Laying Sod over Existing Grass

I have a patch of dead grass in my lawn, and I’d like to repair it with sod. Do I need to dig out the old grass, or can I lay the new sod right on top of it? -David

Whether or not to remove the old grass before laying sod is a long-standing debate. There’s the “remove it all” camp, the “till it in” camp, and the “just lay the sod on top” camp, with all sides reporting success with their methods. I tend to be in the “dig it up” camp, because if I’m going to the trouble of planting something, I want to give it every possible advantage.

However, if you’re having problems with dead spots in your lawn, I’d definitely recommend digging out the sod before patching, and here’s why.

Advantages of Removing Grass Before Sodding

  • Soil problems: Do you know why that patch was dead to begin with? If you’ve got poor or compacted soil, insects, or diseases, then the new sod won’t fare any better than the old grass. Before you waste your time and money on more sod, make sure you’ve corrected the underlying problem.
  • Height: If you place a patch of sod directly on your lawn, it will be higher than the surrounding soil, and not only will it show, but it will dry out faster than the rest of the lawn. With some careful digging, you can install the patches at ground level so that they’ll never show. If you’re resodding your entire lawn, this is less of a problem, although you’ll probably want to dig out around walkways and curbs to slope the sod around the edges.
  • Access to Soil: The delicate roots of your new sod need to be able to reach out into the soil to enable the turf to be firmly rooted. You wouldn’t plant a flower by simply sitting it on top of the ground; likewise, your sod will establish faster if it’s nestled firmly against good soil.
  • Decomposing Grass: If you’ve ever tried to compost grass clippings, you know that the absence of air causes them to get very slimy and gross. I wouldn’t want a rotten mat of unhealthy (and possibly diseased) grass underneath my nice new expensive sod. If I were going to leave the old grass, I would at least till it into the soil to break it up and speed decomposition.
  • Unwanted Plants: If you’re covering up weeds or unwanted grass species, there’s a chance they could survive and infiltrate into your new sod. Digging out the old grass will give you a fresh start.

Further Information