Sort Black Roof Streaks on Airdrie Properties
How to tell if it's black roof streaks
Four tells we look for on every Airdrie survey before quoting.
- Dark vertical streaks running from ridge to eaves, worst on north- or east-facing pitches
- Streaks that look worse after rain and appear to 'dry lighter' — that's the algae rehydrating
- Neighbouring houses on the same row showing similar staining
- A slightly rough or matte texture on tiles that used to look smooth
Why it happens on Airdrie properties
Uncleaned gutters spill water back onto tile edges, keeping the underside of ridge courses damp and accelerating streak formation from the top down.
The black streaks running down concrete or clay tiles are almost always a cyanobacteria called Gloeocapsa magma, feeding on the limestone filler in the tiles themselves.
In Airdrie specifically, sitting 470ft up, airdrie is consistently colder and frostier than glasgow — north-facing slate roofs hold moss for longer here than almost anywhere we cover — which is the single biggest reason this issue is more stubborn here than in a drier inland town.
Our Airdrie fix — step by step
- 1Roof survey
Ground and drone-level inspection to confirm tile type, pitch, condition and any slipped or cracked tiles that need addressing first.
- 2Manual moss removal
Where moss is present alongside the algae, we soft-scrape by hand before wetting the tiles — never with a pressure washer.
- 3Biocide soft-wash
A low-pressure application of a professional-grade sodium hypochlorite/benzalkonium biocide blend, dwelled and rinsed at low pressure.
- 4Gutter clear-down
Every roof clean includes a gutter clear — algae debris will otherwise wash straight into blocked runs.
- 512-month cover
A residual biocide film keeps regrowth at bay for a season; annual top-ups are optional and cheaper than a full re-clean.
Airdrie-specific considerations
Sandstone tenements around the town centre, large 1970s ex-council schemes in Petersburn and Rawyards, and a wave of new-build silicone-render homes around Calderbank and Plains.
Sitting 470ft up, Airdrie is consistently colder and frostier than Glasgow — north-facing slate roofs hold moss for longer here than almost anywhere we cover.
Junction 5 of the M8 puts us on site fast — most ML6 quotes are scheduled within seven days. Nearest motorway is the M8, with routes via M8 and A89.
What NOT to do
Common mistakes we see on Airdrie properties before we're called in.
- Do not jet-wash the tiles — it strips the mineral coating and the streaks return worse within 12 months.
- Do not use household bleach — the concentration is wrong and it will scorch adjoining render and planting.
- Do not paint over the streaks — coatings peel within a season on damp Scottish roofs.
Chemistry & materials we use
- Sodium hypochlorite at controlled concentration for algae kill
- Benzalkonium chloride residual for 6–12 month regrowth cover
- Neutralising surfactant so run-off is safe for driveways and planting
- Never high-pressure water — pressure cracks the tile surface and voids most roof warranties
One day for a typical 3-bed semi, two days for large detached or steep-pitched properties.
Airdrie quote to job completed is usually under two weeks.
£320–£620
£ per typical 3-bed roof
Every Airdrie quote is fixed-price in writing — no on-the-day surprises.
Black Roof Streaks — questions from Airdrie customers
Can you treat one pitch only?+
Yes. On many Airdrie semis the streaks are only on the north or gable-facing side, and treating one pitch alone is significantly cheaper.
Do black streaks damage the roof?+
Long-term, yes — the algae etches the mineral coating on concrete tiles, which then absorb more water. In Airdrie that matters, because sitting 470ft up, airdrie is consistently colder and frostier than glasgow — north-facing slate roofs hold moss for longer here than almost anywhere we cover. Cleaned early, tiles are restored without replacement.
Will the streaks come back?+
The 12-month biocide layer prevents regrowth in that window. After that a light top-up spray every 12–18 months keeps Airdrie roofs clear — much cheaper than a full re-clean.
Is your roof cleaning insured for my property?+
Yes — £5m public liability, and North Lanarkshire Council addresses are on file weekly. Certificate sent before the job starts.
Talk to the North Lanarkshire team
Fixed-price quote for black roof streaks on your Airdrie property. Fully insured, North Lanarkshire Council-covered, 12-month guarantee on the work.
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