K-rend, monocouche and painted render · Hertfordshire, Bedfordshire and NW London

Render cleaning in Hertfordshire

Green, black and grey render brought back to the colour it was originally rendered in. Cleaned at low pressure with a biocidal treatment, because cleaning at high pressure with a jet lance will damage delicate render.

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Cleaned render on the front of a mock-Tudor house in Hertfordshire after soft washing
Soft washing a rendered house wall with cleaning foam
What we do

Render cleaned with chemistry, not force

Render cleaning is the removal of algae, black mould, lichen and atmospheric dirt from a rendered wall, returning it to its original colour. Herts Pressure Washing has cleaned render across Hertfordshire, Bedfordshire and NW London since 2008, and it is the type of work we are asked for most after drives and patios.

The green and black staining on a rendered house is living growth, not dirt sitting on top of it. Kill it and it lets go. Blast it and you drive water into the render, risking damage and opening up the surface to go green again faster than before. So we treat it, let the chemical do the work and rinse. Perfect results every single time.

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Finishes

Every kind of render on a Hertfordshire house

Every finish is cleaned the same way – low pressure and a biocidal treatment. What changes is the care each one needs, from keeping the colour even on K-rend to keeping the paint on a painted wall.

K-rend and through-coloured render

Thin-coat silicone render cleaned without opening up the surface or leaving patchy lighter areas where the colour has been scoured.

Monocouche render

Single-coat scraped render cleaned with the texture left intact, including the tricky shaded elevations that go green first.

Painted render

Painted, pebbledashed and roughcast walls cleaned at low pressure with a biocidal treatment, so the paint stays on the wall.

Walls, porches and garden walls

Rendered boundary walls, porches, bay returns and chimney stacks done at the same time so the whole property matches.

Rendered gable end after low-pressure biocidal cleaning, algae and black mould gone
Method

No high pressure. Ever.

This is the one rule we will not bend. High-pressure jetting on render blows the top coat off, forces water behind the finish and leaves stripy lance marks that never come out. Plenty of people still do it, and the repair costs more than the clean ever did.

Instead we apply a foamy biocidal treatment by pole, at low pressure. The foam clings to the wall rather than running off it and kills the algae and black mould at the root. The wall is then rinsed down at low pressure. The growth dies rather than being scraped off, which is why it stays away longer.

How soft washing works
Wide view of the rear of a rendered house after soft washing, render and garden walls cleaned together
The method behind it

Render cleaning is soft washing

The correct process of cleaning render is called soft washing. The same low-pressure biocidal method works on painted masonry, brick garden walls and other exterior walls, not only on render, and it has its own page covering where else we use it and which towns we cover for it.

You can see more of our render and wall cleaning work on our specialist site, Herts Render Cleaning.

Soft washing

Render cleaning across Hertfordshire, Bedfordshire and NW London

Rendered house owners across the area come to us from St Albans, Harpenden, Watford, Radlett, Welwyn and the Barnet belt, along with Luton and Dunstable in Bedfordshire. In business since 2008, CSCS accredited and an approved contractor for seven councils and organisations, with £5m public and employers’ liability cover from Hiscox.

Areas we cover

What customers say

  • “Ours was a K-rend job that hadn’t been done for over 10 years – we were concerned that some discolouration was past saving and permanently stained. We were wrong. Alex did a brilliant job and it really does look like new. This is how good he is: he pointed out a tiny yellow stain the size of a grain of rice and said he couldn’t do anything because it was a discolouration in the raw material. I couldn’t even see it. And on top of that, he was punctual, at a fair price, and he left the place looking spotless.”

    Barry Knichel

FAQs

Render cleaning questions

Can’t see your question here? Give us a call or drop us a message on WhatsApp and we’ll give you a straight answer.

Yes, if anyone uses high pressure on it. A high-pressure jet lance will strip the surface, drive water behind the finish and leave permanent lance marks. We never jet render. It is cleaned with a low-pressure biocidal treatment applied by pole and rinsed off gently.

Yes, both, and they are most of what we clean. Thin-coat silicone renders like K-rend and scraped monocouche finishes are cleaned by treatment rather than pressure, which is what keeps the texture and the through-colour intact instead of scouring pale patches into the wall.

Yes. Sound paint is unaffected because there is no scouring involved – the treatment kills the growth and the wall is rinsed at low pressure. Paint that is already flaking or blown will come away wherever it has lost its key, and we will say so before we start.

Render is priced by the property, not by the square metre – the number of elevations, the height, how far the growth has gone and the access all change the figure. The minimum charge is £250 and we are not VAT registered. Photos usually get a price back the same day.

Longer than after a jet wash, because the treatment kills the algae at the root rather than removing what you can see. Most render stays clean for three to five years before it needs doing again, a little less on shaded and north-facing walls.

Normally not. The treatment is applied from the ground with extension poles, which is faster and cheaper than putting up access equipment. Occasionally a job with difficult access – no side access, for example – needs scaffolding or other access equipment, and we will tell you when we quote.

Because algae needs damp and shade. North-facing elevations, walls under trees and anything shaded by a fence or a neighbouring house stay wet for longer, so growth takes hold there first. It is the normal pattern and not a fault in the render – although overflowing or leaking guttering can cause it too.

Yes, but that is a different job with different chemistry, so it has its own page. Carbon staining on brick and stone is lifted with acid-based treatment rather than the biocidal method used on render.

Get in touch

Get a fast, no-obligation quote

Send us a couple of photos on WhatsApp and we’ll come back with a price – usually the same day.

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Established 2008

4.9★ from 80 Google reviews

Council approved