Lydney roofs, specifically
Why roofs in Lydney collect moss: estuary weather on one side, the Forest on the other.
Lydney is squeezed between two things that are hard on a roof. To the south and east is the Severn estuary, wide and open, and the westerly weather that crosses it arrives wet. To the north the ground climbs towards Bream and the Forest of Dean, and the closer a house is to that higher, wooded side of town, the more shade, leaf fall and airborne spores it gets. Moss, lichen and the black streaking algae that shows up on so many local roofs all thrive on that combination of regular rain and slow drying.
Where you live in Lydney makes a real difference to how fast a roof greens up. Houses on the flatter, more open ground towards the harbour and the A48 catch the wind and dry out reasonably quickly after a shower. Roofs on the slopes up through Allaston and Primrose Hill, or tucked under the mature trees around the edges of town, stay damp for much longer, and their north-facing pitches are usually the ones we find matted with moss and shedding it into the gutters.
The housing itself is a mix of eras. The older streets around Newerne, Hill Street and Tutnalls grew up in the 19th and early 20th centuries, when the harbour, the canal and the railways were shipping Forest coal and the town had its tinplate works, and many of those terraces and villas still carry their original Welsh slate. Around them are inter-war and post-war semis, later estates on concrete tile, and a large amount of new housing built in the last fifteen years or so on the east side of town and around Allaston.
Each of those roofs needs a slightly different approach. Century-old slate is scraped by hand and cleaned at low pressure at most, because it is brittle and expensive to match if a slate breaks. Concrete tile on the estates holds moss in its texture and in the overlaps, so we lift the bulk off by hand or with a low-pressure clean. Whatever the roof, it finishes with the same biocide treatment, which is what keeps it clear for up to two years.