wrote:

As for "looking up engineered joists", I studied that subject some forty
five years ago as part of a 5 year City & Guilds indentured apprenticeship
[2] - and used some of the stuff in later years during works on public
buildings.

[2] You do remember those don't you? And you may even have a few
building construction qualifications yourself.


Cash

You should see my joists... 2x4" notches everywhere thanks to a ham fisted
plumber, a few of the 8" joists are actually 4x2" on top of the original
4x2" ceiling joists in a roof conversion (and some of those have 2x4"
notches). Everything warped to buggery...

I just plated both sides with 7" x 8' lengths on 1/2" odd thick ply of no
particular grade, covered in PU glue and a bugger of a load of screws to
stiffen the whole lot up and bridge the notches (which are infilled with
scrap wood). The ply's job is mostly to prevent joist-joist sliding, so it's
absolute strenght is not particular important, which is not quite the case
here.

The fact it wasn't actually deflecting in a bad way before (no ceiling
cracking below, been like it for 3 decades), I just did it to add a bit of
stiffness and make notch repair easier. It was at that point I learnt to
stop worrying too much...


--
Tim Watts