Chimney waterproofing that lets the brick breathe in Buena Vista

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.

How much product a chimney takes

The amount of repellent a chimney needs depends on the surface. Porous, rough brick takes more than dense, smooth brick. Mortar joints and earlier patches can take different amounts again. The test area gives a good guide.

We base the estimate on the faces to be treated and on the product's coverage for that kind of surface. We do not dilute or stretch a product to cover more. If the test shows the brick is thirstier than expected, we tell you before continuing, rather than applying less than it needs.

Why chimneys get wetter than walls

A chimney stands above the roof with no eaves or overhangs to shelter it. Rain hits every face, and water that lands on the top runs down the sides. Brick industry guidance names chimneys among the masonry most exposed to water.

That exposure is why chimneys are one of the places a repellent can make sense, once repairs are done. It is also why the top matters so much. A chimney that sheds water from its top and roof junction gives any treatment on its faces a much easier job.

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