Brockworth roofs, specifically
Why Brockworth roofs green up so fast in the shadow of the scarp.
Brockworth sits at the foot of Cooper's Hill, right where the flat Gloucester vale runs up against the steep western edge of the Cotswold escarpment. It's a lovely place to live and a hard place to keep a roof clean. The hill rises sharply to the south-east, wooded and north-facing, and it does two things to the village below: it throws shade across rooftops for a good part of the day, and it holds damp air down against the houses where the warm vale meets the cool slope. Shade and damp are exactly what moss, lichen and gloeocapsa algae feed on, so a roof here tends to carry noticeably heavier growth than an identical house out on the open, drier ground towards Gloucester.
You see it most clearly on Brockworth's big modern estates. Coopers Edge, built from 2006 onward on the land that was once the Gloster Aircraft Company's airfield, runs to well over a thousand homes, and almost all of them are roofed in modern interlocking concrete tile. People assume a roof that's only ten or fifteen years old is too young to have a moss problem — but the textured face of those concrete tiles gives airborne spores something to grip, and tucked under the scarp in this microclimate, even fresh tile starts to carry a green film within a few years and proper moss in the laps not long after. The newer Perrybrook, Cotswold Chase and Crickley Fields developments off Mill Lane and Ermin Street are going the same way as they age.
Away from the estates, the older village core is a different roof but the same problem. Around St George's Church, Court Road and the lanes off Ermin Street — the old Roman road that still runs through the village — you find aged clay tile and stone slate on properties decades or centuries older than the new builds. Those mat up just as heavily in the damp, but they're brittle and need lifting by hand rather than soft-washing. Whether it's a 2010 Coopers Edge semi or a far older cottage in the village, the cause is the same Cooper's Hill damp, and so is the fix: get the growth off properly, then treat the tile so it stays off.
One thing that's specific to Brockworth is how much of the village went up at once. Coopers Edge, Perrybrook and the other modern phases were built across compressed timeframes, so whole roads of near-identical roofs reach the point where moss is impossible to ignore at roughly the same time — which is why, once we're booked on one house, we'll often end up doing two or three more on the same street that same week. It's also why we don't blast decade-old concrete tile with high pressure: the factory surface coating is what slows regrowth, and hammering it with a jet wash takes years off the tile to buy you a single clean season. A soft-wash that lets the biocide do the work is gentler on the tile and lasts far longer — which matters on a roof that still has decades of life ahead of it.