How long does it take to clean a roof?

Four things decide it more than anything else: how big the roof is, how steep it is, how thick the growth is and how we get up there. A bungalow with plain slopes and clear ground around it is a different task from a three-storey terrace with a rear roof only reachable from the next yard.

The survey records each of these before a date is agreed, so the time we allow is based on your roof and not on an average. If a job is going to run to more than one visit, we tell you at the start, with the reason. A rough figure given blind over the phone, before anyone has looked, is not worth the paper it would be written on. Our roof cleaning price factors page covers the same variables from the cost side.

Before any product touches the roof, the ground below is prepared. Plants and ponds are covered or moved where possible, windows are checked closed, and the working area is marked off. If access equipment is needed it goes up first, and on a scaffolded job that is its own block of time.

Putting scaffold on a public pavement or road means a highway licence and advance notice, so it can shift the date even though it is not time on the roof. Setting up properly is not wasted time. It is what keeps the garden, the drive and the neighbours' property clear of mess. Many houses need no scaffold at all.

On the roof, heavy moss is lifted by hand first, working from the top down so that nothing is trodden into the tiles. The debris is bagged and the valleys and gutters are cleared as the work goes. Then the treatment is applied evenly across each slope. Thin growth skips the first stage and goes straight to the product.

The pace is deliberate. Rushing an application leaves streaks and missed patches, and rushing hand work risks chipped tiles. Heavier roofs naturally take longer than light ones, and a roof covered with fragile tiles takes longer still. When the work is done the site is cleared, the waste is taken away and we photograph the finished roof. For the working method, see how moss is removed from a roof.

People are sometimes surprised that the roof is still changing after the team has packed up. This is the biocide at work. It goes on during the visit, but the dead growth takes weeks to fade and wash off, and in that period nothing more is needed from anybody.

It helps to think of the job as two clocks. One is our time on site, which is short and planned. The other is the weather's time, which is slower and less predictable. Judging the result before the second clock has run its course is a common mistake. Our guide to how long a biocide takes to work sets out what to expect at each stage.

Wind, rain and a wet roof are all reasons to move a date. Treatment applied just before heavy rain can wash off before it works. High wind makes working at height unsafe and carries spray where it should not go. A slippery roof is never worked on for the sake of keeping to a programme.

For this reason, we book with some flexibility and tell you in good time if the day has to change. A calm, dry spell is best, but a cleaner who insists on a fixed date regardless of the forecast is putting their calendar before your roof. Our quote is put in writing once the survey is done, and the date is fixed after the roof has been seen.

A roof clean disturbs the house less than most building work, but it still helps to plan. Expect the drive or the path beside the house to be used for equipment. Cars may need moving the evening before, and side gates need to be unlocked. If the gutters are being cleared at the same time there will be some noise and some mess on the ground, which is swept up before we go.

Tell us about anything that affects the day: a child asleep in a front bedroom, a pet that needs keeping indoors, a neighbour with a shared drive. If you work from home, a quick word on the first morning goes a long way. Most of the time you can carry on as normal inside. Our main roof cleaning and moss removal page describes the whole job, and the survey comes first, so that the time we allow is based on what we found.