Roof cleaning & surface treatment
In short
Cleaning a roof is done by hand with a biocide, and it improves appearance and clears the gutters of what would otherwise fall into them. What is worth avoiding is anything involving high pressure, and any offer to seal or coat the roof afterwards.
Also called: Clean roof tiles · Roof wash · Soft wash roof · Roof coating
Signs you need this
- Heavy moss, lichen or algae staining across the covering
- Gutters repeatedly filling with organic debris
- A roof that looks tired ahead of a sale
- Green or black staining on a shaded slope
- An unsolicited offer to clean and coat the roof
Roof cleaning is a legitimate service and a heavily mis-sold one, so it is worth separating what it does from what it is claimed to do. Done properly, it removes moss, lichen and organic staining, it stops that material washing into the gutters, and it makes an old roof look considerably better. It does not extend the life of the covering in any structural sense, and it is not a repair.
Method is the whole argument. Hand scraping and brushing, followed by a biocide applied to kill the growth at the root, is the correct approach — and 'soft washing', which is a low-pressure biocide application, is a legitimate variation of it. What is not correct is high-pressure washing, which erodes the surface of concrete tiles, drives water under the laps, and on slate lifts and breaks the covering. A roof cleaned at pressure looks best on the day it is done and is worse off for it.
Timing helps. Treating in the growing season gives the biocide the best result, and the roof carries on improving for months afterwards as the dead growth weathers off. A homeowner expecting an instant transformation on the day is usually being sold a pressure wash, because that is the only method that delivers one.
Then there is coating, and it deserves a plain answer. Roof coatings and sealants sprayed over an old tiled roof are widely sold, usually alongside cleaning, and they are generally a poor idea. They do not restore a tile that has lost its surface. They can trap moisture in the covering. They make future individual tile repairs considerably harder. And they have a habit of appearing as a query on a surveyor's report at sale, which is the opposite of adding value.
The reason they are sold so hard is that they carry a large margin on a job the homeowner cannot inspect. If a roof's fixings and battens have failed — which is what actually ends a concrete tile roof — a coating over the top does precisely nothing about it, and it has been applied to a roof that needs stripping.
The honest position is that cleaning is worth doing occasionally, for appearance and to keep the gutters clear, and that anything beyond cleaning should be treated with scepticism. If a roof genuinely needs work, it needs roofing — and if it does not, it needs a clean and leaving alone.
What the job covers
- Hand scraping and brushing, or low-pressure soft wash
- Biocide applied to kill growth at the root
- Gutters, valleys and outlets cleared afterwards
- Covering inspected properly while the access is up
- A written note of anything found that needs attention
- No coating, sealing or spraying sold on the back of it
What it costs
We don't publish a price for this yet, because a number pulled out of the air is worse than no number at all — your roofer has to honour it. On roofing it would also be close to meaningless: access is often the biggest single factor, and it varies enormously house to house. You'll get a firm price for your actual job when they ring you back, before any work starts. The quote itself is free and there's no obligation either way.
Common questions
Will cleaning make my roof last longer?
Not in any structural sense — a clean roof and a dirty roof have the same battens and the same nails. What it does is improve appearance and stop moss filling the gutters, which does prevent damage. Anyone claiming a clean adds years to a covering is overselling it.
Should I have my roof coated or sealed afterwards?
Generally no. Coatings do not restore a worn tile, they can trap moisture, they make future repairs harder, and surveyors frequently flag them at sale. They are also almost always sold alongside cleaning at a high margin. If the fixings and battens have failed, a coating does nothing about the actual problem.
What is soft washing?
A low-pressure application of a biocide rather than a high-pressure blast. It is a legitimate method and much kinder to the covering than pressure washing. The trade-off is that it works over weeks rather than in an afternoon — the growth dies and weathers off gradually.
Why does everyone offer roof coating?
Because it carries a large margin on work the homeowner cannot see or check, and because it is easy to sell to somebody who has just been told their roof looks bad. That is not a reason it is never appropriate, but it is a reason to get a second opinion before agreeing to it.
Need this doing in Macclesfield?
Tell us the job and it goes straight to our local roofer — one call back, usually the same day. Free quote, no obligation.