How to Clean Previously Painted Concrete Walls

Written by michael davidson
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How to Clean Previously Painted Concrete Walls
Paint is effective for decorating concrete walls. (Hemera Technologies/ Images)

Concrete walls are highly durable, but they do require regular cleaning and maintenance to keep them looking their best. Concrete shows dirt and staining easily because of its grey colouring and even painting concrete walls won't completely disguise dirt and mould build-up. If you're cleaning a concrete wall that has been previously painted, care needs to be used to prevent the paint from being damaged. You can protect the paint and clean the wall effectively with the proper cleaning materials.

Skill level:
Moderately Easy

Things you need

  • Mild detergent
  • Bucket
  • Sponge
  • Scrub brush
  • Hose
  • Oxalic acid
  • Oxygen bleach

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  1. 1

    Mix warm water with a few drops of mild detergent in a bucket.

  2. 2

    Apply the detergent mixture to the wall using a scrubbing sponge. The detergent is strong enough to remove dirt and stains but should not be strong enough to damage the paint on the wall, unless the paint is already peeling.

  3. 3

    Scrub any stains remaining on the wall with a nylon brush to further work in the detergent.

  4. 4

    Rinse the wall with a hose.

  5. 5

    Blend an oxalic acid cleaner with water in accordance with the cleaner's instructions to take care of any remaining rust stains. Test the mixture on a small part of the wall to test its effect on the paint. Add more water to the solution if the paint is affected. Once you're comfortable with the solution, apply the mixture to the rust stains and scrub them with a scrub brush. Rinse the cleaner away after the stains are gone.

  6. 6

    Mix oxygen bleach with water like you did the oxalic acid for any remaining stains in the concrete. Colour test the solution on the wall and then apply it with a sponge and let it sit on the stains for several minutes. Scrub it in and rinse it off.

Tips and warnings

  • Always wear rubber gloves when working with bleach or acid cleaners because they are highly corrosive.
  • Wear a protective, disposable face mask to protect yourself from fumes.

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