"Tim W" wrote in message
...
Why?
wibbled on Saturday 10 October 2009 14:51


To increase stiffness I agree about the herring bone or solid
strutting but is is worth it on 4" joists
If you have four inch joists on top of the existing that is not good
as all it is is extra weight UNLESS you add a piece of ply to the side
of both and make them one

You've just given me an idea...

If I install 8' ply strips (ie strips from a full sheet) along my stacked
joists and stagger the joints on each side (because the joist span is
longer than 8') then I'll not only be re-inforcing the damaged bits, I'll
be leaving them better than before.

That's what I said earlier when someone said their roof was too thin.
do it in thinner ply two on each side with joints staggered and it will be
even stronger.
Add a strip of metal into the sandwich and its even stronger.