Quick AnswerChimney waterproofing means applying a breathable, vapor-permeable sealant to the brick and mortar that blocks rain from soaking in while still letting existing moisture escape as vapor. This is different from paint or film-forming sealants, which can trap moisture inside the masonry and actually make freeze-thaw damage worse. It's typically done after any needed tuckpointing or crown repair, not as a substitute for those repairs. Most chimneys need reapplication every 5 to 10 years.
What’s Included
Brick is naturally somewhat porous, which is fine as long as any water that gets in can also get back out. The problem is that a lot of do-it-yourself sealants and paints form a solid film on the surface that blocks water going in, but also blocks water vapor from escaping, so moisture gets trapped inside the masonry instead. When that trapped moisture freezes, it does more damage than if the brick had never been sealed at all. We use a vapor-permeable water repellent instead, which blocks liquid water from the outside while still allowing the brick to breathe.
- We inspect the chimney first and address any existing cracks, open mortar joints, or crown damage before sealing, since waterproofing over active damage just locks moisture inside.
- The brick surface is cleaned of dirt, mildew, and any old coatings so the new sealant can penetrate the masonry properly instead of sitting on top of debris.
- We apply a siloxane or silane-based vapor-permeable sealant, which repels liquid water on contact but still allows water vapor to pass through and escape.
- Application covers the full exposed chimney, not just the areas that look damaged, since untreated brick nearby will keep absorbing water and eventually show the same problems.
- We avoid film-forming, paint-like sealants entirely, because trapping moisture inside brick that's already been through Ohio winters accelerates spalling instead of preventing it.
- The sealant is given time to cure fully before we consider the job complete, and we'll tell you plainly when it's safe to expect it protecting the chimney through the next rain.
Signs You Need This
- Brick that darkens noticeably and stays damp-looking after rain
- Spalling or flaking brick faces, especially on north-facing sides
- A chimney that's never been sealed and is more than 10 years old
- Recent tuckpointing or crown repair that needs ongoing protection
- Visible mineral staining (efflorescence) that keeps returning after cleaning
Our Process
Masonry inspection
We check the brick, mortar joints, and crown for existing damage, since sealing over cracks or open joints traps water instead of blocking it.
Repairs first, if needed
Any tuckpointing, crown sealing, or flashing issues we find get addressed before waterproofing, so the sealant isn't covering a problem that will keep leaking underneath.
Surface cleaning
The chimney exterior is cleaned of dirt, algae, and old coatings so the vapor-permeable sealant can properly penetrate the brick.
Applying the sealant
We apply a breathable siloxane-based water repellent across the full exposed chimney and let it cure before considering the job finished.
How Much Does It Cost?
Waterproofing is priced as a flat fee based on the size of the chimney and whether any repairs need to happen first, and we always inspect before quoting rather than guessing over the phone. Your written estimate covers the full job, so if we recommend addressing a cracked crown or open mortar joint before sealing, that's itemized separately and approved by you before we proceed. We don't apply sealant over damage just to get a job done faster, since it wouldn't actually protect the chimney and we'd rather tell you that upfront than have you pay for it twice.
FAQs
Not necessarily. Film-forming sealants and paints can trap existing moisture inside the brick, and when that moisture freezes in a Cleveland winter, it does more damage than if the brick had been left alone. A vapor-permeable sealant avoids that problem by letting the brick still breathe.
A quality vapor-permeable sealant typically lasts 5 to 10 years before it needs reapplication, depending on sun exposure and weather. We can check its condition during a routine chimney inspection.
Waterproofing complements tuckpointing rather than replacing it. Fresh mortar joints are still porous brick and mortar, so sealing them afterward with a breathable repellent adds another layer of protection against the next round of freeze-thaw weather.