
Large Tiles , hollow spots . Help
So I recently had large 48x48 tiles installed. I had them install Schluter Ditra over the concrete slab and then the tiles were installed over the Ditra. I have a tap tool I used to tap the tiles and I'm finding what sounds like hollow spots. Is this a failed job or is this normal? What should I do ?
Any pros out there? Help please. will add link to video.