I have a customer who's dog has torn up her yard. The yard is basically complete dirt now. She wants me to mulch an area 60' x 40' using a chipped wood mulch. I know how much to charge but should I take any further steps other than just laying the mulch? She is afraid of massive weeds and grass growing up through the mulch. Should I lay the black paper stuff or just spray the area with weed and grass killer? Will the mulch itself prevent the weeds and grass from coming through? Any ideas or comments will be useful. Thanks.