A duplex that looks like a single house

In two developments within the past year, Wolff Lyon Architects of Boulder, Colorado, has produced two-family houses that have two fronts. As designed by principal Tom Lyon, each of these duplexes has one façade that faces a street and another façade that faces the opposite direction — onto another street or onto a green or courtyard.

Each of the façades of what the architects call a “back-to-back duplex” features a sizable front porch and the main door to a unit. “Because of the back-to-back design, the home feels like a single-family home, offering all the privacy of such, in an attached product,” says Megan Cuzzolino of Thistle Community Housing, a nonprofit affordable housing developer that built six duplexes (12 units) in the Blue Vista development in Longmont, Colorado.

The units work well for people who want a house and yard, but do not have the time or desire to care for a large outdoor area, say Joanne Brothers, project development manager at Blue Vista. The individual yard is big enough that the occupants “can have a small dog, a barbeque, green grass,” Brothers says. Visually, the design meshes well with single-family houses. “The scale,” Brothers says, ”is very appealing.”

John Wolff, a partner with Lyon, says the design gives each unit more privacy than would be possible if both units had their front doors and front porches on a single elevation.

The first back-to-back duplex, containing two-story units of about 1,000 sq. ft. each, was built in 2004 by the nonprofit Affordable Housing Alliance in the Northern Lights section of the Holiday neighborhood in Boulder. Recently Wolff Lyon has designed back-to-back duplexes in Dartmouth College’s Sachem Village project in West Lebanon, New Hampshire, as well as in Longmont. Thistle sold the approximately 1,100 sq. ft. units in Blue Vista for $135,000 to $146,000 — about $35,000 less than they would command on the open market.

Wolff says back-to-back duplexes are especially worth considering when the available lot is fairly shallow — between 80 to 140 feet deep — and has exposure to streets or greens in both directions. This building type produces “reasonably high densities, in the 15 to 20 du/acre range,” he says. If no off-street parking is provided, a back-to-back duplex can fit on a lot as small as 3,200 sq. ft. If parking is provided in the side setback between buildings, the lot for two units would need to increase to 3,500 to 4,000 sq. ft.

“These lot sizes compare favorably with the most aggressive row house configurations and create similar density,” Wolff says. “However, they can create superior individual identity, better day lighting, and privacy for each home.”

Because there is no back yard, the duplex is not suitable for people who want a large and very private outdoor space. Wolff notes, however, that each household can be supplied with a sizable porch (8 by 20 feet in some designs). “In addition, front yards can be delineated with picket fencing and walls,” he adds, and landscaping can create “half-hidden gardens,” providing additional privacy “while still presenting a gracious front to the street or green.”

Korkut Onaran, a principal in Wolff Lyon, says that for corner lots, the firm sometimes designs “corner duplexes.” In this design, one unit and its porch face one street, while the other unit and its front porch are at 90 degrees, to face the other street.