Which non cement based adhesive for bonding Wedi board to hardwall - Tile Advice

[Andysblacksoul]

Long time lurker first time poster

I'm currently planning a wet room in an extension which was built a year ago. 3 of the 4 walls are thermalite with Hardwall but no finish plaster. The hard wall is very flat and keyed as my builder knew I planned to board out the room (it's also very dry as it's had a year to go off).

My question is what adhesive to use to bond Wendi boards to it since cement should be avoided with gypsum?

The boards will be mechanically fixed as well at centres appropriate to the tile weight I end up choosing...

 

[One Day]

Why a non-cement adhesive? I use any old decent cement adhesive and back up with fixings afterwards.
Kerdi-board would be ok with gypsum adhesive - no cement.

I'm not even 100% that the cement face on Wedi is hydrated, so definitely not suitable for gypsum adhesive. I believe it is sprayed in some weird technique. Can't quite remember where I heard that though...!

 

[Andysblacksoul]

It's not so much about the cement in the Wedi board (it's polymer modified) but the the Hardwall (Gypsum) I want to stick them to.

In a normal plaster finished room, I'd use flexible cement based tile adhesive to stick the boards up, but everyone I ask says cement based adhesive onto Hardwall is a no no... (just like tiling straight to Hardwall is a no no...

Any non-cement adhesives that people have experience with?

 

[NZ_Tiler]

If the gypsum is well primed then cementitious adhesive is fine

 

[Andysblacksoul]

Ah OK, so what primer (not PVA) would you recommend? something like SBR?

 

[NZ_Tiler]

Ah OK, so what primer (not PVA) would you recommend? something like SBR?

Sorry don't know SBR.
Mapei man... primer G is fine but use the primer from your adhesive manufacturer.

 

[Andysblacksoul]

Great, thanks for your help

 

[NZ_Tiler]

Great, thanks for your help

No worries. If you google "primer g pdf" open it up, it will give you pretty clear instructions.