Backer board or plasterboard

[Super_Paulie]

Good evening my friends.

As the football is over and my working year comes to a close (university) it means I can get down to business so I'm ordering my supplies. 

 

My shower will be pressed against the only external wall in the room, it's currently back to brick so I was going to backer board that wall, the type with the foam core. I'll just MR board the rest of the room. The room is very small, any centimetre gained is a bonus. What are my options at the shower area, tile adhesive, foam directly to the wall followed by screws and washers? 

Cut my space loses, batten the wall out with 20mm deep battens and go against that? If so, insulation between said battens?

 

Sack off all of the above, MR pasteboard and tank? 

 

Opinions welcome.

 

Edited Wednesday at 21:09 by Super_Paulie

[JohnMo]

Never seen a need to tank a shower room and in my 60 plus years and never seen an issue. Only ever used moisture resistant plasterboard around the shower and normal elsewhere. Tiles direct to the plasterboard. If you foam the plasterboard on or batten and screw it's not going anywhere quickly.

[Russell griffiths]

Where’s the pipework, that might dictate what you do, are you going to chop into that wall or build a stud wall in front of it. 

[Beau]

My 10 pence worth is if the wall has not got EWI I would use XBS bonded and screwed back to the whole wall. It's not going to add a lot of insulation but it will reduce condensate and in turn mould.  You can tile and plaster XBS boards 

[Mr Punter]

I really like the XPS backer boards.  Lots of thicknesses, lightweight, easy to cut and fix, waterproof.  Fix with adhesive foam or screws and washers.

[Super_Paulie]

There is no EWI, it's a cavity wall though.

 

So direct connection to the wall with say 12mm XPS backer board is my best option here? 

[Nickfromwales]

On 03/06/2026 at 22:37, JohnMo said:

Never seen a need to tank a shower room and in my 60 plus years and never seen an issue. Only ever used moisture resistant plasterboard around the shower and normal elsewhere. Tiles direct to the plasterboard. If you foam the plasterboard on or batten and screw it's not going anywhere quickly.

This is pretty crap advice?

 

I've done a LOT of insurance work over the 30+ years of me doing 'this kinda thing' and tanking would have saved so many homes from very significant, long term erosive water damage; all caused by leaking tiles / grout / sealant / shifted baths and shower trays etc etc.

 

Tank the FECK out of it and you'll never look back.

[Nickfromwales]

On 04/06/2026 at 19:18, Super_Paulie said:

There is no EWI, it's a cavity wall though.

 

So direct connection to the wall with say 12mm XPS backer board is my best option here? 

This is best, if you don't want to lose GIA with insulated stud walls.

 

Dab the boards on and apply the dab to the boards. Poke a hole through the centre of each dab before applying to the wall, as markers, and when the dab is dry you drill back through and mechanically fix with corrosion-resistant fixings and washers. Foam at the footer, header, and sides. Leave a 3-5mm gap between the boards to inject foam in the gaps as dab must NOT be allowed to come through these gaps. That would bridge both cold and moisture, in the worst case.