Check out a Fairfax County, Virginia McMansion that was intentionally built to contain four townhomes:

This is the Great House, a four-unit townhouse designed to look like a large, single-family home. Like DC and Montgomery County, Fairfax requires developers to build affordable units in new developments, but they often stick out like a sore thumb. When Carrington was being built in 2001, the county worked with builder Edgemoore Homes to help subsidized, $120,000 townhomes blend in with homes several times as expensive.

Each Great House is comparable in size to its neighbors and uses the same materials. But instead of one, 5,000 square-foot house, you have four, 1,200-square foot townhouses. Only one of the doors faces the street. A driveway runs around the back, where each townhouse has a two-car garage…

The Great House could be a particularly useful housing type as the region grows. A recent study from George Mason University’s Center for Regional Analysis estimates that the DC area will need 548,000 new homes over the next 20 years. About half of those units will need to go in the District, Montgomery, and Fairfax counties. And 60% of them will need to be townhouses or apartments…

Those things don’t really matter to neighbors who spend lots of time and effort to “maintain the integrity” of their single-family neighborhoods. But seeding their neighborhood with a few Great Houses that provide housing diversity while blending in could be a compelling alternative to building traditional apartments or townhouses there instead. Of course, they aren’t possible under most zoning laws, which only allow single-family homes in “single-family neighborhoods.”

This sounds like a fascinating compromise: help provide cheaper housing in a region that needs it while at the same time keeping the single-family home character of these neighborhoods. I wonder just how many “Great Houses” a typical suburban neighborhood could handle without social life changing or the McMansion owners complaining a lot.

I also suspect that some would argue building townhouses that look like this only perpetuates some of the problems of McMansions, including bad architecture and emphasis on sprawl and auto dependence. At the same time, a key factor in helping affordable housing succeed is that it needs to look like normal ousing so it doesn’t stand out and draw the attention of nearby residents.