Why do fascias and soffits turn green so fast? (And does it actually matter?)

Fascias and soffits don't get much attention until they've gone from white to a patchy grey-green, and by then most people assume it's just age catching up with the plastic. It isn't. It's algae, and it builds up a lot faster than the boards themselves wear out.

If your fascias are looking tired, the good news is it's almost never the plastic's fault.

It's not dirt, it's a living thing

The green and grey streaking on PVCu fascias and soffits isn't ground-in grime - it's algae, and in damper parts of the country like Blackburn, the Ribble Valley and the wider Lancashire area, it has ideal growing conditions for most of the year. Fascias and soffits sit under the roofline, out of direct sun for long stretches and regularly damp from rain running off the tiles above. That combination of shade and moisture is exactly what algae needs to establish itself.

Once it's there, it spreads. Slowly at first - a faint grey tinge along one edge - then more noticeably as it colonises more of the surface. It rarely happens evenly either. The north-facing side of a house, or the bit that sits under an overhanging tree, will usually be several shades darker than the rest.

Does it actually damage anything?

Cosmetically, yes, straight away - a house with green-streaked fascias looks tired even when everything else about it is in good order. Structurally, it's slower, but it's not nothing.

Algae holds moisture against the surface of the fascia and soffit board for longer than it would otherwise sit there. Over years, that constant damp can degrade the surface finish, particularly on painted timber boards, and can accelerate discolouration on PVCu that would otherwise stay looking new for a long time. It's not usually urgent. It is usually avoidable.

Why it's easy to miss

Fascias and soffits sit above eye level, at the edge of the roofline, which means most people genuinely don't look at them from one year to the next. Gutters get noticed because they overflow. Driveways get noticed because you walk on them. Fascias just quietly discolour above your head until a photo, or a neighbour's freshly cleaned house next door, makes the difference obvious.

How often does this need doing?

Roughly every one to two years, similar to gutter cleaning - which makes sense, since it's driven by the same algae and grime that builds up on the roofline generally. Properties with more shade or overhanging trees tend to need it nearer the one-year mark. Open, sunnier properties can often go a little longer.

It's worth pairing with a gutter clean where possible. We're already up there with the same equipment, and fascias sitting directly below a gutter often pick up extra run-off staining that's worth dealing with at the same time.

Is a soft-wash the same as pressure washing?

No, and that's deliberate. High pressure can strip the surface finish off PVCu and force water behind panels that were never designed to get wet from the front. We use a gentle, biodegradable cleaner with a long-reach soft-wash brush instead - enough to lift algae, lichen and bird mess without putting the boards or the paint behind them at any risk.

The bottom line

Green fascias aren't a sign your house is falling apart. They're a sign that algae has found a shaded, damp spot to grow, which happens to almost every roofline eventually. Left alone it keeps spreading and keeps holding moisture against the boards. Dealt with every year or two, it's a straightforward job that keeps the whole roofline looking as good as the rest of the house.

Whether you're in Blackburn or anywhere else across Lancashire, if you can't remember the last time your fascias were cleaned, that's usually the answer to how overdue it is.