One of the most basic components, yet one of the most crucial structural elements of any yurt is the rafter ring. This device holds each rafter in place, ensures geometrical and structural integrity of the building, allows for installation of the essential dome vent and must be installed so as to apply uniform weight and pressure to each rafter at the same time that each rafter equally holds it in place. There are a number of pieces that make up this assembly, whether it is designed and constructed in-house or custom ordered.
The ring, in some instances, is built from one piece of wood. However, this is quite a costly venture, relative to the total cost of the yurt. Other wooden rings use a layered approach, sandwiching a layer of OSB between pieces of dimensional lumber, or the reverse. Other rings are constructed from metal, or metal and wood combinations, while a few are built of polymers. Since most yurt-dwellers have a core of self-sufficiency, I recommend constructing the ring completely from dimensional lumber, in layers.
For this piece of your modern Mongolian yurt, you will need fourteen eight-foot lengths of one by six spruce, fir or pine planks. As well, one quart of carpenters glue and one hundred eighty two-inch construction screws complete your parts inventory. For tools, you will need a variable speed drill, ½ inch drill bit, screwdriver bit, jig saw with blades and a small paint brush.
Begin by cutting all of the eight-foot lengths of planking into four-foot lengths. Lay them side by side, using nine pieces on the first layer to form a near-square. Due to the actual width of a six inch plank (5.5 inches) he total width should be 49.5 inches – slightly wider than the length. At this point, this is not important. Next, tie these boards together temporarily, using one of the four-foot lengths screwed across the centre point of the nine boards. Apply a liberal coat of carpenters glue to the surface.
For the next layer, lay the second set of nine boards perpendicular to the first layer, with the leading edge flush with one side of the 49.5 inch width. This will leave 1.5 inches of the first layer exposed. Later, that surplus will be removed. Put one screw at each end of the nine boards of the second layer. Since there is no lateral security using single sets of screws, you now are able to square the assembly, using a standard two foot square. Holding the setup in place, set one screw every six inches, alternating from one side of each board to the other. The screws will protrude beyond the bottom side of the first layer at this time.
Flip the two layers over, applying a layer of carpenters glue to the underside of the first layer. Lay the third layer of boards perpendicular to this first layer, and attach exactly as you did with the second layer. Allow the assembly to dry, then use a saw to remove the 1.5 inches of excess width on the second layer.
Use two strings from alternate corners of the square, so that the two strings cross over precisely in the centre of the box. Secure a nail here, then tie a string that is exactly the length of the distance between the centre and any side to the nail. Be sure that the string or twine is not stretchy. If necessary, use a thin piece of wire. Hold a pencil at the very end of the string, and arc it around the outside of the square, drawing a perfect circle. Now, shorten the string by eight inches, and draw a second circle.
Using your jig saw, cut the exterior run of the first circle. Drill a hole at any point of the inner circle, then use your jigsaw o cut out the centre piece. You have constructed your basic rafter ring. However, for added reinforcement, you may want to screw a band of medium thickness aluminum ring around the circumference of the ring. Alternatively, a ring of 3/16 inch plywood may be glued and screwed to the outer edge.