How to keep render and roofs clean after soft washing, and the best time of year to book

Updated 6 November 2026 · By the Soft Wash team

Short answer: A soft wash typically keeps render, brick and roofs clean for several years. To make it last, keep gutters and downpipes clear, fix leaks and overflows, trim back overhanging trees and shrubs, and consider a light maintenance biocide treatment every one to three years. Spring to early autumn, in dry and mild weather, is usually the best time to book.

How to keep render and roofs clean after soft washing, and the best time of year to book

How long a soft wash lasts

Surface and situation	Typical time before regrowth is noticeable
Render, sunny open elevation	Often three to five years or more
Render, north-facing or under trees	Often one to three years
Roof tiles, open position	Often several years
Roof tiles, under or near trees	Often two to three years
uPVC fascias and soffits	Often one to three years
Timber fences and sheds	Often one to two years

These are rough guides. Shade, damp, nearby trees, local air quality and the surface itself all make a difference.

Simple aftercare

Keep gutters and downpipes clear so water does not overflow down the walls
Fix leaking gutters, joints and overflow pipes
Trim back trees and shrubs that shade walls or drop leaves on the roof
Keep climbing plants off render, or accept they will hold damp
Keep soil and mulch below damp-proof course level and away from render
Avoid pressure washing the cleaned surfaces in between treatments

Most regrowth happens where water lingers. Fixing the reasons a wall stays damp is the single best way to keep it clean.

Maintenance treatments

Rather than waiting until a wall or roof is heavily stained again, a light maintenance treatment every one to three years keeps growth at bay. It uses a milder solution, takes less time and usually costs less than the original clean. On roofs, a slow-acting biocide applied every few years is a common approach.

If a contractor offers a maintenance plan, check exactly what is included and how often, and compare it with simply booking a treatment when you start to see the first signs of green.

Best time of year

Season	Suitability	Notes
Spring	Good	Mild and often dry, growth is active and responds well; check for nesting birds on roofs
Summer	Good with care	Avoid hot, sunny spells when solution dries too fast; work early or on cloudy days
Autumn	Good	Mild and damp but often settled; clean before winter growth sets in
Winter	Limited	Frost, short days and rain make it less effective; mild dry spells can still work

Biocides work best when the weather is mild and dry for a few hours after application. Most contractors are busiest in spring and early summer, so booking ahead helps.

Wildlife and garden considerations

Wild birds, their eggs and active nests are protected by law, which matters for roof, gutter and fascia work in the nesting season, roughly March to August. Bats are also protected and sometimes roost behind fascias, soffits and roof tiles. A good contractor will check before starting and pause work if active nests or bats are found.

In the garden, plan cleaning for a time when vulnerable plants are less exposed, and protect ponds and vegetable beds. Rinsing plants thoroughly before and after treatment is the key protection in any season.

Signs it is time to treat again

A faint green tinge returning on north-facing walls or under sills
Small dark spots of mould or new lichen circles appearing
Green film reappearing on fascias and soffits
Moss starting to collect in roof valleys, along ridges or in gutters
Gutters overflowing or downpipes running slowly

Catching regrowth early makes the next treatment quicker, lighter and cheaper. Walk round the property once or twice a year, ideally in autumn after the leaves have fallen and in spring, and look at the shaded elevations and roof first, as these always show the early signs. Taking a photo from the same spot each year makes it easy to see whether growth is returning.

If a wall greens up again much faster than the rest of the house, look for a cause. A leaking gutter joint, a dripping overflow or a sill that sends water down the face of the wall will keep that area damp, and fixing it often makes more difference than any cleaning product.

Planning cleaning with other work

Clean before repainting render or masonry so paint is not applied over live growth
Clean before selling or re-letting so photos show the property at its best
Combine roof, walls, fascias and outbuildings in one visit to save on access costs
Have gutters cleared and repaired at the same time as a roof clean

If scaffolding is going up for other work, such as roofing or window replacement, ask whether soft washing can be done while it is in place, as access is often the biggest cost on taller buildings.