Is waterproofing necessary on a brick wall that has been plastered?

[miked]

Hi
We have a shower mounted above a bath. If the shower head is accidentally knocked so the spray is directed onto the tiles rather than into the bath, water penetrates behind the cracked grout and/or silicon seal. If the shower runs for some time water will run behind the tiles and drips from the ceiling below. This has only happened in the last year, it was installed 20 years ago and we are now updating the bathroom.
When the tiles are replaced is it acceptable to fix waterproof tiles directly to the plaster once it is dry, use waterproof grout and waterproof sealant or is it necessary to waterproof the area where the water may penetrate first? Note the walls are brick not plasterboard.
Thanks miked

 

[Bond]

I think it best to go belt and braces and waterproof the shower walls prior to tiling. ( for all the additional cost, why wouldn’t you).

 

[Ajax123]

tank it. For the sake of what it costs it could save a world of trouble if the sealant or grout cracks again