Here in Venice, where there is a tight housing market (but not unaffected by the current deep downturn), if you want to knock down the ugly old and put up your new janga-box architectural, but don’t want to hassle with the permissions to do a new construction, you can leave one wall standing and call the project a remodel. Incredibly open loop-hole, that.
This is a curious relationship between design and politics. Ostensibly, city authorities want to clear specific new construction for a variety of factors, including the design of structures, their contingent aspects in relationship to existing structures, and the landscape as a whole — relative heights, home footprint, secondary resource strains, like street parking (always a factor here), noise, etc. (Many homes here, on originally tiny lots that kept small beach cottages, or modestly sized homes, occupy their entire lot with built material..literally no lawns, the houses go up to the sidewalk and the next property line so as to obtain as much “home” as possible.)