I think the french drain really does go by the foundation. That is
SO
much work though it may be worth paying someone to do it, or pay them
for their advice. For example, does a french drain function the way
you want it to in clay soil ? I have no idea. I cannot imagine
shoveling a trench in clay soil but if your crawl is wet it's gotta
be
done.

If you install the french drain by the foundation, don't forget to have
termite treatment reapplied. Disturbing the soil near the foundation
breaks the termite barrier and it will need to be reestablished.

Bob S.