Cob: straw bales and cob

[Amanda Peck]

the quick and dirty way is to let the weight of the roof compress the bales. 
  Might not be good enough for a hybrid system.  Wouldn't work at all if you 
had a gable roof and were using straw bales on the gable ends.  Then you'd 
get to use fairly heavy duty versions of the kind of strapping they use to 
bale up cardboard.  Put up the plate--around the top of your walls. Your 
roof is going to set on and fasten to this, so it gets to be pinned down 
into your wall as well. And then strap the whole mess down.  This avoids 
little scallops where the straps are, spreads out the load, and gives you 
something hard and smooth to fasten to.

A few years ago the usual method of compressing the straw was to let it sit 
for a month or so.  Probably worked fine in the dry season in places that 
have a dry season.  Was an invitation to rotting straw if you had to try to 
put tarps over it for the duration, during a couple of high wind 
thunderstorms.  It may have been good that two inches of concrete was also 
normal, inside and out, on the walls.

But being able to cob up to a roof has its advantages.

I don't think lowering the roof onto a building is a do-it-yourself 
first-timer task for much more than, oh, say Heart House, but I'd think 
there are some hybrid ways to do this.

If you're still working with approximately the same plans, a hip roof is 
only marginally more difficult to plan and presumably spreads the weight out 
a little better--with one of those tubular skylights or a tiny dormer to put 
light into your loft.

I just looked at the Taunton Press book on roof framing (i.e., it's a 
collection of articles from Fine Homebuilding).  some suggestions there, 
including a picture of a crane swinging roof framing onto a building, and a 
good example of how NOT to design a roof unless, as an experienced framer, 
you've got a couple of weeks to figure out how to put the thing up.  the 
simpler the better.  Browse before you buy, it may not be for you.  The 
current issue of the magazine has an article on how to use those i-beam 
affairs to frame your roof, that gave me hope that I don't have to 
completely change my plans.


..............
Also, if you know, it says to have the bales pre-compressed before adding 
the roof. What does this mean? How do I do that?
Jill


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