Are there tables anywhere for the dry weights of timber of different
species by volume? I realise it's all likely to be somewhat hand-wavy...

I'm going to need to jack up parts of our old timber-framed barn as I work
on the end wall*, and being able to estimate the size of floor jacks
needed would be useful (and I'll add on a wide safety margin, of course).

* for some very strange reason they ran poured concrete round three
walls (up to about 3' high), but only did half of the fourth. Of course 60
years of moisture hasn't been kind to the 'missing' section where the wood
extends down as far as ground level - the framework's gradually rotted
from the ground up, dropping about 3" in the process along that section.
Thankfully it's an end wall, not side, so doesn't have all of the roof
weight on it...

It's a bit of a longer-term project, but figured I'd ask and then I could
keep an eye out for the necessary jacks in the meantime.

cheers

Jules