My home was built in the 50's the hard wood floors are in need of replacing, we want to put down ceramic tile. underneath the wood floor is a layer of black tar or something that wood was set in then the hard wood nailed to these peices. Do I need to remove the black tar, (the concrete beneath this is not vey smooth it has a rough bumby texture) and if so what is the best way to get this up, it does not yeild to a scrapper. Is it possible to tile over this tar? Will the mastic adhere to this? Thanks for any help you can give me on this.