I pressure washed my patio yesterday but despite that it’s still looking tired. The slabs (most of them anyway) have developed spots on them
I tried patio cleaner on them, even trying a bit of neat solution, pouring it on spreading it out with a scrubbing brush, leaving for 20 minutes and then using the scrubbing brush again without success.
Sodium Hypochlorite has been suggested, but I’ve also been told that as a bleach it will fade the patio. The guy that suggests this, suggested Hydrochloric acid.
There are far better brains then I on here so I am hoping someone can steer me in the right direction.
Cheers.
Probably a daft question, but your pressure washer head is the one that fires the pin point jet in small circles, right? The one that’d take the skin off your finger if you put it anywhere near the jet?
I ask because my patio had similar spots and my Karcher patio jet ripper head took it mostly straight off.
I had a few tiny bits remain but thought it made the patio look nicer than when new. It adds a bit of patina.
I have the same issue. Spots remain after a thorough wash with the kaercher. Ive been advised to use vinegar... Basically pour some of it on the stains, let it sit for an hour or so, and then pressure wash again. I haven’t tried it yet but plan to do so soon.
Yep that’s the one. A Nilfisk in my case though. Took the grime off in a flash but wouldn’t touch those black spots.Originally Posted by mr noble
I’d suggest trying a treatment of Wet & Forget.
R
Ignorance breeds Fear. Fear breeds Hatred. Hatred breeds Ignorance. Break the chain.
I have the same issue with sandstone flagstones. I'm told it's mould growth, I've washed some of the spots out by carefully pointing the tip of the pressure washer right on top of the mould spot. Trouble is some of the spots remain which I hated at the time but now see it as a patina, plus I live in a victoriana house so see it as part if that aging process now.
I'd suggest getting it as clean as you can and then applying a sealer. Be careful if you go this route as some can give a gloss finish to your slabs. Also be carefully if you use a pressure washer as you can wash out the grout from between the slabs which happened to me basically I messed up and used the wrong stuff.
I've just had to relay and grout the patio
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I'd try bleach on a small area. It will 'bleach' organic matter but shouldn't affect stone.
Don't use hydrochloric acid on limestone, it will dissolve. Might be ok on sandstone but again, try small area.
I've just had to sort out the very same problem, the below works.
If you spray some patio magic on that when you know it's not going to rain for a few days it will get rid of those black spots, takes a few days but it kills all the growth and they look pretty much new again
Or I bought this stuff on Amazon which is the same thing, just get a sprayer, mix 4:1 with water, spray on patio when dry and leave it alone to let it do it's thing, you'll notice it gets noticeably better each day
https://www.amazon.co.uk/gp/product/...?ie=UTF8&psc=1
Sprayer
https://www.amazon.co.uk/Flostream-L...rds=8l+sprayer
It doesn't kill your lawn either if some runs onto it, it also works as an inhibitor to stop it growing back, ideally spray once a year in the Autumn and it stops it growing over the Winter
Last edited by Vanguard; 16th May 2018 at 10:08.
Try Jeys fluid.
Read up on Rogers Jollop...
I had exactly the same situation with my indian stone. I looked into the expensive solutions costing anything from £25 - £55 for 5 litres. However, as I have in excess of 100m of stone it simply wasnt economical.
I eventually went down the sodium hypochlorite route. £16 for a 25 ltr drum. I diluted it 5.1 with water in a watering can and sprinkled it over the wet stone. 30 mins later jetted it off. No more black spot, I used a Karcher at 160 bar and its come up like new. And I still have some hypo left, I have been told if you apply it periodically in a very weak solution it will prevent re growth of blackspot and mold. Deffo recommend this stuff.
Stuart
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Sodium hypochlorite (household bleach) also acts as a very effective weedkiller, it'll kill everything and poison the soil for 6 months. I would think carefully about drainage etc before using it on a patio.
Paul
I've been impressed with this stuff - works very slowly but it does work
I was going to suggest the same - fortunately my father has a swimming pool so I use him for supply but any swimming pool shop should sell you 5 or 20 litres and is much stronger and more economical than buying from the supermarket or similar.
It also inhibits re-growth and for a long time too.
Currently undertaking a lot of stone cleaning and it'll definitely be getting the W&F treatment once I've finally finished.
R
Ignorance breeds Fear. Fear breeds Hatred. Hatred breeds Ignorance. Break the chain.
Wet and forget does work, but you have to be patient as it does take a couple of months .
Soda blasting is the way to clean 'most anything.
Good timing, I have a 25lt drum of Sodium Hypochlorite tonight in the back of the car for this very purpose!
I was told that the black spots are most effectively removed with bleach. Just need to get the dilution ratios right now. Also told to pre-soak the stone first and do not leave the bleached sections dry prior to cleaning.
This. I gave a coat of Wet & Forget to get rid of moss/algae/green marks a few weeks ago and it's done wonders on the patio slabs so far, although as mentioned above it's not a quick fire solution..
I wet mine before sprinkling a 5-1 ratio on and the flags came up like new. A watering can is fine for the application and you dont really need an awful lot on each flag. Jet off after 20 mins or so and job done.
Stuart
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I would suggest this, had the same on our patio and fixed it
Great, thanks.
Any issues with grass or plants getting burnt or dying off with the run-off water?
Concentrated Sodium hypochlorite will definitely do the job I use once a year on block paving and it comes up like new and kills weeds like nothing else
But.... be cautious
Wear old clothes
Wellies are a must as are gloves
Don’t walk on grass or get it near lawn.
Don’t inhale it if possible
It will lift tarmac
Have a hose nearby just in case
Use a soft brush to move it around not a hard yard brush which flicks it around
And be careful with 25ltr tub as you pour as you can get splash back when putting down, that will make sense to those who have done it.
Sorry I sound like a HSE official but it’s powerful stuff
If left for 30 mins you will have a new patio.
My patio need repointing. There were some weeds and the like coming through the gaps and these have gone, but the jetwash i use is pretty powerful and this got some out. I have not noticed an awful lot of the surrounding grass being badly affected though, just bits here and there, nothing major. And grass will probably regrow anywhere.
Stuart
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+1 for Jeyes but get the dilution right and the tin suggests trying a small patch for the possibility of staining.
I did mine with sodium hypochlorite it’s about 10x stronger than bleach. Wet the patio first, put down the SH give it a brush over and leave for half hour. Rinse off and like new. Kills any weeds in the grout lines. Ruins your trainers 😁
Thanks folks.
I will give it a go over the weekend or early next week.
Well, gave it a go today.
Strong stuff, did the front early as I did not want the neighbours giving out about the smell.
It needs to be respected and worked on in the open air. Wellingtons and gloves, I wore glasses when mixing it.
Worked out alright. Need to give is a go again. I did not leave it for long enough. I left it for about 10-15 mins.
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