Belfast·SPG003 Residential Design·Page 34·3.1.42
Daylight provision using angle rules
Adjacent dwellings must be sited using the 45 degree rule to ensure adequate daylight, while opposite dwellings must use the 25 degree rule.
To ensure that adequate daylight is provided to all dwellings, dwellings that are adjacent to one another should be sited using the 45 degree rule and dwellings that are opposite each other should be sited using the 25 degree rule.
Source — /Users/richardhill/Documents/planning-arch-project/data/documents/belfast/SPG003 Residential Design.pdf