I put in a simple fire pit last fall consisting of a 12' x 12' array of pavers with 4' x 4' hole in the middle for the fire. It has been great to have the neighbors over for an evening around the pit. The land is flat, sufficiently far from trees and I put landscape fabric (used) down before l laid down the pavers. I wanted to keep it simple - no excavating, no gravel, no concrete. The result was a disaster - this spring grass and trees are growing between the pavers. Was the problem caused by using used fabric? Would new fabric prevent growth? I have considered thicker material - shower pan liner, roll asphalt roofing, pond liner - but I am running these alternatives on TBN to get your ideas because I do not want to experiment and have to do it again. Your ideas are welcome.