Professional Render Cleaning in Lancashire

Why render goes green across Lancashire

Render is a porous surface facing the weather, and Lancashire gives it plenty of weather. A metre and a half of rain a year in the hills, long damp spells and westerly wind carrying spores off open moor and farmland.

Algae lands on the render, finds a damp textured surface, and colonises it. On a north or east elevation, which never gets enough sun to dry out properly between October and March, it can go from clean to visibly green in three or four years.

It is worth saying plainly: green render is not dirt and it will not wash off with a hose. It is a living organism rooted into the surface, and it has to be killed rather than rinsed.

The render types we deal with, and how they differ

Modern silicone and acrylic thin-coat systems, the K-Rend family and similar, are what has gone on most Lancashire new builds for twenty years. They are tough but they are thin, and the colour is through the coat rather than painted on. Damage them and you cannot touch it in.

Monocouche is a through-coloured single coat, common on estates from the 2000s onwards, and it scratches more easily than people expect.

Then there is traditional sand and cement render, often painted, and pebbledash, which is everywhere on interwar and post-war housing across the county. Pebbledash holds dirt and growth in every crevice and is the one most likely to be attacked with a pressure washer by somebody who should know better.

Soft washing is the only method we will use

Every render clean we do is a soft wash. The elevation is wetted down, a biocide solution is applied and left to dwell, and it is rinsed at low pressure. The growth dies and carries on dying for months afterwards.

That is why a soft washed wall stays clean for years while a pressure washed one is green again in eighteen months. Pressure removes the visible growth and leaves the roots. Biocide kills the roots.

It is also the only method that does not damage the render.

What a pressure washer does to render

On thin-coat silicone systems it blows the coat off, and because the colour runs through the material there is no patching it. The repair is re-rendering the elevation.

On monocouche it leaves lance marks and a lighter, opened-up surface that then gets dirty faster than the rest of the wall. On pebbledash it strips the stones off and leaves bald patches. On traditional render it opens the surface and drives water into the substrate behind.

If a contractor arrives at a rendered house with a petrol pressure washer and a turbo nozzle, that is the point to stop the job.

Cracks, damage and the things we look for first

We survey before we clean, and the main thing we are looking for is whether water can get behind the render. Cracks, failed sealant around windows, blown or hollow-sounding sections, damaged bellcast beads at the bottom.

Cleaning a wall that has a route for water behind it makes the damp worse, so we flag it and let you get it repaired first. We would rather lose the job than cause a problem.

Staining from a leaking gutter or downpipe is the other common one, and there is no point cleaning that off until the leak is fixed, because it will be back by next winter. Often the honest answer is to do the gutter cleaning first.

Organic growth is not the same as staining

Green and black algae, and the red or orange growth you sometimes see on north elevations, all respond to biocide. That is the straightforward case.

Rust streaks, mortar run-off, paint splashes and tannin staining from overhanging trees are not organic and will not respond to a biocide. They need different treatment and sometimes they cannot be fully removed. We will tell you which one you have got when we look, rather than promising a perfect finish and then explaining afterwards.

How often, and what it costs

Most Lancashire render wants doing every three to five years. North-facing, shaded and tree-covered elevations sit at the shorter end. A properly biocide-treated wall goes considerably longer than one that has only been washed.

Price comes down to the area of render, the number of storeys, how bad the growth is and access. Scaffold is rarely needed because we work from the ground with poles where we can.

Fixed price before we start, in writing. See render cleaning for the full method, or areas we cover for where we work.