A mansard conversion adds a considerable amount of space to a loft room, usually at the back. Brick sides built off the party wall and a flat roof combine to create maximum headroom and floor space within the converted loft area. With a flat roof, the walls slope into the room at an angle of 72° while the windows are built into small dormers. Daylight is provided either by vertical windows, by recessed windows or by roof windows set in the same plane as the mansard slope. Although primarily used in the conversion of buildings with London roofs, this style of loft conversion can also be a solution to the problems faced when trying to convert any property with the existing roof at a very shallow pitch. Planning permission will usually be required for this type of conversion.