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Removing Stains From Patios and Walls

How to Clean Bricks, Stone and Concrete


It's inevitable: brick patios and walls get exposed to the elements or something else creates a stain: mortar, mildew, rust, paint and 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.


brick stacked stone
Photo &copy Lisa Hallett Taylor
What, exactly, is efflorescence? You've probably seen it numerous times, but just didn't know what it's called. Efflorescence is that white, or grayish 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?

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


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.


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.


Ah, rust -- it finds its way onto every metal and nonmetal surface in your yard, on your porch, patio -- everywhere outdoors. First, 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 rinsing.


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 the brick or stone.


Did you put your teenage son onto a painting project last summer, and he got a bit lazy, sloppy or carried away with the paint? And did he clean up afterwards? What stains? He doesn't see any wasabi green stains on the red brick patio!

Next vacation or school break, give Jason Jr. a putty knife to scrape off as much paint as possible from the patio or wall. After he's given it his all (five minutes, tops) he can 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. Find another project for Jason Jr., preferably something that doesn't involve a brush of any kind.


Yes, grafitti happens -- in every neighborhood. Drive to your local hardware store, buy a spray paint remover and follow directions. Repeat if necessary.

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