Belfast·SPG004 Residential Extensions and Alterations·Page 41·4.3.22
Impact on daylight access to neighbouring rooms
Planning permission is likely to be refused where an extension would reduce light entering a window of any room (excluding halls, landings, bathrooms and utility rooms) to an unreasonable degree.
In terms of the impact of a proposed extension on access to daylight, the effect on all rooms, apart from halls, landings, bathrooms and utility rooms will be considered. Where an extension would be likely to reduce the amount of light entering the window of a room (other than those indicated above) to an unreasonable degree, planning permission is likely to be refused.
Source — /Users/richardhill/Documents/planning-arch-project/data/documents/belfast/SPG004 Residential Extensions and Alterations.pdf