Entire houses roll out of Colorado factory

The Whole House Building System is off to a good start, producing complete townhouses and detached dwellings in a traditional neighborhood development (TND) setting.

“Imagine if Ford Motor Company tried to build a proper automobile in your driveway,” David Cohen suggested. A succession of workers would come to your property and go about their tasks in rain, snow, or other sorts of weather, without the efficiencies of an assembly line. Such a system, if you can call it that, would be costly and error-prone. Cohen, CEO of Cohen Brothers Homes in Denver, says this unhappy scenario is in fact the method by which most houses in the US are currently built.
In “Newbridge at Tollgate Crossing,” a development in suburban Aurora, Colorado, Cohen is pioneering what he sees as a more dependable and cost-effective approach. Early last summer Cohen Brothers erected a 30,000 sq. ft. factory in Newbridge, the most innovative section of Tollgate Crossing’s 441 acres. Newbridge has many TND characteristics, although it is single use. In the high-ceilinged factory, Cohen’s crew of slightly more than 30 employees has since been assembling entire houses, an average of one every 25 days (see photo on page 1).
New Urban News visited Tollgate in November and saw four completed units of a six-unit group of townhouses, plus additional houses under way in the plant. By the time Newbridge’s 64 acres are built out, 237 units selling from about $185,000 to the mid-300s will have come from the factory — a mix of two- and three-story townhouses, 1,500 sq. ft. cottages, and detached houses ranging up to 2,800 square feet.
The process calls for each house to be built on a structural steel frame and fitted with everything from utilities, to carpeting, to appliances, to granite kitchen countertops. The house is subjected to a high-voltage pulse test which detects whether any part of its electrical system is loose, nicked, or improperly shielded. A “duct blaster test” tells whether the heating and cooling system is as air-tight as it’s meant to be. Then the 40-foot-wide door of the plant opens, and the house is pushed out. A self-propelled mechanism transports it, at about a walking pace, to a foundation no more than about a quarter-mile away.
If the design calls for a brick-faced exterior, the masonry is installed after the dwelling is placed on its foundation. If there’s to be a free-standing garage, as is common at Newbridge, the garage is built separately at the home site.
Gene Myers, president of Denver-based New Town Builders, says the Cohen Brothers’ Whole House Building System “has great potential.” New Town, which is involved in several TNDs in Colorado, is the first company to have Cohen Brothers put the system into operation. In a conventional project, New Town would coordinate 25 to 30 subcontractors to build houses. At Newbridge, New Town contracted to have Cohen Brothers build and equip the houses and place them on foundations. New Town does the land development, builds the foundations, and does the landscaping and any exterior masonry.
Better than modular
“We have proven some important things,” Myers said. “Can you move an entire house without ruining it? Yes. The conveyance takes minutes. The part we thought would be a big technological leap [moving houses from factory to foundation] is easy.”
A factory mode of homebuilding has been a goal in the US since the 1940s. Various factory methods, including modular construction, have become established, but they’re far from perfect. Modular units — large, boxy enclosures that are assembled at the homesite — may twist during their long trips over highways. Nails may pop. “Modular has a stigma,” said Myers.
The Whole House Building System, in his view, is superior in that it “eliminates the stitch, the seams, the duplication of structure” associated with modular. Also, it allows ample design freedom. Designs are not limited by the size of box that can be hauled long distances. The plant at Newbridge is using house designs that have won awards.
Compared to on-site (or “stick-built”) construction, the Whole House system cuts construction time and reduces waste of materials. The system may alleviate a liability problem as well. Myers says of conventional homebuilding: “The cost of liability insurance is $4,000 to $5,000 per house.” In moving construction into a factory, “we can make sure mistakes aren’t made in the first place,” he reasons. Labor can be adequately trained, and the workers do their jobs in a climate-controlled atmosphere.
Cohen Brothers’ goal is to get the construction time per house down to eight to 16 working days. Myers thinks the Whole House method will make it possible for local or regional developers like New Town to compete on price with large mass-market builders. The method is best suited to developments of more than 500 houses, a scale that makes it worthwhile to establish a plant. When a project is complete, the plant could be converted to another use, such as an athletic or community facility.
Cohen Brothers has been talking with a number of other companies interested in possibly buying licenses to use the Whole House system. Many are in locales where the conventional homebuilding labor force is inadequate or where climate is a strong factor. About half of them are new urbanist, he said.
“It’s a great fit with new urbanist design,” he said. “New urbanist design tends to be more compact, more vertical, as contrasted to sprawling ranch houses.” The compactness makes new urbanist dwellings promising candidates for fitting within a factory and rolling down a neighborhood street.