Non-complying building

A non-complying building departs from its district's current bulk rules — too much floor area, too tall, too little yard — but stands lawfully because it complied when built and the rules changed around it. Zoning tolerates the condition while constraining it: the non-compliance generally may continue and may not be enlarged, and demolition typically forfeits it, since a replacement must fit today's envelope.

The status explains a large share of the city's apparent anomalies and drives real decisions: an overbuilt building can be worth more standing than its cleared lot, precisely because its excess floor area cannot be rebuilt. Distinguish the non-conforming use — the same grandfathering logic applied to what a building houses rather than its bulk.