Expert: Bruce E. Johnson - 9/24/2008

Question
I am looking into building a circle type home out of cinder block and rebar. Here is my question. If I build a basement as the same dimentions as the upper floor what type of floor/ceiling support should I be looking for as far as weight load for the upper floor? I am looking at 400 sq ft dimensions  for 1st floor and basement. I am excited about my design but friends have told me it isnt a stable design. Help!

Answer
HI Bob, I don't know why your design wouldn't be stable.  If you have ever seen a castle with a round turret you can see that it must be stable, most of the those buildings have been around for centuries.  In fact a circular building is naturally more stable than a square box because it is self bracing.  It is the nature of the circle/arch.  As far as the floor system goes you would run a support girder in the location of where your diameter line would be on a drawn circle.  This girder would hang on girder buckets built into the masonry wall with a couple of filled cells underneath each end.  Then you would hang your floor joists or floor trusses on the girder and on the masonry wall.  Now you don't do the joists like a wagon wheel's spokes.  The joists would come off the girder in right angles and die into the masonry walls into skewed joist hangers.  This way you are not special cutting every piece of floor sheathing you would only have special cuts around the perimeter.

The roof system would be similar.  You would have a main girder across the middle and then your other rafters or trusses would hang on the girder.  A truss manufacturer can easily accommodate this type of roof system into a nice package, including your floor system.

I hope this information helps feel free to write again regarding this or other matters, sincerely bruce e johnsons..bejohnsonconsulting.com