Rubber Liner-like Product?
I really like the look of garden beds that are edged in low dry-stacked stone walls. However, in full sun areas where the grass is more aggressive, I find that the grass has a tendency to run under the wall and into the beds. I was thinking of using a Rubber Pond Liner-like product to run vertically about 4 inches down into the soil along the outside edge of the wall to create a barrier underneath the wall and keep the grass out. I would then fold this rubber barrier so that it also runs flat underneath the stone wall. I hope that makes sense.
I know that a lot of folks on here are pretty savvy/knowledgeable about Rubber Line-like products and was wondering what you might recommend. It doesn't have to be quite as thick as a regular pond liner, but I'm looking for flexibility and durability as it will be in contact with soil for hopefully 30+ years or so. If cost were no object, I'd simply use pond liner and I'll probably start with pond liner scraps I already have.
I'm thinking that a Roofing Underlayment or an Ice & Water Shield might fit the bill.
Any suggestions/inputs/ideas are greatly appreciated.