Illustrative comparison; not a verified customer job.What causes white render to go green?
Algae can thrive wherever moisture persists. Not every dark patch is organic growth: atmospheric staining, rust, water marks and defective coatings need different remedies. Cleaning cannot permanently cure a drainage fault.
Why white finishes need a careful approach
Any uneven cleaning or existing patch repair may be particularly visible on white surfaces. A discreet test area helps set expectations before treating the whole wall.
Soft wash and biocide options
Depending on the substrate, a contractor may use a compatible low-pressure treatment and appropriate algae control. Follow manufacturer guidance on every product and allow for weather and garden protection.
- Photograph the greenest and least affected areas
- Check damaged sealant and overflowing gutters
- Discuss how the cleaner will protect windows and plants
- Ask whether some residual staining may remain
When to repair rather than wash
If you see cracking, delamination, loose paint or water penetrating the wall, the priority may be repair, not cleaning. Choose an appropriate render professional before washing a compromised surface.
Helpful answers from manufacturer and UK industry guidance
Short answers with links to check the supporting guidance.
What gets green algae off white render?
Green marks are often biological growth that can be treated with an appropriate algae cleaner or biocide. The method must suit the render finish and its condition; where rinsing is required, keep it gentle and follow the product’s instructions. A harsh jet can damage a delicate surface.
Can white render be cleaned instead of painted?
Often, yes. Dirt, algae and weather film can make sound render look discoloured, and K Rend advises gentle cleaning to refresh its appearance. Painting should not be the first assumption, although permanent stains, cracks or other defects may call for separate repairs.
Is household bleach safe for white render?
Do not assume household bleach is compatible with the render, landscaping or drainage. Cleaning products should be selected for the particular surface and used according to their label. If a biocide is required, choose an appropriate authorised product and ask the contractor how runoff and nearby plants will be protected.
Frequently Asked Questions
Will green algae make white render fail?
Organic surface growth may be mainly cosmetic, but underlying moisture defects should be assessed separately.
Will cleaning make every white wall look brand new?
Not always. Existing discoloration, cracks, previous repairs and aged coatings can affect the final appearance.
How do I keep white render looking cleaner?
Keep gutters functioning, reduce prolonged trapped moisture where practical and follow the render manufacturer’s maintenance advice.