Green fascias and soffits: what causes it and how to clean uPVC safely

Why fascias and soffits go green

The green film you see on white uPVC is algae, often with a little moss or lichen mixed in. It isn't dirt in the usual sense — it grows. The fascia is the board running along the edge of the roof, and the soffit is the panel underneath it, and both sit in exactly the spot where rain, shade and dirt collect.

Three things make it worse:

• Shade. North-facing rooflines, and any that sit under trees, stay damp for longer, and algae needs damp.
• The weather. Greater Manchester is mild and wet for much of the year, which is close to ideal growing conditions.
• Overflowing gutters. A blocked gutter spills dirty water down the fascia, and that damp film of dirt is exactly where algae takes hold.

Homes near trees and on shaded streets — plenty of Stockport, Trafford and the older leafy suburbs — go green fastest.

Soffits are usually worse than the fascias, because they face downwards and stay wet for longer. They're also the part nobody looks at, so by the time the green is obvious on the fascia board, the soffit underneath has normally been growing for a while.

Is it just cosmetic?

Mostly, yes. Algae on uPVC is a surface growth and it doesn't eat into the plastic. But two things make it worth dealing with.

The first is kerb appeal. Green streaks down a white roofline make a well-kept house look neglected, and if you're selling or letting, it's one of the first things a viewer notices from the pavement. It's also the kind of thing that makes people assume the rest of the maintenance has been skipped too.

The second is the black streaks. Those come from overflowing gutters rather than algae, and they do point to a real problem upstairs. If your fascias are streaked black under the gutter line, the gutters need clearing — not just cleaning.

Left alone, the growth feeds itself. Algae holds a thin film of moisture against the board, which is all it needs to spread further along the drip line and eventually onto the brickwork below. A clean done after the gutters have been sorted tends to last. One done before doesn't.

What not to use on uPVC

• A pressure washer on full power. It forces water behind the boards and into the roofline, and it can strip the surface.
• Bleach-heavy or abrasive cleaners. These can discolour uPVC and dull the finish permanently.
• Scouring pads and wire brushes. They scratch the surface, which gives algae a better grip next time round.

Warm soapy water and a soft brush is the safest thing to try yourself, on the parts you can safely reach from the ground. Be careful what you use if there's a conservatory or glass roof below the roofline, because whatever you put on the boards ends up running down onto it.

How a professional roofline clean works

1. The gutters get cleared first. If the gutters are still overflowing, everything below them will be green again within a season.
2. The uPVC is treated with a uPVC-safe, non-abrasive product that lifts the algae rather than scrubbing at it.
3. The boards are agitated and rinsed clean, so nothing is left behind to feed the next growth.
4. You get before and after photos of the roofline, so you can see exactly what changed.

All of it happens from the ground, using telescopic poles and a high-reach system. No ladders, no scaffolding, and nothing rested against the boards. If the gutters turn out to be blocked, that's sorted as part of the same visit rather than a separate appointment.

How long does a clean last?

It depends on where the house sits. An open, south-facing roofline can stay clean for a year or more. A shaded, tree-lined one will start to green over sooner — and if the gutters above it are left to overflow, the black streaks will be back before the green is.

Timing helps as well. A clean done in spring tends to stay ahead of the growth for longer than one done in late autumn, when everything is already wet and the algae has had a full season to establish itself. Keeping the gutters clear is the single biggest thing you can do to make a roofline clean last, and if yours are due it's worth reading how often gutters should be cleaned to get the timing right.

Doing it yourself vs booking a clean

You can reach the bottom edge of a fascia from the ground on a single-storey extension or a porch, and warm soapy water will lift a light green film. What you can't do safely is the full roofline, the soffits underneath it, or anything above the ground floor. Reaching up with a brush on a pole from the ground is the limit of what's sensible — anything that needs a ladder is worth leaving alone.

A gutter, fascia and soffit clean covers the lot, and it makes sense to have the gutters cleared at the same visit — that's the gutter clearing service. Doing both together is the cheapest way to get the whole roofline sorted, and it stops the green coming back as quickly.

Gutter, fascia and soffit cleaning starts from £148, and you can see your fixed price and book online in about a minute.