Monocouche render cleaning

Through-coloured monocouche render cleaned at low pressure to remove algae and dirt and restore an even colour without scrubbing marks. Typical UK costs.

In short: Monocouche render cleaning removes algae, mould and dirt from through-coloured single-coat render using a low-pressure biocide treatment and an even rinse. It suits homes finished in monocouche systems that have gone green, grey or streaky. Cleaning a typical semi-detached house usually costs £300 to £600 in the UK, depending on area, height and growth.

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Monocouche means single coat. It is a cement-based, through-coloured render applied in one thick layer, typically around 15 to 20 mm, and usually given a scraped finish that leaves a slightly open, textured surface. Because the colour runs right through, it never needs painting, but that open texture gives algae and dirt plenty to hold on to, and staining can work into the surface rather than sitting on top.

That makes monocouche particularly vulnerable to bad cleaning. High pressure can wear away the surface and expose fresher, darker colour underneath, leaving stripes and wand marks that never fully disappear. Strong bleach-based cleaners can also lighten pigmented render unevenly. The right method is a biocide suited to cementitious render, applied at low pressure, given time to work, and rinsed evenly across the full wall so the colour comes back consistent.

What is included

Identifying the render as monocouche and checking its condition
Testing the cleaner on a small area if the colour is unusual
Protecting plants, glazing, vents and paving
Low-pressure biocide application suited to cement-based render
Extended dwell time on heavily stained or textured areas
Even rinse of whole elevations to avoid patchiness
Optional protective treatment after cleaning

Who it is for

Homes and extensions finished in through-coloured monocouche render
Walls that have gone green, grey or streaked
Render previously pressure washed and now patchy
Properties being prepared for sale or letting
Developments with large areas of monocouche to maintain

How much does it cost?

As a guide, monocouche render cleaning usually costs £4 to £8 per square metre, or £300 to £600 for a typical semi-detached house. Heavily stained or high walls needing extra access cost more. See our full cost guide.

How it works

How monocouche render cleaning works, step by step

Inspect and test

The render and colour are checked, cracks noted, and a test area treated where colour sensitivity is a concern.

Protect the surroundings

Planting is soaked and protected, and windows, doors and vents are covered.

Treat the growth

The biocide is applied at low pressure across whole elevations and left to dwell on algae and mould.

Rinse evenly

Each wall is rinsed from top to bottom in one consistent pass to avoid tide marks and patches.

Monocouche render cleaning: FAQs

How do I know if my render is monocouche?

Monocouche is usually a single, fairly thick coat with the colour running all the way through, often with a scraped or lightly textured finish. If you chip a small edge, the colour inside matches the surface. Thin-coat silicone or acrylic renders have a different coloured base coat underneath. Paperwork from the builder or the original render installer is the surest way to confirm.

Can monocouche render be pressure washed?

It is not recommended. Pressure washing can erode the surface of monocouche render, exposing darker colour beneath and leaving visible stripes. It can also force water into fine cracks. Low-pressure cleaning with a suitable biocide removes the growth without damaging the finish.

Can faded monocouche be brought back to its original colour?

Cleaning removes algae, mould and dirt, which is usually most of what makes it look tired. Some colour fading from years of sunlight is natural and cannot be cleaned away. Where colour has faded unevenly, specialist render paints or coloured coatings are available, but that is a separate job from cleaning.

What causes the dark streaks under my windows?

Water running off window sills carries dirt and keeps the render below damp, so algae and atmospheric dirt build up in streaks. Cleaning removes them, and sills with proper drip grooves or overhangs help stop them coming back. Blocked or missing drips are worth checking at the same time.