prime p/board shower area

[terence7556]

hi folks can i have some advice. the job is ceramic tiles in a shower area .background is new skimmed p/board. im using homelux matting with bal rapidset flex adhesive and superflex wall grout.
should i brush and prime the p/bd before the matting goes on, with bal prime apd or bal bond sbr
also would you add admix gt1 to the grout or not
thanks in advance
ps the plaster dried over 4 weeks ago

[Dave]

APD is fine and you cannot add gt1 to superflex...