Sort Green Render Algae on Hamilton Properties
How to tell if it's green render algae
Four tells we look for on every Hamilton 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 Hamilton properties
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.
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.
In Hamilton specifically, hamilton's east-facing slopes towards the clyde catch a lot of morning damp — slate roofs in burnbank in particular hold moisture and grow lichen faster than the surrounding area — which is the single biggest reason this issue is more stubborn here than in a drier inland town.
Our Hamilton 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.
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.
Hamilton quote to job completed is usually under two weeks.
£220–£480
£ per typical rendered semi
Every Hamilton quote is fixed-price in writing — no on-the-day surprises.
Hamilton-specific considerations
Older stone terraces around Burnbank and Hillhouse, a strong belt of 1960s ex-council semis through Eddlewood and Fairhill, and a growing patch of K-Rend new-builds rising around Silvertonhill and Chatelherault.
Hamilton's east-facing slopes towards the Clyde catch a lot of morning damp — slate roofs in Burnbank in particular hold moisture and grow lichen faster than the surrounding area.
Ten minutes from our base. We can run multi-property quotes (drive + roof + gutters) on the same visit, which most Hamilton customers take advantage of. Nearest motorway is the M74, with routes via M74 and A723.
What NOT to do
Common mistakes we see on Hamilton 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.
Green Render Algae — questions from Hamilton customers
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 Hamilton property first and only proceed once we've confirmed no colour lift.
How long before the render greens up again?+
On a north-facing Hamilton 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 Hamilton 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.
Get green render algae sorted this month
Fixed-price quote for green render algae on your Hamilton property. Fully insured, South Lanarkshire Council-covered, 12-month guarantee on the work.
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