Posts tagged ‘whole tree timber framing’
There are many trees holding up our house that I remember with the same detail.
Where they stood, why we selected them, working on finishing them, watching them come together into the timber frame of Underhill House.
It’s easy to forget how much we rely on these amazing plants. The trees we depend on for so many aspects of our lives are usually ground down and reconstituted to the point where they no longer seems like something that grew and lived. It seems like a commodity that you just order, and it appears. That’s a very short-sighted notion.
I love how Underhill House constantly reminds me of what we owe to these stalwart creatures.
Last spring as we were peeling, sanding and painting the timbers for Underhill House, the question of how we would get the roof rafters up on top of the bents was often on our minds. In previous houses built by Whole Trees Architecture and Structures, rafters have been hoisted up by ingenuity and muscle power, but Underhill House is an extra story taller than any previous Whole Tree house.
I moved timbers from their resting place on the ground up onto saw horses for individual attention and back again many, many times, and often considered the danger of hand hoisting those logs up onto the roof. I breathed a sigh of relief when Bryan decided to use a crane.
After the typical setbacks and delays on a building project, the bents were finally up, and the rafters were ready, and Wednesday was set for Crane Day. We just needed the right weather. Storms were swirling around the Midwest, but they always seemed to just miss our area. However, Wednesday’s forecast called for winds of 20 mph. Doug and I wondered if the rafters could be lifted into that much wind.
Dan Gingerich, who was bringing his crane from McGregor IA, said he could do it. We arrived bright and early. Time was of the essence. We wanted to make the best possible use of Dan’s crane and finish in one day. The thing that made using a crane costly was that the crane would need to pause after every lift while the rafter was fitted into place and fastened to the beams.
The crew had moved all the rafters over to the house site, put them in the order that they should be lifted up and numbered them. The plan was to work till noon and if it seemed like we wouldn’t finish in a day, then they would start affixing every other rafter and put the others up loose across the beams to be wrestled into place the next day.
The crew took their posts on the roof.
Two rafters span the three bents. Michael was stationed on the south bent, Brad on the north and Bryan and Prairie manned the middle bent on which the two rafters meet. Prairie would cut each north rafter to fit flush against its southern counterpart and then each mated pair was drilled and either screwed or nailed to the beams.
I ran around taking photos and acted as gofer when needed.
Dan showed Doug how to tie a rope to the trailing end of each rafter to help guide them into position. On such a blustery day, this was doubly important in order to prevent rafters from swinging wildly over the vulnerable heads of the busy crew members who were often looking down at their work instead of up at the next swinging timber, which resembled a battering ram with wings.
Dan showed Doug a really cool knot to tie the rope to each rafter. He called it a cowboy hitch. While it successfully held for every single rafter flight, it could be untied simply by jerking on the dangling tail of the rope. Dan said that when he was taught this knot, he was told that it’s the same one used in rodeo calf roping and tie-down. Doug looked it up in Gordon Perry’s book “Knots: A practical step-by-step guide to tying over 100 knots” and the closest cousin he could find was the Highwayman’s Hitch, aka the Draw Hitch. Dan’s version looked the same except for an extra bight added at the end of the knot, apparently for added security. Even so, in Perry’s book, this quick-release knot comes with a warning: “not considered safe for human descent purposes”. In any event, it sure worked well for us.
As the morning went on, there was very little waiting on Dan’s part. The crew was wrangling each rafter into place at high speed. By lunch break, we were all cautiously optimistic that we would get them all anchored in place with the crane before the day was done.
In the afternoon, the wind picked up, making the flying rafters strain against the rope like a frisky puppy, and we had a couple of what looked like close calls to me, but everyone assured me they never felt it was too risky.
As the day wore on, the pace of progress slowed down. The temperature topped out at 92 degrees and the wind was gusting to over 40 mph. Everyone was hot and getting tired, and we all began to worry about running out of drinking water.
