The short answer
It depends on the size of the roof, how it is reached and the method used, so there is no single answer. A small roof reached by ladder is a shorter job than a large two-storey roof needing scaffold. Treatment also carries on working once we have left, so the roof keeps improving for some weeks afterwards. The plan and the number of days come with your written quote.
What makes one roof clean quick and another slow, how weather changes the plan, and how the days are laid out.
What sets the number of days
Four things set the length of a job. Area comes first: a long roof has more tiles to clear than a short one, and a roof with many hips, valleys and dormers takes longer than a plain gable of the same size. Access is next. A low bungalow may need nothing more than ladders and a hooked roof ladder, while a tall house usually needs scaffold, and putting up and taking down scaffold is part of the programme.
Then there is how much growth is up there. Light algae needs only a treatment, but thick moss has to be lifted off by hand before anything else can happen, and that is slow, careful work on a pitched roof. Last is whatever turns up under the moss. Broken tiles and failed pointing have to be put right before the roof is finished, which can add time, and the survey is there to spot most of it beforehand.
A semi-detached house and a detached house with an extension are different jobs for these reasons, even if the postcode is the same. Our page on manual moss removal explains why hand work is slower than spraying.
A typical running order
A visit to look at the roof comes first, with pictures for you to keep. After that comes a single written total, along with the number of days we expect to be on site. Day one is for access: ladders or scaffold go up, the work area is made safe, and drives and cars are covered or moved where needed.
Loose moss and debris are then cleared by hand, gutters are cleared, and any damaged tiles are dealt with. Treatment follows on a dry roof. On a roof with heavy growth the hand clearing may take most of a day on its own; a lightly affected roof may be ready for treatment almost at once.
The last visit takes access down, clears the waste and checks the gutters and the ground. We tell you what is happening each day, so you know when to keep windows shut and when to expect the scaffolders. The roof does not look finished at the end, because a treatment shows its results only as the dead growth lets go and washes off, and that can take weeks of ordinary rain.
How the weather changes the plan
A biocide needs a dry spell to do its work, and the label says how long the roof must stay dry. Rain too soon after treatment washes the product off before it has soaked in. That does not stop the clearing work, which can go on in damp conditions, but it can move the treatment to another day.
High wind is the other limit. Wind makes work at height unsafe, carries spray where it should not go and blows loose moss around the garden and the neighbours' cars. Hard frost glazes the tiles, and nobody should be on a slope in those conditions. Our page on roof cleaning in winter goes through what is and is not sensible in cold months.
Because of this, a start date is a plan, not a promise. When the forecast turns, you hear from us straight away and we agree another day together. Rain on the day after treatment does no harm once the product has had time to soak in, as the label sets out.
Planning around the work
A little preparation shortens the job. Move cars off the drive, bring in washing and garden furniture, and tell neighbours if scaffold will stand near a shared boundary. Should the scaffold stand over the pavement, the highway authority may require a licence for it, which we arrange with the scaffolder. Scaffolding wholly on your own drive or land needs none.
Tell us about anything that might change the plan: a small child's nap, a night worker, pets that need keeping in, or windows that cannot be opened. We build these into the day plan.
For a rough idea of cost, Checkatrade's April 2026 table gives typical UK prices of £8.50 to £14 per m² for roof cleaning, while your own figure comes in writing after the survey. Our roof soft washing page describes the gentler method, and the roof cleaning and moss removal service page covers the rest. Photos of each slope, plus the address, let us give you a realistic idea of the days before we visit. Tell us too whether the garden has a side gate, because carrying equipment through the house is the slowest way to start.
More on this in Roof Cleaning & Moss Removal in Crawley
Two more timing questions
Must someone be in while the roof is cleaned?
Not for the whole job, but it helps to be reachable. We need access to the garden, outside taps and sometimes a side gate. You will want to know the day the scaffolders arrive and the day treatment goes on. Tell us your plans and we will work around them, and we will name the last visit.
When will the roof look clean after treatment?
Not straight away. The moss that was lifted by hand is gone on the day, but algae and lichen die back slowly and wash off in the rain. Expect the roof to improve over several weeks. Heavy shade and a dry spell slow that down, so judge the result after a few wet spells, not a week.