A Guide to Removing Stains From Patios and Walls

It’s inevitable: brick patios and walls get exposed to the elements or something else creates a stain: mortar, mildew, rust, paint, even graffiti. Before you attack it with your power washer, find out the best remedies for your patio or wall’s particular stain, or it will not-so-mysteriously find its way back onto your brick masterpiece. Remember: there’s never a quick-fix, one-size-fits-all solution to anything.


bricks and mortar

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When using mortars, workers—do-it-yourselfers included—sometimes get sloppy. What results are mortar smears, which show up after the mortar has dried. To remove stains, use a muriatic acid solution:

    • Dark bricks or stone: 1 part acid to 10 parts water
    • Light: 1 part acid to 15 parts water.
    • Caution: Pour acid slowly into water; never pour water into acid. Apply as directed, allow to stand for 10 to 15 minutes, then rinse thoroughly.


brick stacked stone

Lisa Hallett Taylor

Efflorescence is that white, or greyish white substance that shows up on brick, stone, paver and other outdoor construction projects in which mortar is used. It happens when mineral salts in the mortar are dissolved by water and can also be referred to as calcium hydroxide or free lime.

It usually appears a few weeks after the project has been completed, creating a certain anxiety for the homeowners. Before complaining to your contractor though, why not tackle the cleaning project yourself?

Wear a ventilation mask, long sleeves, protective eyewear, and strong, synthetic gloves when applying acid. Use a long-handled, coarse-bristled brush.


mildew on wall

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For mildew stains:

    • Use a solution of 1 part regular household bleach to 3 parts water, with a small amount of mild laundry detergent or trisodium phosphate mixed in.
    • Allow to stand for 15 minutes, then rinse.
    • Repeat, if necessary.


rust stain on concrete

Jill L Wainright/EyeEm/Getty Images

    • Try scrubbing the rusty object with a household bleach solution of 1 part bleach to 1 part water and allow it to stand for 15 minutes, then rinse.
    • If that doesn’t do the trick, attack it with a solution of 1 pound of oxalic acid to 1 gallon of water.
    • Allow this to stand for about five minutes, then rinse thoroughly.
    • Test the oxalic mixture on a small, out-of-sight area first, to make sure it doesn’t create another type of stain on the ​brick or stone.


garden chairs being painted

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    • Scrub at the hardened paint splotches with a metal-bristled brush and cold water.
    • If and when that doesn’t do the job (seven minutes), you can have at it with a commercial paint remover, testing on a small area first to make sure it doesn’t stain the brick or stone.


graffiti and paint

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Yes, graffiti happens—in every neighbourhood. Drive to your local hardware store, buy a spray paint remover and follow directions. Repeat if necessary. If it doesn’t work, consider painting the wall or retexturing the surface.

By Lisa Hallett Taylor