What is the best time of year to clean a roof?

When is the best time of year to clean a roof?

Spring and early autumn usually give the best conditions: mild temperatures, drier days and enough daylight to finish the job. Summer and winter work too, with some limits.

A guide to conditions, not a rule. The weather on the day matters more than the month.

Why does the weather matter for a roof clean?

A roof clean has two parts: removing the moss, then treating the tiles with a biocide that kills the spores and roots. The weather affects both:

• The biocide needs a dry spell. If heavy rain follows straight after, it can wash off before it has worked, and the moss comes back sooner.
• Cold slows it down. Biocides work best in mild weather. They are slow in near-freezing temperatures and shouldn’t go on a frozen roof.
• Wet or frosty tiles are slippery. Working at height on a wet or icy roof isn’t safe, even from roof ladders, scaffold towers or a cherry picker.
• Wind carries spray. Strong wind blows the cleaning solution and biocide off target, onto walls, windows, cars and gardens.

That’s why the forecast for the day, and the day after, matters more than the time of year. Washmates cleans roofs in dry or mild weather and in light rain, and never in heavy rain, frost, ice or high winds.

Is autumn a good time to clean a roof?

Yes. Moss grows most in the cool, damp months, so autumn is when it starts to build up again after a dry summer. Cleaning it off now has three benefits:

• Less frost damage. Moss holds water against the tiles. When that water freezes, it can speed up wear on the tiles over winter. See whether moss damages roof tiles.
• Clearer gutters. Moss that comes loose in winter storms ends up in the gutters, on top of the autumn leaves. Every Washmates roof clean includes clearing the gutters.
• A head start. The biocide keeps working on the tiles through the following months, so the roof stays clear for longer.

If your roof is already green, don’t wait for spring. Thick moss gets harder to remove, and it holds more water against the tiles the longer it stays. You can see typical roof cleaning prices by type of house in our cost guide.

What about birds nesting on the roof?

In the UK, it’s against the law to damage or destroy the nest of a wild bird while it is in use. The main nesting season runs from about March to August, and birds such as house sparrows and starlings often nest under roof tiles, in gutters and behind fascias.

A careful roof cleaner checks for active nests before starting and works around them, or comes back once the young have left. If you know birds are nesting on your roof in spring or summer, mention it when you ask for a quote. Autumn and winter avoid the issue altogether.

Can you clean a roof in winter?

Yes, on the right days. A mild, dry spell in winter is fine for a roof clean, but frost, ice, snow and short daylight hours mean fewer days are suitable. In winter, we wait for a suitable day rather than work on a frosty or icy roof.

The method matters more than the season. A soft wash at low pressure, followed by a biocide, is safe for the tiles at any time of year. A high-pressure jet wash is a risk in any season; see whether pressure washing damages a roof.

How often should you clean your roof?

A roof cleaned and treated with a biocide usually stays clear for two to four years; shaded, north-facing roofs or roofs under trees need cleaning sooner. Our guide to how often you should clean your roof covers what speeds moss up and the signs it’s time.

A quick look at the roof each autumn tells you how it’s doing. If moss is building up, tell us about your roof and we’ll send you a fixed price, usually without a site visit.