Subfloor prep and tanking advice

[Coops]

Hi Guys,

I have got loads of good information from you guys from reading through the posts on this forum but I still have a few questions I hope you can help with.

I am building a wet room on the second floor. I am planning to drop the floor to joist height with ply and then 20mm Jackoboard over it with a wedge board down to a linear drain. I will also jackoboard the walls.

My questions are:

Should I prime the ply floor/joists? If so, what with?

What single part adhesive would you recommend for bedding the jackoboard to to the ply? Would you recommend the same adhesive for setting the tiles?

My final question is regarding tanking, I would like to use Ardex WPC as I like that it can be mixed to two different consistencies but will this be suitable for the join between stainless drain flange and jackoboard? If so I am guessing scrim tape the flange joint and then tank over? I welcome a better option if there is one?

Thank you,

James

 

[Old Mod]

Use gorilla glue, make sure it’s the waterproof one, to secure the flange plate on to the jakoboard and weight it down til set.
It’s a partial expanding foam and will seal the plate fully, make sure you wet the areas to be stuck before you install it.
The wpc is not designed for that task even tho it may work.
Then tape and tank over the board and plate.

Yes prime the timber, make sure it’s diluted enough to soak in and not form a skin on top.
I use a weak solution of sbr, 4-1 with water.
If it appears to have completely soaked in I’ll give it another coat generally.

Doesn’t really matter what adhesive you use to secure the board to the ply, with the addition of wedi washers and screws to mechanically Fix it to the ply. The idea of the adhesive is to cope with unevenness in the floor beneath, all the fixing is taken care of by the screws and washers. You can tighten them just enough to pull them flush. Tape and tank over them to seal the hole you’ve made with the screws.
Stainless would be ideal, they won’t rust.

 

[Coops]

Hi 3_fall, thanks for your reply, very helpful.

I had planned to glue the drain down but had not thought of using gorilla glue, I will use it now tho thanks.

My drain placement is right against the wall so I only have the 20mm flange of the drain to create the tanking joint between floor and wall. As such i need something that really adheres to the metal. Is the wpc scrim tape and liquid suitable for this or am I better off using a tanking tape and then wpc over the lot? All Jackoboard floor to wall joints will be overlapped and glued using no more ply mega strength or Jackoboards’s own (unless you suggest differently?) and all butt joints will be glued as well so in theory it should be water tight without tanking but clearly it is sensible to tank as well. I hope this makes sense, I really don’t want a wet downstairs!

Thanks