Frampton on Severn roofs, specifically
Why Frampton on Severn roofs green up faster than the higher ground around them.
Frampton on Severn sits low and flat on the Severn Vale floodplain, a few miles south-west of Gloucester, strung out along one of the most photographed greens in the country. Rosamund's Green runs for the best part of half a mile through the middle of the village — at around 22 acres it's reputedly the longest village green in England — and the tidal Severn lies just to the west, the River Frome to the east, with the Gloucester & Sharpness Canal threading along the western edge past Splatt Bridge. It is a beautiful, watery, low-lying place. It is also, for exactly those reasons, somewhere roofs green up badly.
The geography does most of the damage. This is floodplain ground barely above the level of the estuary, drained and worked since the eighteenth century but never really dry. With the tidal river on one side, the Frome on the other, three ponds sitting on the Green itself and the canal running the length of the village, the air stays heavy with moisture for most of the year. Moss, lichen and gloeocapsa algae live on precisely that — constant ground damp and humid, still air — so a Frampton roof carries noticeably heavier growth than an identical house a few miles up onto the drier Cotswold edge towards Stroud. The north-facing pitches nearest the canal and the waterside stay green the longest.
Then there's the material. The houses ringing the Green are mostly Tudor and Georgian — timber-framed, brick and render under hand-made clay tile, natural Welsh slate and the odd run of Cotswold stone slate, much of it a century or three old. Those surfaces are porous and textured: they hold damp, give spores something to grip, and in a shaded waterside position they never really dry out. By the time someone calls us, a north-facing pitch above the Green is usually a thick green-black mat sitting in the tile, with rust weeping off old valley metal and the gutters packed with washed-down growth.
This is why method matters here more than equipment. You cannot pressure-wash a porous stone-slate or old clay roof — the force splits the slates, blasts out the lime bedding and drives water under the laps, and a cracked stone slate has to be replaced with a reclaimed one to match. So on Frampton's heritage roofs we lift the moss off by hand, working from a roof ladder that spreads the load, and then treat with biocide. It is slower than blasting a modern tile, but it's the only way to clean a fragile old covering without taking years off its life — and on a roof that costs a small fortune to replace, that's the whole point.
Not every roof in the village is heritage, mind. On the later infill — the closes and lanes built off Whitminster Lane and around the edges of the old core — you'll find modern concrete interlocking tile on newer houses. Those are a different job; they can take a more robust clean where it suits. But in this damp floodplain microclimate they green up too, and they get the same bulk-removal-then-biocide treatment so the result actually lasts. Whether it's a 17th-century house on the Green or a 1990s home off the lane, the cause is the same Severn-Vale damp, and so is the cure.