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Sources checked 12 November 2026
Roof moss removal: is it needed, and how should it be done?
Before paying for roof moss removal, it helps to know what tile makers and the roofing trade body actually say. This guide sets out the advice from Marley, the NFRC and Wienerberger for homeowners in Luton and nearby towns, so you can decide whether your roof needs cleaning at all, and how to do it without damage.
Get the roof looked at
Name, number and postcode is enough. We phone back to hear what is happening and set a time to see the roof.
Does moss damage roof tiles?
Usually not directly. Marley says that under normal circumstances moss is not harmful to roof tiles or slates.
The concern is water. NFRC Guidance Note GN58 says the primary effect of moss on a roof is that it holds water. Wienerberger, which makes Sandtoft tiles, says moss absorbs moisture and retains it even after rain has stopped, and that this can leave clay tiles prone to delamination, where the surface of the tile flakes away.
So a light covering on a sound roof is mostly cosmetic, while a thick, spongy layer that stays wet for weeks is worth dealing with, especially on older clay tiles and on slopes that rarely see the sun. The local climate gives moss plenty to work with: the Met Office's 1991 to 2020 averages for Rothamsted, near Harpenden, show about 120 days a year with at least 1mm of rain.
Can moss block gutters and cause leaks?
Yes, and that is the more practical risk. Marley says a heavy build-up of moss and lichen will inhibit the flow of water off the tiles, and its maintenance FAQ adds that in some extreme cases this growth may affect the drainage of water down the roof.
Clumps of moss also wash down into gutters, valleys and outlets. A blocked gutter overflows behind the fascia or down the wall in heavy rain, which can look like a roof leak from inside; our guide to a roof leaking in heavy rain explains how to tell. Clearing the gutters can matter more than cleaning the slope. Which? (22 October 2026) puts cleaning front and back gutters at £75 to £350, and our gutters, fascias and soffits page covers the rest of the roofline.
Why is pressure washing a roof advised against?
Because it can drive water into the roof and damage the tiles. NFRC GN58 says it is not recommended to remove moss by pressure washing, as this can force water into the roof space. Marley says pressure washing is not recommended by most roofing professionals, and its FAQ warns that high-powered jet washes can damage the surface of the slate or tile.
Wienerberger says jet washing can damage the tile finish and strip away colour from concrete tiles. If a washer is used at all, it advises setting it to low pressure and directing it from the apex of the roof downwards, never upwards, so water follows the laps instead of being forced under them.
Older garage and outbuilding roofs need extra care. HSE says asbestos can be present in any building built or refurbished before 2000, and lists asbestos cement roof tiles and slates among the places it occurs. Homebuilding & Renovating, citing HSE, says asbestos cement should never be drilled, scraped or dry-sanded, so scraping or washing a roof like that is not a job to take on yourself.
How should moss be removed safely?
By hand, working down the slope, from safe access. Moss is scraped off gently from the top down, and anyone doing it is close enough to spot cracked or slipped tiles along the way, which is often the most useful part of the job. The gutters and outlets are cleared at the end.
Access matters more than the tool. HSE says sloping roofs require scaffolding to prevent people or materials falling, and keeps ladders for short duration work measured in minutes rather than hours, so a full clean of a two-storey roof is normally a scaffold job.
Once moss is off, NFRC GN58 says copper strips can be attached across the high level of the roof, to discourage it from coming back.
Is there a wrong time of year to clean a roof?
Yes: the bird breeding season, and any time bats are using the roof. GOV.UK says it is an offence to intentionally take, damage or destroy a wild bird's nest while it is being used or built, advises timing building work to avoid the breeding season, and notes there is no licence that permits disturbing nesting birds for building work.
Bats are protected all year. Historic England says almost all UK bat species have been found roosting in roofs, and GOV.UK lists roof work among the activities that can affect them, with up to 6 months in prison and an unlimited fine for offences. If you have seen bats round the eaves, the Bat Conservation Trust's National Bat Helpline gives free advice before work starts.
