[Strawbale] Concrete posts

[David Neeley]

Gene,

First, I would not wish to use large structural supports such as
sizable tree trunks within my house space, as they take up a
considerable amount of room.

That said, as wonderful as strawbale walls can be, I am strongly of
the opinion that they are among the worst ceiling/roof insulation
materials around. The key to their long-term durability is keeping
them dry enough--which, over the years, is a large concern in an attic
space. Roofs may eventually leak, blowing rain may enter through
cracks, etc. In addition, bales are quite heavy for that use, not to
mention the potential fire risks. Finally, a bale is not all that
efficient in terms of insulation either per inch or per pound. In a
ceiling, I would think you would want something that is relatively
light weight but with high insulation value--after all, that is the
pathway for about 60 or 70 per cent of the heat gain in Summer and
loss in Winter. Finally, the reason bales work well in wall structures
has much to do with the render-which also makes them more
fire-resistant. In a ceiling plan, you are not going to do much
rendering of bales!

For example, a three-string bale wall is said to test at about
R40--but it's several feet thick and perhaps 25 or 30 pounds per
square foot. That amounts to a rather sizable load, and of course
takes up a great deal of space.

I have seen homes that used tree trunks for support--several of whom
had a large one located centrally and uncovered. Residents enjoyed the
view of the tree trunk in the middle of the house, while it supported
the peak of the roof structure. One design I recall very well had a
circular stair winding around the trunk--and it was quite beautiful,
too.

Finally, there is little doubt that a non-load-bearing design is a
help in being able to store the bales under cover while you construct
the walls. Beyond that, like any home, it all depends upon how the
details are executed as to the relative success of the project.
Personally, I don't see roof attachment as a reason either pro or con
in the consideration of load-bearing or non-load-bearing. Either can
be done quite successfully and with relative simplicity. If I were
building in an environment with lots of rain, I would consider a bale
infill design. But then, a while back on the Net I saw photos of a
project in England in which a temporary plastic structure was erected
over the entire site, allowing the whole thing to be done out of the
weather. So, there are always methods of accomplishing what you wish
if you are clever and plan sufficiently.

David