Another sub-floor query

[Phillay]

Hi, seen and read quite a few posts in relation to installing a proper sub-floor for when tiling an upstairs bathroom.

My bathroom's sized about 2.5 x 1.5m. The flooring is made up of 100mm wide x 20mm thick tongue and groove floorboards (ex council home built in the 70s). The joists below are 6" x 2" and are around 400mm centres.

We're refurbing the bathroom, and of course my wife wants floor tiles.

I know that the correct way would be to rip up the floorboards and start again, but it's going to be pretty impossible to do that as the internal dividing walls between the bathroom and hallway are old breeze block built, directly off the floorboards, so I'd end u disturbing their support and stability.

But like so many others I'm sure, I don't really want to be stepping up into my bathroom... I read in a previous forum post someone suggesting 6mm cememt board ontop of floorboards. To be fair, that ontop of the floorboards and then tiles to finish wouldn't be too bad regards height... I just don't know if it would be strong enough to stop the dreaded cracklines.

Advice greatly appreciated!

 

[Andy Allen]

it depends how much deflection (movement) there is in the floor, dose the floor squeak when you walk on it, is there much movement in the floor boards..?

 

[Mark S]

There are a number of fibre-reinforced renovation screeds designed to go over timber floors, the key is the amount of movement that the floors boards have. Easy then to tile to a screeded floor, provided there is no movement to crack the screed.
These screeds are designed to be 5-10mm typically. I would check with the likes of Mapei, Ardex etc for a spec from them including the adhesive as well if you want a 'system' from 1 manufacturer

 

[Phillay]

There is bounce in the floor, yes, which is my immediate concern. Not in all areas, but as you move around the room, some parts creak slightly.

The floorboards were nailed when laid, so there is the possibility I could drive screws into every board to attempt to make it more stable.

 

[Ajax123]

If there is deflection overlay it with a smooth board and lay vynil tiles instead. Alternatively if no deflection overlay it with hardibacker glued and screwed and tile on that.

 

[Mark S]

Phillay
with the deflection/movement you have described, a glued and screwed board would seem the best option pre tiling