Rafter Dimensions

[Dan R-M]

A bit of dialogue I picked up on between Jafo and Blondie on "The Yurt Raising" piqued my interest, but I was a bit late in the thread to ask. Anyway, my question probably fits in better here. (I'm secretly changing the name of "Everything Else" to "Renovating a Screwed-Up Yurt").
As noted somewhere else, our SM Yurt came 11 rafters short of its full tale of 30, so I fabricated the missing ones. They're 2x4's, and my father-in-law commented that he didn't think that was really enough. The yurts he's looked at apparently all have 2x6's (I think they're Pacific's and Colorado Yurt Works').
Anyone have thoughts on the matter?
The long range upgrade will probably involve 1) making a new

center ring

, cause the SMY one doesn't have the handy bevel that the rafters butt up against, 2) putting studs under every third rafter or so, and 3) switching from 2x4 rafters to 2x6 rafters.
By the way, beautiful situation there, Blondie, if you've got the water!

[Jafo]

I guess the answer is: it depends. How much snow load do you expect to get? That is the only reason I upgraded to 2X6's, otherwise my Pacific Yurt would have came with 2X4's. If your snow load is moderate, you could just use bracing on the ring. How many rafters do you have?

[Dan R-M]

Thirty rafters (currently 29 due to the most recent windstorm). They seem fine to me. We never get more than 24 inches at a time of snow, so I wouldn't worry about any kind of significant load there.

[Jafo]

You probably are fine. If you are really concerned, you can add more rafters I believe. We have 50 in mine. You may also want to brace the

center ring

with some 4X4's. I know the support and sales staff at

Pacific Yurts

recommend this for heavy snow loads (if you do not get their center pole addon). There is a local sawmill here and I know the owner well and he is going to cut me 4 16' 4X4's out of spruce this fall for bracing in my yurt for a grand total of $60. Since I don't have access to the yurt when it snows, unless I use snowshoes or a snowmobile, I am going to brace mine. We sometimes have winters up here with many many feet of snow and my yurt insurance does not cover snow damage.

[HawaiiYurts]

2x6 rafters are usually found only in the snow load upgrades of the major yurt manufacturers. I've heard a lot about SM yurts... eek. Did you buy yours new or used, Dan? The most important thing is to try to keep things evenly weighted. I wouldn't add 2x6 rafters to a yurt that's designed for 2x4's. Improper weight distribution is a major factor in many yurt fails. Bracketing added rafters would also be an easy way to avoid the corkscrew affect that SM and some of the younger yurt manufacturer's don't yet include a solution for. The corkscrew affect is DANGEROUS. It must be corrected or it can and will come down at some point.

30 rafters seems slim for a 30' diameter yurt. How wide is the ring at the top? You could do angled cuts and bracket them on at the ring in the spaces left. Just be sure you're doing it evenly, all the way around. Good luck!

[Dan R-M]

You can read the positive version on my blog at royermillers.blogspot.com (I tried to purge my bitterness before committing it to internet immortality), but basically it was a second-hand purchase from sketchy folks who'd had it collapse in a major windstorm on their watch.
Cynically speaking, I think it's a stretch to say it was designed with anything in mind, but I suppose they were think about 2x4's. I'm convinced by discussion here that 2x6's are overkill for me.
The center ring is about three feet across, I believe. I've been thinking about making another one that is beveled where the rafters meet it, because currently it is rounded there. How much sense does that make? The rafters can rock against it.
Describe the "angled cuts" thing for me, could you? Maybe post a picture or a drawing? I can envision what you mean by corkscrew - I don't see any evidence of it now, but I can see how it could develop.
Thanks again for your perspective and ideas!

[HawaiiYurts]

The angled cuts I mention would be at the end of the rafter, where it connects to the ring. Of course, that would depend on your ring... sometimes no angle is needed.

The corkscrew effect happens when the ring 'spins'. The rafters all push in an angled direction instead of pushing just up and in, the way they should. Eventually this will cause rafters that are connected with pegs to dislodge or break and drop the rafters/ring everywhere. This is one of the reasons we quit raising Great American yurts. They inherently spin and that is a bad situation for a yurt set up crew. Once they're in place with the cable attached it isn't as bad, but we had a Great American yurt's whole roof system come down on us because of a sudden corkscrew. We were lucky that day. They may have addressed that by now. It was many years ago.