Hi before I became disabled and now have sites w concrete pads I use indoor out door carpet and because I have a truck if need be I can put it away in the bed and take it home a spray it down w hose and dry it out and fold it up again. As for the indoor outdoor carpet killing grass yes if left down for long periods it will as no sun no grass but a typical weekend or a week or two I don't think so and yes I have used mine that long. And if needed I can use mine on the concrete pads to help control the dirt that otherwise would be in the TT. And I won't kill any grass either :B