The short answer
Most exterior cladding is cleaned with warm water, a mild detergent and a soft brush, working top to bottom and rinsing as you go. Tackle green algae and mould — common on shaded, damp UK walls — with a suitable exterior cleaner or a dilute fungicidal wash, following the product instructions. Avoid high-pressure washing on timber and render, which can drive water behind the boards, raise the grain or strip render; if you must use a pressure washer on tougher surfaces, keep it low pressure and at a distance. Match the method to the material: uPVC and fibre cement tolerate firmer cleaning, while timber and painted finishes need a gentler touch. Always test on a small area first.
Cleaning keeps cladding looking right and lets you spot problems early. The safe approach varies by material, so the sections below cover method, green growth and what to avoid.
Cleaning cladding safely
- Default methodwarm water, mild detergent, soft brush
- Directiontop to bottom, rinse off
- Algae / moulddilute fungicidal wash
- Avoid on timber/renderhigh-pressure washing
- Alwaystest a small area first
The general method
For nearly all cladding, the safe routine is the same:
- Brush or rinse off loose dirt and cobwebs first.
- Mix warm water with a mild detergent and apply with a soft brush or sponge, working in sections from the top down so dirty water does not streak cleaned areas.
- Pay attention to shaded, north-facing and low-level areas where algae build up.
- Rinse thoroughly with clean water before the detergent dries.
- Let it dry and inspect — cleaning is a good time to check for splits, lifting boards and failed sealant.
Do this once or twice a year and most cladding stays clean without aggressive treatment. Pick a dry, mild day and avoid cleaning in strong sun, which dries solutions too fast.
Method by material
The biggest mistake is treating all cladding the same. Soft, porous and coated surfaces need care, while inert boards tolerate more:
| Material | Recommended | Avoid |
|---|---|---|
| Timber | soft brush, mild detergent, wood cleaner | high pressure, harsh solvents |
| Composite (WPC) | warm soapy water, soft brush | abrasive pads, strong chemicals |
| uPVC / vinyl | soapy water; specialist uPVC cleaner | abrasive scourers |
| Fibre cement | soft wash; low-pressure if needed | wire brushes, acids |
| Render | soft brush, fungicidal wash | high-pressure on weak render |
Indicative guidance; always check the manufacturer's own cleaning advice and warranty terms.
Dealing with algae, mould and green growth
Green and black growth is the most common complaint, especially on shaded or damp elevations. It is mostly cosmetic but can hold moisture against the surface. To treat it:
- Use an exterior fungicidal wash or a proprietary cladding cleaner, diluted per the instructions.
- Apply, leave for the stated dwell time, then brush gently and rinse.
- Some treatments are designed to be left to weather off and keep working — read whether rinsing is needed.
- Address the cause where you can: cut back overhanging vegetation, clear blocked gutters dripping onto the wall, and improve airflow so the surface dries.
Avoid neat bleach and strong acids, which can damage coatings, discolour timber and harm plants and drainage below.
Cleaning safely and protecting the finish
Working at height is the real hazard with cladding cleaning. Use stable access, ideally cleaning from the ground with a long-handled soft brush or a telescopic system rather than over-reaching from a ladder, and consider a professional for upper storeys. Protect plants and surfaces below from run-off, and check that any cleaner you use is compatible with your cladding and its coating — some chemicals void warranties or strip finishes. After cleaning timber, it can be a good moment to assess whether the coating needs refreshing. Finishing with a thorough rinse prevents detergent residues that attract dirt and can leave streaks.
Timing, frequency and prevention
How often cladding needs cleaning depends on its position more than its material. North-facing, shaded and tree-lined walls grow algae faster and may need attention twice a year, while open, sunny, well-ventilated elevations can go longer between cleans. Coastal homes pick up salt deposits, and properties near busy roads collect more traffic grime. Cleaning is generally easier in spring or autumn, on a dry but not hot day, so solutions do not dry too quickly and there is time for the surface to dry afterwards.
A little prevention reduces how often you clean. Keeping gutters and downpipes clear stops dirty water streaking down the wall; cutting back overhanging branches and climbers improves airflow and light so surfaces dry; and making sure splashback from paths and borders is not constantly wetting the lowest boards slows algae at the base. Where a wall is persistently green, the underlying cause is usually shade and trapped moisture, so improving drying conditions does more than repeated cleaning alone.
Frequently asked questions
Can I use a pressure washer on cladding?
On tough surfaces like fibre cement it can be used carefully at low pressure, but it is best avoided on timber and render, where it can drive water behind boards and strip finishes. A soft brush and mild detergent is safer for most cladding.
What removes green algae from cladding?
A dilute exterior fungicidal wash or proprietary cladding cleaner, applied per the instructions, then brushed gently and rinsed. Tackling the cause — overhanging plants, dripping gutters and poor airflow — stops it returning so quickly.
How often should cladding be cleaned?
Once or twice a year suits most homes, more often on shaded, damp or coastal walls that grow algae quickly. Regular light cleaning is easier than occasional heavy cleaning and lets you spot splits, lifting boards and failed sealant early.
Sources & further reading
Figures on this page are typical UK ranges drawn from published sources and depend on your specific property. They are guidance, not a quotation.