We have never considered tanking as an option. As far as we are concerned if a bath or shower is to be fitted, it should be done correctly.
So what is tanking? Put simply tanking is a waterproof membrane. Tanking systems are used in wet areas before the tiles are fitted. The tanking systems can either be liquid based in which case they are painted or rollered on, or sheet membranes which are much like wallpaper. The idea of the system is that once it has been fitted, the area is completely watertight. The background surface (such as plasterboard) cannot be damaged by water.
The reason why many companies don’t fit tanking systems is that it is an extra cost which has to be passed on to the customer. This cost is usually around £100 for supply and application of a wet system so in other words, it’s a cheap insurance for the life of the bathroom. Another reason why it isn’t fitted is because people believe that tiles are waterproof anyway. For the most part they are unless you are using natural stones such as travertines or marbles. People also believe grout to be waterproof and here’s where the confusion lies. Manufacturers advertise grout as being waterproof because it does not degrade in the presence of water. It is still a cement based product so it will still soak up water in the way any cement product would. That water can then transfer to the background surface such as plasterboard and that’s when the real damage starts to occur.
If you find that your shower area constantly has mould growing along the grout lines, chances are that yuor shower area was never tanked. Water has been absorbed by the grout and passed to the plaster behind which is now an ideal growth spot for mould.
Tanking is a necessary part of fitting a shower or bath area correctly and if it hasn’t been suggested to you then really you should be asking why not?