...like tar? we removed old clay tiles from our living room floor to put down laminate wood flooring and under the tiles was some black tar like stuff do we need to remove it off the concert
You can go over it provided it is smooth, and secure to the floor. If not, try your best to scrape it up with an ice scrapper (the type you'd use on your driveway). It is important that the floor be level otherwise your finished project will be bumpy at best.