Lawn on top of membrane?
Good evening, how many inches of topsoil would I need to lay of top of weed membrane, ( I've zapped with chems turned over ground and removed what weeds/roots i could by hand) in order for lawn to take hold,(not seeding)????
Outside United States
Thank you for your question. Extension services do not recommend using weed membranes, since they often cause more problems than they are worth. They do not prevent weeds from germinating and growing--often through the membrane--having been dropped by birds, carried by wind and rain and animals on top of the topsoil. We also do not recommend 'zapping' the soil with chemicals, which may be unnecessary and kill valuable soil microbes (bacteria, fungi, nematodes, etc.) which are critical to soil health. Using good old elbow grease to remove weeds (or pre-emergent applications in the spring, to keep the weeds from germinating) is a more eco-friendly approach.
In specific answer to your question, grass in lawns typically grow 4 to 6 inches deep, so having topsoil at least that deep will insure they have room to grow over the membrane. Since I don't know your whereabouts, I can't recommend a specific lawn seed, but here is an article about the topic in our part of the world: https://catalog.extension.oregonstate.edu/ec1521