Yurt platform on grade versus sunken piers

[Corey]

We expect to start building our 30' foot yurt next spring (very excited about it too). This will be our year round home and the building location is in north central Vermont.

My question is about the piers for the

yurt platform

. We got some basic drawings from the yurt manufacturer we plan on purchasing our yurt from and we have looked at similar plans from other manufacturers. Some go with piers sunk below the frost line and some go with simple concrete blocks on the grade. The plans we have show both options. I called the manufacturer and he seemed to think using blocks on the grade was just fine. This seems a little sketchy to me but the prospect of saving myself a few thousand dollars is tempting.

What are other people's experiences in this area? Thoughts?


Thanks.

[Jafo]

I think your skepticism is warranted. In VT, I would definitely seek piers unless of course you are sitting on granite.

[Corey]

Thanks Jafo. There's some ledge in the area but not a nice slab of it right on the surface. A couple of outbuildings at my current place are just on stacked stone and have been there forever so that gave me some hope that I could get away with not having to sink the piers.

[stephanwik]

We've got lots of granite in Sweden. I simply bolted my platform posts to the rocks using a rock drill and some special shoes that have a piece of rebar welded to them. Drill in 30cm 22mm hole, pop in the shoe and secure with either some large galvanised nails or a bit of cement and Bobs your Uncle.

We've just had two 25 m/s storms and the platforms have not moved at all.

[Bob Rowlands]

Look around the building site that should tell you. If there is evidence of frost heaving where you are siting the yurt, and you want a level platform for the long term, then placing piers below frost level would be a wise option.

If not, then block piers will be fine. Be sure to install rebar pins in the core mud. Definitely fill the cores with mud. Don't skip that step to save a few bucks.

To my way of thinking, yurts are transitory structures. That's one of the beauties of the design. Considering such, I wouldn't go to thousands of extra in expenses, unless the ground heaved every winter. Good luck.

[Corey]

Originally Posted by Bob Rowlands

Look around the building site that should tell you. If there is evidence of frost heaving where you are siting the yurt, and you want a level platform for the long term, then placing piers below frost level would be a wise option.

If not, then block piers will be fine. Be sure to install rebar pins in the core mud. Definitely fill the cores with mud. Don't skip that step to save a few bucks.

@Bob Rowlands: I am not sure what you mean by "core mud"? Is that wet cement?

@stephanwik: Do you remember who manufactured those shoes? Or what product name I could search for?

I guess I never thought about it before but once the ground thaws this spring I could sink a few test holes to see how consistent the ledge depth is.

[stephanwik]

They're pretty standard in Sweden and available at any builder's merchants. No idea where (if) you could get them in them elsewhere.

[Bob Rowlands]

Yes, 'mud' is construction slang for concrete.

[Corey]

Originally Posted by Bob Rowlands

If not, then block piers will be fine. Be sure to install rebar pins in the core mud. Definitely fill the cores with mud. Don't skip that step to save a few bucks.

Bob - Sorry for the late follow up; I had meant to ask this earlier along with the mud question: When you refer to filling the cores with mud, what cores are you referring to? The block piers I have seen are solid blocks. By cores do you mean Sonotubes?

Thanks.

[Bob Rowlands]

Standard 2 hole concrete blocks.

FWIW, my 'on grade' (uninspected) choice, on our sandy flat site, was to build a conventional treated 2x4 platform frame, anchored with Simpson Strong Ties, to 4" concrete filled sonotube pads that simply lay atop the ground. The top of the 2x6 decking is a mere 9" above ground level. I anchored each lowest 'cross' of my yurt walls to the 2x6 decking with 3/4" steel angles I custom made. Absolutely bombproof deck and yurt anchorage.

If there is any issue with frost, deal with it. You got your yurt investment to support. I suggest build a free standing wood deck atop concrete filled sonotube piers set down to frost level. Sway brace between your wood posts as the site and deck height dictate. Anchor your yurt to the decking. Preferably like mine. lol

If you need engineered, and inspected, for

insurance

and code reasons, tell the engineering firm you plan to anchor your yurt to an affordable conventional free standing deck. I'll bet he will propose the exact platform I described.

Remember YOUR investment rides on that platform. Don't screw around. Good luck.