How to clean concrete mold and moss

How to clean concrete mold and moss

There are a few things that do not look promising on structures. Mold and moss are two of them, as they promote moisture and dirt that let them prosper in the before mentioned structure.

You might have noticed some, and tried removing mold and moss, but it keeps growing back twice as hard.

While natural growth can be beautiful in places where we want it, like old soil support structures, 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 coming back no matter what.

Now you don’t have to worry about mold and moss growth any longer, as there are ways to get rid of them for good. You 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 shortly

To understand why something happens, it’s good to look at the process.

A natural occurrence for concrete is that it will appear weathered when exposed to cycles of moisture over a long period. Concrete surfaces that remain wet for extended periods promote mold and moss growth.

Either the place or other factors won’t let it dry.

Is moss on concrete harmful? In some places, it is not, but as it promotes moisture with time, it can turn out to be harmful to the structure.

Depending upon the cycle time that it takes the concrete surface to dry, the weathered surfaces can appear grey, black, or green.

Several products on the market today 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 cheaply?

You probably have one or two everyday household items in your house right now that can produce the same results at a fraction of the cost. The first common item is 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 explain both of them. Vinegar is also better for porous surfaces like concrete and 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 recommended to wear clothing 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 with a tip that fans out the spray. Then it would help if you had a stiff bristle scrub brush and a garden hose with a pressure nozzle.

For cases with heavy mold or moss concentrations, you may also need a power washer.

Light moss and mold and staining

This is the damage I’m most optimistic about when cleaning with bleach. If there is only light mold or moss, chances are it doesn’t run too deep and there is a good percentage for success.

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.

If you’re concerned with the surface changing color, you can also dilute the mix. It’s just not as effective.

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.

Depending on how deep the moss and mold are in the pores, it might be hard for the bleach to work perfectly. For moss, it shouldn’t be that much of a problem; you can also affect its growth by exposing it to a less moist environment.

Before committing to the process, I’d consider how much the process would cost for the area. If it’s cheap, why not try it out?

Heavily molded surfaces and heavy moss

For severely weathered surfaces, you will need to do the trial and error method. First, apply the bleach and then use a power washer or visa-versa. 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, wash the garden sprayer with purified 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.

For moss, this should work out as it’s good for killing plants and such. But for deep-run mold, it might not be enough.

Using bleach to clean concrete might promote more mold growth

How to remove moss and mold from concrete naturally

Vinegar can be synthetic or naturally obtained. If it concerns you, you can look up one from an organic source.

Vinegar might be harmful to the skin, so it’s also good to use protective gear here. The 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.

What is different here is that vinegar, being more organic, maybe, needs more time to work out well. It’s also a matter of how deep in the pores of concrete the problem is.

It needs to be on the surface for around 60 minutes before brushing. Again, this is a process we repeat until we have a good-looking concrete surface. When you’re finished, wash the concrete 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 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. Avoiding those is good; if you have some, consider adding some protection to them.

Will vinegar kill moss on concrete? Yes, and mold too.

The final part is sealing

As mentioned before, our problem is that we have a porous surface. So we should aim to fix this problem permanently by filling those pores with something useful.

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

It will seal the pores, so growth has a more challenging time sinking in. As the concrete stays clean and is easy to keep, you will have an easier time with these 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 an excellent reason to take preventive measures if you don’t enjoy mold and moss. I would seal the surfaces for easier cleaning, as mentioned before.

In the ultimate bad situation where nothing works, and I’m tired of cleaning the surfaces, I’d go for the 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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