Shrinkage of stuff (was re: Cob: Insulation)

[Mark Piepkorn]

>Does this same type of thing happen to lumber (vigas, or 
>whatever they are called) embedded through a cob wall for 
>rafter type things to support a roof (or a second floor)?

	Typically mud and wood both shrink when they dry. Typically when they're
used together, they shrink away from each other. If gaps develop around
protruding wooden members, they can be tuckpointed with more cob, which may
or may not be a lasting application due to seasonal expansion &
contraction, movement, etc. Can use caulk if you want to; it won't combine
with the cob, but it'll stick to the wood and be flexible. There's a recipe
or two for making caulk (as well as paint and grout etc) in some book that
came out last year. Shoot, I just can't think what it's called or the
author's name. Something like Healthy, Nontoxic, and Natural. It's sort of
a Heloise thing, but tree-hugging. It was reviewed in last year's Resources
issue of The Last Straw.

>It would seem that would be the case. Is this not such a 
>large issue since these are fewer than the pieces in a 
>cordwood wall?  Not that I care if my house leaks a bit... 
>it is good for you, lets out the nasty air and lets in the 
>clean air...

	I'm originally from Minnesota, so I tend to think in terms of prolonged
severe cold, and heat loss, and stuff like that. Usually the biggest
culprit of heat loss is direct air leakage. If it's not much of a concern
where you live, then I agree - as many air changes per hour as you can do
in a house is good. Everything's situational, and balance is a worthy
pursuit. And depending on how the roof is made and if there's any ceiling
hung off it, those gaps could be incorporated as part of a ventilation
system. But I'm starting to move away from simplicity...