But the last rafter went on at about 4:30. It was a start-early and work-late day, and I really appreciated everyone sticking with it to the end. As the third to the last rafter was rising into the air, I hopped into the car and made the mile+ run to Ridgeway for some cold, local beer (Man Moon from New Glarus Brewery and Arena Premium from Lake Louey). We all gathered in the relatively cool, shady basement and shared some building horror stories while wetting our whistles.
In my first post on our timber framing process (Whole Tree Timber Framing Begins at Underhill House ) I stressed the patience required to start a whole tree timber frame project.
Fitting whole tree timbers, with their sinuous and branching forms, takes a fusion of engineering and imagination that has me in awe of our timber frame team, Bryan, Prairie, Michael and Brad. All three bents were fitted together and laid out – two on the floor of the house and one on the ground, and everything was in readiness Wednesday when the crane arrived.
What’s a bent, you ask? According to Wikipedia, the word “bent” is probably an archaic past tense of the verb to bind, referring to the way the timbers of a bent are joined together. Whatever the origin of the word, a timber frame bent is a framework that forms the cross-section of a structure. In Underhill House, there are three bents, each made up of five posts that hold up a beam that runs the full length of the house plus several more feet needed to support the external soffits. There’s one bent that runs the length of both the north and south walls of the house, and a third that runs down the mid line.
As the crane truck pulled up the drive, our construction manager Bryan, wondered out loud if it would be up to the task. It was smaller than the cranes of the concrete pumper trucks and the well drilling rig we have recently watched compacting the soil ramped up around the building site. When one of these behemoths rolls in, they tend to churn up the hard-pack, leaving deep ruts, and they’re not very manageable on site if the ground is wet. Fortunately for us, Wednesday was a dry, calm day.
The first step was to level an area where the crane could set up shop, and the sandy clay was re-graded to form a temporary, flat foundation. Then the first of the bents was lashed in two places using some heavy duty straps capable of supporting it on its short journey from horizontal assembly site on the floor to its final vertical location.
Dan Gingerich, the crane operator, told us that for timber frame jobs, he always launders his straps ahead of time. A crane finds itself hauling all kinds of grungy, gritty things into the air – corn silos, wind mills. Dan even has a yearly appointment to hoist a big, frozen carp. On New Year’s Eve, Prairie Du Chien, Wisconsin hires him for the Droppin’ of the Carp, at midnight in Lucky Park, similar to the ball drop that marks each new year in New York’s Times Square . It’s a good thing Dan cleans those straps. We’d rather not have any lingering aroma of Mississippi River carp haunting our timbers.
Raising the bents can be hard on timber frame joints. While they’re designed to resist the force of a building superstructure pressing down from above, they’re not nearly so strong laterally, and once in place, they don’t need to be. To protect them on their short journey from prone to upright , come-along straps were ratcheted tight to pull each custom-fit post snugly against its beam.The strategy Bryan developed was to lower each bent at a slight angle, fitting the eastern-most post onto its pre-mounted steel anchor bolt, then the next post and the next until the west-most post was dropped in place.
The first few posts went home effortlessly onto their bolts, but the last one of the first bent proved to be s the toughest of all to get into position. It took about 10 minutes of effort to make the fit.
The final bent was lifted off the ground and flown into place without incident. As a temporary measure, all the bents were braced in place with boards that will later be used to frame out interior rooms.
Bryan had arranged for an early start, expecting that raising the bents could take a full day and then some. But with all of the extra time we now had, Dan said, “Come with me for the photo opportunity of a lifetime.”
I followed him saying, “Oh, I love those,” wondering what could top the photos I had been snapping all morning.
He had placed a plank between the sturdy lifting straps and invited me to have a seat. I thought the photo op was going to be me swinging from the crane like some gigantic playground swing, but Dan began to instruct me on how to fit my arms between the straps and assured me I would be quite safe. That’s when I realized he was offering to fly me over the building site.
I didn’t hesitate. Who wouldn’t take a small risk to see the grounds they’ve been lovingly tending for years from a birds-eye view?
Watching our whole tree timber frame erected against the blue, blue sky was thrilling.
For those readers old enough to remember the Mickey Mouse Club, do you also remember that Wednesday is Anything Can Happen Day?
