Chimney service
Chimney Waterproofing
A breathable sealant that sheds rain while letting masonry dry outward. The last step after repairs, never a substitute for them.
Seal a wet chimney and you have not stopped the water. You have locked it in.
Brick is porous by design — it takes on moisture and gives it back. Chimney waterproofing uses a breathable siloxane or silane formula that stops liquid water entering while still letting vapor escape outward. That distinction is the entire job. A film-forming sealer, or any paint-on product that leaves a visible sheen, traps moisture inside the masonry where it freezes, and spalls the brick faces off from behind. Which is why the sequence matters: repairs first, then sealant, and never the other way round.
How it goes on
Flooded, not brushed thin
Applied to visible run-down so it soaks in. A thin brushed coat sits on the surface and wears off in a season.
On this pageSigns you need this3 sections+2
Signs you need chimney waterproofing
Brick faces flaking off
Freeze-thaw damage already under way. Sealing over spalled brick locks moisture behind the coating. This needs the brick replaced first, then sealing.
White chalky staining on the stack
Salts carried out by water moving through the masonry. Proof the wall is taking on water, and the clearest case for sealing once the entry point is fixed.
Mortar joints eroding back from the face
Open joints let water in faster than any face ever will. Sealant over failed pointing is money spent on the wrong problem. Repoint, wait for the cure, then seal.
Sand and grit on the roof after rain
Joints washing themselves out. The stack is shedding material every storm, and that has to be put right before anything goes over it.
A stain on the ceiling near the chimney
An active leak somewhere above. Sealing the exterior will not touch it — the water is coming through the crown, the cap or the flashing, not through the brick face.
Sound brick that has never been treated
The best case there is. Masonry in good condition, sealed before damage starts, is the version of this job that actually earns its price.
How the visit works
The same four steps every time, whatever the repair turns out to be.
- 01
Inspection first, always
A look at the crown, cap, flashing and exterior masonry, then the flue, damper and firebox — with a camera where the job calls for a level 2 scan. Whatever needs work gets shown to you, not just described.
- 02
A written estimate before anything
Scope, price and what is not included, in writing. Nothing starts until you approve it, and an emergency is not a reason to skip this step.
- 03
The work itself
Matched materials and the manufacturer's spec, not whatever is on the van. Drop cloths down, and the room left as it was found.
- 04
Verification and a report
A second scan after the work, and written findings you can keep, hand to an inspector, or send to an insurer.
The jobs this actually includes
Not every job on this list is equally urgent, so they are ordered that way. A cracked liner stops you using the fireplace tonight; waterproofing can wait for a dry week.
The job — most urgent first
What it involves
On site
Repairs first, then sealing
StructuralRepointing or brick replacement, a full mortar cure, then the sealant. It is two visits and it is the only sequence that works. Sealing damaged masonry is the mistake this service is best known for.
On site: 1–2 days plus cure
Removing a previous film sealer
StructuralStripping an old paint-on or acrylic coating that has been holding moisture in. Unpleasant, slow, and necessary before anything breathable can do its job.
On site: 1–2 days
Breathable siloxane treatment
Stops waterVapor-permeable siloxane or silane, flood-applied to saturation rather than brushed thin, over sound masonry. Leaves no sheen. This is the product that belongs on a chimney.
On site: Half a day
Crown sealing
Stops waterA flexible elastomeric coat over the crown, which is a different product from the brick treatment because a crown moves and cracks where a wall does not.
On site: Half a day
Reapplication on treated masonry
PreventiveA good siloxane treatment lasts seven to ten years on a chimney, less on the weather-facing side. Reapplying on schedule is cheaper than the pointing it prevents.
On site: Half a day
Times are for the work itself, not for scheduling. Masonry needs roughly 40°F to cure properly, which is what limits this work in a northern winter rather than whether a crew is free.
Why chimney waterproofing quotes vary so much
- The surface area of the stack, and how much of it is above the roofline
- Roof pitch and height, and whether scaffolding is needed
- Whether repairs are needed first, which is a separate job and a separate visit
- Whether an old film-forming sealer has to be stripped
- Product grade — a proper siloxane costs several times a hardware-store sealer
Sealing a sound, accessible stack is a half-day job and priced modestly. What changes the number is everything that has to happen first: repointing, brick replacement, or stripping a previous coating. If a quote for waterproofing arrives without anyone having looked at the mortar, it is a quote for the wrong job.
The people behind every visit
Founded by Ryan Carter in 2019. Every page you read here is reviewed by Ethan Miller, our chimney specialist. A written estimate before any work, and the findings in writing whether or not anything needs doing.
More about who we are →
The VIO Standard
- A written estimate first
- License and insurance checked
- Nothing starts without your OK
Common questions
Does chimney waterproofing actually work?
On sound masonry, with the right product, yes — a breathable siloxane cuts water absorption dramatically and stops the freeze-thaw cycle that spalls brick. On damaged masonry it does nothing useful and can do harm. And with the wrong product it causes the exact damage it was bought to prevent. So the honest answer is that it works when it is the last step in a sequence and fails when it is used as a shortcut past one.
What kind of sealer should be used on a chimney?
A vapor-permeable siloxane or silane, applied to saturation. The test is simple: after it cures, the brick should look exactly as it did before, just darker when wet. Anything that leaves a gloss, a sheen or a visible film is a coating rather than a water repellent, and coatings trap moisture in masonry. That includes most general-purpose masonry sealers sold for driveways and patios.
How much does chimney waterproofing cost?
Treating a sound, accessible stack is a half day and priced accordingly — it is one of the cheaper preventive jobs. The cost rises with height and access, and it rises a lot if repointing or brick replacement has to happen first, because that is a separate job with its own timeline. Professional-grade siloxane costs several times what a hardware-store sealer does, and that difference is the whole product.
How long does chimney waterproofing last?
Seven to ten years on a typical stack, and less on the face that takes the prevailing weather. It does not fail suddenly; it wears off, and the sign is that the brick starts darkening in the rain again where it used to shed. Reapplying on schedule costs a fraction of the repointing it defers.
Can I waterproof a chimney myself?
The application is straightforward — it is flood-applied with a low-pressure sprayer, bottom up, to visible run-down. The two things that go wrong are working at height and buying the wrong product, and the second is the more expensive mistake. If you do it yourself, buy a siloxane water repellent from a masonry supplier rather than a general sealer from a hardware shop, and be honest about whether the mortar needs work first.
let's get it on the calendar.
Tell us your ZIP code and what you need. The pro who covers it quotes the job in writing, and nothing starts until you approve the number.