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How to Remove Mildew from Concrete Without Bleach

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If you’re dealing with a mildew problem on your concrete, your first instinct may be to reach for the bleach as it is known to remove those unsightly black marks and stains. However, removing mildew from concrete is far more effective (and much safer) if you ditch the bleach altogether. So how can do it? It’s simple, just follow the top cleaning tips for your home exterior below and learn how to remove mildew from concrete without bleach.

The Mildew and Concrete Problem

Mildew is a type of mold which usually appears as a thin or fine dusting of a black, grey, or sometimes white growth. Mildew relies on three essential elements for growth – moisture and food. Although your concrete is not a direct source of food, that unsightly mildew gets fed plenty of essential nutrients by the fine layer of dust that sits on the surface of your patio, path or walls. The same goes for the temperature requirements of mildew – it’s happy to grow in any temperature you live in. And of course, concrete is also a major moisture magnet!

Outdoor mildew can grow on hard surfaces such as concrete patios or the floors of your basement. Not only can mildew ruin the appearance of your concrete and make the surface slick and slippery, it can also become a health hazard. Some people have allergies or sensitivities to mildew which can result in serious reactions, especially in people who have weak immune systems or respiratory conditions. For many reasons, if you have an issue with mildew, you want it gone, and quickly.

Blue and white bleach bottle

The Bleach Problem

Bleach is the first go-to product for many people facing a mildew infestation. But did you know that bleach does not actually kill mildew? In fact, bleach lightens the outer layer of the organism, which enables it to survive deep beneath the surface. Bleach is also one of the environment’s biggest enemies.

When you use bleach outdoors, you run the risk of killing plants due to harsh chemicals in the runoff. Even using it indoors can filter dangerous chemicals into the air. While the removal of mildew form concrete does require some heavy-duty cleansing, many bleach hazards are gaining lots of negative media attention which is causing people to reconsider how they clean.

Before you think of bleach as your power agent against mildew, look at these facts:

  • Bleach can cause mildew to grow in new places.
  • Bleach may temporarily get rid of mildew stains, but it will not remove the internal roots.
  • Bleach is classified at the same toxicity level as gasoline.
  • Bleach is highly harmful to the skin. The “oily” sensation you may have experienced when using bleach is the top layer of your skin starting to dissolve!
  • Bleach can be a serious health hazard and it can make your mildew problem worse in the long term.

Solving the Mildew Problem

With all this in mind, it makes sense that you should avoid bleach when tackling your mildew. So how can you successfully remove mildew stains without reaching for the bleach? Follow our simple tips below:

Make a Water and Vinegar Solution

A homemade water and vinegar solution is one of the most effective ways of creating an inhospitable environment for mildew spores and removing mildew from concrete.

Here’s our step-by-step guide on how to do it:

  1. Make sure you wear rubber gloves to protect yourself from the mildew spores and to prevent the acidity of the vinegar from irritating your skin.
  2. Pour 9 parts water and 1 part distilled white vinegar into a spray bottle and stir the liquid to ensure the vinegar is properly distributed throughout the water.
  3. Spray the mixed solution onto the areas of mildew and gently scrub the surface with a sponge to eradicate the black layer of the mildew. Wipe the mildew away with a clean paper towel.
  4. Dip a clean sponge in undiluted white vinegar and wipe the mildew infested area. Make sure you apply enough vinegar to fully saturate the surface.
  5. For minor mildew problems, leave the vinegar to dry for 15 minutes. If the mildew issue is more severe, leave the vinegar for at least one hour.
  6. Pat down the surface with a paper towel until it is dry.

Continue with this method once a week until the problem has completely subsided.

Apply Water Pressure

Sometimes, it’s the simple things that have the biggest effect, and when it comes to removing mildew, water is certainly one of them. You can use water and a pressure washer to remove mildew from concrete, whether the problem is outdoors or indoors. Ensure the pressure washer is powerful enough to strip the mildew from the concrete. A gas powered pressure washer such as the Simpson MSH3125 does great at these kind of jobs and is an affordable solution compared to the pricier models.

Holding thumb over water hose to build pressure

Simply set the power sprayer on the highest power setting and blow the mildew off the concrete. As you see the mildew being blown away, use a vacuum to suck up any wastewater. You can also sweep away the water into a sump pump. If you’re tackling an indoor mildew problem, use a wet vacuum at the same time as you use your power sprayer. Who’d have thought that water is all you need to remove pesky mildew from concrete?

Pressure washers are more useful than most think. Check this out to find out some of the more unusual uses that people are using their pressure washers to complete.

Dig Out Your Baking Soda

That baking soda you have at the back of your cupboard could be a handy tool in the kit when it comes to removing mildew from concrete. Baking soda (or sodium bicarbonate) has a pH of around 8-8.1, which provides an alkaline environment, making it incredibly difficult for mildew to grow or thrive in. You can use baking soda as a disinfectant when scrubbing away at your concrete, which can also be an effective way to break up the slimy structure of mildew. By mixing the rough crystals of baking soda with water, you can create an awesome scrubbing solution for mildew removal.


When it comes to using bleach on mildew, the simple answer is to avoid it. Lots of people put their health and the environment in danger. As such, they run the risk of worsening their mildew problem just because they don’t realize there are many safe bleach-free solutions. If you have a mildew problem on your concrete, try one of the above solutions before putting your health at risk with an ineffective bleaching solution.