How often should commercial skylights be cleaned?
Start with the manufacturer’s manual, if you have one. The advice varies: Duplus expects cleaning and maintenance checks at least every six months on its rooflights, while Rainclear’s flat glass rooflight manual leaves the interval for the glazing to the owner.
If there’s no manual, let the site decide. We’d start from this table, then adjust it after the first clean, based on how quickly the dirt comes back.
| Your site | Starting point | Why |
|---|---|---|
| Open site, away from trees and heavy traffic | Once a year | Dirt builds slowly, but a yearly visit still catches damage and failed seals |
| Trees close to the roof | Every 6 months, with one visit after leaf fall | Leaves and shade keep the surface damp, which helps algae grow |
| Dust, fumes or extraction vents on the roof | Every 6 months, or more often | Dust and grease settle on the sheets and stick |
| Pigeons or gulls on the roof | Every 6 months, and deal with the birds | Droppings build up quickly and stain the sheets |
| Set light levels or an insurance audit to meet | Whatever keeps you within the requirement | The audit or a light reading sets the interval, not the calendar |
These are starting points, not rules. A survey of your roof will firm them up.
Does the law say how often skylights must be cleaned?
No, but the Workplace (Health, Safety and Welfare) Regulations 1992 still matter in England, Scotland and Wales:
- Regulation 8 says workplace lighting must be suitable and sufficient and, so far as is reasonably practicable, by natural light.
- Regulation 16 says skylights in a workplace must be designed or built so they can be cleaned safely. Equipment used with the skylight, and devices fitted to the building, can be taken into account.
Your insurer may go further. Insurance audits of factories and commercial buildings can make clean skylights a requirement, often with light levels that have to be met. Check your latest audit report if you’re not sure.
Why does it matter if skylights are dirty?
You lose daylight. Dirt, grime and algae cut the natural light reaching the floor. On previous jobs, we’ve raised natural light levels enough for some clients to cut back on lighting during the summer months. We can’t promise a saving, because it depends on your lighting and how the building is used.
The skylight can deteriorate. GRP (glass reinforced plastic) is the main concern. If it’s left untreated and exposed to moisture, the fibres start to break down, which leads to costly repairs or replacement. Duplus makes a similar point about its own products, saying cleaning “contributes considerably to the effective life of the system”.
Faults go unnoticed. A cleaning visit puts a trained person next to the skylight, where they can spot cracks and other damage before it becomes a leak.
How can you tell skylights are overdue for a clean?
You can check most of these from inside the building:
- Green or black staining visible from below
- Parts of the floor that look darker than they used to
- Lights going on earlier in the day, or staying on in daylight
- Leaves, moss or silt showing against the sheets
- Bird droppings on or around the skylights
- Water marks or drips below a skylight, which may mean it needs a repair as well as a clean
Don’t go onto the roof to check. Ask for a survey instead.
Who should clean commercial skylights?
Someone trained and equipped for roof work. HSE says falls through fragile surfaces, particularly fibre-cement roofs and rooflights, account for 22% of fatal falls from height in construction. It also says people doing small, short-term maintenance and cleaning jobs are over-represented in the injury figures.
Anyone planning the work should know three things:
- Rooflights can be hard to see. HSE warns that some are difficult to spot in certain light conditions, and that others may have been painted over.
- Treat the roof as fragile. HSE says all roofs should be treated as fragile until a competent person has confirmed they aren’t.
- “Non-fragile” doesn’t always last. The National Association of Rooflight Manufacturers says many roofs that are non-fragile when new may become fragile later as other parts of the roof deteriorate, even if the rooflights themselves haven’t.
HSE says work on or near fragile surfaces needs a combination of stagings, guard rails, fall restraint, fall arrest and safety nets. Our operatives are trained to work safely at height. We reach most skylights from mobile elevating work platforms (MEWPs), and use crawler boards or scaffolding where the job calls for it.
How are commercial skylights cleaned?
We start by loosening and removing debris and dirt from the surface. Then we brush clean or power wash, depending on the condition of the skylight.
The material matters too. Rainclear’s manual for its glass rooflights, for example, asks for a mild detergent and a clean water rinse, and rules out abrasive cloths and acid-based cleaners. That’s why we carry out a site survey before any cleaning starts.
How do you set up a skylight cleaning schedule?
- Find any manuals or records for the skylights, and your latest insurance audit.
- List what’s on the roof: how many skylights, what they’re made of and where they are.
- Book a site survey and a first clean, and take photos from inside before and after.
- Check how quickly the dirt comes back, then set the interval.
- Plan each visit around shutdowns and any other roof work.
We carry out regular cleans as well as one-off deep cleans, so the schedule can change as you learn how the site behaves.
What else can be done during the same visit?
Safe access is a big part of any roof job, so it makes sense to plan other work around it. We can combine a skylight clean with gutter cleaning and pressure washing for building exteriors. If birds are part of the problem, we can look at bird proofing at the same time.
We also repair and replace skylights. Cleaning removes dirt, but it can’t reverse weathering, so a sheet that stays cloudy after a clean may be due for repair or replacement. See our skylight cleaning and repairs service for more.
