There are two answers to how long roof cleaning takes — how long the team is on site, and how long until the roof actually looks done. These aren't the same thing. The on-site work is usually a single day. The full result, after the biocide has done its job, takes around 3–6 weeks to fully reveal. Here's the breakdown.
On-site time by property type
Mid-terrace house: 2–4 hours. Small roof, single visit.
Semi-detached: 4–6 hours. The Manchester standard.
Detached house: 6–10 hours. Often a full day for two technicians, sometimes split across two visits.
Bungalow: 3–5 hours. Easy access but usually heavy moss to remove.
Add 30–60 minutes if we're clearing the gutters as part of the job.
Why the roof keeps changing colour for weeks afterwards
If we're using a soft-wash with biocide (and we almost always are — see our soft washing vs pressure washing guide), the chemistry continues to work after we leave. Within a few days the moss starts going brown. Over the next 3–6 weeks, the moss dries out and either drops off or washes off in the rain. By the 6–8 week mark, you'll see the full result. This is normal and expected — and it's why a soft-washed roof stays cleaner for years.
What can extend the timeline
Heavy moss. A thick moss carpet sometimes needs two visits — the second is a quick top-up after the bulk has dropped off.
Bad weather. We don't work in heavy rain or strong winds. We may reschedule with 24 hours' notice.
Difficult access. Restricted side access or a long ladder run can add an hour or two.
What you need to do during the job
Almost nothing. Stay inside, keep windows closed during the active wash, and move any soft furnishings under washing lines. Pets are fine indoors. We bring our own water and power.
Get a timing estimate for your property
Call us on 07841 595419 or request a quote online. We can usually give you both a price and a likely time-on-site within an hour of seeing the property.
