We have a galley bathroom with original (i.e, 100 years old) subway and penny tile. We love the look but want to update it. The floor has large cracks and the subway tiles are literally falling off the walls--the grout has simply disintegrated. We were hoping to handle most of this retiling job ourselves but decided to get a couple contractor opinions. One told us it would be impossible to retile without a gut job--that is, putting up new drywall to replace both the plaster walls and the concrete upon which the subway tiles appear to have been set. Same for the floor. Another contractor, however, encouraged us to tile right over the existing floor and attach new subway tiles to the outer concrete layer on the plaster walls. Who is correct, in this case?