Local sandstone built most of old Bradford, with stone slate on the roofs or Welsh slate on later streets. Stone slate weighs a lot, and the rafters holding it up are often undersized by modern standards. That is why a Bradford survey spends longer in the loft than a Wakefield one. It rarely causes trouble, but the installation team wants to see the structure before committing to a panel count on a Great Horton, Eccleshill or Undercliffe terrace.
Hills count for as much as stone. The city sits in a bowl with suburbs climbing the sides, so Wibsey, Clayton, Queensbury and Idle have roofs pointing every way. An east to west street gives terraces a south-facing pitch with room for six to eight panels. A north to south street gives you pitches facing east and west, which still produce about 85% of what a south-facing roof does. For the simplest roofs in the district, look at the 1930s semis in Thackley, Wrose, Bierley and Low Moor.
Along the Aire valley, in Shipley, Saltaire, Baildon, Bingley and Keighley, heritage comes into it. Saltaire’s World Heritage status brings a buffer zone of over a thousand hectares, and Little Germany, Ilkley, Haworth and the old village centres are conservation areas. Roof solar on the listed mill-workers’ terraces in Saltaire itself needs consent. Most houses in the buffer zone are unlisted and can go ahead with some care.