Chimney Waterproofing
Brick and mortar absorb water. Waterproofing a chimney means keeping water out of the masonry without trapping the moisture that is already in it, and it only works if the chimney is sound first.
What waterproofing is, and is not
Chimney waterproofing is the application of a water repellent to the masonry. Good products are vapor-permeable, so they let moisture escape while repelling liquid water. They do not fix a cracked crown, failed flashing or open mortar joints, and applying them over those problems traps trouble inside.
Fix first, then protect
| Condition | What comes first |
|---|---|
| Open or cracked crown | Repair the crown. A repellent does not seal a crack in concrete. |
| Failing mortar joints | Repoint |
| Damaged brick | Replace or repair it |
| Leaking flashing | Repair the flashing |
| A missing cap | Fit a cap |
When a repellent helps
- The masonry is sound but absorbs water, with dark patches after rain
- The chimney has just been repaired or restored and you want to protect it
- The brick is porous and prone to freeze damage
- There is efflorescence, the white staining that shows water moving through brick. See our guide.
How it is applied
The chimney is first cleaned and repaired, and the masonry has to be dry. The repellent is then applied to the brick and mortar by spraying or rolling, so it soaks in. Weather matters, since it should not be applied in rain or just before it. We explain what to expect and how the chimney should look afterward. Repellents wear over time, and we tell you what to watch for.
A water repellent is not a cure for a leak. If water is coming into the house, the answer is to find the source. See chimney leak repair.
What the work involves
How waterproofing goes
- InspectWe check the masonry and what is letting water in.
- RepairCracks, joints and flashing are fixed first.
- ApplyA vapor-permeable repellent is applied to dry masonry.
- ReviewWe explain how long to expect it to last and what to look for.
Related services
Chimney Leak Repair
Finding and stopping a leak.
Learn moreChimney Repointing
Make the joints sound first.
Learn moreChimney Restoration
The whole chimney.
Learn moreWe work throughout New Jersey. See our service areas, or browse all services.
Questions
Frequently asked questions
Will waterproofing stop my chimney from leaking?
Not by itself. It reduces water absorption in sound masonry. Leaks need their source repaired.
Does it change how the brick looks?
A good product leaves little visible change. We explain what to expect.
How long does it last?
It depends on the product, the masonry and the weather. We tell you what to expect and how to tell when it has worn.
Is it needed on every chimney?
No. We tell you honestly if yours does not need it.
Ready to have your chimney looked at?
Call us, or send a scheduling request. We will contact you to confirm a time. Your appointment is not confirmed until we do.