Green Render Algae in Stepps — Fixed Properly
Most Stepps enquiries for green render algae follow the same pattern: it looks bad, it's slowly getting worse, and a couple of quick-fix jobs from generalists made no difference. On 1960s 80s semi and modern new build stock in Stepps, the fix is method-specific and the guarantee is only useful if it's underwritten. Here's what we actually do.
How to tell if it's green render algae
Four tells we look for on every Stepps survey before quoting.
- A green cast on north- or east-facing gables, worst after wet weather
- Pink or orange staining on south walls — that's a different algae but same fix
- Darkening below window sills where water drips
- A textured, slightly rough feel where the render was originally smooth
Why it happens on Stepps properties
Splash-back from paved paths and driveways drives spores upward onto the lower 1–2m of render, which is why the greening is often worst just above ground level.
New-build estates share the same render batch across dozens of homes, so once one façade is affected the same streaks appear on neighbours within a season.
In Stepps specifically, open ground on the eastern fringe of glasgow — windblown debris from surrounding farmland keeps gutters busy through autumn — which is the single biggest reason this issue is more stubborn here than in a drier inland town.
Our Stepps fix — step by step
- 1Test patch
We test a 1m² patch first to confirm no colour lift on your specific render batch — silicone renders vary.
- 2Soft-wash application
Low-pressure application of a render-safe biocide, worked from bottom up to avoid streaking.
- 3Dwell
10–20 minutes contact time depending on staining severity.
- 4Low-pressure rinse
Rinsed at under 500 psi — high pressure damages the render's silicone binder.
- 5Protective biocide film
A residual biocide is left on the surface to slow regrowth for 12–24 months.
Stepps-specific considerations
1960s semis around Hornshill, large modern detached across Cardowan Moss and a strong run of bungalows along Cumbernauld Road.
Open ground on the eastern fringe of Glasgow — windblown debris from surrounding farmland keeps gutters busy through autumn.
Off the A80 — Stepps slots into our north-east Glasgow run and is usually combined with Moodiesburn or Bishopbriggs visits. Nearest motorway is the M80 / M73, with routes via A80 and M73.
What NOT to do
Common mistakes we see on Stepps properties before we're called in.
- Never jet-wash silicone render — it blows the finish off in patches, and re-rendering costs thousands.
- Never use household algae killer diluted from a garden centre — the pH is often wrong and marks the render.
- Do not paint over the algae — it grows straight back through the paint film within 6 months.
Chemistry & materials we use
- Sodium hypochlorite at render-safe dilution (typically 3–5%)
- Non-ionic surfactant so the biocide sheets evenly, no drip marks
- Neutralising rinse compatible with silicone render binders
- No acid-based cleaners — they etch the finish and void manufacturer warranty
Half a day for a typical semi, one full day for a large detached with wrap-around render.
Stepps quote to job completed is usually under two weeks.
£220–£480
£ per typical rendered semi
Every Stepps quote is fixed-price in writing — no on-the-day surprises.
Green Render Algae — questions from Stepps customers
How long before the render greens up again?+
On a north-facing Stepps wall, expect 18–24 months clear with the biocide left in place. South-facing usually stays clear longer.
Do you clean brick and stone as well as render?+
Yes — sandstone, blonde stone and brick all clean well with the same soft-wash chemistry, which matters in Stepps where mixed façades are common on older streets.
Will run-off harm my planting?+
No — biocide is neutralised on rinse and diluted heavily by the water volume. We still sheet plants where they sit directly under the wash zone.
Is soft-washing safe on my K-Rend?+
Yes — soft-wash is the manufacturer-recommended method for K-Rend and Weber renders. We test a small patch on your Stepps property first and only proceed once we've confirmed no colour lift.
Free quote for Stepps — same day
Fixed-price quote for green render algae on your Stepps property. Fully insured, North Lanarkshire Council-covered, 12-month guarantee on the work.
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