We have a narrow border (about 400mm) round the front garden which is paved. my idea is to take the weeds out, dig down about 100mm, put about 50mm of mot sub base in, then top of with slate chippings, would this be alright, or should i put a weed membrane in, only i heard the membrane isn't much good, there is no traffic over the border, but I want to do the job right, should I put weedkiller down before i start.