Hammock hang out in a hall

[slowhike]

if you could have the tarp under your hammock & coming up & over the windward side, then extending out like a porch on the leeward side, leaving one side basically open, that would allow for some venting of moisture.
might not be to bad in some situations.

[Rubes]

Ah I was meaning more in the case of you find yourself without a hammock. I suspect most folks would rig the tarp as a tent type arrangement and have a dry but uncomfortable night's sleep on the ground.

You would need to be careful of the orientation, as you say, as the "open" side will always be susceptible to leaking. Anything that gets in will pond in the hammock. The ridgeline should be included within the whipping and not placed over the top for this reason.

[Just Jeff]

Hanging from horizontal support beams might work...the horizontal force gets put into the beams as compression - which shouldn't be a problem. But if you put multiple hammocks on a series of vertical supports, like you find in some scout huts, you might bring down the roof.