Residential Render Cleaning in Northampton (2024-2025)

Across 2024 and 2025, we completed a large number of residential render cleaning jobs around Northampton. These ranged from full-house softwashes on modern K-Rend and silicone render to targeted treatment of stubborn red and orange algae staining that had built up over several years. The images here show a cross-section of those jobs and the kinds of results we were achieving.

What We Were Dealing With

The most common issues across these properties were:

• Green algae - the most widespread form of biological growth on rendered walls, especially on north-facing and shaded elevations where moisture lingers
• Black biofilm (Gloeocapsa) - dark patches and streaking that builds up gradually, often mistaken for general dirt but actually a cyanobacterial growth
• Red/orange algae (Trentepohlia) - a tougher organism that penetrates deeper into textured render finishes and does not always respond to a single treatment

The Challenge

On many of these properties, the staining was uneven - concentrated on certain elevations and lighter on others. Runoff from gutters and windowsills had created visible streak patterns down the render. Around windows and under rooflines, the discolouration was often more intense, making the overall appearance patchy and inconsistent even on relatively new-build homes.

Red and orange Trentepohlia staining presented an additional challenge. Unlike green algae, which typically lifts in a single softwash application, Trentepohlia embeds deeper into textured render and often requires a controlled bleach-based treatment with repeat applications to clear fully.

Our Approach

1. Method selection - low-pressure softwash - Every job started with a surface assessment. Rendered walls are cleaned using low-pressure application only - no high-pressure washing, which risks driving water behind the render or damaging the finish.
2. Standard softwash for green algae and biofilm - For the majority of properties, a single softwash cycle was enough. We apply a cleaning solution at low pressure, allow appropriate dwell time for the treatment to break down the organic growth, then rinse thoroughly.
3. Tackling red/orange staining with NaOCl - Where Trentepohlia was present, we used a controlled sodium hypochlorite (NaOCl) application at appropriate dilution. This type of staining often needs more than one pass - we managed expectations with homeowners about this upfront.
4. Controlled rinse and detail work - After treatment, each elevation was rinsed methodically from top to bottom. We paid close attention to window surrounds, junction lines, and areas near downpipes where residual staining tends to linger.
5. Optional aftercare - regrowth control - On request, we applied a biocide treatment after cleaning to help slow the return of algae growth, keeping the render cleaner for longer between washes.

Results

Across these residential jobs, the consistent outcome was render that looked brighter, cleaner, and more uniform. The difference was most visible on:

• Previously green or black-stained elevations returning to their original render colour
• Window surrounds and detail areas where streaking had been most noticeable
• Full-house cleans where every elevation was treated, giving a consistent finish all round

For properties with Trentepohlia, results varied depending on severity - some cleared fully in one visit, others required a follow-up application. We always advise homeowners on what to expect before starting.

Related Services

• Render Cleaning
• Commercial Exterior Cleaning