tent groundcloths

A woven fabric will hold up well, and it may be mostly waterproof, but it may be heavier and more costly.

A plastic sheet like a painter's drop cloth comes in different thicknesses, and it will not hold up so well, and it may be very waterproof, and it is cheap.

Tyvek is a non-woven fabric. It seems to hold up well, be mostly waterproof, and it could weigh several ounces. It costs more than plastic.

–B.G.–

I don't use any ground cloth with my lightweight single-wall tent. The silnylon floor is sufficient barrier. I have never had any problems, either from stuff under the floor (I do remove sticks and stones before setting up the tent) or from my dog's claws in the tent. Of course with a floorless shelter or a tarp, I definitely would use a ground cloth, such as this one: http://www.gossamergear.com/cgi-bin/gossamergear/polycryo_ground_cloth.html.

If you really want a ground cloth under your tent, a cheap plastic painters drop cloth can be cut to fit your tent floor (cut it an inch or two short of the edge on each side so it won't funnel water underneath the tent). You can get up to half a dozen out of each drop cloth and they weigh only a couple of ounces. They are more or less disposable, lasting only a few trips, but you'd have to buy almost a lifetime's worth to equal the cost of a commercial footprint!

IMHO, the footprints sold with many tents made by mainline corporations are pure sales hype, intended to lighten your wallet and weigh down your pack.