Professional Softwashing
For Render, Cladding & Exteriors
London & Surrey

Softwashing is a specialist exterior cleaning method that uses low-pressure water delivery combined with biodegradable chemical cleaning solutions to safely remove algae, mould, lichen, red algae (Trentepohlia), black streaks and other biological contamination from building surfaces. Unlike pressure washing, softwashing relies on chemistry rather than force — the cleaning solution does the work, not the water pressure.

This method is essential for surfaces that would be damaged by traditional high-pressure washing: K-rend and silicone render, painted surfaces, timber cladding, uPVC cladding, pebbledash, brick, natural stone walls and heritage masonry. Pressure washing these materials forces water behind the surface, causing damp, cracking, paint failure and render delamination.

If your property has green or red algae staining on rendered walls, black streaks running down from gutters or windows, or a general grey-green discolouration across the facade, softwashing is the correct solution. It is also the only safe method for cleaning thatched properties, listed buildings and surfaces near open windows or ventilation points.

After cleaning, we apply a biocide treatment that continues working for months, killing remaining spores within the surface pores and inhibiting regrowth. This preventive treatment is what separates professional softwashing from superficial cleaning — it addresses the cause, not just the visible symptom.

Biological growth on building exteriors is not just an aesthetic issue — it actively damages the surface materials it colonises. Algae and moss hold moisture against render, cladding and masonry, preventing the surface from drying properly between rain events. This constant moisture loading accelerates material degradation.

On rendered surfaces (K-rend, monocouche, silicone render, cement render), sustained moisture causes hairline cracking that allows water to penetrate behind the render layer. Once moisture enters the wall structure, it causes internal damp, mould growth and — in freeze-thaw conditions — can cause entire sections of render to delaminate and fall away. Render repairs typically cost £1,500–£5,000 depending on the area affected.

Red algae (Trentepohlia) is particularly common on north and west-facing rendered walls in London and Surrey. Despite its colour, it is a type of algae rather than a stain, and it cannot be removed by scrubbing or domestic cleaning products. It requires specific biocide treatment to kill the organism and prevent regrowth.

Many property owners make the mistake of hiring a general pressure washing service to clean their rendered walls. Standard pressure washing at 2,000+ PSI destroys render surfaces — forcing water through the render layer, stripping paint, damaging the aggregate finish on K-rend and leaving the surface more vulnerable to regrowth than before. The damage is often invisible initially but manifests as damp patches and paint bubbling within weeks.

Insurance companies are increasingly scrutinising exterior maintenance when processing damp-related claims. Evidence of biological growth and neglected maintenance can reduce or invalidate claims — making regular professional cleaning a financial protection measure as well as an aesthetic one.

Safe for Delicate Surfaces

Pressures below 500 PSI mean zero risk of render damage, paint stripping, water ingress or material degradation — unlike traditional pressure washing.

Kills Growth at the Root

Chemical treatment penetrates surface pores to kill organisms at the cellular level. Pressure washing only removes the visible layer while leaving live organisms behind.

Long-Lasting Results

Residual biocide treatment prevents regrowth for 12–18 months, keeping your property cleaner for significantly longer than pressure washing alone.

Prevents Damp & Render Damage

Removing moisture-trapping biological growth protects your render, cladding and masonry from the water damage that leads to costly repairs.

Suitable for All Exteriors

Render, cladding, brick, stone, timber, painted surfaces, heritage buildings — our method adapts to every material without compromise.

Environmentally Responsible

We use biodegradable cleaning solutions approved for residential use. All products break down safely and will not harm your garden, soil or drainage systems.

Our softwash system operates at a maximum of 500 PSI — approximately one-quarter of the pressure used in standard driveway cleaning and one-eighth of the output of a typical hire-shop pressure washer. At these pressures, there is no mechanical force acting on the surface; the water serves only as a delivery and rinsing medium for the chemical cleaning agents.

The active ingredients in our cleaning solutions are primarily sodium hypochlorite (at concentrations between 1% and 5%, depending on the surface and contamination level) combined with surfactants that help the solution adhere to vertical surfaces. For sensitive surfaces like timber, painted finishes and certain types of natural stone, we substitute with quaternary ammonium compound-based biocides that are gentler but equally effective.

K-rend and silicone render are the most common surfaces we softwash in London. These renders have a textured, aggregate finish that traps organic matter and provides ideal conditions for algae growth. Softwashing cleans between the aggregate particles without disturbing the surface texture — something that pressure washing invariably destroys.

Pebbledash and tyrolean render are rough-textured finishes that are particularly vulnerable to pressure damage. The aggregate is surface-mounted and bonded with a thin cement layer that high pressure can blast away, leaving bare patches. Softwashing is the only safe method for these finishes.

Painted exterior walls present a different challenge. Paint films can be softened or stripped by overly strong chemical solutions, so we test concentration levels on a discrete area before full application. We use reduced-strength solutions and shorter dwell times on painted surfaces, building up to the required cleaning effect gradually.

Brick and natural stone walls are softwashed at slightly higher concentrations to penetrate the porous surface and kill growth deep within the mortar joints. Historic and listed buildings require particular care — we consult conservation guidelines and can provide method statements for listed building consent applications where required.

Commercial softwashing — office buildings, retail units, schools, care homes and multi-storey residential blocks — follows the same chemical principles but requires different access solutions. We work from mobile elevated platforms (cherry pickers), rope access or scaffolding depending on the building height and configuration. Full RAMS documentation is provided for commercial contracts.

Common Questions

Frequently Asked Questions