How Manchester's density and weather wear a roof
Density is the first thing weather does to a Manchester roof. Houses sit close together and under street trees, so sections of roof stay in shade for most of the day, dry out slowly and grow moss and dark algae streaks on north and east slopes. Paved streets and rooftops hold summer heat, which cooks south-facing shingles harder than in the open towns nearby. Winter brings inland snow and ice like the rest of the county, and ice dams form at the eaves of older houses with warm attics. Wind matters most on the exposed upper gables of the mill houses and on the hilltop streets, where lifted tabs show up after storms.

