If your rendered walls have turned green, black or streaky, you're not alone. Render cleaning is one of the most common exterior cleaning jobs we carry out across Exeter and Devon. The region's damp, mild climate creates perfect conditions for algae, mould and pollution staining to take hold on rendered surfaces — but the good news is that professional cleaning can make them look like new again.
What We Cover
Why Rendered Walls Get Dirty in Devon
Devon's climate is the main culprit. Our combination of high rainfall, mild temperatures and coastal humidity creates ideal growing conditions for the biological organisms that stain rendered surfaces. Here's what's actually happening to your walls:
Green Algae
The most common issue on rendered properties in Exeter. Algae thrives in damp, shaded conditions and spreads quickly across textured render surfaces. North-facing walls are particularly affected.
Black Mould
Often appears as dark patches or streaks, particularly around gutters, windowsills and areas where water runs down the wall. Devon's persistent moisture makes this especially common.
Red Algae
Less common but increasingly seen on lighter-coloured renders in the Exeter area. Appears as pink or reddish staining and can be stubborn to remove without the right treatment.
Pollution & Dirt
Road-facing properties and those near busy routes pick up general pollution staining. This combines with biological growth to create the grey, tired appearance many Exeter properties develop over time.
Did You Know?
Exeter receives around 800mm of rainfall per year, and Devon's mild winters mean algae and mould can grow almost year-round — unlike drier parts of the country where cold winters kill off biological growth.
Different Types of Render and How They're Affected
Not all render is the same, and the type of render on your Exeter property affects both how it gets dirty and how it needs to be cleaned.
Monocouche (Through-Coloured) Render
Very common on newer Exeter properties and housing developments. This factory-coloured render is designed to be maintenance-free, but Devon's climate has other ideas. The textured surface traps moisture and organic matter, making it a magnet for algae. White and cream renders show staining worst, but all colours are affected over time.
Silicone Render
A premium option found on many newer builds and refurbished properties around Exeter. Silicone render is more water-repellent than standard render, which does help, but it's not immune to biological growth. The good news is that it responds very well to soft washing and stays cleaner for longer after treatment.
Traditional Sand & Cement Render
Common on older Exeter properties. This render is more porous than modern alternatives and absorbs more moisture, making it particularly susceptible to algae and mould growth. It also requires more care during cleaning to avoid damage.
Pebble Dash
Still found on many properties across Exeter, Newton Abbot and the wider Devon area. The rough, textured surface collects dirt and organic matter in every crevice, making it one of the hardest renders to keep clean — but also one that benefits most dramatically from professional cleaning.
How We Clean Rendered Walls
The method we use depends entirely on the type of render, its condition and the type of staining. Getting this wrong can damage the render surface, which is why professional assessment matters.
Soft Washing — Our Go-To Method
For most rendered properties in Exeter, soft washing is the safest and most effective approach. This uses low-pressure water combined with specialist biodegradable cleaning solutions that kill algae, mould and lichen at the root. Unlike high-pressure washing, soft washing won't damage the render surface or force water into the wall.
- ✓ Specialist biocide solution applied to kill all biological growth at the root
- ✓ Low-pressure rinse to remove dead growth and surface dirt
- ✓ No risk of damage to the render surface or water ingress
- ✓ Biocide continues working for weeks after treatment, improving results over time
- ✓ Results typically last 2-3 years in Devon's climate
Pressure Washing — When It's Appropriate
For tougher staining on robust render types, or for sand and cement renders that can handle higher pressure, we may use controlled pressure washing. We always test a small area first and adjust the pressure to suit the specific render. This is never our first choice for modern thin-coat renders, which can be damaged by high pressure.
Warning:
Using a domestic pressure washer on render without understanding the surface type and correct pressure settings is one of the most common causes of render damage we see across Exeter. Too much pressure strips the surface coating, creates water ingress and can leave the render looking worse than before.
DIY vs Professional Render Cleaning
We understand the temptation to have a go yourself — but render cleaning is one of those jobs where DIY attempts often cause more problems than they solve.
DIY Risks
- • Pressure washer damage to render surface
- • Water forced behind render causing damp
- • Household bleach damaging render and killing plants
- • Incomplete cleaning that returns within weeks
- • Working at height without proper equipment
- • Streaky, uneven results
Professional Advantages
- • Correct method matched to your render type
- • Commercial-grade biocides that kill growth at the root
- • Even, streak-free coverage across all walls
- • Results that last 2-3 years, not weeks
- • Safe access equipment for upper floors
- • Plant and surface protection throughout
Render Cleaning Costs in Exeter
Render cleaning costs depend on the size of the property, the extent of staining, access requirements and the type of render. Here's a rough guide for typical Exeter properties:
We always provide a free, no-obligation quote after seeing the property. Every job is different, so we'd rather give you an accurate price than a rough guess.
Keeping Your Render Clean for Longer
After professional cleaning, there are a few things you can do to extend the results and keep your rendered walls looking fresh:
- 1. Keep gutters clear — overflowing gutters are the number one cause of localised staining on rendered walls. Clean them at least twice a year.
- 2. Trim back vegetation — plants growing against rendered walls trap moisture and encourage algae growth. Keep a gap between plants and walls.
- 3. Check for drainage issues — splashback from hard surfaces or poor drainage near walls accelerates staining at ground level.
- 4. Consider a biocide maintenance wash — a light annual treatment can prevent algae from re-establishing and extend the time between full cleans.
Our Recommendation:
For most Exeter properties, a professional render clean every 2-3 years keeps things looking great and prevents staining from getting so bad that it becomes harder and more expensive to remove.
Need Your Render Cleaned?
We clean rendered walls across Exeter, Newton Abbot, Exmouth, Dawlish, Topsham and the wider Devon area. Get in touch for a free, no-obligation quote.
Get a Free Quote