still confused about depth of wbp

[patl]

There's just too much info here. The more I read, the more confused I get, so please be gentle :smilewinkgrin:

I'm ripping out our existing bathroom that's 3mx3m. The current chipboard floor isn't all in great shape, and most of it is water damaged or covered in old tiles so would just require extra work to remove the old cement etc.

My current plan is to remove the lot, pack the joists where necessary to get it as level as possible and put an 18mm wbp subfloor down in its place. I was planning on covering this with 6mm ekoboard or similar, then ufh, then slc. Depending on how flat it ends up I'll see whether I feel confident of putting the 300x600 tiles down or whether I get a tiler in.

Now I'm starting to think that instead, maybe I should go for 22mm wbp, sacrifice the insulation board and go with durabase-wp or similar. I also wonder whether an extra 4mill of ply really makes any difference in a 9m2 room as long as the ply is securely screwed at 300mm centres.

As the chipboard+tiles are only around 20mm currently, I'd rather not add any more height than necessary, so any help would be appreciated.

Thanks,

Pat.

 

[mikethetile]

I would say 18mm wbp as a replacement for your 18mm chipboard and overboard with 6mm hardibacker to give the ideal surface to tile to

it really is down to how much deflection you have in the floor but if you brace the floor and as it is a relatively small room you should get away with 18mm

for a larger room with potentialy more deflection I would bump up to 25mm wbp as a belt and braces approach

 

[aph257]

i'm with you Mike. 18mm ply but with "No More Ply" for me.

 

[diamondtiling]

I think you answered your own query pat, 18mm plus 6mm backer boards is fine.

 

[patl]

Thanks, I felt I was going round in circles. Its nice to get a second opinion

 

[doug boardley]

personally I'd go for 22mm wbp, ekoboard, ufh, slc and then uncoupling membrane, oh and then tile

 

[david campbell]

it depends on the size of the room,18mm is the min i would think about but i would add extra noggins and make sure the floor has no movement,if the floor was larger i would be looking at 22mm or 28mm then the 6mm cement boards

 

[patl]

the trouble is, everything adds to the height, that route takes me to 22mm + 6mm board + 3mm membrane + 3mm ufh + say 5mm adhesive + 10mm tiles = 49mm vs around 20mm currently (ok my current plan is already only 6mm less than this but...), the step is growing.
In the fullness of time, I'll have to overboard the rest of the upstairs to match the height of the bathroom but I'd rather not lose any more height than I can get away with.

 

[doug boardley]

if you lose the ufh, that'll bring the floor depth down quite a lot

 

[White Room]

Why use themal boards on a timber ply floor, it dos'nt suck the heat out like a screed floor