This Wednesday was Everything Can Happen Day for me at Underhill House, a day when I achieved lift off both figuratively and literally.
Thank you, Dan!
Thank you, Bryan, Prairie, Michael and Brad.
Thank you, Della Hansmann, the architect of this project.
Thank you, universe!
Building a whole tree timber frame house is an exercise in patience.
We have been working with these timbers for almost a year now — selecting them from our 44 acres last summer, peeling and felling them, then working out a master plan for how their individual branching natures could fit together trunk-to-branch in homage to the forest they came from.
This winter and spring we worked alongside the construction crew as the surface of each timber was shaped with draw knives and angle grinders, sanded smooth, and then painted or stained. In the process I have come to know some of the more distinctive timbers very intimately, working an orbital sander over every rise and fall along their sinuous length.
The first step after the concrete foundation walls were poured was to frame out a conventional, 2×8 milled lumber wall on top of the slip form masonry wall that forms the walkout portion of the basement. (The milled lumber came from the Ridgeway lumber yard less than two miles up the road.) It was a powerful sensation to actually feel the enclosure of that space. We invited some friends over the Friday before last and hosted our first dinner – a picnic within four walls and under the vast and darkening sky.
Over the last two weeks, the main floor has taken shape above that space.
The first whole tree that was put in place was the main beam, a massive oak tree trunk that spans the full 28 foot length of the basement. Getting it situated was the work of many meticulous hours. The biggest single beam in the structure, it was carted up to the house on the fork lift and balanced carefully on the concrete foundation walls.
There was only a few inches of leeway on either end of the beam. If one end had started rolling faster than the other, it would have rolled at an angle off the wall and thundered onto the basement floor. Moving it into place was done very slowly, using cant hooks and constant feedback between two crew members on each end.
Unfortunately communication was confounded when the well digging trucks arrived in the middle of the process. The roar of the drilling rig drowned out even shouting. Sign language and a lot of running back and forth finally got the beam positioned and lowered into its pocket.
Between the two ends of the beam, along its entire 28 foot span, the only support is a stout, branching elm trunk placed right in the middle, sitting on a reinforced concrete footing that goes down to stone and packed earth, just a few feet above the bedrock below.
It’s not necessary for the joists to be exactly level. After the metal decking is attached to the tops of the joists, the floor is covered with concrete, and that surface was leveled.
What we will see between the joists and rafters from below is a surface formed of taught hemp fabric that is stapled to the tops of the beams. Above them several layers of insulation were spread out and finally a layer of metal topped them to form the base for the concrete pour.
Read about the saga of our concrete pour in my post …..
At long last, the stage was set for the assembly of the whole tree timber frame that will form Underhill House’s contours and create its tone. This week that process began.
Timber framing is always part art and part engineering, and that is what forms such undeniably compelling structures. Whole tree timber framing takes both the art and the engineering to a higher level.
Fitting together timbers that have not been milled into uniformity for the convenience of the builder takes imagination and finesse. It’s been a joy to watch the dance involved in selecting and fitting these branching members together.
Underhill will have three bents: the highest one on the south wall to let in light and solar heat, the shortest one on the north wall to hunker down against the winter winds, and one in the middle bridging between them.
First to take the stage was the middle bent. The central beam is formed by joining two massive trees with bolts and a steel plate. Its natural bends will create the curve of the roof.
The north bent was the next to be fit together.
The final, tallest, south bent will be assembled on the ground in front of the house because there is not enough room for all three to lay out on the concrete floor.
Next week a crane is scheduled to fly them all into place. I can hardly wait to see their clear, white forms etched against the blue, blue sky!
I am so happy to be building a home of wood in a way that honors the shape and provenance of the wood and benefits from all the strength that each tree created year by year, responding to the forces around it, bending and branching to reach the light and withstand the wind.
Preparing and fitting together these whole tree timbers has taken more time than putting up a frame of milled lumber, but that time has meant employment in our community for some dedicated and skilled sustainable builders. It’s also the greenest and most beautiful way I know of to build our house.