Commercial roof cleaning: is it worth it?
Updated 23 October 2026 · SEO Dons Editorial
Commercial roof cleaning means removing moss, lichen, algae, silt and debris from membranes, metal sheets, insulated panels and fibre cement roofs. It is a maintenance task with safety, environmental and guarantee implications, so the first question is why it is being done. Domestic tile cleaning is outside this guide.
Is getting a commercial roof cleaned worth it?
It depends on the reason. Cleaning earns its cost when it protects drainage or the covering, or when it is a necessary step before a coating or repair.
| Reason for cleaning | Usually worth it? | What the sources say |
|---|---|---|
| Debris or growth near outlets, gutters and sumps | Yes | Bauder's membrane guide lists removing debris from the roof surface, outlets, chutes and gutters as routine maintenance |
| Sharp debris or plant growth on a membrane | Yes | Bauder says sharp debris can damage the membrane and plant growth should be removed without damaging the waterproofing |
| Surfaces that rain does not wash, such as soffits and areas below framed PV | Yes, more often | MCRMA says these have an increased risk of corrosion and coating degradation, which may negate a warranty |
| Preparing for a coating, overlay or repair | Yes, as preparation | LRWA's guidance for coating fibre cement and metal roofs includes a fungicidal wash to kill off moss and algae first |
| Appearance only | Question it | HSE asks owners to consider whether cleaning is necessary, or only aesthetic |
HSE's roof work guidance puts the test plainly: where cleaning is planned, consider whether it is necessary, and if it is required, use a safe system.
What are the risks, and who is responsible?
Cleaning is one of the most dangerous reasons to be on a roof. HSE says many of those killed in roof work are not specialist roofers but people repairing and cleaning roofs, and its fragile roofs sheet says deaths from falls through fragile surfaces occur mainly to people doing small, short-term maintenance and cleaning jobs. HSG33 records a casual worker killed after stepping off a work board onto a fragile rooflight while power-washing a farm building roof.
The duty does not stop with the contractor. HSE says the Work at Height Regulations apply to anyone who controls work at height, naming facilities managers and building owners who contract others. The ACR's information sheet for non-roofer clients (2017 revision, marked valid to the end of 2019) counts cleaning a rooflight and inspecting a roof as minor roof work. It says never to go on a roof yourself unless competent, and the Orange Book says not to let any company inspect or maintain a roof without vetting its skills and safety methods first. The fragile roofs and rooflights guide sets out the owner's duties.
A competent contractor should be able to show, before cleaning starts:
- a method statement, which HSE calls the common way to communicate roof precautions to those involved;
- the roof type and the maker's cleaning limits for it;
- how fragile areas, including rooflights, are identified and protected, and how the roof is reached;
- where wash water, any biocide and the debris will go;
- a check for nests, and a record of what was done afterwards.
Which methods suit which roof?
The roof maker's or coating maker's instructions govern. What the published guidance rules out matters as much as what it allows.
| Roof type | What the sources say |
|---|---|
| Single-ply, felt and other membranes | Bauder says its membranes can be manually washed down with warm water and approved mild detergent. IKO rules out high pressure hoses and tools such as shovels and rakes, and says a compatible fungicidal wash may help where algae or moss grow. |
| Liquid-applied roofs | LRWA describes biocidal washes as preparation before a liquid system is applied, supplied as concentrates to be diluted at the maker's rates and covered by the Control of Pesticides Regulations. |
| Coated steel sheets and insulated panels | MCRMA says unwashed surfaces can usually be cleaned by hosing with water and a neutral detergent, and advises seeking the roof system manufacturer's written approval. |
| Fibre cement and asbestos cement | HSE's sheet a12 says these roofs are always fragile, high-pressure jetting is appropriate only in exceptional circumstances and needs a specialist contractor, and cleaning machines create slurry that must be collected for disposal. See the fibre cement guide. |
Where do wash water, biocide and debris go?
Not into a surface water drain. The government's pollution prevention guidance says surface water drains discharge directly to the environment, that contaminated water should go to the foul drain with the water company's permission or be removed by a registered waste carrier, and that detergents are among the substances that can cause pollution. Bauder adds that debris must not be flushed down rainwater pipes.
