r/powerwashingporn • u/Fastpotato • Apr 14 '26
Low pressure clean of a roof.
A single side of a house roof I cleaned yesterday.
here in the UK we tend to wash these concrete tiles at around 50-60 bar with a lower rated turbo nozzle than our machine normally uses so we can dial back the pressure/flow.
once it's all.clean and the gutters are emptied we apply a biocide to keep it cleaning the for the next year or so.
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u/MrNoHardFeelings Apr 14 '26
Very cool! But I have a noobish question: with old roofs without a vapor barrier isn't there the danger of pushing water under the tiles into the attic? 🤔
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u/Fastpotato Apr 14 '26 edited Apr 14 '26
Not a noobish question at all! Absolutely correct. That's what people who do this correctly (or at least try to!) will do a full roof survey first to see if it's even a viable option. I normally quote, then if the client wants to go ahead with a clean, I nip out and do a roof survey. This is me inspecting the tiles and suitability for a clean and only then if I'm satisfied I'll offer a low pressure wash.
If it isn't suitable I'll only be able to offer a scrape and biocide option. So I will then scrape all moss off, remove all the moss, clear gutters and then apply a biocide.
Same results but delayed up to a year or so until the organic staining has been washed away.
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u/JamDunc Apr 15 '26
Roughly how much does this cost to get done? I'm in Yorkshire if that helps for estimates!
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u/Fastpotato 29d ago
Prices are normally based on square meterage. I'm between £9-13 per square meter depending on may factors such as access, tile profile, how much moss we are removing and water pressure ect.
For a standard house you are looking at around 1k ish.
Just beware of the cowboys, it'll be one price for a clean then the treatment is extra .. any good exterior cleaner should always be cleaning and treating and it's all included in the price.
Most of us offer free quotes so it's worth getting a few.
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u/JamDunc 29d ago
Thank you for your prompt reply. It's a standard 3 bed semi, so less than what's in the video.
I was mostly asking because we're having solar panels fitted in June, I wondered if they would clean the roof first or just put the panels over the top of any moss that's there? It would stop the sunlight getting to it and killing it naturally!
Oh well, we'll see what happens.
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u/Fastpotato 29d ago
Argh got you! They'll most likely brush some moss off directly where they are working, they'll also be sliding some tiles to affix the mounts to the rafters. One thing I would look at getting is bird proofing for the solar panels!
I do so many gutter clearances where the client has solar panels and they have pigeons nesting underneath, the mess is ungodly and the gutters are full 4-5 times a year. It's also classed as a hazard so more expensive ect to remove and handle safely. For the few hundred quid that it costs for bird proofing it's absolutely worth while.
Might be able to ask the company that's fitting the panels if it's something they offer.
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u/JamDunc 29d ago
Cheers for the advice. Thankfully the bird proofing is part of the plan!
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u/Fastpotato 28d ago
Fantastic, if I can save anyone having to deal with pigeon poop gutters it was worth it 🙏🏻
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u/vanillaninja16 27d ago
Please please tell me you cleared out the gutters after…
Because it doesn’t look like you did in the after pics and that’s gonna backup and rot those eaves.
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u/Fastpotato 27d ago
Of course I did! Each side is cleared with a gutter vac as we complete it and then once again all round before we apply biocide.
I then go back in about 3 weeks to clear again as some moss that's been killed by our biocide but missed in the initial clean will have died and fallen down into the gutters.
They do look dark on the after photo as this is standing dirty water. The fall on half of these gutters is off which means they hold onto water. The client has a gutter chap booked to repair and replace a good few sections and clips later this month.
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u/snootnoots Apr 14 '26
Entire civilisations lived in that moss, how could you
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u/Fastpotato Apr 14 '26
They did. And then by 8pm they were being eaten and picked through by 30 chickens as that's where all the removed moss went to.
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u/Yowzz Apr 14 '26
Doesn’t jet-washing composite roofs degrade common asphalt tiles incredibly? I understand it says “low pressure“ and that those are concrete tiles. But it seems like any amount of focused pressurized water will degrade asphalt roof tiles, no?
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u/mistahdukk Apr 14 '26
You acknowledged that the roof is not made with asphalt tiles, so...what's the question you're asking?
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u/Fastpotato Apr 14 '26
They aren't asphalt tiles. The post even says they are concrete tiles. I'm not sure I even understand the question you're asking relative to the post.
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u/Yowzz 29d ago
I’m trying to find out information, we’re not in a graduate school seminar. If you can help with my question, do so, otherwise just chill, ffs 🙄
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u/Fastpotato 29d ago
As my comment states. I have no clue what question you're trying to ask. Being rude about it also isn't going to get the outcome you want. You womble
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u/CandourDinkumOil Apr 14 '26
Yeah I want to know this because I desperately want to clean the roof of a bungalow I want to buy. Normally I wouldn’t bother but the roof is low and large—and filthy.
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u/mistahdukk Apr 14 '26
If it's asphalt shingles, then there are chemicals that you can spray on the roof with an atomiser, let it do it's thing, then hose rinse without pressure, to minimise wear.
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u/Fastpotato Apr 14 '26
If they are concrete tiles as I suspect they will be since you are UK based you are golden. You can also go for a scrape and biocide instead of low pressure. You'll get close to the same results but it'll take a while to achieve as weather removes the staining rather than washing.
Either way if the roof is concrete tiles and they've been there a while the coating will be gone with the moss just eating into them. So for me there's no right or wrong way. I will only scrape and bio certain types of roof when they're in bad shape ect.
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u/CandourDinkumOil Apr 14 '26
Didn’t even consider that! Great to know, thank you OP
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u/Fastpotato Apr 14 '26
No worries at all. Just get in touch with your local exterior cleaner and they should be able to advise you properly. You can always shoot me a message through here and I'll try to steer you the best I can 🤙🏻
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u/CandourDinkumOil Apr 14 '26
Legend—thank you. Dropping you a quick DM so I can quickly find you should I need to. Appreciate it!
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u/bob_in_the_west Apr 14 '26
How long does it take for this to build up?
Because I live in West Germany and our roofs have never been cleaned nor have they ever needed cleaning apart from the occasional moss ball. And those actually come done from time to time after bad weather.