Snow Loads

[Judy Rump]

Just a word of caution to all you Yurt owners who live in snowy regions, clear the snow from your Yurt roof. I was once a Yurt owner whose yurt collapsed. It will be two years at the end of March when it occurred and it still saddens me to this day that our beloved yurt collapsed. Our

insurance

company did not compensate us one cent because their forensic engineer came to the conclusion that snow load may have been the cause of the collapse and that the yurt specs did not meet the snow load building requirement for our region. Our Ontario, Canada sales rep. and the B.C., Canada yurt company did nothing for us.

[hierony]

I'm sorry to hear you lost your yurt! That sounds like it would've been quite the ordeal. I certainly agree with your word of caution, but I'd add a few bits.

The calculation to figure out the snow load on rafters/roof poles is fairly straight forward. I actually checked this when I was trying to make my own yurt, as it was a reasonable concern (circles make things complicated though so I didn't do proper crown ring calculations --I'm not an engineer).

Snow loads for the general area when I live are anywhere from 25 psf to 80 psf or more. There can easily be several tons of weight on a yurt roof at the lower rating!

There's a slew of factors that go into this, but in general a smaller roof won't have as much snow on it, more rafters can hold more weight, bigger rafters can hold more weight, and shorter spans can hold more weight. That last one is particularly neglected in a lot of yurts--the crown ring supports/baganna aren't included but they HALF the span of the roof, making it _much_ stronger. Slippery surfaces, steeper roofs, and heated roofs also reduce loads from snow.

[Jafo]

What company made the yurt?

[Bob Rowlands]

My trad styled yurt is 16' diameter, with no bagana. Rafters are 1x3x8', with no studs under the rafters. Cable is cheapjack home depot 1/4". Laths are 5/16ths, 1/4" bolts at the lath crosses. I do have an extremely stout roof ring. I built the yurt from scratch btw"

The largest load I have had on the roof was probably about a foot to maybe a foot and a a half of very wet spring snow. I could tell the load was substantial by poking around on the canvas and rafters with my hand from inside the yurt. The roof had lost its 'springiness'. That was more then enough weight. I might get two feet up there with no collapse, but three feet would probably cause collapse. Just going with gut feeling, no math.

Anyone considering a yurt in an area with the potential for a few feet of snow without the roof being cleared should buy the top rated snow roof a company offers. I know there are yurts up in the Rocky Mountains, Sierras, and Cascades that can withstand massive loads.

[Bob Rowlands]

One more comment. Structurally it is an advantage to anchor the wall lath, and the snow load studs, to the deck with ell brackets. I have a bracket anchored to the deck at every lath cross, and the threshold screwed to the platform as well. A yurt free floating and unanchored atop the patform will reduce the load capacity of the roof. All that load atop the tent swaying in a storm will cause a collapse even if the yurt can take the load. Lateral shifting can cause collapse where otherwise the load could be supported. Good luck.

[Bob Rowlands]

OK and yet another point. There is no cross bracing in any yurt design. The wall and rafter junction can flex somewhat in the wind. Usually flexing is a good way to dissapate stress, but in the case of a substantially loaded roof, it can cause collapse.

My yurt has been up now for two and a half years. The wind here is from the northwest. The smokestack from my stove WAS plumb and centered in the smokehole. Now, it is a bit out of plumb. The circular 'footprint' of the rafters where they rest on the khana must be slightly ovalized due to wind pressure. Nothin dramatic but slightly askew just the same. Just sayin. Poke me with a fork I'm done. lol

[Ivan]

We just completed our Yurt install ( White Mountain Yurt) In New Hampshire. This was my only worry, so we did install 2x4 snow load studs beneath each rafter, and installed steel plates on both sides of rafter to stud joint. as well as at the base , both sides. Still I do worry and plan to install a center support below

center ring

, but only if we are to leave it unattended for extended period of time.. I would like to do all that I can, so was wondering if it is worth while bridging between rafters? 2x6 ? or does that create another problem, as it seems that the flexibility is part of its strength ?

[Jake]

I would absolutely have the center supports. Look over the Mongolian ones, those center supports save their yurts, and lives.

On the Differently Yurts site is a snow load calculator. There is no way I would build a yurt of any size in snow country without center supports.