Roof rooms/ attics should be included when accessed via a permanent fixed staircase such that one is able to walk downwards facing forwards. Does not necessarily contain habitable rooms. For a roof room to be classed as such and not a separate storey, the height of the common wall must be less than 1.8 m for at least 50% of the common wall (excluding gable ends or party walls). The common wall is a vertical continuation of the external wall of the storey below. There is no explicit allowance for dormer windows except to include in the floor area of the roof rooms. The Lifespan SAP Team