flooring and tray

[G1zm0]

hi guys, refurbishing bathroom doing walls and floor, ive ripped all mdf up from floor and replacing it with 18mm far eastern ply .
my questions are , threes about 1 inch of mdf i cant lift up as its on the joist and its on the support wall

can i just leave this and when i put the floor down (using grip fill, screws and batons to support floor) and then tile over the 1 inch mdf?

the shower tray will be going on to this 1 inch as well (top side of it) , whats best way to affix this to the ply, with tile adhesive, mastic or weak cement mix?

ive read its ok to tile straight on to the ply as long as there's no movement so eliminating tile backerboard, just need to find a god adhesive that will do floor and wall tiles , was thinking bal flexable or mapie

 

[PrenticeBoyofDerry]

MDF is not the best material to bond to, but one inch ain't going to be such a big issue. Make sure prime it well.
Bedding tray would depend on the level of the floor, lots of methods to bedding the tray, silicone is as good as any, if there are any dips in floor packing out with slithers of wood or PVC window packers is advisable.
I would nearly always recommend using Bal flexible rapidset on the floors, although Weber and Mapei products are okay. The walls would depend on the tile format being used, medium to large format stick with rapidset, if smaller format a ready mix can be used such as white star in wet areas.

 

[G1zm0]

cool whats best primer to ise i am going to be tanking the walls when i put up the green moisture resistant plasterboard, so will the tanking do for the mdf floor as well .

if i could remove the inch i would but its a supporting wall with 50 g of water above it , so wont take chance , the inch will be less when the plasterboard goes on.

will grips all do for the tray ? making sure theres no voids in the area, its a stone resin tray

 

[PrenticeBoyofDerry]

Grips will do, your not trying to adhere the tray to floor, just trying to bed it to avoid too much flex in it.

With regards to primer on MDF, as stated previously not a good substrate to bond to, APD maybe.

 

[G1zm0]

hi thanks for reply, I wasn't going to use primer I was going to tank, the wall and the mdf part of floor ,

when putting tray down should I put the plasterboard up first or should I cut the tray into the wall and plasterboard it up to the top of the tray (ive no plasterboard up yet, doing full bathroom remodel )

 

[PrenticeBoyofDerry]

You can do either as the tiles, grout and sealant should deal with ingress of water, I would suggest that you consider the the enclosure size and tolerance prior to making that decision.