Tanking a domestic bathroom - is Tanking the bath necessary?

[SpencerFrank]

Hi. Thanks for reading this post.
I am just about to tile my bathroom. The new shower cubicle is stud/exterior ply, and the rest of the room is plaster (one wall) and stud/ 12mm plasterboard (3 walls). I am going to use Bal WP1 to tank the shower cubicle, and the technical advisor at Bal has said I need only go as high as 1 m in the shower cubicle ( I questioned how their kit is sufficient for 1 domestic shower unit as advertised).
The questions I now have are:
1) is it general good practice to also tank the tiled area around the bath? My family are now in their teens and the days of drenching the area at bath time are long gone, so I am thinking that Tanking this area may be overkill.
2) Also what extra measures do I need to take around the area where the showerhead outlet comes through the plywood/tiled wall and the area around the mixer (I am thinking about the holes in the ply that were cut slightly larger than the 2 mixer valves, which even though there is a 'chrome' face plate incorporating a seal there must be potential for water to creep in there.)
Thanks

 

[Richard C]

Ply, even WBP, is an extremely poor choice for a wall tile base, let alone in a shower enclosure with concealed shower valve & pipe work. Ply is timber & timber in not dimensionally stable when exposed to damp, even if you tank the front (tile base) moisture can still affect the back & if it warps there go your tiles. Apart from expensive epoxy products, waterproof adhesive & grout is only waterproof in the sense it won’t disintegrate when wet, it’s not impervious so it’s very important that your tile base is waterproof. You can use Moisture Resistant plasterboard (not standard wall board) in dry areas but in wet areas, I would disagree with BAL; fully tank it if you want it to last. Even so its still a second rate option compared to a decent waterproof tile backer board over studs which I would advise you replace it with before going any further.

What is the wall around the bath made up of? What type/size/weight are your tiles? Plaster in good condition has a maximum weight limit of 20 kg/sqm including >4 kg/sqm for the adhesive & grout.