Cutting Down to Size

Here are some tools communities are using to restrict the spread of oversize houses, according to the National Trust for Historic Preservation:

· Conservation districts or historic districts, which permit a special zoning overlay that allows local review of design plans and can be tailored to suit specific blocks or neighborhoods. Also known as special planning districts or overlay districts, they are being used in Phoenix, Raleigh, N.C., and Memphis, as well as Annapolis and College Park.

· Design review, triggered if a house exceeds a certain size.

· Restrictions on floor-area ratio, or the buildable floor area in relation to lot size. This has been used in Gulf Stream, Fla., and in Rehoboth Beach, Del., where last year the city reduced the allowable ratio from 70 percent to 60 percent.

· Setbacks, or the distance a building must be located from the road, and open-space requirements to protect greenery and trees.

· Bulk limits to restrict the size of the house, often including height restrictions. In Fairfax County, houses can be no taller than 35 feet.

· Development incentives and bonuses to permit additional density for houses that contain features cities find desirable, such as front porches, detached garages or the use of exterior brick.

· Downzoning to discourage construction of large multi-unit apartments in single-family neighborhoods. It's legal but can be politically unpopular.

· Historic preservation outreach to encourage residents to build additions in keeping with the character of local neighborhoods. The process is aided by distribution of historic-style pattern books, which illustrate ways to expand houses without changing their character. College Park plans soon to provide pattern-book designs to guide residents.