In message ,
harry writes
On Saturday, 23 July 2016 15:50:59 UTC+1, Tim Lamb wrote:
One for the structural engineers...

The architect has specified manufactured dormer trusses. When I asked
him to supply a drawing for the manufacturers, showing the two studwork
partition walls which are below the new timber (90deg. roughly midway),
he said it was not necessary as they are not load bearing.

Now I was only ever electrical but they still made us do applied
mechanics. A simple beam carrying a load has to deflect whether the load
is distributed or not. Any deflection must cause some of the load to be
carried by the walls below?

Unless the roof is tiled before the studding is installed.

The trusses are made to standard size/spans, ie no allowance is made
for any additional support.
If the roof is heavier, they put them closer together.

This is domestic loading (bedroom/bathroom). I vaguely assumed they
might reduce the floor joist thickness because of the additional
support.

--
Tim Lamb