Feb 212012

When meeting with clients about prospective timber frame projects, we often tour some of our completed projects. And I try to take clients to see projects that bear a resemblance to what they are dreaming of building for themselves and show them what is possible with timbers. Nowhere are there more design options than in a roof system: what we can do with roofs is darn exciting!

It is a rare day in which we build a house that has a real attic, where the roof structure is hidden out of view with all those old boxes of stuff. With a timber frame and the complete exterior enclosure and insulation system of Structural Insulated Panels, “under the roof” is often the most architecturally exciting place in the house. In short, we like to flaunt our roofs. And we especially love building trusses.

Trusses are structural configurations of timbers that allow for large spans without the need of intermittent posts. As such, they allow for open floor plans and dramatic vaulted ceilings. Many of the trusses we have built over the years originated in the Middle Ages, and were used for great halls, churches, and bridges.

Here are some examples:
Raised cord king post trusses: This intimate living room with a fireplace at the end utilizes red oak timbers to do the real work of holding up the roof. The horizontal cross member that connects the two principle rafters of each truss is called the cord; the vertical center post of each truss is the king post, and the branch like curved elements going up to the principle rafters on the right and left are called struts. The raised cord gives the room a taller and more curved ceiling feel, but allowed us to keep the height of the side walls and ridge lower.

King posted trusses; one with a “live-edged” cord: For this “vehicle barn” that we built for our own family use, we wanted a garage-sized space with no internal supports. We wanted to create a building that was attractive and demonstrated our timber framing skill. We also wanted to use some of our left over timbers from our northeastern forests or timbers harvested from our land. As such, we have pine, hemlock, ash, red oak and white oak timber in this structure. The front king post truss has a curved red oak beam (often called a “Tyco Beam” in Japanese timber framing) that we sawed flat on 2 sides, which allows us to appreciate the interior grain of the log—something that does not happen when building with logs. The king post is also “live-edged”, and the “live-edged” struts are “book mated” by sawing from the same log and opening the faces to each other. The middle roof element is also a king post truss, but with a straight cord that is positioned at the eave height. Note that the kids’ barn swing that is attached to the ridge timber, is being enjoyed by my wife, Nan.

Hammer Beam Trusses: The trusses originated in the “Great Halls” of Medieval Europe. The utilize rigid triangular configurations of timbers that transfer the roof loads out to the walls. Dramatic and eye catching, they often crown modern great room spaces. These trusses are fabricated from old growth and very fine and dense Douglas Fir timbers salvaged from forest fire burned areas in Oregon. To see more photos of this beautiful home, check out the Ray Brook House in our Gallery section.

Burr Arch Trusses: This style of truss was designed for covered bridges that require large and strong spans. In such bridges there would be two trusses, flanking both sides of the road way, and the roof rafters would sit perpendicularly on top of the upper horizontal cords. The Burr Truss used an arching timber element to help transfer loads out to the end support walls or abutments. These trusses were designed for the roof system of a great room, and made of laminated red oak. We were able to fully fabricate and assemble each of the four trusses in our shop, load them on a truck, and transport them to the site and install them with a mobile crane.