Tiling Bathroom

[RicHax]

I am thinking of tiling the bathroom (1.9M * 1.7M). The floor is 18mm (green) tounge and groove chipboard, and seems very solid, although it is not screwed down.
Based on what I've read I think I may need to overboard with 12mm wbp ply.
I am however a little worried by the weight - 18mm + 12mm + 8mm (tiles) + 3mm (BAL) = 41mm onto 7"* 2.5" joists approx 14" inches apart. Are they adequate for this weight?
Also, if I screw down the chipboard do I really need to overply? The chipboard is ony three pieces (600mm depth * the width of the room) and, seems totally firm even without screws.
Many thanks for your advice.

 

[lancenotalot]

7"* 2.5" joists approx 14" inches apart. Are they adequate for this weight?

Most joists are 6-8" by 2-2.5" so they should be fine.

Also, if I screw down the chipboard do I really need to overply? The chipboard is ony three pieces (600mm depth * the width of the room) and, seems totally firm even without screws.

You would be best to overboard but you will still need to screw down whats already there.

I have used backerboards before where there is a height issue (only 6mm thick),no come backs.............yet

 

[MHTILER]

hi,joists are fine,always screw down floor to make a solid base,then you should always board over chipboard because it is not waterproof,stupid to use it in wet areas anyway,not calling you stupid,anyway use either marine ply,or hardybacker,screwed down,then prime,then tile.

 

[Richard C]

anyway use either marine ply,or hardybacker,screwed down,then prime,then tile.

You don't need Marine ply, it's too bloody expensive & may not be easy to get hold of; exterior grade WBP is all you need & don't prime the tile surface unless the adhesive manufacturer recommends it & many don't!

 

[RicHax]

Thanks for the advice everyone.
I shall screw the floor down, then cover with 12mm WBP ply, and screw that down.

"stupid to use it in wet areas anyway"

Actually it was fitted by a pro builder (4 weeks ago) who replaced the floorboards. I didn't specify what to use, but was a little surprised when I saw it, expecting ply. Even more surprised to discover (when thinking about tiling) that it was not screwed down at all!

 

[MHTILER]

forgot to mention,screw down at approx 150mm intervals,make sure your screws are not to long,