The Super-simple Gambrel Roof

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TRIANGLES AND DOGLEGS

After all the rafters had been cut, we made our plywood brackets (which, because of their shapes, we dubbed "triangles" and "doglegs" (see Figs. 1-A and 1-B). Here, all we did was [1] trace the outlines of the truss joints onto pieces of cardboard, [2] cut templates from the cardboard with scissors, and [3] use the templates as patterns for sawing the brackets out of half-inch plywood.

ASSEMBLING THE TRUSSES

To assure uniformity, we assembled all our roof trusses on the ground between stakes. The doglegs and triangles were attached with 8-penny nails, and (as you can see from Figs. 1-A and 1-B) all joints were also tied together with strap metal, the kind with which bundles of lumber are bound. (You can obtain this metal free at most any lumberyard. We cut ours into 8" to 12" lengths and used a punch, mallet and vice-grip pliers to make nailing holes through each piece.)

After binding the rafter segments together with doglegs, triangles and metal straps, we finished each truss by nailing a short length of 2 x 6 between its dogleg joints to act as a stiffener (and to serve, later, as an attic joist).

When we were through prefabbing the gambrel frames, we stacked all the trusses flat on a level surface with spacer blocks placed between them.

RAISING THE RAFTERS

The procedure we used to erect our semi-triangular frames on top of the cabin can be summarized as follows: First, we'd lay one flat across the joists with its "feet" butted against one of the joists, then we would [1] tilt it partway up, [2] nail a pair of two-by-fours to the truss's short horizontal crosspiece, [3] push the structure upright, and [4] nail the two-by-fours to the loft floor to act as temporary braces. (Note: We took great pains to ensure that the first truss was absolutely plumb at this point, since we intended to align succeeding trusses relative to it.) Afterwards, we nailed the frames' feet to the loft joist and bound them to the supporting sills with metal straps (as depicted in Fig. 1-C).

As successive trusses were erected, we tacked them together with horizontal braces, (to see in more detail, view PDF), to hold them in position. (These braces were removed after the roofing plywood was nailed in place.)

The last couple of frames had to be hoisted into position from the ground, since there was no room to lay them atop the loft before raising them. This, however, was merely a matter of [A] leaning an upside-down frame against the cabin, [B] supporting the frame's peak a few feet off the ground on a stepladder, and then [C] pulling the truss into place by means of a rope and pulley fastened around the crosspiece (attic joist) of an already-standing truss.

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