In September 2025, we completed a full-house render clean on a residential property in Northampton. The exterior was heavily affected by black algae staining, which can leave render looking patchy and weathered—especially on shaded elevations, gable ends, and around window details.
To restore a clean, uniform appearance, we used a controlled bleach-based softwash to break down the staining, then applied a biocide treatment to help inhibit regrowth and extend the clean finish.
Black algae on render tends to:
The job required an approach that removed staining effectively while keeping the process controlled around windows, trims, and surrounding surfaces.
Before treatment, we protected sensitive areas where needed (e.g., around windows/fixtures) to keep the process clean and controlled during application and rinse-down.
We applied a bleach-based softwash treatment to target black algae staining. This is often the most effective way to lift stubborn dark growth from render without resorting to aggressive pressure that can damage the surface.
After dwell time, we rinsed carefully and checked elevations for consistency—especially on large wall runs where patchiness is easy to spot.
Once cleaned, we applied a biocide treatment to help inhibit organic regrowth and keep the render looking cleaner for longer between maintenance visits.
If your render is showing black algae staining or patchy weathering, send a few photos plus your postcode and we’ll advise the safest method and provide a clear quote.
