We have hard clay soil also. I started with raised beds a few years ago and just added compost and mulch to the soil in the beds and tilled it in. I just didn't like the grass and weeds creeping in to the beds so I went with the weed barrier this year. The soil where I've been adding organic material is actually getting pretty nice after a few years of working with it. I can actually dig in it which is hard to do in the summer when that clay gets hard as rock.