I have white limestone on my house. The north side that is not under my porch has a lot of what I assume is black mold. What is the best way to clean this rock without damaging it?

I also have some pillars of limestone on my entrance that have a lot of black on them too. Looks like crap.

Help.

I believe it's typically Mildew. I had good luck with a pressure washer, but you have to be careful if it's a high pressure one.

I have a similar problem and was about to ask the same thing. One thing I read suggested a mixuture of OxyClean and water. I know I've used that to clean grout before, and it works well. It did not seem to help at all with the exterior stone, though. I also read you should not use a pressure washer, as it could damage it.

jtraggie99 said:

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I have a similar problem and was about to ask the same thing. One thing I read suggested a mixuture of OxyClean and water. I know I've used that to clean grout before, and it works well. It did not seem to help at all with the exterior stone, though. I also read you should not use a pressure washer, as it could damage it.

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I read that about pressure washing it too. I may try a small spot to see what pressure washing does.

I have limestone. I have mold. I blast it with a 3000 psi washer. It does not remove it all and as stated, it can degrade it.

Check out JoMax at Home Depot. I use this to wash houses and it does pretty well. You do add bleach and I believe it works pretty well. Results appear overnight. You may need to do it multiple times but I'm certain you will have to clean chemically rather than physically.

I have limestone on the house that stays fairly clean but I do have some slabs that grow mildew pretty quickly. I wet them, scrub with a bleach solution, and then power wash with a wide tip.

Also recommend Wet and Forget. Works on brick as well. Spray a little past where you see the discoloration. You will think it is not working, and then one day you will notice a big difference, in other words, it takes weeks, not days.

I read a lot of reviews about wet and forget. Should arrive tomorrow. Gonna give it a try first. Thanks.