Originally Posted by
Rowan
Except a piece of reasonably thick plastic can be obtained from a hardware shop for few dollars... and my next one will be cut from the nice thick plastic bag covering my new mattress for home... for nothing.
Or just find some plastic on the side of the road, you'll see enough of it. But if it's dry, a groundsheet can still be used for things like covering your bike up so dew doesn't collect on it... Myself, I just use two large trash bags for my groundsheet which you can get for nearly nothing or free if you ask.
And like the previous poster said, using a groundsheet will allow you to fold and pack your tent without the dampness or dirt getting mixed in the bag. Easy enough to shake out a groundcloth.