Ledbury roofs, specifically
Sheltered by the Malverns, damp from the Leadon: why Ledbury roofs go green.
Ledbury lies low beside the River Leadon, which probably gave the town its name, in a sheltered spot under the western slope of the Malvern Hills. The hills keep off the weather from the east. That's pleasant to live with, but it leaves damp air hanging still over the valley floor, and still, humid air is ideal for moss, lichen and gloeocapsa algae. The eastern edge of the parish is in the Malvern Hills AONB, where the wooded slopes facing the town hardly dry out from October to spring.
In the old town, Church Lane — the cobbled lane up to the parish church, lined with leaning black-and-white timber-framed houses — and the High Street below it are crowded with tall old buildings. They shade one another most of the day, the lanes are too narrow for much sun to reach the lower slopes, and old clay, stone and hand-made tile stay wet much longer than modern tile. Left untreated, a High Street roof usually ends up carrying thick moss in the laps, often with rust stains from old lead and valley metal.
The newer HR8 estates — Hopfields off Leadon Way, The Arches off Bromyard Road beside the viaduct, and the homes around Mabel's Furlong — are mostly modern concrete tile. Its textured face gives spores a hold, so even a roof only a few years old can start to show green on its north side in this sheltered air. A fifteenth-century cottage on Church Lane and a new house at The Arches have the same cause, Leadon-valley damp, and the same fix.
Ledbury is also orchard and hop country, with vineyards and woodland on every side, and the town's history is tied up with cider, perry and hops. All that greenery puts spores into the air, and they settle on roofs across the parish and the villages nearby. On weathered tile we won't use high pressure: the surface coating has thinned, and blasting it takes years off the tile for one clean season. Taking moss off by hand and applying biocide is gentler and lasts longer, whether the roof is centuries old or nearly new.