Picked up a new customer this morning who's having a problem. About 5 weeks ago another company killed her backyard off with round-up and about 10 days after that aerated, verticuted and seeded with fesuce. Absolutely no results at all after 3 weeks. Not one single new blade of grass. To top it off about 25% of the grass wasnt killed so now he has mostly brown spots and a few green from the stuff that was left over. She is now wanting me to sod the entire backyard. My question is can I just lay the sod down on top of the dead grass or do I need to prep the area somehow?