What will happen if I lay old sheets and towels down as the barrier between the current sod and the raised beds? The fabric would meet the criteria of being impermeable by weeds and plant roots but permeable by water and moisture. And they will disintegrate over time, so I won't need to worry about removing them someday. A brief internet search tells me that this approach is not very common…nothing turned up indicating anyone condemning or condoning the idea. It sounds like an easy, safe barrier to me. And I’ve been wanting to cut down on the number of linens in my house…completely unnecessary!