On Mon, 17 Aug 2009 21:52:42 +0100, The Natural Philosopher wrote:

Hugo Nebula wrote:
On Mon, 17 Aug 2009 11:49:31 -0700 (PDT), a certain chimpanzee,
sm_jamieson randomly hit the keyboard and
produced:

Does anyone know how much can generally be notched from the bottom
corner of a joist when it is sat in
a joist hanger, in order to adjust the height for variations in the
brick coursing ?

Rafters can be birdsmouthed, and up to one third is a rule of thumb,
so I assume joists are the same.

Don't assume. Rafters are largely in compression. Joists are pure
bending moment.

Definitely worth checking. All the out-buildings around here (barn aside)
have the rafters cut to about half their depth where they meet the walls,
and it doesn't seem to cause any issues - but then maybe that's due to
the way they're anchored (and anything toward the outer edges beyond the
cut doesn't exactly have to support a lot). As you say, joists probably
have quite different loading characteristics, particularly at the ends.

However having said that joist are way too STRONG in order to meet
deflection/loading targets.

So you can probably notch massively

Probably, assuming they're not all like that. My gut feeling* - and
that's all it is - is that I wouldn't want to take more than about 20%
of the total height though, if I could help it. But then surely more than
that suggests a brick structure below which has some major issues of its
own? :-)

* I tend to massively over-engineer stuff - and if it's around long after
I'm gone, well that's generally no bad thing...

cheers

Jules