Building Gypsy Rose

Yesterday, I finished the braces for the equipment shed frame. Thirty-four of them are now stacked neatly alongside the finished posts and tie beams. In the coming week I’ll start on the floor joists and finally the rafters. The top plates will be the last pieces cut as they will not fit inside the greenhouse and I’ll wait for warmer outdoor temperatures before cutting their joints. (The top plates consist of an 18-foot beam and a 12-foot beam connected by a scarf joint for a resultant 30-foot length. Three of them run the length of the building, holding the bents together at 10-foot spacing.)

As I see the stack of what was once rough cut timber being transformed into a life-sized collection of Lincoln Logs I’ve been experiencing mixed emotions. There is the satisfaction of seeing the posts and beams displaying freshly cut mortises and tenons – the shop drawings come to life. There is also the anxiety that creeps in whenever I think about the fact that I’m placing complete faith in my human capacity to implement mathematical calculations that have no tolerance for error. There is the potential (the doubting side of me frets) for bringing all the pieces together on raising day and discovering that a mistake or a series of mistakes have been made that can potentially render the entire stack of posts, beams, and braces unusable – a nightmare, indeed.

The advent of computer aided design software in recent decades has made the mathematical calculations far easier than the longhand methods employed by timber framers in years gone by. Pythagoras is a name that I associate with high school geometry, but his theorem, along with many others, now hide within the code of the Google SketchUp program I used to lay out the building plans. Pointing and clicking on the contemporary drawing board, I convert the overall plan into individual shop drawings – one for each component of the frame.

Once in the shop, the process of laying out the joints in the timber begins with an inspection of the beam. Considerations include the run of the grain, the location of knots, and crown. Once I’ve determined the orientation I’ll use, the sides are labeled and the joints laid out by either scribe or pencil.

“Measure twice, cut once.” The old adage rings truer than ever when mistakes may not rear their head until much later in the process. I check and double check each mortise and tenon layout. Quite often I’ll have the saw in hand, ready to begin the cut and I’ll stop, grab the tape and measure again.

When I first began working on this project I knew very little about the craft of timber framing. “How hard can it be?” I thought. “It’s a barn, right? Little need for precision, right?”

I’ve learned a lot in recent months! Timber framing is, in many ways, like large-scale furniture building and, yes, precision matters.

Brace mortises (above) present the least tolerance for error. A sixteenth of an inch difference in their positions can have an impact on the ultimate trueness of the frame. No pressure, Kevin. You won’t know for sure until spring.

Day by day, wood is removed. Corners are squared. Shoulders are planed. Final measurements are checked. Another piece takes shape and is returned to the stack.

At first I worried whether the software was generating correct numbers. I double-checked using longhand until I was satisfied. The math is correct. I won’t know about the human translation until fitting the pieces in the spring. I wish I weren’t so prone to worry.