For Category 2 M4(2) in every dwelling which has a principal double bedroom, it is deemed reasonable to require that the dwelling has a bathroom containing a WC, a basin and a bath as described in paragraph 2.29b. These requirements are assumed for properties with two or more occupants. For smaller one-person dwellings (for instance, a 1b1p as defined by the Nationally Described Space Standard) it may be reasonable for a shower to be provided instead of a bath as a permanent layout providing that the requirements of Diagram 2.5 for clear access zones continue to be met.