Sign In to join the community | Help

Black Mold Spots Everywhere!

Many of the square concrete pavers we laid some years ago as a walkway to the back yard & as a patio have developed black spots and large black areas in the spaces between and on their surfaces.  Two solid concrete patios that were built by the home's prior owner, also are turning black.  We hired a guy to clean some areas with soap & a power sprayer, but the mold returned.  I tried a product made for removing outdoor mold on concrete, but it barely worked.  I'll pull up some pavers and check for standing water, but i know there's no standing water beneath the patios.
      Does anyone have advice on how to remove the mold and keep it off?
Not what you were looking for ? Try posting a question
Posted 2017-09-06T21:33:33+0000  by BNatalie BNatalie
Hello BNatalie.

Black mold can be difficult to get rid of.  There is a fairly new product that you dilute in 5:1 and spray on.  It will yield quick results on moss, mildew, algae and green mold, but black mold may actually take a few weeks to disappear.  The product is called Wet & Forget.  It looks like this:

You can find it here online:



Posted 2017-09-07T13:19:06+0000  by Chris_HD_CHI

Image result for images of black mold on patio stones

Greetings BNatalie,

Fungus and mold are a result of conditions that are perfect for their growth and development.

Is there a possibility that some trees, once grew at the sight where the patio now stands? Could there be decomposing trunk and root systems below the concrete patio?

Do you have pets that live, play and use the patio?

I ask the questions because the breakdown of organic matter beneath the surface can sometimes result in reactions on the surface. Mushrooms, also a fungus, can be found growing in colonies above a decaying root system where a tree once grew.

Once a fungus or mold starts to grow because the conditions are right…then they can spread from spores on surfaces, mold and mildew can grow with virtually no roots, but love to become seated and take hold within cracks and crevasses…. which explains the mold between the pavers.

It sounds like you have taken action to clean things up a few times, but mold and mildew are persistent and any leeway given they will take up residency again and again….I feel that you need to change the soil make up and structure under and around the stones.

If you do have pets keep them away from this whole prosess from beginning to the end…entirely!

My first step would be to clean the stones again, I know it is redundant but you must stop the spores from having a chance to spread and grow. TSP and a stiff brush mixed with cold water, use gloves and a mask. (Baking soda, vinegar and ammonia is an old recipe that helps break down mold, and of course a good scrub) Clean the surface of the stones in a circular motion with stiff brush to break down the growth pattern and growth habit of the mold.

Allow to totally dry, even the soil around and between the pavers, on path and patio. Some soils naturally hold water because of compaction and soil structure…that needs to change! I feel that you need to change the soil make-up by adding lime and gypsum.

Once all is dry, sweep limestone across the pavers pushing excess into crevasses and margins of the patio and walkway. Leave a bit of lime on the stones, the lime will breakdown with moisture possible absorbed into the porous stone. Raise up some of the pavers and apply lime under the stones if you can. The lime is going to change the pH of the soil to inhibit growth of fungus, change perfect cultivating conditions.

Gypsum is a totally different amendment to add to your soil, lime changes the pH of the soil, gypsum alters the structure…sort of spreading apart soil particles, changing structure…once again interfering with the perfect growing conditions for fungus.

I hope this information helps, it must be very frustrating to have to keep dealing with the black mold…One more question: Are there any trees that overhanging the patio and path that drop leaves or fruit onto the stone surface?

Let us see what the other community members have to add, and I hope we can come up with a resolution to you problem!

Please keep us updated, let us know if you have any other questions,  Maureen




Posted 2017-09-07T14:09:31+0000  by Maureen_HD_BOS
Not what you were looking for ? Try posting a question