The Right Way to Fix Green algae on render / K-Rend in East Kilbride
How to tell if it's green render algae
Four tells we look for on every East Kilbride 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 East Kilbride properties
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.
Silicone-based renders such as K-Rend, Weber and Parex have a slightly porous face that holds airborne moisture — perfect for green algae (Trentepohlia and Klebsormidium) to establish.
In East Kilbride specifically, sitting around 600ft above sea level, east kilbride catches more wind and driven rain than central glasgow — gutters fill quickly with windblown debris from the town's mature tree-lined estates — which is the single biggest reason this issue is more stubborn here than in a drier inland town.
Our East Kilbride 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.
What NOT to do
Common mistakes we see on East Kilbride 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.
East Kilbride quote to job completed is usually under two weeks.
£220–£480
£ per typical rendered semi
Every East Kilbride quote is fixed-price in writing — no on-the-day surprises.
East Kilbride-specific considerations
Heavy share of 1970s–80s Wimpey and Barratt semis through Westwood and The Murray, a wave of modern Persimmon and Cala new-builds in Stewartfield and Jackton, plus the original 1950s town houses in The Village.
Sitting around 600ft above sea level, East Kilbride catches more wind and driven rain than central Glasgow — gutters fill quickly with windblown debris from the town's mature tree-lined estates.
We're based locally, so most East Kilbride jobs are quoted same-day and scheduled within the week — no callout fee inside G74 or G75. Nearest motorway is the M74, with routes via A726 and A727.
Green Render Algae — questions from East Kilbride customers
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 East Kilbride property first and only proceed once we've confirmed no colour lift.
How long before the render greens up again?+
On a north-facing East Kilbride 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 East Kilbride where mixed façades are common on older streets.
Talk to the South Lanarkshire team
Fixed-price quote for green render algae on your East Kilbride property. Fully insured, South Lanarkshire Council-covered, 12-month guarantee on the work.
Other fixes we handle in East Kilbride
Related pages for East Kilbride
Jump to a specific service, a nearby town, a postcode mini-hub, or an audience-specific package — all fully local to South Lanarkshire.