Hi all,
We are considering building a geodesic dome (in Vermont), and I have been looking into ICFs for the foundation (it may be a walk out basement), and possibly the main level.  The floorplan of a dome is polygonal, having something like 10-14 sides (numbers are a guess, and it varies by type).  I've seen info on making radial ICF walls, but not so much special angles like this, but I understand it's completely doable as well.  What kind of special considerations are involved?  Extra bracing or connections, especially for the corners?  How do the blocks fit together at an angle - do they just butt up flush on the cut edge, rather than overlapping?  Are there any ICF types that would be better or worse for this kind of thing?  (Vermont ICF seems to be the leader in the area, using AMVIC blocks.)
Thanks for the info - I'm really enjoying the forums!

I know of a mitering formula with Integraspec that can accomodate any angle desired.
Here a link to finding the nearest distribbutor. http://www.integraspec.com/Newyork.htm.
Hope you find what your looking for!

milkdemcows,

What type of roof have you considered for this unusual shaped home?

I presume we'd go with some kind of shingle, given the many cuts and seams that would take place (each triangle has edges between 6' and 10'), but I haven't looked into specifics yet (rubber?).

Here are two of the dome manufacturers that we're looking at:
Timberline http://domehome.com/
Natural Spaces http://www.naturalspacesdomes.com/
Both are built one a "strut and hub" system to which you apply triangular plywood sheathing. I'd like to insulate with a spray foam, maybe paired with fiberglass. Some people go with a 5/8 proportion or similar dome (the percentage of a sphere), where the first row doubles as a vertical wall, but I'm leaning more towards a low profile, 3/8 dome, set on normal height walls - the dome portion would then be for the second floor and roof.

Arxx has an "adjustable" form that our customers have used many times.  It swivels to create any angle up to 90 degrees and is easy to use, saving labor over cutting and pasting, glueing, etc.   We have even seen it used at a full 90 degrees to make rounded corners on the exterior of a custom home.    They also make a 45 degree block if your angles are 45.   One thing to bear in mind is that this foundation/basement is more complex than your conventional box; this will require additional bracing, taping, etc.    Multiple angles will all take a bit more time than slamming straight block down one after another and there will be considerable labor in steel bending, placement, etc.   Your contractor may be wise to get rebar pre-bent for the angles you are dealing with.  This is all very do-able, but it will be a bit higher in cost.  There also may be more entertainment later when you are finishing the drywall in all those corners...   But, when you are done, you will like your ICF basement!

Choose the most versatile product and all will be well along the numerous finishes.
Regarding costs of block, it sounds to me like all odball angles. If so with Intergraspec you would only need standard panels and not have to pay for specialty corner panels. The mitering formula is to accomodate any angle with the use of standard panels and virtually no waste.
Cheers!

Posted By milkdemcows on 26 Apr 2010 01:44 PM

Here are two of the dome manufacturers that we're looking at:
Timberline http://domehome.com/
Natural Spaces http://www.naturalspacesdomes.com/

Have you looked at this one? http://www.monolithic.com/ Looks to me like it might be a worthwhile option to consider.

Thought I'd pipe in on this one.  I built a doube geodesic home in 84.   Two geodesics seperated by a 50' deck.  Not that exciting except that both homes

needed to be on level so the deck between would line up properly.   Many issues with geodesic designs.  90% of the interior walls were, by design, not square.  Several were fan shaped with 8' base plate and 10' top plate where the top plate was twisted 10 degrees off plane.  The waste rate on material was 30%.  Imagine cutting drywall in triangle sections.  The dome structure itself was said by the manufacturer to have ONLY vertical forces on the five base plates.  That turned out not to be true.  The flexibility of the wood allowed for considerable outward latteral forces at the base plates.  Unaccounted for, the thing wanted to pancake and would have pushed the block walls outward.   ICF corners after pour would be GREAT for this application creating a very strong rim.  The dome triangle pannels did not come with built in ventilation pathways which lead to countless issues.   The said energy savings of the dome structure do not compare with ICF walls and a super inslated roof system.    If you could build it out of SIP panels, well then you'd really have something.
MK

have to add...

The geodesic kit was not adjustable.  The foundation had to be built within 1/4" dimensions of the dome specified dimensions.  Typically, foundations go up more or less accurate and the framing adjusts to the foundation.  Not so with the kit dome.   It can be done, but it dose require a lot of careful work.

MK

Had this happen 4yrs ago, crazy angles, one I can remember was 37 degrees. What we did was take 2 2x12's for each corner and put 3 stap hinges on each one. Then we made a pattern that was acceptable to the owner for each angle.. We used Simpson galvanized plates that I found at the local lumberyard and attached the plates at the top and bottom of the 2x's to hold the angle against the pattern. Cut the forms as close as possible and foamed the rest with the 2x having been covered with 6 mil poly. Screwed thru the 2x into the closet web. When we got 3 courses up we ran some galvanized fence wire thru the 2x to hold the angle in the center, brace on either side of the 2x and braced the inside as normal.