Render cleaning: how long it takes and what to expect on the day
Updated 6 November 2026 · By the Render Cleaning team
Typical timings
| Property | Typical time on site |
|---|---|
| Single wall or gable end | 2 to 4 hours |
| Terraced house, front and back | Half a day to a day |
| Semi-detached house | One day |
| Detached house | One to two days |
| Large or three-storey house | Two to three days |
Heavy growth, textured finishes such as pebbledash, and walls needing towers or powered access all add time.
Weather and timing
Biocides need time on the wall to work and should not be washed off by rain straight away. Most products also need temperatures above a minimum, often around 5°C, and should not be applied in freezing conditions or very hot direct sun that dries them too quickly. Many render cleaners prefer a dry spell from spring to autumn, and will move a booking if heavy rain is forecast for the day. Ask your cleaner what conditions their product needs.
Light drizzle after the work is finished is not usually a problem once the product has had time to dwell and the wall has been rinsed. Wind is more of an issue during application, as it can carry spray onto windows, cars and neighbouring gardens. A short delay for better weather almost always gives a better and longer-lasting result than pushing ahead in poor conditions.
How to prepare
- Move cars, bins, garden furniture and pots away from the walls
- Close all windows and doors and keep pets indoors
- Let the cleaner know about ponds, vegetable beds or delicate plants
- Tell neighbours if their drive, wall or garden is close to the work
- Check there is an outside tap, or ask whether the cleaner brings water
- Mention any known cracks, loose render or leaking gutters
- Clear access along narrow side passages
What happens during the clean
Plants near the walls are soaked with water so they absorb clean water rather than product, and delicate planting is covered. Windows, doors and vents are protected where needed. The cleaner applies the biocide at low pressure, usually working one elevation at a time, and leaves it to dwell. The wall is then rinsed evenly, normally from the top down, so there are no patches or tide marks. Planting is rinsed again at the end.
Some cleaners use a two-stage approach on heavy growth: a first application to break down the bulk of the algae, a rinse, then a second application left on the wall without rinsing so it keeps working over the following weeks. If that is the plan, the walls may look slightly patchy for a few days before evening out, and it helps to know that in advance.
Do I need to be at home?
Not always for the whole day, but you should be available at the start to agree the walls, point out plants and any concerns, and at the end to walk round and check the result. The cleaner will need access to every wall being cleaned, including side passages and rear gardens, and usually to an outside tap. If neighbours' land is needed for access, for ladders or a tower on a shared boundary, ask their permission in advance.
- Leave side gates unlocked or give access arrangements
- Make sure the outside tap works and is not frozen or switched off
- Keep windows shut all day, including small top lights
- Move cars that could be caught by mist or rinse water
- Keep children and pets away until the walls have been rinsed
How it looks straight after and weeks later
| Timeframe | What you should see |
|---|---|
| Straight after | Most green algae and surface dirt gone, wall still damp |
| Once dry | More even colour as the render dries out |
| One to four weeks | Remaining faint staining continues to fade as the biocide works |
| Several weeks to months | Dead lichen breaks down and washes away in the rain |
Damage that was hidden under growth, such as cracks, flaking paint or old repairs that do not match, will be more visible once the wall is clean.
Clean walls can also look slightly uneven while they dry, as shaded and sunny parts dry at different rates. Judge the final colour on a dry day a few days after the clean. If one area still looks green once everything is dry and a few weeks have passed, let the cleaner know, as it may need a second application.
Checks before the cleaner leaves
- Walk round each cleaned elevation together
- Look for any patches or streaks missed on the rinse
- Check windows, doors and sills have been rinsed
- Check plants and paving have been rinsed down
- Ask which remaining marks are expected to fade
- Ask about a protective treatment and when to plan the next clean
Related guides
- How much does render cleaning cost in the UK? (2026 guide)
- Why is my render going green? Causes and how to fix it
- Can you pressure wash render? Safer ways to clean it
- How to choose a render cleaning company: questions to ask and red flags
- What type of render do I have? How to identify it before cleaning
- Clean, repaint or re-render? Choosing the right fix for tired render
- How to keep render clean: maintenance and aftercare guide
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