Natural stone patio - cleaning help


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Old 04-08-22, 10:44 AM
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Natural stone patio - cleaning help

Hi there. I have a 900 SF flagstone patio made from a stone called “bronte.” I think that is a sandstone but not 100% sure. Never been sealed.



anyway, part of the patio never gets any sun and so had accumulated some mildew and last year I used a cleaner rated for natural stone and I guess I left it on too long because A couple got a bleached out look. And so this time I am going to try to just use pressure washer. Time to redo the poly sand joints anyhow So not worried if they get blown out.



wondering what the best way is to combat that bleached out look. And there are A couple others that have been discolored by grease or oil from our outdoor kitchen. So was wondering about the use of abrasives or even some mechanical cleaning of some sort. But worried about damaging the sandstone particularly because it has a riven or waved texture on top. I don’t mean like a diamond cup that you would use for stone tile or anything, I was thinking just more some kind of really stiff wheel attachment for a rotary or oscillating tool maybe? Or even some kind of pad/wheel that you could put on an angle grinder? To get enough of the less than perfect surface off and get down below that layer Just worried about swirls and scratching that could look just as bad. If not worse. Maybe a poultice and just good old elbow grease for the oil stains….but what about the bleached out looking top layer on the others?



Any advice appreciated !

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Old 04-08-22, 11:47 AM
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You can pressure wash first to mechanically remove as much dirt and algae as you can. I find that a bleach (chlorine) solution is best to remove and keep algae and moss at bay. I use a pump garden sprayer and apply enough to thoroughly wet the surface. Apply at the beginning of the season and clean the patio and then reapply as needed, maybe in several months.

You could try a floor scrubber with either a bristle brush or scrubby pad but that's uncharted territory. I think it could work well but I think a pressure washer is the better tool.
 
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Old 04-08-22, 03:37 PM
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Look up pressure washer plate cleaner. it's an attachment for a pressure washer and it's designed for flat surfaces. It's a lot milder than using a wand as it's in constant motion, it's what I use and will be using this weekend to clean my walkway(s) and patio.

Do not use anything abrasive you will most likely damage the surface, start mild and work your way up.
 
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Old 04-08-22, 06:19 PM
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Follow up

Thanks Dane and Marq! Maybe I didn’t really phrase/frame my question the right way. I have a surface/plate attachment (cheap one). What o am really asking I guess is…those bleached-out spots and those oil-saturated spots…those are not going to respond to pressure washing.

is there a way to sort of sand/grind/rub off those damaged areas? Like skim off the damaged top layer and get to an undamaged layer below? Or by doing so, am I just going aggravate the problem by highlighting that these few tiles don’t look like the other because I ground it down to the point it lost its texture? I was hoping there might be a really stiff Dremel or angle grinder attachment that might work. To just BARELY sand off the top enough to get past the discoloration but not blast it flat

I guess I can bang out the few pavers and just replace. I have extras.

Thanks for the info!
 
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Old 04-09-22, 07:01 AM
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Any kind of oil will have soaked into the stone, it's porous, not sure what the white spots are. There is really no way your going to grind the surface off and have it look bad. Try the cleaning, it that doesn't work just pop them out and install new ones!

Never been sealed.
​​​​​​​Probably will now after cleaning and repair!
 
 

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