Green Render Algae in Moodiesburn — Fixed Properly
How to tell if it's green render algae
Four tells we look for on every Moodiesburn 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 Moodiesburn properties
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.
North-facing walls that dry slowly stay damp for weeks after rain, and Scotland's ~170 wet days a year keep them within the algae's growth window most of the year.
In Moodiesburn specifically, exposed setting between glasgow and cumbernauld — north-facing render greens fast and gutter debris is heavy after westerly storms — which is the single biggest reason this issue is more stubborn here than in a drier inland town.
Our Moodiesburn 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.
Half a day for a typical semi, one full day for a large detached with wrap-around render.
Moodiesburn quote to job completed is usually under two weeks.
£220–£480
£ per typical rendered semi
Every Moodiesburn quote is fixed-price in writing — no on-the-day surprises.
Moodiesburn-specific considerations
Heavy mix of modern K-Rend new-builds across Marnoch and Auchengeich, with older ex-council stock through Glenboig and Annathill.
Exposed setting between Glasgow and Cumbernauld — north-facing render greens fast and gutter debris is heavy after westerly storms.
M80 J3 on the door — Moodiesburn jobs are quick to schedule and usually combined with Stepps and Cumbernauld stops. Nearest motorway is the M80, with routes via M80 and A80.
What NOT to do
Common mistakes we see on Moodiesburn 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
Green Render Algae — questions from Moodiesburn customers
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 Moodiesburn 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 Moodiesburn property first and only proceed once we've confirmed no colour lift.
How long before the render greens up again?+
On a north-facing Moodiesburn wall, expect 18–24 months clear with the biocide left in place. South-facing usually stays clear longer.
Book a Moodiesburn render survey
Fixed-price quote for green render algae on your Moodiesburn property. Fully insured, North Lanarkshire Council-covered, 12-month guarantee on the work.
Other fixes we handle in Moodiesburn
Related pages for Moodiesburn
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