I have a friend that lives in one of those box style homes in neighborhoods going up all over the place. I saw her yard a couple of weeks ago and the area that was sod looks terrible. It's hard as a rock, is so overcome with thatch, sits directly on top of hard clay, and doesn't really even grow at all. She has a few fairly small areas where there was some sinking, but not really bad. I went through and dethatched for her last night, but it didn't really pull that much of it up. I told her the conservative approach would be to try to save it by dethatching/aerating and possibly putting some lime down as I heard that helps break up the clay. Overseeding will be an absolute must as well. I said the most aggressive and most successful would be to just pull up all the sod, put down 4" or so of top soil, and then seed. Any thoughts???