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How to Clean Concrete: Banishing Stains in the Suburban Blight

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In my childhood neighborhood, summer started when the first dad connected a garden hose to clean his concrete driveway. Soon, the other dads, clad in khaki shorts with blindingly white legs and the infamous black-sock-and-sneaker combo, joined in. 

In our corner of suburbia, concrete stains were an embarrassment. You cleaned them, or your friends’ parents would start asking about your parents’ health. I live thousands of miles away now in an area where people go by other standards, but I’m still fussy about this task. 

If you’re fed up with the sight of mold, moss, grease, or rust stains messing up your concrete surfaces, stick around. I’ll guide you through using simple tools like a hose, bucket, and broom, along with some common household items from your laundry room or kitchen, to effectively remove those stubborn stains. 

General Concrete Cleaning

To get rid of winter grime on concrete surfaces, dissolve 1 cup of baking soda in a 5-gallon bucket of hot water and add 1 tablespoon of a grease-cutting liquid dish soap. Use a push broom to spread this around, scrubbing dirty spots as needed. Then rinse with the hose and let it dry.

Cleaning your concrete surfaces with this method monthly prevents discoloration from pollution and weathering. It’s a great way to wrap up a garage deep-cleaning, too. Then spot treat lingering stains using the methods below.

Did You Know?

Your driveway is more like a sponge than you think. As concrete dries, tiny spaces called pores form. Many concrete stains result from things soaking into these pores and getting below the surface. 

Mold, Mildew, or Moss Stains

Quick, what do mold, mildew and moss have in common? They all need moisture to grow, which the concrete provides after absorbing water from the air (as in, humidity) or through direct contact (like rain or snowmelt).

To clean mold, mildew or moss stains left on concrete after general cleaning, mix 1/4 cup of oxygen bleach into 1 gallon of hot water. Apply to the stained area, ensuring it stays wet for 30 minutes for mold or moss, and 15 minutes for mildew. Scrub with a broom, then rinse and dry.

Of the three, mold is the most challenging stain to clean on concrete since it sends roots, known as hyphae, beneath the surface. On the other hand, mildew and moss are surface stains. All three will regrow if you don’t completely eliminate them.

Pro Tip

A mix of equal parts water and vinegar can also tackle mildew or moss stains. Spray it on 10-15 minutes before general cleaning as part of ongoing monthly maintenance.

Rust Stains

Concrete surfaces pick up rust stains paint or garbage cans sitting on them in humid weather to wet patio furniture or grills. Fortunately, it’s not hard to clean rust off concrete. You can scrub it with 3% hydrogen peroxide, or that cleaning duo of baking soda and vinegar can do the trick with a twist.

First, make a paste of baking soda and water and apply this to the area with a damp cloth. Let this paste sit pulling the rust out of the concrete for a couple of hours up to overnight. Then spray the area with undiluted vinegar to finish lifting the stain. Once the fizzing action stops, rinse the area to neutralize the vinegar so it doesn’t etch your concrete’s surface.

Greasy or Oily Stains

Remember what I said about concrete being porous? Since you can’t send your garage floor or driveway to the aesthetician for a facial, you’ll have to give it a clay mask to clean those pores then wash it away with a good cleanser.

Cover the greasy concrete stain with a thick layer of clay cat litter and let it sit for 24 hours to absorb the oil. Check every few hours. If the top layer shows grease, add more cat litter to continue absorption. After a day, sweep or vacuum up the mess. Scrub the area with hot water and degreasing dish soap, then rinse and let dry.

Tips to Keep Concrete Clean

Although getting rid of stains on concrete isn’t a hard job, it can be time consuming. So here are some tips to keep them from happening in the first place:

  • Clean up spills ASAP.
  • Use drip mats under cars to catch oil.
  • Place outdoor rugs beneath patio furniture to prevent rust stains.
  • Use raised storage in your garage to keep things off the floor.
  • Sweep or blow storm debris and fallen leaves off concrete surfaces promptly.
  • Apply sealant every 2 to 3 years, or get a professional application that can last up to 20.

Of course, if you look forward to spending Sunday mornings soaking up sunshine while you clean concrete around your home, go for it and let the neighbors look for something else to talk about for a change.

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8 Comments

  1. Help, I have a stain in my basement cement from soda that wasn’t found for a while that stained into the cement and its black. What is a safe way to try to get rid of it.. TIA

    1. Katie Berry says:

      I’d try oxygen bleach and water to start.

  2. I have a stamped concrete patio and just power washed it so that I can apply a wet look sealer. After power washing the patio, the areas under where the table and grill were located have a different and darker look to them (concrete has a stamped dark tone originally). Could this discoloration just be due to less wear and tear from sun and weather elements? Or should I look into a cleaning agent for those areas? Thanks for any response that you can’t provide.

    1. Katie Berry says:

      Since your stamped concrete is dark-toned, my guess is that the other areas have faded with exposure to the elements. Probably not much you can do about that, but you might want to ask a concrete professional.

  3. 5 stars
    I have white cauking smears on my cement door threshold and surrounding brick from a bad installation. How can I remove these stains?

    1. Katie Berry says:

      Hi Gerry,
      Mineral spirits and a good scrub should do it. You can also find caulk residue removers at most hardware stores.

  4. Here is a tip. If using a push broom with the cat litter, flip it over and grind the litter in with the wooden side of the broom first. It will work great to grind up the litter and force it into the stain.

    1. Katie Berry says:

      That’s a helpful tip, Dale. Thank you for sharing!

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