Gave an esimate for 15 yards of woodchips ($85/yd installed) for "ground cover" in this guy's backyard. He wants to go with me but then wanted an estimate for laying stone down instead so that he wont have to re-mulch every year. I've never worked with stone...... would I first lay down a plastic lining then put the stone on top? How many inches of stone? Are there any names for stone mixes that would work? Thanks!