Notes from Windward: #67
Building the Octangle Yurt
Now that the risers are in, it's time to start the process of filling in the center of the yurt in preparation for installing the self-draining, insulated floor. In order to settle the fill, it's necessary to do the work a few inches at a time. After loose dirt is added and raked level, it's dampened and then tamped down to compact it. Because the floor will float, we don't have to worry too much about settling, but it's good to get a firm base anyway.
The next step involves constructing the first two primary bents. A "bent" is a timber frame term that refers to a truss assembly. Here's how Timber Frame Magazine describes the concept.
The complex joinery necessary to build free-standing timber frames was developed in the so-called Dark Ages. The strength of these timber frames could carry the structural weight of a house and made the building of great cathedrals throughout Medieval Europe possible. Central to their construction is the timber frame truss. There are several basic truss designs that have literally stood the test of time. These are incorporated into "bents," which include the posts and beams and literally make up a series of cross-sections in the frame.
In timber frame work, a bent is usually put together flat on the ground and then stood up into place--in this case, we're creating the bents in place. One result is that there's so much scaffolding involved that it's probably hard to see what's structural and what's temporary, but have faith, dear reader, and all will become clear in time.
As it goes when dancing with nature, when the harvest is ready, it's time to focus on getting it in, so not much has happened on Octangle for a few days. But as the rush to process the ripest fruit winds down, attention can return to working on the first bent.
The first bent isn't complete yet, but it's there enough that you can see the general outline that the roof is going to take.
The fall rains have started, and much of our attention is focused on transitioning our systems from summer to winter configurations--with the result that projects such as Octangle have to go on stand-by as tasks which are more time dependent get taken care of. Still, windows of opportunity do open to allow us to keep progress going forward.
While our attention is currently on creating the "bents" that will form Octangle's roof, there are other aspects of the project which can go forward as well. As pictured above, the first task had been to add, dampen and tamp in enough fill dirt to create a level floor about six inches below the concrete risers.
We've had soaking rains for the past couple of days, and that's helped to settle the fill, so yesterday we brought in a pickup load of "three-quarters minus" crushed rock to form the base of Octangle's floating floor. It's a floating floor in that it isn't actually connected to the building; rather it will float on a combination of crushed rock, sheet plastic, dense foam insulation and heavy-duty particle board--eventually covered with commercial carpet that we get from friends who install commercial carpeting and let us rummage through what they remove before sending it on to the landfill. Eventually we'll install some form of renewable flooring such as bamboo, but we figure that re-use is good enough for now.
A 3" thick layer of gravel was put down, raked smooth and tamped into place. This will create a balast mass that will give the floor stability and also allow for drainage. There's always some water that will wick its way up from the ground, especially on the uphill side of a structure, but the gravel will drain it away and prevent hydrostatic pressure from lifting the floor.
The remaining crushed rock was used to fill in some erosion ruts left over from last winter's run-off, just another one of the tasks that need to be attended to before winter comes.
We've been busy tending to many of the tasks that need to be done as we make the shift from summer to winter systems, but most of that is routine and proceeding apace. So in between the fall rains and internship fairs, we endeavor to find time to keep work going forward on Octangle in hopes of getting it roofed before serious winter sets in.
The details of how the bents were to go together was worked out in place using heavy construction screws to temporarily secure the components. Now that we're satisfied with the design, it's time to take the bent apart one element at a time so that it can be glued, screwed and then shot into place using heavy construction staples. The staples are especially effective because they punch a hole as they go in, and because they're covered in hot-melt glue that is activated by friction as the staple is driven into place.
Between the fall rains and things happening off-site, work on Octangle fell behind, but we're taking advantage of a break in the weather to get back to working on the roof. Now that the two main bents are in place, the next step involves connecting them to create a rectangular structure called a cupola.
Meg applies glue to the bents
The northern side of the cupola will be closed off and insulated since little light or heat comes into a passive structure from that direction, but the east and west sides (Meg is gluing up the west side in the pic) will have windows that open to allow hot air to rise and exit the yurt during warm summer days. During the winter a fan will circulate the warm air back down into the main area.
The glass in the southern side of the cupola will let in lots of light.
Added the southern set of half-bents today--the pagoda-like profile is becoming more distinct.
Notes From Windward - Index - Vol. 67