Portable Yurt Floor Design

This article is part of a how-to-guide for building a semi-solid wall yurt.

The floor, like the rest of this yurt, is designed to be lightweight, portable, easily assembled and disassembled, inexpensive and durable.  These may seem difficult standards to reconcile, but are surprisingly simple.  Materials consist of high density rigid foam insulation,  plywood clips, 2 by 2s, one-by-six lengths of spruce, pine or fir, one-by-three lengths of SPF, 7/16 (or ½) OSB or plywood and a small quantity of 2”, 2 ½” and 3” deck screws, as well as a few pieces of scrap wood for levelling the floor on uneven surfaces.

Begin by cutting seven lengths of eight-foot 1*6 into 94.5 inches for each of the eight-foot by eight-foot sections of the 16 by 16 foot yurt platform .  If you are planning on including a deck in the design, allow for two more sections of platform.  Mark along the face of each 1*6 the depth of the rigid insulation that you will be using.  (Minimum recommended thickness is 1.5”).

Next, cut twelve pieces of one-by-three to 94.5 inch lengths per platform section.

Using wood or carpenter’s glue, apply a liberal amount of adhesive to the side of a one-by-three, then align the one-by-three top edge with the marks on each one-by-six and clamp together.  Using the 2” screws, join the two pieces, placing screws offset from each other at one-foot intervals.  Each 8*8 section will require two of these joined sets.

Using the same process, attach one-by-threes to each side of a one-by-six.  You will require five of these sets per eight-foot section of platform.

(Note that the use of 1 by 6 joined floor joists is intended to provide the most lightweight option for your portable yurt floor. If you are unconcerned about weight and portability, substitute this assembly for 2*6 joists, with 1.5" (or 2", depending upon thickness of your rigid insulation) deep by 0.5" wide notches on either side of the joist, allowing the insulation to rest in these channels upon completion)

Next, cut two 1*6s into four lengths of 14.5 inches and two lengths of 13.75 inches per board (per platform section)

Mark two 1*6s at 16” intervals.  Lay out and temporarily screw together the assembled 1*6/1*3 combinations to each of the marked 1*6s, so that the 1*6 parts of the combinations are centred on the 16” marks, forming a framework of seven joists and two 1*6 headers.

Using the first 13.75 piece of 1*6, fasten it on the inside of the 1*6 marked header, between the first and second 1*6/1*3 combination joist with three 2” screws and wood glue.  This piece should fit tightly between these segments.  Do the same between the last two joists of the section, and repeat on the other header.  Using each of the 14.5 inch pieces, screw them in place between each of the remaining joists.  All pieces should fit snugly in place.  If they do not, re-measure and realign the spaces between the joists, keeping in mind that the 4by 8 foot sheet of OSB that will be used later as a subfloor must align precisely along the centre of the 1*6 joist.

Cut two 2*2s into four lengths of 14.5 inches and two lengths of 13.75 inches per board (per platform section).  Aligning the 2*2 top edge with the top edge of the 1*3 part of the 1*6/1*3 combination, fit one of these pieces between the joists at the 2.5 foot distance from each header.  This will provide additional support for the rigid insulation that will rest in the channels created by the joist assemblies.

Cut four pieces of 2*2 into ____ lengths, with 45 degree end cuts.  Toenail one end of the first piece to the third joist where the cross brace 2*2 meets the joist, and the other end along the adjacent fourth joist.  Fasten the second piece in the same manner between the fourth and fifth joist.  Fasten the third piece between the second and third joists on the opposite end, and the fourth between the fifth and sixth joist.  These braces provide diagonal support while you complete the assembly, and help to support the rigid insulation.

Cut the 1.5 inch rigid insulation into four pieces measuring 14.5 inches wide by 94.5 inches.  Cut two pieces of rigid insulation measuring 13.75” by 94.5”.  Fit each of these pieces into the cavities between the joists, using the narrow 13.75” pieces on each end.

Lastly, lay out the two sheets of OSB across the joists, parallel to the joists and with the edge of the sheet exactly aligned along the centre of the fourth joist.  Ensure that all outer edges align, as well, with the edges of the joists and headers, so that the structure is square. Screw OSB into place using 2” deck screws. 

Your floor deck is complete, and may be finished using indoor/outdoor carpet loosely laid on top.

Time to cut and assemble floor: 1.5-2.0 hours per 8*8 platform section.

Build A Yurt Rafter Ring, Version Two

There are several designs of yurt rafter rings, each serving a particular purpose, and working best in specific environments.  Snow load, wind and even humidity play a role in determining the most appropriate design.  For the majority of yurt applications, the laminated design that I described in a previous article is the most effective.  However, the design described in his article is suitable for smaller yurts (less than 32 feet diameter) and in low humidity locations.  While it will withstand moderate snow loads, it is less structurally stable than the laminated version.

When designing a yurt roof, the same considerations that are factored into stressors on conventional housing roof rafter chords come into play.  That is, you need to consider the tensions (both lateral and gravitational) on the angled chords.  Truss chords endure two primary stress forces: the tendency of the bottom of the chord to push walls outward and the pull of gravity that causes slump in the riser chord.  Use of collar ties works to ameliorate the gravitational warping, but, simultaneously, actually increases the stress on the top plate-to-chord heel point of contact.  Fortunately, yurt roofs are so light that collar ties and webs usually are not needed. 

