Thatch occurs in lawns when clipping, stems and other organic matter have built up in the lawn. This takes place directly on top of the soil near the roots of the growing grass. The problem with thatch is that, when it is allowed to accumulate to heights of over 1/2 inch, the lawn is susceptible to pests and disease. Thatch occurs from overwatering, overfertilizing and soil compaction.
Use a fan-shaped rake and run the rake across your lawn while applying a slight amount of pressure. You need to apply enough pressure for the rake tines to penetrate the thatch at the bottom of the growing grass. This method can be used for smaller lawns.
Purchase or rent a dethatching machine if you have a yard that is over 2,500 square feet. Set the blades on the machine so that they are at a height of 1/8 to 1/4 inch above the ground. You will want the blades to be close to the ground to be able to remove all of the embedded thatch.
Run the dethatcher in several directions for best results. Start out by running the machine in vertical rows much like you would a regular lawn mower. Once you have done the whole yard, change directions and use the dethatcher in horizontal rows. It may take several passes.
Rake up all of the thatch that has been removed. Place the thatch into lawn bags to be hauled away, or rake it onto a tarp and drag it into an area used for compost or lawn refuge.
Use an aerator on your lawn to remove soil plugs once you have removed all of the thatch. This will provide your lawn with the best drainage and allow you to reseed. Dethatching leaves your lawn with holes, so you should reseed any problem spots.