In flexible wall yurts – the most popular designs – the outward stress is counterbalanced by a line of aircraft wire strung through the vertical wall lattice, and tensioned using a turnbuckle system. The rafters notch into this cable, pressing outward in a uniform manner. Because of the circular shape, every resting point of the heels of the truss chords applies equal pressure, and thus, each truss offsets each other truss. At the apex of each chord, the rafter ring bears the weight and pressure of the upper end of the truss, equally and counterbalancing each other truss. This design is simple, but its simplicity means that there is a maximum diameter of yurt that can be built.
Solid wall yurts have both drawbacks and advantages over the lattice wall design. While they offer greater protection from exterior elements, the ability to be designed taller than lattice wall units, the flexibility to incorporate conventional doors or windows and the capacity for greater insulation, they also have the drawback of being built in a multitude of wall segments, as opposed to the continuous wall format of lattice walls. Solid wall yurt systems require, because of the individual wall panels, supplementary structural support.
When designing my solid wall yurt, I incorporated not one, but four rafter support concepts.
The first was the conventional aircraft cable, strung through the heels of the rafter chords (reinforced with a metal ring, to prevent cutting through the wood of the rafter. Secondly, I used hurricane ties on each chord heel. Thirdly, I nailed steel mending plates at the top and bottom of each joined segment.
The fourth concept provides unique structural support for the walls, offers exceptional wind resistance, and ensures that the rafters do not place excessive force against the top of the walls, causing them to bow outward.
My yurt is twenty-eight feet in diameter. Using forty-four two-foot wide panels, I placed each panel at an eight-degree angle to the adjacent panel (resulting in 352 degrees of curve, rather than the full 360). By using 2 by 6 studs and cutting an eight degree “V” shaped 1.5 inch wide, I was able to generate 12 top plate segments from each eight foot length of wood. Each piece has two arms extending from the apex of the “V”, with each arm twelve inches long.
These pieces are nailed on top of two adjacent panels, with the “V” placed precisely where the two pieces meet, and extending one foot into each panel. They are secured with three nails in each arm. As added reinforcement, I used the same system as the bottom plate for the walls.
This unique top and bottom plate system has worked exceptionally well, with the yurt enduring wind gusts of 115 kph (73 mph) without any problems. In fact, in 2011, shear wind toppled a tree with a trunk diameter of fifteen inches, less than 100 feet from the yurt. The yurt barely quivered! 2010 winter snow loads failed to bend or bow any of the truss chords. Although I clearly have implemented more structural reinforcement than is normally required, the strength of the design provides comfort and reassurance in the harshest weather.