I need to re-grout my bathroom tiles. However, over most of the wall surface, the existing grout is virtually flush with the surface of the tiles. So I can't just simply apply new grout over the top of the old, because there is nothing to key onto.
I've tried chipping away at the old grout with an old screwdriver, but it's rock hard and would take a month of Sundays to remove.
Ideas anyone?