Sort Black Roof Streaks on Glasgow Properties
Black Roof Streaks on a Glasgow property isn't cosmetic — left long enough, it costs real money to reverse. This page is the version we wish every Glasgow customer read before phoning three firms and getting three different stories. Straight facts, City of Glasgow-relevant, no jargon.
How to tell if it's black roof streaks
Four tells we look for on every Glasgow 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 Glasgow properties
West-of-Scotland roofs sit wet for long stretches — north-facing pitches, tiles shaded by trees, and gable ends that catch driven rain all give the algae the moisture it needs.
Once a colony establishes, spores travel airborne to neighbouring properties — which is why streaks tend to appear in clusters along a street rather than one house at a time.
In Glasgow specifically, glasgow averages around 170 wet days a year and sits in a damp west-coast climate — perfect conditions for north-facing roofs to grow moss and for red sandstone to streak with black algae — which is the single biggest reason this issue is more stubborn here than in a drier inland town.
Our Glasgow 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.
One day for a typical 3-bed semi, two days for large detached or steep-pitched properties.
Glasgow quote to job completed is usually under two weeks.
£320–£620
£ per typical 3-bed roof
Every Glasgow quote is fixed-price in writing — no on-the-day surprises.
Glasgow-specific considerations
A real mix of Victorian sandstone tenements in the West End and Southside, post-war semis in Knightswood and Pollok, and modern detached new-builds across Bearsden and Newton Mearns.
Glasgow averages around 170 wet days a year and sits in a damp west-coast climate — perfect conditions for north-facing roofs to grow moss and for red sandstone to streak with black algae.
We cover the whole city seven days a week and can usually be on site within 48 hours of a quote being accepted, M8 traffic permitting. Nearest motorway is the M8, with routes via M8 and M77.
What NOT to do
Common mistakes we see on Glasgow 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
Black Roof Streaks — questions from Glasgow customers
Is your roof cleaning insured for my property?+
Yes — £5m public liability, and Glasgow City Council addresses are on file weekly. Certificate sent before the job starts.
Can you treat one pitch only?+
Yes. On many Glasgow 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 Glasgow that matters, because glasgow averages around 170 wet days a year and sits in a damp west-coast climate — perfect conditions for north-facing roofs to grow moss and for red sandstone to streak with black algae. 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 Glasgow roofs clear — much cheaper than a full re-clean.
Get black roof streaks sorted this month
Fixed-price quote for black roof streaks on your Glasgow property. Fully insured, Glasgow City Council-covered, 12-month guarantee on the work.
Related pages for Glasgow
Jump to a specific service, a nearby town, a postcode mini-hub, or an audience-specific package — all fully local to City of Glasgow.