How to clean concrete mold and moss

How to clean concrete mold and moss

Do you have mold or moss on your concrete and it’s not a decorative point you want to make? Or maybe you have tried to remove mold and moss, but it keeps on growing back twice as hard?

While natural growth can be beautiful in places where we want it, it can be an annoying problem if it’s happening with your new driveway. You try to wash it with a pressure washer, but it keeps on coming back no matter what.

Now you don’t have to worry about mold and moss growth for any longer as there are ways to get rid of it for good. You just have to prepare to work smart about it. I’ll show you two cheap alternatives and you can check if they would fit well.

Concrete life cycle

A natural occurrence for concrete is that when it’s exposed to cycles of moisture over a long period of time, it will appear weathered. Concrete surfaces that remain wet for extended periods of time promote the growth of mold and moss. Either the place or other factors won’t let it dry.

Depending upon the cycle time that it takes the concrete surface to dry, the weathered surfaces can appear grey, black, or green. There are several products on the market today which can renew the appearance of these materials. However, they are usually in the fifteen to twenty dollar per gallon price range. So what to use to clean concrete cheap?

You probably have one or two common household items in your house right now that can produce the same results at a fraction of the cost. The first common item is called bleach, which you probably purchased for under two dollars per gallon. The second one is vinegar which also should be in the same price range.

One noteworthy thing is that bleach only kills mold from the surface. There are also claims that it can promote mold growth. Vinegar is another traditional and less toxic alternative so I’ll give run through for both of them. Vinegar is also better for porous surfaces like concrete and it can kill mold and moss on a deeper level.

How to clean concrete with bleach

Knowing the effect that bleach can have on clothing, it is recommendable to wear clothing that you are willing to throw away after you’re done. It is also a good idea to wear rubber gloves that cover your arms, and of course, protective eyewear.

Depending on the size of your project, you will probably need a pump style garden sprayer. One with a tip that fans out the spray. Then you need a stiff bristle scrub brush and a garden hose with a pressure nozzle. For cases where there are heavy concentrations of mold or moss, it is possible that you will also need a power washer.

Light mold and staining

The first thing that you need to do is to pour the bleach undiluted into the garden sprayer. Spray the bleach directly onto the surface evenly and allow it to sit on the surface for a few minutes. You will see the transformation occur almost immediately.

For badly weathered surfaces, you will need to brush the bleach into the surface. After allowing the bleach to remain on the surface for a few minutes, rinse the surface thoroughly with clean water. If needed, you can repeat the same process over again.

Heavily molded surfaces

For surfaces that are severely weathered, you will need to do the trial and error method. First, apply the bleach and then using a power washer, or visa-versa. Personally, I’d start with washing with a pressure washer to see how much will leave by water.

After the surface is washed, the previous bleach and brush process can be repeated. Also, be careful with a pressure washer, you don’t want to wash it too roughly or it will leave marks on the concrete. Depending on the power of the pressure washer.

After the bleaching process is completed, you should wash out the garden sprayer with straight water. Make sure to spray the water through the hose so that you do not leave any bleach in the spraying mechanism, which could cause corrosion.

Using bleach to clean concrete might promote more mold growth

How to clean concrete with white distilled vinegar

Vinegar might be harmful to the skin so it’s good to use protective gear here as well. Good thing is, it is even more harmful to mold and moss so if bleach isn’t working, this should do the trick.

The cleaning process here is pretty much the same. We need to spray white vinegar on the mold and moss. We can use the vinegar undiluted so it works better if the problem is stubborn.

It needs to be on the surface around 60 minutes before brushing. Again, this is a process we repeat until we have a good-looking concrete surface. When you’re finished, give the concrete a wash with a garden hose and let it dry.

Concrete is porous and sometimes the mold and moss are deep in it, waiting for chances to grow back. In those kinds of situations, you should repeat the process and let it affect the concrete even longer. Eventually, they should give in.

Also as a warning vinegar is harmful to some surfaces like iron and some natural stones. It’s good to avoid those if you have some consider adding some protection to them.

The final part is sealing

After allowing the cleaned surface to dry out completely, you can then apply a penetrating sealer to resist the weathering process from re-occurring.

It will also seal the pores so growth has a harder time sinking in. As the concrete stays clean and is easy to keep clean, you will have an easier time with these kinds of problems.


Mold and moss can be hard to get rid of as they can go deep into concrete and removing them might provoke fast growth. In that sense, vinegar is good for removing them as it sinks deep into the concrete.

This is also a good reason to take some preventive measures if you don’t enjoy mold and moss. I would personally seal the surfaces for easier cleaning as well as mentioned before.

In the ultimate bad situation where nothing works and I’m tired of cleaning the surfaces, I’d go for ultimate resort and grind the surface and resurface it. After that, I’d do whatever decoration I’m planning and seal the surface for eternity.

This is probably the most you can do without removing the slab.

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