Breathable waterproofing for chimney brick in Overtown

A test area comes first

Product makers ask for a small test area on each surface before the whole chimney is treated. It shows how the masonry absorbs the product, whether the appearance changes and how much material the surface takes.

The test should include any earlier patches or repairs, because those can behave differently from the original brick. On a chimney in Overtown, we apply the test with the same method we would use for the full job. If the result is not what you want, for example a darker look, we talk about it before going further.

Choosing a product with a track record

Brick industry guidance recommends products that have performed well on similar brick, in similar exposure, over a meaningful period. A new or untested product may look fine at first and behave differently later.

We use products whose makers publish full technical data, including the surfaces they suit and their limits. Our estimate names the product, and its data sheet is yours to read. If you have a product in mind, tell us, and we will explain whether it suits your chimney.

What the word sealer can hide

Products sold as chimney sealers vary widely. Some are breathable penetrating repellents. Others form a film on the surface. Preservation guidance notes that repellents are often wrongly called sealers, which adds to the confusion.

Read the product data, not the front of the can. It should say whether the product penetrates or forms a film, which surfaces it suits and whether it lets vapor pass. We explain the product we propose in those terms, so you know exactly what kind of treatment is going on your chimney.

What a breathable repellent does

A breathable repellent, applied to sound masonry, changes how the brick handles rain. It is useful protection within its limits, and the list below sets out what it can do.

Those are real benefits on the right chimney. They depend on the repairs done first and on the product suiting the masonry, which is why we check both before recommending treatment.

• Reduces how much water the brick and mortar absorb
• Helps the faces shed rain and dry sooner
• Can slow staining that comes from absorbed water
• Lets water vapor leave the masonry