Breathable waterproofing for chimney brick in Harbordale

Make the top watertight first

Repellent makers ask for the top of a wall to be capped and watertight before treatment. On a chimney, the top is the crown and the cap. If rain can get in at the top, treating the sides will not stop it, and trapped water can do harm.

We check the crown, the joint around the flue and the cap before recommending waterproofing. If the top needs work, it goes on the estimate first, under its own name. Treatment of the faces follows once the top is sound.

Mineral deposits and breathable repellents

Water moving through masonry can carry salts to the surface, where they dry as a white deposit. A repellent may reduce the water and therefore the salts. But if salts are trapped behind a surface that does not let vapor out, they can build up and damage the brick.

That is one reason we recommend only breathable repellents. It is also why any heavy deposits are cleaned off and their water source dealt with before treatment. We explain what the deposits on your chimney suggest and how the treatment plan takes them into account.

Questions to ask about a sealing proposal

A proposal to seal or waterproof a chimney should answer a few basic questions. These help you check any quote, including ours.

If a quote cannot answer these, it is worth asking why. Our estimate addresses each in writing, and we are glad to go through them in person.

• Does the product penetrate or form a film
• Which repairs will be done before it goes on
• Will a test area be done first
• What happens to glass, roofing and plants nearby

When the brick maker is known

Brick industry guidance suggests consulting the brick manufacturer before choosing a clear treatment. On an existing chimney, the maker is usually unknown, and the brick may have come from several sources over the years.

If you do know, from building papers or a stamp on spare bricks, tell us. It can help with the choice. If not, the test area does the same job in practice. It shows how this particular brick takes the product and how it looks afterward.