to prime or not to prime

[wobblyheed]

Hi all.

Got the Mapei Shower Waterproofing kit. Going to be waterproofing moisture resistant plasterboards around a bath.
The kit says to "prime all porous substrates and gypsum plaster with the enclosed primer"
So I was wondering, do I just need to prime where I've filled and taped the joints in the boards, or should I give the whole surface of the board a coat of primer?
TIA

 

[doug boardley]

won't do any harm to do the lot, it'll only take minutes although it will take longer to dry on WRP

 

[wobblyheed]

Cheers doug. Thought I'd better check. Should I also be priming the MRB's that aren't being tanked? I'm going to be using Mapei P9 adhesive.

 

[grumpygrouter]

Priming won't hurt and can have advantages...cleaning off of excess adhesive for one!