Over periods of time, small pieces of grass and roots die which gather just below and above the soil in your lawn. This organic matter is called thatch and in limited amounts can help your turf. However, if too much thatch is created and the naturally occurring process cannot break it down, this unintended barrier can prevent your lawn from receiving the air, water and nutrients it requires for the development of roots.
We have dethatching machines that look similar to a lawn mower. Instead of a blade for cutting crass, the power rakes will comb and knife your lawn with "teeth" and that remove the thatch. The remaining thatch or debris is generally raked afterwards. This also allows a perfect time to lay additional seed in poor performing areas.