The 45-degree rule is applied to the plan as well as the elevation. A line drawn at 45 degrees from the center of the nearest ground floor window of a livable room in a neighboring property shall not be exceeded by an addition. If such an addition goes over this line, the person building it needs to ensure that it does not look out of balance with its context - otherwise known as "out of scale". This applies not only to traditional stick-built homes but also to any addition built into a wall of a house, such as a bay window or patio. For example, if a family builds themselves a custom home and decides to add on to it later, they would need to follow the 45-degree rule when doing so. It's important to note that the rule is based on proximity to neighboring properties, not distance. So if there are three buildings across the street from each other, but one is larger than the others, then it wouldn't matter which one you chose as your reference point, since all three are closer together than the required minimum distance from neighbors. For example, say there are two smaller single-family homes and one larger multi-unit apartment building. The apartments don't meet the requirement because they're not close enough to each other.