Houses in Multiple Occupation amenity guidance
7.1 All habitable rooms shall have an adequate level of natural lighting, provided via a clear glazed window or windows and/or door(s), the glazed area to be equivalent to at least 1/10th of the floor area and to extend normally to a point 1.75m above floor level.
Basement rooms used for human habitation shall, in addition to the requirement above, have sufficient natural lighting for their purpose.
All staircases, landings, passages, kitchens, bathrooms and toilet compartments shall be provided, where practicable, with a window. Windows to bathrooms and toilet compartments are to be glazed with obscure glass.
Adequate electric lighting points shall be provided to all habitable rooms, staircases, landings, passages, kitchens, bathrooms and toilet compartments. All lighting to common parts to be provided maintained and paid for by the landlord or their agent. Lighting to staircases, landings and passages may be controlled by time switches or other devices having a similar effect.