The Incredible Box-Beam House

originally published in Fine Homebuilding #72, 1992
by Bruce Greenlaw

Canadian builder Ari Wloski likes to test unconventional building techniques before putting them to work.

Prior to embarking on his latest project, a six-story home and office near Montreal, Canada, he built a simple, 22-foot long by 16-inch high box beam (a hollow boxlike beam) out of spruce 2x6s and 1/2-inch exterior plywood. Then he raised the beam onto a pair of supporting stanchions, hung a 1989 Dodge Caravan from the center of the span and left the whole thing alone for more than a month. At the end of the test period, the beam showed no signs of deflection.

Now under construction, Wloski's new building incorporates dozens of site-built box beams in its walls, floors, and roof.

Given the host of available structural alternatives, such as solid timber or gluelams, why use beams?

"The idea is to get cavernous interior spaces uninterrupted by structural support members, while using only a fraction of the wood required for conventional stick-built and timber-framed houses," says Wloski. "Box beams not only help to conserve a valuable resource but they can save money too."

Site-built box beams are a particularly sensible alternative for remote locations; plywood and 2xs are a lot easier to transport than solid-wood beams and manufactured lumber.

Wloski also likes box beams because their relatively light weight allows all but the largest ones to be raised by hand. Extra-large beams can be built in place. As a bonus, the insides of the box beams make convenient raceways for heating ducts, wiring, and plumbing.

Each of Wloski's box beams consist of a 2x spruce frame sheathed on both sides with 1/2-inch plywood skins. The frames resemble stud walls, having single or double top and bottom plates and "studs" (called stiffeners) spaced a maximum of 24-inch off-center. The stiffeners separate the flanges and prevent buckling. Frames are assembled with 16d nails, and plywood is fastened to the frames with air-driven, 6d ring-shank nails spaced about 1 1/2-inch off-center.

Perhaps the most intriguing part of Wloski's box beam house is the joinery. Where the box beams join at right angles, they're connected using one of six different joints devised by Wloski with the help of a structural engineer. None of these joints require the use of metal connections (for one variation, see the drawing).

The design of Wloski's beams was inspired by two booklets-Nailed Plywood Beams and Design of Glued and Nailed Plywood Web Beams-published by Canada's Council of Forest Industries. The current editions are almost sold out, but updated versions will be available later this year (contact the COFI Bookstore, 1200 555 Burrard Street, Vancouver, BC, Canada V7X 1S7).

In the United States, the American Plywood Association (PO Box 11700, Tacoma, WA 98111-0700; 206-565-6600) publishes a detailed booklet (No. S812N; US$1) on the design and construction of glued-and-nailed box beams in which the 2xs lie flat between layers of plywood.

According to Wloski, his building will also showcase all sorts of energy - and resource-efficient goodies, including Trombe walls fitted with airtight woodstoves, a grey water recycling system and photovoltaics. The completed structure will house his family and accommodate the headquarters of his fledgling research and educational center.

This diagram published in issue #98.