flagstone discoloration from pressure washing?

by dan

Hi-- I had a flagstone patio laid on 4" fiber reinforced slab (regular cut).

the mason used a water based sealer. half of the patio turned out perfect, the second half, the larger and more used part, he said he tried to put on the sealer heavier because of the traffic... for some reason, the stone bled onto the grout, so there were sections of grout that were bluish or greenish, coincident with the adjacent stone.

so he went back with a pressure washer around the joints of the stone to remove the seal and tried to remove the staining on the grout, then resealed the whoel patio (another coat)

I dont know if he pressure washed to much, but even after resealing, you can see all the areas he pressure washed (they are darker) and you can actually see the swirly lines from his pressure washer...

so like 1/3 of the stones now have darker perimeters that correspond to where he pressure washed, when compared to the inside, and the whole patio is resealed, and it still looks like this.

I can see the pressure washer lines in the stone, and all the edges are darker then the rest of the stone... is it possible he pressure washed too hard, and took the stone down to a diff/darker layer then the top layer of the stone that was presviously sealed and not pressure washed?

each stone looks like it has a coaster ring of a darker color on the perimeter.... and some of the stones actually have definitely obbvious daker color lines that correspond to where he pressure washed!

I can give a pic tomorrow if you need one...

what do you think happened, what can be done, and what should i have him do???


Comments for flagstone discoloration from pressure washing?

Click here to add your own comments

pressure washer lines NEW
by: Anonymous

Same problem happened when my contractor used pressure washer to get rid of grout, leaving behind circular lines. I have large area of quartzite stone and wetting the stone or sealing it with a color enhancer seems to hide the lines thus far. I tried sealing it on certain areas and so far so good. I'm just wondering if anybody else has any other ideas as the seal will eventually fade :/ Thanks.

Owner/D&D Stone Brokers
by: Don

I haven't been able to access your pics, please send them to d.mack.56@hotmail.com and I will be glad to give my opinion, but don't let your mason acetone or anything else until you get a second opinion.

by: Anonymous

here is a picture of a section where the sealer turned out good


here are 2 pics where it didnt turn out good and you can see the rings on the perimeter... does this look like power washing damage or could it just be from not removing the sealer from the stone totally before applying sealer again??? what should i have the mason do???



by: Anonymous

the mason says what he wants to do is to remove sealer from a small area, using paint thinner to remove the sealer with towels, and then acetone the surface clean. what he thinks is that he should have removed all the sealer before resealing, instead of selective removal of sealer. he says that is why there are different colors, and he doesnt think the pressure washer can really damage the stone like that.

think there is any merit to that? i can provide a couple pictures if that helps- let me know, i am new to this site.



I agree with Don
by: David

Dear Dan,

I think Don is correct. You should power wash the whole patio again until you get it looking the way you want. Give it a few days to dry off before you think about using any sealers.

If that doesn't work, then you might have to sand blast which makes a big mess.

Great luck!


Owner/D&D Stone Brokers
by: Don

Your mason has cut into the stone , because he got to close to the stone with the pressure washer nozzle, you have cut into the next layer of stone and I don't know that you can fix the stone unless you pressure wash all the stone at the same depth.

Click here to add your own comments

Join in and write your own page! It's easy to do. How? Simply click here to return to Flagstone Question.