Thank you for the reply! I will try to answer as many questions as possible, but as I dont have your quoted text, I might forget couple. Let me start by saying that the primary driving factor behind my decision making is getting dried in asap. I live in Montana, in high altitude mountains and we are pushing December. We did not appreciate the monumental scale of our project and started too late in the season, but we are here now and cannot afford to wait out the winter for a myriad of reasons.
The diameter of the house is 30 foot to bag center. They are little over 12" wide, so true OD/ID is 30.5/29.5 approx.
We are drilling our own holes, on site, in the roof itself for the factory tabs (once it has been lifted in place). The drilling in place was the brainchild of the bin companies engineers.
We are heavy duty poly strapping 3 bag layers down.
Not sure of exact wind loads, but they are signifigant in the valley below us. Much less in the mountains here, but some heavy gusts find there way through here.
Our climate is dry, mild high alpine. Cold in winter, hot in summer. Middle of the road snow loads.
Two courses of barb wire per row and 440 twine.
One substantial opening. 6 foot straight away for french doors. Planning on flanking it with pine posts after the roof is in place to offset loads to this weak point. I intend for these to be the only posts.
I worry a turnbuckle cable would ruin aestics, and is furthermore not possible due to the the loft. However, there are external steel bracing rings on the roof, serving a similiar purpose I believe.
Speaking of which, the bond beam will be at a finished height of 11' 6". The loft floor is at 8' 6" and poses a great challenge, as we are relying on the steep pitch of the roof to make up most the space of the loft.
I have a contractor friend who will be bringing in a grade all to hoist the roof into place, where it will be gently lowered one click at a time with a chain hoist. We crunched the numbers and it is viable. We wish to assemble on ground for two reasons. First we may complete the bond beam and roof simultaneously rather than consecutively (the time thing). Secondly, to head off the bracketing position nightmare. As we must place each bracket as we go and drill custom holes in the roof. The logistics seemed daunting as opposed to supporting the completed roof in place, and placing the brackets wherever they should land.
I am currently trying to come up with a sub roof plan that can be accomodated post grain bin roof, as it we will be wintered out here too soon to get a lead out on it. But the ongoing thought is to do a matching lightweight compression roof. Basically a yurt roof with plywood backing to hold blow in or foam. I know it will be tricky, but I was planning on simply mitering the ends of small dimension lumber or thin pine and finding a way to bolt them directly to the bond beam on one end and a fabricated compression ring on the other. The plan is still evolving. Unfortunately both foam and blow in seem prohibitively expensive. May try to work in bats by some miracle. Open to suggestions here as well. All I know for sure is I want to give the roof a coat of closed cell foam to seal and strengthen it. Is it possible to spray foam the roof with little additional structure? Would it be insanely spendy?
Due to time and financial constraints, I am afraid I will not have the resources to fabricate any more complicated brackets than the culvert ones described. I believe it to be a step up from metal roofing which every engineer I touched base with believed to be strong enough to make the brackets out of. I suppose strength in numbers as far as they are concerned. If its any consolation, the culvert is old style industrial grade salvage. It feels like it could stop a bullet.
Not sure if I covered everything. This is our first building adventure, and we are touch and go every day on the learning curve. I know thats not the ideal way to build a structure, but I dont execute anything without a prefessionals blessing. Earthbags is a strange area for many though, as most guys have only ever worked with lumber and make educated guesses based on loads.
I certainly appreciate you taking the time to reply, and I will take your advice under great consideration. Have you attached grain roofs you have assembled to earthbags before? If so, how did you do it in those situations?
Thanks again!
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