According to the House Builders Federation , it is uneconomic and probably illegal to build a Georgian terrace. For instance, the raised pavements and steps up to the front door (which allow an extra, lower ground floor) are in breach of Regulation M, governing disabled access. Sash windows are in effect outlawed by Regulation L, governing insulation. And any house with more than three storeys must have a fire escape and fire doors. Moreover, a new consultation on staircase regulations is likely to see them made wider and shallower so they take up yet more precious room.