Residential Render Cleaning in Northampton (2024–2025)

Across 2024–2025, we completed a large number of residential render cleaning jobs around Northampton, restoring stained elevations back to a cleaner, more uniform finish. On modern render systems, the biggest culprit isn’t “dirt” — it’s biology: green algae, black biofilm, and the more stubborn red/orange staining that can embed into textured surfaces.

This page consolidates multiple smaller domestic jobs into one place, showing the typical problems we see across Northampton neighbourhoods and the methods we use to clean render safely and consistently.

What we were dealing with (and why it matters)

Residential render discolouration usually falls into three buckets:

• Green algae: classic green shading on damp, shaded elevations and behind vegetation.
• Black staining / dark biofilm: often appears as darker streaking or patches, especially where moisture lingers. Studies of building biofilms frequently note Gloeocapsa among organisms associated with darker patinas.
• Red/orange algae staining: commonly associated with Trentepohlia-dominated biofilms/patinas. This one matters because the pigment can be more visually persistent and can require a more targeted chemical approach.

In practice, homes often show a mix of these, with different elevations colonising differently depending on shade, aspect, rainfall exposure, and nearby trees/green space.

The Challenge

Even when render “only looks a bit tired,” it’s usually:

• Unevenly stained (north-facing/shaded sides are typically worse)
• Streaked by runoff (beneath rooflines, parapets, and around downpipes)
• Patchy around windows and corners (microclimates + texture)

The goal is a consistent finish without damaging the surface — which is why we don’t treat render like a driveway.

Our Approach

1) Method selection: low pressure first

We use softwashing principles: treatment-led cleaning at low pressure, then controlled rinsing. This aligns with manufacturer guidance that focuses on biocide-led cleaning for organic growth on render/masonry rather than aggressive pressure.

2) Standard softwash for green + lighter organic growth

For green algae and lighter biofilm, we apply an appropriate cleaning solution, allow dwell time, then rinse carefully to prevent streaking and patchiness — especially important on large gables and textured finishes.

3) Tackling red/orange staining (the stubborn one)

For red/orange staining linked to Trentepohlia-type patinas, we often need a more intensive approach than standard green growth:

• More targeted application
• Longer dwell time
• Repeat applications in heavier areas

In some cases, this includes a controlled bleach-based (sodium hypochlorite) treatment as part of a professional softwash process — used carefully to manage risk to plants, finishes, and surrounding areas.
(We don’t publish mixing ratios on-site pages — correct strength and handling depends on the surface, conditions, and site controls.)

4) Controlled rinse + detail work

We rinse methodically and detail around:

• window reveals
• pipe runs / downpipes
• corners and returns
• bands beneath eaves/parapets

That’s where streaking shows first if you rush.

5) Optional aftercare (regrowth control)

Where appropriate, an after-treatment can be used to slow regrowth and extend the clean appearance, depending on exposure and the client’s maintenance goals.

Results

Across the set of properties in this 2024–2025 round-up, cleaned render was left:

• brighter and more uniform
• with green and black staining reduced/removed
• with red/orange staining significantly improved, often requiring extra treatment attention compared with standard algae
• with noticeably cleaner visual lines around windows and roof bands

Want your render assessed?

If your render is showing green shading, black streaking, or red/orange staining, send a couple of photos plus your postcode and we’ll advise the safest method and what level of improvement to expect for your specific contamination type.