In article ,
Tim Watts writes:
On 30/05/10 19:34, Kipper at sea wrote:

The 3" x 3/4" or 75mm x 19mm timbers are there for a pacific reason.
They are not temporary supports; they are all part of the stress of
side movement on truss roof construction. It was found that in the
early days of truss roof use, that when the weight of the roof tiles
was loaded the trusses would sway. The diagonal braces, as they are
called. Were introduced to stop sway. If you’ve ever work on a truss
roof without bracing, as you moved about it was a bit unstable. They
are not put into position until all the trusses have been erected.

Interesting...

Any reason they didn't strap the rafters with diagonals?

In fact. I have seen under-rafter strapping on my old rented house
(modern truss roof) - so I'm *guessing* it was down to how the builders
felt on the day?

They work best on the timbers which are nearest to being vertical.
The rafters usually are the least vertical in a trussed roof.

--
Andrew Gabriel
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