I was removing a solid wooden floor today in a customers kitchen only to find a black tackie substance on the floor , seems to be permanently flexible product , which sticks to the scrapper when trying to remove it! I've never came across this before and was wondering could it be a floor adhesive or some sort of damp proof barrier ! What's the best way to remove it , or would it be ok to score it with a grinder and apply slc over it? Cheers , sorry no pictures provided !