The zoning for the site limits new construction to a floor-to-area ratio of 6.02.
Limiting most construction to one-family homes on large lots helped to discourage people of limited financial means from settling there.
Michael Parley, a zoning consultant, said the law effectively limits construction on such sites to about eight stories.
Since Shusha had limited urban construction in the 20th century, it preserved its historic architectural-planned composition.
The builders are now racing the clock to beat zoning changes recently announced by City Hall that would limit new construction.
Efforts to limit construction, critics say, can affect all types of housing, from apartments to mansions.
When the program was introduced in 1968, its backers said these strict building codes would limit construction along the coast.
The citizens of this historic seaside town have voted three times since 1999 to limit residential construction, but the area's commercial growth has presented another challenge.
The measure, similar to the San Francisco law, would limit new construction to the equivalent of one 40-story building a year.
In addition, he said there has been limited new construction, keeping demand ahead of supply.