In my prototype solid-wall yurt, I employ several redundant reinforcements for the chords.  A series of mending plates, hurricane ties, aircraft cable and unique angled top plates create a structure that resists very significant outward stress.  These concepts will be presented in future articles.

The rafter ring design in this article consists of two layers of ½ or 5/8 inch oriented strand board (or plywood, if OSB is unavailable) and a collage of two-by-four blocks.  Other materials needed include a pound and a half of 3 ½ construction or deck screws, a pound of 1 ¾ inch construction screws, enough 3 ¼ inch framing nails to allow for four nails per block, and a quart of carpenters glue or three tubes of construction adhesive.

Begin by cutting a four by eight sheet of OSB into four-by-four pieces.  Scribe a circle four feet in diameter in the first piece, and a circle three inches smaller in the second.  These will form the upper and lower  layers of the “sandwich” ring. 

Cut as many four to six inch lengths of 2 by 4 as you will have truss chords.  Lay out the pieces around the perimeter of the larger OSB circle, equidistant apart, with the pieces pointing toward the exact centre of the ring.  Mark the location of each piece.  Apply a layer of carpenter’s glue to each piece, and re-secure them in the spots as marked.  Once they have dried sufficiently, turn the assembly over and secure the pieces using two 1 ¾ inch screws per block. 

Measure the distance between each block at the inner edge.  Cut pieces of 2 by four that will fit accurately between each 4-6 inch piece.  Do not worry too much about angling the cut edges precisely, as these pieces simply act as stabilizers for the main blocks.  Apply glue to the long edges of these blocks, slide them into place between each 4-6 inch block and secure them using 3 ¼ inch screws, toenail angled into place.  Use one nail per longer block to nail the spacers into place.

Turn the assembly over again, apply glue to the exposed edge of all of the blocks, and attach the second ring, with its centre aligning exactly with the centre of the larger ring.  Use two screws per block, as in the prior side of the sandwich.  Turn the assembly over once again, and screw in two screws per spacer block.

This rafter ring is much lighter than the laminated version described in prior articles, and is much easier to raise into place.  With the smaller ring on the lower side of this sandwich design, the truss chords, once cut on the proper angle, will slide into the notches quite easily and will hold themselves in place as each truss in installed.  However, the drawback to this design is the tendency for the OSB to expand and weaken if it gets wet, or for the screws to pull through if they are set too deep in the OSB.

Making A Yurt Rafter Ring

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.

Building A Solid Wall Yurt, Part Two

This is the second article on building a solid wall yurt. 

Although yurts both are vastly lighter in weight than conventional housing and offer minimal wind resistance, they, like any house, still require solid piles on which to rest. 

There are a number of options available to provide a solid base for your yurt, with the simplest and most solid being beams on pad, with no posts and no piles. 

When you opt to construct a solid wall yurt, rather than tarpaulin and lattice, you add significant weight to the structure, but, through the use of innovative top and bottom plates, cable reinforcement, hurricane ties and mending plates on the walls, you can build a yurt that equals any house for structural integrity.

To design a base system for a yurt by boring piles is an illustration of overkill, however.  Not only do you change the definition of your building for zoning and permitting purposes, you provide a degree of reinforcement that is quite unnecessary.

The most cost effective and structurally sound combination of bases for your yurt is a simple pad system.  However, you may, depending upon the grade and type of soil, need to use posts and pads, notched pads, crossties and webbing, saddle brackets and so on.

Let us look at the most simple design: beam on pad.  Whereas conventional wood frame homes may require 2 by 12, 2 by 10 or doubled versions of each for beams, imbedded joists, grade beams, piles, etc., yurts, even as large as forty-two feet in diameter, will require no more than single 2 by 10 or 2 by 8 beams under 2 by 8 or 2 by 6 joists. For flat terrain with packed soil and good drainage (or in high wind regions), use a basic patio pad.  For sloped ground, gravelly or soft soil or windy regions, use notched pads, or notched pads on patio pads secured with anchor bolts. 

Begin by ensuring that all pads are level with each other. Simply lay the beam into or onto the pad, and then tie the joists into position, sixteen inch on centre separation.  Beams should be spaced a minimum of eight feet apart, with pads spaced four feet apart for greatest stability.  Reinforce the beams by nailing cross supports between beams at eight foot separation.  As in conventional housing, joists should be tied together with webbing (2 by 2s).

To use post and pad on heights not exceeding twenty-four inches, use four by four double saddle brackets and double the beam using a second eighteen inch length of beam material in the upper saddle bracket.  Set the foot of your four by four pile into a slotted deck pad, ensuring that the top of each four by four posts is level versus each other post top.

To use post and pad systems on heights exceeding two feet, be sure to use diagonal cross supports extending from the bottom of each post to a nearby beam or joist on two adjacent sides, alternating sides with each sequential post location.

After laying the joists into place on the beams, be sure to install appropriate headers, using a minimum of four 3.5 inch nails per joist-to-header connection, and three nails, toe-nailed into place on each beam intersection.

Since you already have ensured that the structure is level (by levelling either the pads or the tops of the posts), you should only need to check level of the joists to ensure that nothing has shifted during construction.  Now, lay your underlay into place, using 2.5 inch nails.  The tongue-and-grove ¾ inch OSB or plywood should be placed so that edges meet at the centre of the joist.  Use plywood ties between joists for added structural strength.  Your next layer of flooring will be installed at right angles to the underlay, at a later time.