As I mentioned in an earlier entry, in other urban areas, certainly Nashville, we seem to be headed in a somewhat different direction. When Nashville first adopted zoning back in the early part of the 20th century, all residential areas were permitted duplexes, that is, there were no single-family residential districts per se. Certainly you could have a single-family home but that’s only district would also allow a duplex.
Over the last 40 or 50 years, we have moved in the other direction, adopting a series of new zoning district switch permit only single-family residences and exclude duplexes or more than one home on a single zone lot.