When can you not refinish hardwood floors?

You cannot refinish hardwood floors in several situations where sanding would cause more damage than benefit. First, if your floors are engineered hardwood with a very thin veneer layer less than 2 millimeters, you cannot sand them because you will sand through the veneer to the plywood core, only solid hardwood or thick veneer engineered floors can be sanded. Second, if floors have already been refinished many times and are now too thin, less than 3/4 inch thick, or nails are showing, there is not enough wood left to sand safely. Third, if floors are severely water damaged, cupped, buckled, or have large gaps and rot, sanding will not fix structural damage and replacement is needed. Fourth, if floors are laminate, not real wood, they cannot be refinished at all because laminate is a printed image with a wear layer. Fifth, if floors are badly termite damaged or have extensive pet urine that has soaked deep into wood and blackened it, sanding will not remove the stain. Sixth, if floors have asbestos-containing tiles or mastic underneath, sanding can release hazardous fibers. In these cases, alternatives like screening and recoating, replacing boards, covering with new hardwood, or installing luxury vinyl over the old floor are better options than full sanding.