What to expect on soft washing day: how long it takes and how to prepare

Updated 6 November 2026 · By the Soft Wash team

Short answer: Soft washing the walls of a typical UK house usually takes half a day to a full day, and a roof a day or more depending on size and access. Before the day, clear access around the house, move cars, furniture and pots away from the walls, and make sure an outside tap is available. Expect most algae to go on the day, with lichen and some staining fading over the following weeks.

How long it takes

Job	Typical time on site
Fascias, soffits and gutters, typical house	2 to 4 hours
Render or walls, terraced or semi-detached house	Half a day to a full day
Render or walls, detached house	One to two days
Roof soft wash, semi-detached house	One day
Roof soft wash, detached house	One to two days
Garden walls, fences or outbuildings	1 to 4 hours

These are rough timings. Heavy growth, three-storey elevations, awkward access and the need for scaffold or a cherry picker all add time.

Before the day

Move cars away from the walls and off the driveway if possible
Move garden furniture, pots, toys and bins at least a couple of metres from the walls
Make sure an outside tap is working and accessible
Unlock side gates and give access to all sides of the property
Close windows and roof lights, and tell us about any that do not close fully
Bring in washing and cover or move anything you are worried about
Let neighbours know, especially if their car, garden or wall is close

If you have a pond, a vegetable bed close to the wall or particularly valuable plants, mention them in advance so extra protection can be planned.

On the day

The day normally starts with a walk round to confirm the surfaces, check for any defects and plan protection. Plants and lawns along the walls are soaked with water and delicate ones covered. Windows, doors and vents are checked and protected.

The solution is then applied at low pressure, usually working from the bottom of the wall upwards to avoid streaking, and left to dwell for the right length of time. Surfaces are rinsed, glass and frames washed down, and plants rinsed again. You will notice a smell similar to a swimming pool if a hypochlorite-based product is used, which fades within hours.

Pets, children and being at home

Keep pets and children indoors while the solution is being applied, and until the surfaces have been rinsed and are drying. Keep pet bowls, toys and bedding indoors. You do not usually need to be home, as long as access and the outside tap are available, but it helps to be around at the start to confirm the job and at the end for the walk round.

Weather

Soft washing is best done in dry, mild weather. Heavy rain soon after application can dilute the solution before it has worked, while strong sun and heat can make it dry too quickly and increase the risk of streaking or marking plants. Strong wind carries spray. If the forecast is poor, the job may be moved to the next suitable day, which is in your interest.

Freezing conditions are also unsuitable, as water left on surfaces can freeze and the treatment works less well in the cold.

How the results develop

Green algae and black mould usually disappear during the clean or within a few days
Black lichen spots and some staining fade over several weeks
Roofs often take a few months to look their best as rain washes away dead growth
Rust, paint, efflorescence and water run-off marks are not organic and need other treatment

Try not to judge the result while the walls are still wet, as damp render and stone look darker and patchier than they will once dry. Look again after a few dry days.

After the team leaves

Keep windows closed for an hour or two after the job if a hypochlorite-based product was used, until any smell has cleared. Leave plants alone for a day or so, and water them well that evening if the weather is dry, as this dilutes any solution that reached the soil. Wipe garden furniture before use if it was close to the work and not moved.

Check the walls, roof and windows once they have dried, ideally in good light. Note any patches that look different from the rest and take photos. A few spots of lichen or faint staining fading over the following weeks are normal, but if anything looks streaked, marked or missed after a couple of weeks, contact the contractor with your photos so it can be looked at. Fixing leaking gutters or overflow pipes soon after the clean stops the same areas staining again.