are doing you are able to clear the area and then place newspaper and cardboard over the entire area. Then you soak this area down until the fiber you have placed to cover the area is completely saturated. The reason for doing this in the dark is all the earth under your old grass needs to set germination of weed seed is one flash of UV sunlight, and all your work to cover with weed barrier and rock, or mulch will be frustrated as weeds push their way through.

Keeping things dark, prevents this access to UV sunlight and then placing your weed barrier and rocks or mulch will prevent growth from underneath. However weeds will still find a way to settle above, but they will be easy to see and remove and be a minor problem.