: The "waterproof" fabrics I've had contact with (no pun intended)
: are waterproof for awile from rain, snow etc. but eventually they seem to
: wick up the moisture and then become much less "waterproof". I
: would also worry that the moisture coating would mean that whatever you'd
: use to truely waterproof the fabric then wouldn't penitrate well an might
: not stay stuck.

: Bill H.

I found the same using Tyvek as a tarp. It's really important to pitch it so there's no pools of water as they start to drip through. If it's nice and taut it's waterproof.