On Tue, 18 Aug 2009 14:29:21 +0100, dennis@home wrote:
If rafters are in compression what keeps the walls from spreading out?

Usually the ceiling joists to which the rafters are fixed or collar ties.
Except for an old barn I have responsibility for, where there are no
ceiling joists and the collar ties are not substantial enough. The walls
are spreading out.

6 mm stainless wire stretched across is incredibly strong.

That's been done to our garage... badly :-)

Evidently the walls started spreading at some point, so they just punched
holes in either side wall at the top halfway down the length, and ran 3/8"
cable across.

It's a really sloppy job, but the cable must be under a hell of a lot of
tension (and I don't know how weak the walls would be without it) - so I'm
not inclined to try and tidy it up. I just put "rebuild garage" on the
to-do list instead as that's a much more interesting DIY project

cheers

Jules