joints or failed flashing seals water into the masonry at every point where the water is already getting in behind the treated surface. The correct order is: fix the crown, repoint the joints that need it, sort the flashing, cap the flue, and then waterproof the sound masonry. We will not quote waterproofing alone on a chimney that needs masonry work first, and if that is what we find we will say so rather than taking the easy job.
Signs Your Chimney Needs Waterproofing
Water damage in masonry is cumulative and quiet. By the time it is obvious indoors it has usually been going on for years, so these early signs are worth acting on.
How Waterproofing Runs
The whole job is usually a single day on a chimney that needs no repair. Where repairs are needed they come first and the sealer follows once the masonry has cured.
Inspection and honest order of work
We assess the crown, joints, flashing and cap. If any of them need work, that is quoted first and the sealer waits, because sealing over a water path traps water behind the treated surface.
Clean the masonry
Efflorescence salt staining and surface dirt are removed, because a sealer applied over salt deposits bonds to the deposit rather than to the brick. This is a separate line where there is heavy staining.
Mask and protect
Roofing, gutters, landscaping and any adjacent painted surfaces are protected. The sealer is clear but it is still a solvent product and we do not want it anywhere it was not intended.
Apply to saturation, two coats wet-on-wet
Siloxane is applied flood-coat to the point of refusal, then a second coat while the first is still wet, which is how it achieves penetration depth rather than a surface film.
Crown coat and final check
Where a crown coat is included, the flexible membrane goes on after the masonry sealer. Then a final walk, photographs, and a note of when the treatment will want renewing.
Chimney Waterproofing — Frequently Asked Questions
Where We Provide This Service
Waterproof Your Chimney Before the Rains
Breathable siloxane sealer, applied to repaired masonry in the right order, with no change to the appearance of the brick. We book up through October. Serving the San Fernando Valley and East LA from 6330 Camellia Ave, North Hollywood, CA 91606.
Chimney Repair by City
Dan covers the whole Valley and East LA — CSIA-certified, written estimate first.