quote Sparetime: "Would a lightweight painters tarp work? "
I tried to use a painters tarp for a ground cloth in my winter tent. It was the canvas kind with the super thin plastic on the back. well it did not work well at all. It soaked up everything. the thing weighed 10 pound soaking wet when I packed it up to head home. My after thought was. "well I suppose that is what it was made for." I do not recommend it. the only thing that was nice about it was that it was not slippery like a poly tarp. what I am using now is a coated nylon tarp from CAMPMORE. It was 34.99 for a 9x9. It works great! its water proof,cheap and, not slippery. Give it a try.
I typically use a poly tarp but just in the area of the tent where we sleep. During the day we roll up our whole sleep system into the tarp and push it into the corner of the tent. If your standing or setting up chairs I would recommend doing it on the ground as to not soak your tarps and sleep systems. That's what has worked for me.
You do NOT want a ground tarp EXCEPT when sleeping. The whole beauty of no ground tarp is you can walk in and not worry about dropping snow. Or drying out your clothes only to get your tarp wet. THERE IS NOTHING BETTER THAN HAVING THE GROUND BARE. That being said, at night fall my buddies lay down a tarp to avoid any punctures to their expeds :)