The geology under Newton has left its mark on the buildings. The area sits on the Pennine Middle Coal Measures, a mix of mudstone, siltstone, sandstone and coal seams. The sandstone was used as a building material, especially before the industrial era, and the mudstone let local collieries, Blackwell among them, make their own bricks. That means the older houses are likely to be stone or brick, and the roofs above are what the years have put on them: slate, clay tile, or later concrete tile.
Each covering is cut differently. Slate wants a flashing that tucks into the courses. Plain clay tiles need a kit made for their small, curved profile. Concrete tiles are bigger and heavier, and a kit made for that thickness gives a clean seal. A VELUX window comes with flashing kits for these variations, which is part of why it suits a village of mixed roofs. The covering gets identified on the survey visit, and the matching kit is ordered from that.
The structure matters just as much. Older houses may have rafters at irregular spacing, and a few have had loft work done by earlier owners. A window that suits the rafters is easier and tighter to fit than one that cuts across them. In a loft with trusses, the opening may be limited by the web of the truss, and then the position is decided by what the structure allows, not what the drawing wants.
The slope and the aspect of the roof decide how much light arrives and when. A south-facing slope is bright and warm, and a window there often wants a blind or solar-control glass. A north-facing slope delivers an even, gentle light through the day, which suits long hours at a desk.