We are finally going to put something up on the parcel of remote land we staked out and purchased over 25 yrs ago. Materials will be dropped on an ocean beach via landing craft from Seward Alaska, and then sling loaded via R44 on to the site.
Our 1st structure will be a 20' Intershelter dome.
There are multiple reasons why we are choosing this as our 1st structure which I won't go into now but would be glad to discuss on a different thread (pros vs cons) if someone wants to start it up... The biggest challenge will be managing and building the foundation, and being completely inexperienced in this regard, we need help figuring it out!
It requires a 20' pad or larger hopefully. The weight of the dome is nothing - only 1100 lbs spread out around the circumference...but the dome construction and material itself is state of the art and incredibly strong.
I'm looking for suggestions on how best to approach this. Our reality is that dealing with a bunch of very large dimensional lumber is just not gonna happen, or if it does it's going to be extremely difficult for us - its Coastal Alaska primary growth - wet forest with giant Sitka Spruce, sloped very uneven ground with lots of rock, etc, so you get the picture.
It's an absolute jewel of a spot but not a place to just throw down a bunch of 75lb pyramid blocks (I'm hoping this won't be my best option)... The pad needs to be 20 x 20 at an absolute min but it would be nice to overbuild to 24 x 24, as any finished and level space (decking),will be super valuable, and we'll need at least some space to facilitate the assembly of the dome. Again I realize that the span is rather large, but the loading is very small. The goal is to plan a foundation which will cover the span, but be minimal in terms of dimensional lumber size (weight), and which can be applied to the difficult terrain - keeping in mind that everything must be helicoptered onto the spot for big bucks, and managed by two 55 yr olds (who aren't quite as mobile as we used to be)...
So laying out a nicely engineered grid pattern and sinking piers will be no more than a pipe dream. Realistically, I plan on clearing off the moss/growth/topsoil to expose the rock or gravel, and then work from there with a difficult rocky, sloping surface. So what are the possibilities? Perhaps I could dig down in a few areas enough to get a sono tube or culvert pipe with cement down to help anchor the overall foundation, but most of the points are going to be floating on the surface via some kind of blocking.... obviously, there is no perma frost issue to deal with there, as the Japanese current keeps things fairly mild with the average temps in Jan in the 20s....and LOTS of snow.
There is no snow load issue with the dome. The goal here really is to build a foundation for a 24 x 24 platform - not for a conventional cabin / building. I want to be safe but realistic on what's really necessary. My very untrained mind is thinking of using treated 4 x 4s which can be accessed underneath and adjusted over time as things move around, and anchored to some kind of pyramid pad. I wouldn't skimp on the floor sheeting, and again, my untrained mind is thinking that the sheeting could go a long way in providing acceptable integrity of the platform, and perhaps make up somewhat for a bit less integrity in the foundation.....
So I know I'm rambling. I've wrapped my head around everything so far except the foundation structure possibilities. I'd like to build the pad 24 x 24 with 8 rows of 24' - 4x4 (2 12's tied together) at 3' intervals. So 8 - 24' runs of 4x4s on 3' centers is what I will have to prepare for....
This IS happening this summer one way or the other! I know you can set this dome cockeyed on uneven ground if you have to but I think we can do better! It's not about what would work in my backyard or some place I can drive to - it's about making this work in an extremely remote and very challenging location..... The whole thing is kind of bizarre really, as the dome itself can be put together in a matter of hours for an almost instant super strong and efficient structure which makes perfect sense for the environment, for us, the logistics - everything really, but the foundation to support it presents a much more formidable challenge!
Any and all ideas / suggestions will be greatly appreciated!
Jack & Sue