Roof cleaning: what's involved, how long it takes and what it costs

What are the key facts about roof cleaning?

A roof clean removes the moss, lichen and algae from the tiles and treats the roof so growth is slower to come back. The table sums up each part of the job, and the guide linked in each row goes into it in full.

What’s involved in a roof clean?

Soft washing cleans a roof with a cleaning solution rather than force. The solution is applied at low pressure, left to work on the moss, algae and lichen, and then rinsed off gently. A biocide finishes the job by killing the spores and roots, so growth is slower to return.

At Washmates, every roof is cleaned with a soft wash at low pressure and then treated with a biocide. We never jet-wash the tiles. A high-pressure jet can crack or dislodge tiles, strip their surface and force water underneath them, and leading UK roof tile manufacturers advise against it; see whether pressure washing damages a roof.

Every Washmates roof clean covers the whole roofline, not just the tiles:

• The tiles, cleaned with a soft wash at low pressure, then treated with a biocide to slow moss regrowth.
• The gutters, cleared, because moss washed off a roof often ends up in them.
• The fascias and soffits, the boards along the edge of the roof.
• Any solar panels on the roof, cleaned at the same time.
• A post-service clean-up, so the property is left tidy.
• Digital before and after photos of the work.

Clay tiles, concrete tiles and natural slate are all cleaned the same way; see whether clay, concrete and slate roofs can be cleaned for what can go wrong with each.

How is the roof reached without walking on the tiles?

We don’t walk on fragile tiles; we use roof ladders, scaffold towers or a cherry picker instead. Tiles and slates can crack underfoot, and a hairline crack may not show at first. Scaffolding is needed on some tall or awkward roofs, and it can add several hundred pounds to the price.

Walking on a roof or aiming a jet up it is also how a clean can let water in. A soft wash applies the cleaning solution at low pressure, so there’s little risk of forcing water under the tiles. Thick moss can hide cracked tiles and damaged flashing, though, so a clean can uncover problems that were already there. If you can already see cracked or slipped tiles, or there’s damp in the loft, get a roofer to look at the roof before it’s cleaned. See whether cleaning a roof can cause leaks.

How long does a roof clean take?

Most semi-detached and terraced houses take a team of two a full day. A large house with a roof of more than 300 square metres can take three to four days. Roof cleaning is normally done by two people: one working at height and one on the ground, for safety and to move the equipment. Big jobs with a cherry picker need three.

Lots of things affect how long a job takes. Bigger roofs take longer, and thick moss, a steep pitch or a cherry picker also add time. Roof ladders have to be moved along the roof as the clean progresses, and each move takes time.

You don’t need to be at home, as long as the team can get through any gates. Washmates sends you a text before starting and another when the job’s finished.

Does the weather affect a roof clean?

Yes. Washmates cleans roofs in dry or mild weather and in light rain, and never in heavy rain, frost, ice or high winds. The biocide needs a dry spell after it goes on, and wet or icy tiles are unsafe. If heavy rain or strong wind is due on the day, Washmates moves the job to another day at no cost.

Spring and early autumn are usually the best times to clean a roof in the UK, but a roof can be cleaned at most times of year. If the moss is already thick, don’t wait. See the best time of year to clean a roof.

How long does a roof clean last?

Every two to four years for most homes. A roof cleaned and treated with a biocide usually stays clear for that long. Shaded, north-facing or low-pitched roofs, and roofs under trees, need cleaning sooner; open, sunny roofs last longer. Without a biocide, moss can be back within a year or two. See how often you should clean your roof.

For what moss and black streaks do to a roof, see whether moss damages roof tiles and what the black streaks on a roof are.

How much does a roof clean cost?

A typical UK roof clean costs between £600 and £1,300, and a large detached house can cost up to £4,000. At Washmates, a roof clean starts from £800. All our prices include VAT. Prices are higher in London and the South East and lower in the North. Roof size, pitch, height, moss and scaffolding also move the price. See typical roof cleaning prices by type of house.

Most of the price is labour, because careful work at height is slow; see why roof cleaning is so expensive. Because a Washmates roof clean already includes the gutters, fascias, soffits and roof panels, it’s also the price of all of them together; see what it costs to clean a roof, gutters and solar panels together. To compare a roof clean with other outdoor jobs, see how much exterior house cleaning costs.

Is a roof clean worth it?

For most homes with moss building up on a sound roof, yes. Re-roofing a three-bedroom semi in concrete tiles typically costs £3,500 to £10,500, far more than a clean. A clean isn’t worth it on a roof that’s already failing: if tiles are cracked, slipping or missing, see a roofer first. Our guide to whether roof cleaning is worth it compares a clean with typical repair and re-roofing costs.

Which roof guides answer the other questions?

Each of these guides answers one roof question in full:

• How much does a roof clean cost?
• Why is roof cleaning so expensive?
• How much does it cost to clean a roof, gutters and solar panels together?
• Is roof cleaning worth it?
• Does pressure washing damage a roof?
• Can you clean clay, concrete and slate roofs?
• Can cleaning a roof cause leaks?
• Does moss damage roof tiles?
• What are the black streaks on my roof?
• How often should you clean your roof?
• What is the best time of year to clean a roof?

When you’re ready, tell us about your roof and we’ll send you a fixed price, usually without a site visit.