Cabin_ Two Brothers, a Dream, and Five Acres in Maine - Lou Ureneck [22]
The fundamental unit of timber-frame construction is the “bent.” This is an assembly of timbers fashioned into the shape of a raised H—two vertical posts connected near their tops with a horizontal beam. The timbers are joined by mortises and tenons, which are pegged, not nailed. The bents are constructed on the ground (or floor) and raised into place in succession to make the frame of the box. One need only look at the frame of an eighteenth-century church in Boston or Newburyport to see that I’m oversimplifying, but that H is essentially the unit that locks together to make a frame and carry the roof. The old-time housewrights elaborated on this theme in extraordinary ways to create soaring steeples, wide worship halls and multi-tiered barns of enormous capacity.
I had made some sketches of a rectangle—the width of the cabin would be sixteen feet, because that was the length of the timbers that I had to form the horizontal line of the bent, the H. For efficiency and a pleasing appearance, the cabin’s length must be in proportion to the width. There’s no classic golden mean for cabins, but a design that is too long would turn the cabin into a bowling alley, and a design too short would sacrifice potential living and storage space. The timbers that I had to connect the freestanding bents, one to the next, were eight and ten feet long. Their lengths would establish the distance between the bents and ultimately—adding them together—the length of the cabin. So the length would be some combination of eight and ten. I struck on twenty-six feet—four bents spaced, after the first, at ten feet, eighteen feet and twenty-six feet.
For the walls I decided to use two-by-four studs between the posts to provide a nailing surface for the interior and exterior materials and as away to hang batts of fiberglass insulation. I had done it this way before, when I had built the house for my family, and knew the process and materials. I went with the familiar.
Then there was the problem of the rafters, the sloped timbers, front and back, that meet to form the peak of the roof and, at the other ends, the eaves. They transfer the weight of the roof to the outside walls. My early and quick inspection of the wood pile told me that the posts and beams were mostly sound, but some of the wood rafters I had hoped to use were questionable. It was essential that the roof framing be strong, safe and reliable. To have a rafter snap would be a catastrophe. I knew I would have to be ruthless in culling any bad rafter material. I decided it would be a good idea to fortify the roof framing by placing standard lumberyard trusses between the big timber rafters. These additional trusses would carry a lot of the roof weight and provide a surface for nailing the boards that would eventually become the ceiling of the cabin.
So, with both the wall assembly and the rafters, I would make use of the big timbers but supplement them with lumberyard materials. I would fit the old lumber into the frame of a new structure. It was not pure timber-frame carpentry, and the serious wood butchers—the guys with Amish-style beards, canvas aprons, and German-forged chisels—surely would mutter, or worse, at my approach; on the other hand, there was reassuring continuity in this method that allowed me to use the old rafters, even if I had to bastardize the frame to force the metaphor. Anyway, it would make a safer building.
For the siding of my timber-frame cabin, I had several choices. I could use clapboards, which are beveled pine boards somewhat less than an inch thick, the one above lapping the one below and showing four inches to the weather. This siding makes the classic look of the New England cape or saltbox, and it was a little too finished for my taste in a cabin. I could use half-log siding, which is nailed with the flat surface of the log to the wall. This would create the impression of