Should I have the roof coated after cleaning?
Check with the tile maker first. NFRC GN58 warns that painting roof coverings after cleaning may invalidate manufacturers' guarantees. A coating also does nothing for slipped tiles, worn fixings or a tired underlay, and on a roof near the end of its life the money may be better spent on repairs or on planning a re-roof.
Be cautious with cold-call offers to clean or coat a roof. Which? advises never dealing with a roofer who knocks on your door, and a contract agreed at home carries a 14-day cancellation period.
When is moss a sign of a bigger problem?
When it hides damage, or keeps a failing roof wet. Heavy moss along the lower courses can hide slipped or cracked tiles, and moss that returns quickly on one slope points to shade or poor drainage that cleaning alone will not change.
If you are unsure, a roof inspection looks at the tiles, ridges, gutters and loft together. We photograph what we find and tell you plainly whether the moss needs dealing with at all. Our Luton roofing team can be reached on 01582 377176.
Questions people ask us
Is moss on a roof a problem?
Under normal circumstances, Marley says it is not harmful to roof tiles or slates. A heavy build-up holds water and slows drainage, so thick moss and blocked gutters are worth dealing with.
Can I jet wash moss off my roof?
It is not recommended. The NFRC says pressure washing can force water into the roof space, and Wienerberger says jet washing can damage the tile finish and strip colour from concrete tiles.
Will a roof coating stop moss coming back?
Ask before you agree to one. The NFRC warns that painting roof coverings after cleaning may invalidate manufacturers' guarantees, so check with the tile maker first.
Sources and further reading
- How do I remove moss or lichen from my roof?, Marley, updated 11 Sep 2024
- Guidance Note GN58: Moss (and lichens) on roofs, NFRC, Nov 2023
- How to Clean Roof Tiles, Wienerberger UK (Sandtoft), metadata 23 May 2023
- Rothamsted location-specific long-term averages 1991–2020, Met Office
- Problems and Maintenance FAQs, Marley, undated
- How much do roof repairs cost?, Which? (N. Turner, V. Purcell), 22 Oct 2026
- Asbestos: why and where, HSE, updated 1 Mar 2021
- Diagrams showing where asbestos can occur in buildings, HSE
- How to Deal with Asbestos, Alison Wall, updated 17 May 2021
- Roof work (construction safety topics), HSE, 5 Jun 2026
- Construction: Work at height FAQs, HSE, 11 Mar 2026
- How to find a reputable trader, Which? (Tom Morgan), 9 Jul 2026
- Consumer Contracts (Information, Cancellation and Additional Charges) Regulations 2013, Part 3 Right to cancel (revised, up to date to 9 Nov 2026)
- Wild birds: protection, surveys and licences (shows 29 Mar 2015)
- Works to Roofs, Walls and Building Services (Building works and bats), undated
- Bats: protection, surveys and licences (shows 29 Mar 2015)
Before you phone
These details help us understand the roof before we see it:
- Where the water shows, and in what weather
- Slate, tile, flat roof or not sure
- Roughly when the house was built
- Any photos, even from the street
- Conservation area or listed, if you know
Written by Luton Roofworks, roofers in Luton covering south Bedfordshire and west Hertfordshire. If your roof needs looking at, use the form or call 01582 377176.
Related roofing work
Gutters, fascias and soffits
Overflowing gutters, rotten fascia boards and tired soffits renewed with care for loft ventilation, nesting birds, bats and older asbestos boards.
Roof repairs
Slipped slates, cracked tiles, loose ridges and drips through the ceiling, traced to where the water really gets in and put right.
Roof inspections
A look at the roof from outside and the loft, with photographs and a written note of what needs doing now and what can wait.
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Tell us about the roof
Give us your name, phone number and postcode, pick the closest match to the problem, and we will ring to discuss it and fix a time to inspect. Or call 01582 377176.