Never! Plastered walls are only able to take a certain amount of weight (usually 20kg per square metre) and tiles can weight a lot. Tiling on top of other tiles means that the weight is doubled plus we don’t know how good the adhesive was under the first tiles. Tiling over old tiles is simply a recipe for disaster and puts your family at risk.
All of our projects involve removing old tiling and most projects involve removing the damaged plasterboard too. By installing new board we know that the job has been done correctly but more importantly, it has been done safely.