Removing stains from masonry

If you are about to put your house on the market and want to increase the “curb appeal” of your home, you may want to consider removing any stains on the outside of your house. Brick houses may develop a few stains and each needs specialized treatment for removal. This article will guide you through removing some common stains from masonry.


Efflorescence is a very common stain or deposit that forms on brick. It appears as a white powder and is formed with the mineral salts that are present in the mortar dissolve in water. While the stains can disappear by themselves in a few years, you may want to get rid of them right away if you are trying to sell your house. You should start by using water with a brush to scrub the area and wait for a few days to see if the stains have gone. If this does not work, you can use some muriatic acid (1 part acid in 15 parts water) and brush the mortar again. Rinse the area with water well so that no acid remains on the brick. Never use acid on marble or limestone.


Mildew can also form on brick walls over the years, especially in the areas that are continually exposed to moisture. Removing mildew is relatively easy. Create a solution that is 1 part bleach to every 3 parts of water. Add a little bit of laundry detergent or some trisodium phosphate to this solution. Use a brush to scrub the wall gently after pouring the solution on. You should leave the solution on for about 15 minutes to get rid of all the mildew and then rinse the wall with water well.

Hardened paint

Hardened paint needs to be removed with a putty knife. After you have scraped off as much as you can with the putty knife, you can use a brush with metal bristles and cold water to try to remove the rest of it. There are also commercial paint removers available for the job but they may stain the wall, so you should test it on a out-of-the-way spot on the wall before using it on a large area.

Mortar smears

Mortar smears can also be removed with a solution of muriatic acid and water. Use a 1-10 parts solution of acid and water for darker walls and 1-15 parts for lighter walls to avoid staining the wall. Let it sit on the wall for about 15 minutes. Make sure you rinse the wall well after you clean the smear.

Be careful and test each solution on a small area before using it on the whole wall.