Adding Topsoil Over Existing Grass: What Happens?

Question: I added 2-3 inches of topsoil to my spotty lawn without killing the old grass. What will happen?

Potential Issues

Many grasses will grow through the new soil, but weeds are easily eliminated. The bigger concern: if the new soil differs from the underlying soil, you may face problems. Three inches isn't deep enough to support grass long-term, and watering will be difficult. You should till the new soil into the subsoil for a uniform texture. Also, covering tree roots with as little as an inch of soil can damage or kill the tree.