How to Clean Mildew Off a Driveway

Mildew and your driveway are not a good combination. The mildew will make any concrete driveway look dingy and dirty. Even black driveways will be marred by this slippery and unattractive substance. It’s a good thing mildew is easy to remove, and, with regular driveway cleanings, it is unlikely to return. Many are tempted to use chlorine bleach to clean off mildew, but this is a bad idea. Not only is it toxic to pets, it will also kill your lawn.

Things You'll Need

  • Push broom
  • Grill brush
  • 2-gal. bucket
  • Garden hose
  • Biodegradable powder dishwasher detergent
  • Rubber gloves
  • Oxygenated bleach (if needed)
  • Power washer (if needed)

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Take your push broom and sweep the driveway. Get all the dirt, sticks, leaves and other debris out of the way so you have a clear space to work.

Fill your bucket 3/4 full with lukewarm water. Then add a 1/2 cup of biodegradable powder dishwasher detergent. (One brand is Seventh Generation.) Stir the solution with gloved hands until you have a rich lather.

Pour the entire bucket of cleaning solution directly on the mildew. Then take your grill brush and scrub at it, using a back-and-forth motion. In most cases, the mildew should come off fairly easily in 15 to 20 minutes. If it doesn’t, switch from your dish detergent solution to one of two parts water to one part oxygenated bleach. (Unlike chlorine bleach, it is nontoxic.) Rinse the driveway with your garden hose.

Check to see if all the mildew is gone after scrubbing with the detergent, bleach or both. If not, rent a power washer from the hardware store. (Tell an employee what type of driveway you have so she can recommend the right one.) Fill the power washer with the oxygenated bleach solution and put it on its high setting. Move the washer nozzle from left to right across the mildewed area in rows. It will provide substantially more pressure than the grill brush alone.

Let the driveway air dry. Check it once a week for any reappearance of mildew. If you scrub it off when it first appears, you’ll save yourself time and aggravation.

Tips & Warnings

  • Consider sealing your driveway once it's dry to help protect it from future stains. If your driveway gets mildewed because of poor drainage, you may have to change the slope of your lawn.
  • Don't use the power washer on parts of the driveway that are cracked. The force could, and probably will, make this problem worse.
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