Broadway roofs, specifically
Why Broadway roofs green up faster than most of the Cotswolds.
Broadway is famous for one thing above all: the honey-coloured stone. The village sits on the eastern edge of the Vale of Evesham, right at the foot of the Cotswold escarpment, and the wealthy wool and cloth merchants who built it dug their limestone straight out of the hills behind. The result is the long, broad High Street and The Green — wide, grass-fringed, lined with chestnut trees and rows of 16th and 17th-century cottages in oolitic Jurassic limestone, with traditional Cotswold stone slate and old clay on the roofs. It is one of the most photographed villages in England. It is also, for the same reasons, a roof that greens up badly.
The location does most of the damage. Broadway sits directly beneath Fish Hill and Broadway Tower, where the ground climbs to over 1,000 feet — the highest reach of the northern Cotswolds. Cold, damp air spills down off that escarpment and settles over the village, the shaded lower slopes and spring-fed valley ground hold moisture, and the tall stone cottages along the High Street shade each other for much of the day. Moss, lichen and gloeocapsa algae live on exactly that — cold, damp and shade — so a Broadway roof carries noticeably heavier growth than an identical house out on higher, drier, sunnier ground.
Then there's the material. Genuine Cotswold stone slate is porous, textured and laid in graded courses, with hundreds of small slates and deep laps that hold damp and give spores plenty to grip. Old hand-made clay does the same. Unlike a smooth modern tile, these surfaces never really dry out in a shaded position, so once moss takes hold it mats into the laps and stays there. By the time someone calls us, a north-facing stone-slate pitch above the High Street is usually a thick green-black mat sitting in the stone, with rust weeping off old valley metal and gutters packed with washed-down growth.
This is why method matters more here than almost anywhere. You cannot pressure-wash a Cotswold stone-slate roof — the force splits the slates, strips the surface and drives water under the laps, and a cracked stone slate has to be replaced with a reclaimed one to match. So on Broadway's heritage roofs we remove the moss by hand, working off a roof ladder that spreads the load, and then treat with biocide. It is slower than blasting a modern tile, but it is the only way to clean a stone roof without taking years off its life — and on a covering that costs a fortune to replace, that's the whole point.
Not every roof in the village is heritage stone, mind. Around the edges, on Snowshill Road, Station Road, Childswickham Road and the later infill, you'll find modern concrete interlocking tile on newer houses and the odd converted plot. Those are a different job — they can take a more robust clean where it suits — but in this damp 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 stone cottage or a 1990s house on the village edge, the cause is the same escarpment damp, and so is the cure.