Preparing bathroom floor for tiling

[jesteh]

I have 22mm floorboards over joists in bathroom, all in very good conditions with very little deflection. I am looking at tiling the bathroom floor with natural stone tiles and having electric UFH in as well. Would it be ok to overboard floor with 6mm tile backing boards and then tile on top of them or should I replace with plywood?


Are there also any tile backing boards which act as insulation boards as well providing extra benefit over plywood floor?


I presume the layers would then be:
-joists
-floorboards
-any primer on floorboards?
-6mm tile backer/insulation board
- decoupling membrane?
- electric ufh/primer
- tile adhesive
- tile




Thanks.

 

[peckers]

You say you have very little deflection, you need to get rid off all deflection especially when tiling in stone tiles!
Take up floor
put extra noggings in between joists at 300mm cntres
put new floor boarding down
stick tile backer board down with flexible adhesive and screw as well
then you heating cable
followed by slc
then your ditra matt
and then your tiles.
hope this helps.
p.s you want a tile backer board for insulation? then marmox or wedi is suitable.

 

[Brinkley]

i would take up floor boards add extra noggins then put down 18mm ply instead of floor boards ,then over board with 6mm cement board

 

[DHTiling]

Deflection needs to be minimal... then ye you can use hardibacker 250.. but IMO 10mm Marmox type board..

 

[jesteh]

When I say very little deflection, what I mean is practically none. I.e. if I put a glass with water on floorboard and whack a rubber hammer next to it, there is no ripple on surface on the water. I can find a few spots on the floor where I can make tiny ripples but its few and its very little. I am expecting that e.g. 10mm marmox type board will make it even more solid and take that out completely.

The floorboards are also brand new so seems a shame to rip them up and replace with ply, if i don't have to. They are screwed rather than nailed in so while it would be relatively easy to lift them and add noggins underneath, there are a lot of pipes and wires which would get in the way so probably only possible in places.

Assuming that I do the water glass test and 10mm marmox boards take out all remaining movement so there is totally none, would it then be acceptable to use following:
- floorboards on existing joists
- 10mm marmox board screwed into floorboards with short screws, no washers
- heating cable
- SLC
- ditra matt
- adhesive + tiles

Also, what would would you expect be the thickness of cable + slc + matt + adhesive assuming I am putting down 10mm stone tiles?

Thanks again (its my first ever tiling attempt)