BRACING OUR ROUND TIMBER FRAME FOR BIG WINDS

It was a fascinating process to watch the branching timbers that form the structure of Underhill House sprout a few new branches last week.

If you would like to learn more about why we believe building with branching timbers is one of the most ultimately environmentally friendly ways to form a structure, check out my post Your Next Building Material – Unmilled, Branching Timbers, which I wrote when the USDA Forest Products Laboratory conducted its first tests on the strength of branching timbers.    You can also check out this YouTube on the topic, A Smashing Party.

I love the concept that branching, unmilled timbers are a strong and sure building material.  I also love that they have a graceful, natural beauty.  Strong and beautiful as they are, last week, some of the timbers holding up our roof got bolstered with an engineered and artisanal upgrade when additional branches were grafted on to make strategic braces to augment the racking strength of the timber frame so that it will stand up to wind load better.

Whether in a traditional milled timber frame structure or an unmilled timber frame building like ours, straight or gently curving braces are used to connect near the tops of posts to a nearby spot along an overhead beam. The braces serve to strengthen the timber frame by resisting racking, an engineering term for leaning or tilting when a force, such as a strong wind, is exerted against the structure.  They also help to carrying the load from the beam above to the post below.

I watched Michael and Prairie craft and graft new branching members as I worked below them on the 18” high slip form stone wall that will hold our straw bale walls up and away from any moisture on the ground.

It was a joy to watch them use art and engineering to construct a handful of additional braces.

One of the first they worked on was actually more of an edit than an additional branch.

Last summer as we walked the woods with members of the WholeTrees Architecture and Structures   Doug and I watched in wonder as Roald Gundersen, and then Della Hansmann and Bryan Dalstrom scanned the trees looking for those with the kind of bending trunks or branching patterns that could define the curving lines of Underhill House.  As the trees were felled and gathered by the barn, Bryan and Della studied them and assigned them all a place in the structure.

But when you are working with these kind of natural forms, there are bound to be a few that don’t quite fit in as planned, and one of the main posts turned out to branch a little too low to use its graceful side branch.  It would have meant knocking our heads every time we turned into the hallway to the bedroom and bathroom.   This was not something we wanted to encounter on a daily basis, and in any event, it probably wasn’t going to pass the scrutiny of our building inspector.

The guys cut off the out of whack branch and set it aside.  Last week, they pulled it back out of the pile  and set it back in place, making a few adjustments in the extension and angle and reconnected almost exactly in its original place, but more upright, to allow both structural strength and the ability to walk past it without a knock on the noggin.

Other timbers in the south and center bents have also had braces added to them. While control over east/west racking was accounted for in the design, Bryan wanted to beef up racking resistance in the north/south direction, perpendicular to the bents.  Especially with the prospect of our strongest winds, hopefully not but possibly up to tornado force, coming up the driveway out of the southwest, Bryan  was determined to add bracing.

I marvel at the care and artistry that Michael and Prairie have employed in this effort, as they have throughout the project.

All the timbers in Underhill House were felled on our own property and chosen because they were crowding other trees, struck by lightning, diseased on in some other way destined to improve the woods with their removal.  They were, for the most part, overcrowded weed trees.  If you look past the original purchase price of our 44 acres, they didn’t cost anything, and they had no miles of transportation, but the flip side of this economy has been the lavish application of care and handling from their initial peeling and sanding through their finishing and their shaping and joining.

I think it’s a good trade off.  Instead of using a lot of fossil fuel to haul them from northern Wisconsin or Washington State or China, the energy going into the building of our house has been human energy imbued with craftsmanship and creativity.

The result is strong and beautiful.  And it honors the source of this amazing building material – self replicating carbohydrate nano fibers.

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