Shiver Me Timbers

For my latest design-build project, I’m helping to build out an existing timber frame into a complete house. The architect, Cillian, made some bold strokes on the plans in pursuit of maximizing thermal and air tightness. He hired me to run structural analyses and give him peace of mind.

In true design-build fashion, Cillian himself is on site every day spinning saws and getting his boots muddy. I took on manual labor this week as well. Our third team member, Ben, is an industrial designer with the most construction experience of the bunch. The mood on site feels different from any I’ve been on before – we’re unusually meticulous and safety-conscious, but also quite ribald. I’m trying to have fun with it.

Ben and Cillian measure the timber frame.

Ben and Cillian measure the timber frame.

Our first task is to build two trusses (which I designed) and attach them temporarily to opposite walls of the timber frame. We’ll use them to lift the frame in the air so we can install an insulated 12-inch-deep floor system underneath. Since the frame has no built-in shear system (it’s anchor-bolted to the concrete foundation via angle brackets at each leg), it would rack and collapse without support high on the legs. A truss allows us to lag to those high points and transfer the weight to supporting jacks outside the structure’s footprint.

Sketch of the proposed truss.

Sketch of the proposed truss.

Ben and I built the trusses from planed 4×8 timbers, which are NOT dimensional lumber. They’re much fussier. First, the actual cross-section dimensions vary. Second, the edges aren’t necessarily square. To prepare a planed timber for use, we use a framing square to determine the edge closest to 90 degrees, then mark the centerline of each face using a chalk box, then use the best edge and centerline as reference points for all subsequent measurements. Diagonals with their angular ends are especially tricky to cut properly, but it’s essential for all the centerlines of a truss connection to intersect at a single point.

The angles for a diagonal cut, showing offsets to account for the exact width of adjacent timbers.

The angles for a diagonal cut, showing offsets to account for the exact width of adjacent timbers.

The timbers are also heavy; a 16-footer probably weighs 150 pounds. A team effort for sure to carry them around.

Particularly in the wake of my summer job in which I watched another company lift a house, it’s exciting to accomplish the same task with my own hands. This timber frame lift is the consummate marriage of design and build. I really hope it works.

Ben gets another timber ready.

Cillian gets another timber ready.

2 thoughts on “Shiver Me Timbers

  1. Pingback: Truss-Tease | PERCH ENGINEERING PLC

  2. Pingback: Two Hundred Fifty | PERCH ENGINEERING PLC

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