How to Paint a Brick Chimney With Sealant and Protect Your Exterior

If you’re ready to tackle this project, there are a few things you should prepare before you apply the sealant. 

Buying Your Sealant

Painting your chimney with regular paint is not a great idea, but using a vapor-permeable sealant is a safe alternative to keep the brick looking fresh and help it last as long as possible. Check out the Chimney Safety Institute of America’s list of approved products to choose the vapor-permeable sealant that’s best for you based on your budget and availability.

For most brick chimneys, one gallon of vapor-permeable sealant will cover 100 to 150 square feet of brick. Measure your exposed chimney area before purchasing sealant so that you don’t spend too much on products you won’t use. 

Choosing the Right Weather

This DIY requires several days to complete, and you’ll spend most of this time waiting for the brick and mortar, caulk, and sealant to dry. Since your chimney is exposed to the elements, choose a mild week with low humidity and no rain in the forecast. The sealant alone takes at least 24 hours to dry, and it’s important that it stays completely dry during this time. Otherwise, you may have to redo your work completely. 

Getting on Your Roof Safely

First, remember: You’re going to have to get on top of your roof. We want to reiterate that this can be very dangerous for someone without experience and should never be attempted without full safety precautions. If this makes you nervous at all, put down the ladder and call a pro instead. If you’re familiar with the safety protocols involved in working on a roof and are confident that you can follow them to a tee, keep on chugging.

Lean your ladder against your home, and don’t place it in front of any doorways. Along with that little piece of advice, follow all other common ladder safety tips to ensure that you don’t fall and end up damaging your home or, worse, injuring yourself or others.

If your roof is slanted at an extreme angle, you need to use a safety harness and rope with a high minimum breaking strain (the force that would make a rope fail). Attach a roof anchor into the rafters at the roof’s peak, then attach your rope to the anchor and your harness. If you do happen to slip while working, this will stop you from taking a very dangerous and potentially fatal fall.

Before you start painting, thoroughly clean your chimney. A sturdy scrub brush and a bucket of water with mild soap or dish detergent will do the trick. Just be sure to get all the cracks and crevices before moving on to the next step.

If someone sealed or painted your chimney in the past, use 80- to 100-grit sandpaper to scrub off as much peeling and flaking material as possible. Then, inspect your chimney for missing or damaged brick mortar. If you find areas that need some attention, patch them using new brick mortar and a drywall knife. Allow your patchwork to dry and set for 24 to 36 hours.

Next, fill in any large holes or gaps in the brick with caulk to ensure a smooth surface and prevent water from ruining your paint. You want to seal any gaps larger than 1/16th of an inch. Let the caulk cure completely before moving on—usually about one to two days for chimney caulk.

Before you begin painting your vapor-permeable sealant onto the brick, cover the roof at the base of your chimney, the ground around your chimney, and the ladder with drop cloths. Use painter’s tape if necessary to secure the cloth to the roof. The drop cloths will catch any stray paint that may fall or blow in the wind, making cleaning up much easier.

Since bricks are porous, it’s much more effective to use a paint sprayer to apply your vapor-permeable sealant. However, if you can’t use a sprayer for any reason, you can use a paint roller and a brush to get the same effect—it may just take a slightly longer time and more detail to get full coverage.

Once you’ve got all the bricks covered, you can come back in with a small touch-up brush to fill in any hard-to-reach areas or odd angles that your sprayer or roller didn’t touch.