Biocides carry their own rules. HSE says to consider whether a biocide is needed at all, and that the label must be read and understood before use; its instructions, including how to avoid harming wildlife and the environment, must be followed. Any waste from a commercial activity is business waste under the GOV.UK rules, so ask how it is carried away and recorded.
How often should a commercial roof be cleaned?
There is no single interval. The published guidance sets inspection frequencies, and cleaning follows what the inspection finds. IKO's maintenance note says a flat roof should be inspected at least twice yearly, in autumn to check it is clear of leaves, dirt and debris with outlets unblocked and in spring to find weather damage, with a more regular regime where trees or bird guano are a problem. Bauder asks for a check at six-monthly intervals as a minimum, ideally spring and autumn, and after storms or plant work. IKO points to BS 6229 for frequency; BSI says BS 6229:2025 supersedes the 2018 edition and updates its care and maintenance clause, so the current text should be checked. MCRMA says surfaces that rain does not wash need cleaning more often than the rest.
How does cleaning fit with guarantees and a maintenance contract?
Bauder warns that failures resulting from a lack of maintenance may not be covered under its guarantee and that the owner should keep a record of inspections and maintenance. IKO asks for a log of annual maintenance as a requirement of its guarantee terms. Even bird deterrents can affect cover: IKO says they should be approved by its technical services before they go on, so as not to invalidate the guarantee. A planned maintenance contract is where inspection, outlet clearance, cleaning and the record come together; see the maintenance contracts page, the planned maintenance page and the guarantees page. Gutters have their own routine in the gutter cleaning guide, and on a let building the lease decides who pays, as the guide to who pays for the roof explains.
Check for nests first. In England and Wales, subject to the Act's exceptions, it is an offence under section 1 of the Wildlife and Countryside Act 1981 intentionally to take, damage or destroy the nest of any wild bird while that nest is in use or being built.
What drives the cost?
No honest price exists without a survey, so this page gives none. The drivers are the roof area and type; how the roof is reached and protected; the extent of growth and whether more than one treatment visit is needed; the handling of wash water, slurry and waste; whether the roof contains asbestos cement; and whether cleaning is bundled into a maintenance contract. A quote that does not price these separately cannot be compared with another. To compare contractors against one survey, you can send an enquiry through the site's form.
Sources
- HSE, roof work, work at height: the law, HSG33 (fifth edition, 2020), GEIS5, asbestos essentials a12 (2017) and using biocides (HSE, checked 22 October 2026)
- MCRMA, GD39 section 5 (June 2022) (MCRMA, checked 22 October 2026)
- Information sheet 3 (2017) and the Orange Book (Advisory Committee for Roofsafety, checked 22 October 2026)
- LRWA Guidance Notes 6, 9 and 10 (LRWA, checked 22 October 2026)
- Bauder, single ply general maintenance (revision V9, May 2026), and IKO, maintenance of flat roof waterproofing systems (June 2025) (manufacturers' own guidance, checked 22 October 2026)
- Pollution prevention for businesses and Dispose of business or commercial waste (GOV.UK, checked 22 October 2026)
- BS 6229:2025 (BSI, checked 22 October 2026)
- Wildlife and Countryside Act 1981, section 1 (legislation.gov.uk, checked 22 October 2026)
Common questions
Does moss damage a commercial roof?
It depends on the covering. NFRC says moss on roof tiles is rarely a problem unless it blocks gutters, outlets and other drainage points, but that is a statement about tiled roofs. For membranes, IKO suggests a compatible fungicidal wash may help where algae or moss grow, and Bauder says plant growth should be removed without damaging the waterproofing.
Can a commercial roof be pressure washed?
Only within the roof maker's limits. IKO rules out high pressure hoses on its systems. HSE says high-pressure jetting of asbestos cement is appropriate only in exceptional circumstances and needs a specialist contractor. LRWA describes water blasting above 150 bar at the nozzle as equipment for surface preparation before liquid-applied systems.
Who pays for roof cleaning on a let building?
The lease and any service charge schedule decide, not the type of cleaning. Check the repairing covenant and the service charge wording before commissioning it, and check whether a guarantee or maintenance condition obliges anyone to keep cleaning and inspection records.