Levelling a chipboard floor . - Tile Advice

[David Bingham]

Looking for some advice ,
Upstairs bathroom is chipboard floor .
I planned to hardiebacker then tile but the floor is out 20mm one way and 12mm the other way .

Floor needs to be level as there’s a traditional rad that has legs and 2 units going in and you will notice it .

What’s the best way of Levelling out?
My first thought was to rip floor up , level and ply it but the airing cupboard wall sits between two joists and the other joist is under neath the hot water cylinder so wouldn’t be able to get under it to support the wall .

Would thick bed adhesive do it? And if so Is it a case of using he thick bed adhesive trowel on the back of tile and on the floor to build it up?
They are glazed porcelain 450 x450 floor tiles

 

[LM]

Make sure there’s no deflection and that the chipboard is screwed (not nailed) well to the joists. Fill any gaps and make a dam with expanding foam at the doorway. There are various manufactures that have a grit primer and fibre levelling compound which could then go on top of the floor.

 

[Flintstone]

Remember to board it first before levelling ! Hardie backer is fine, then do your levelling. Don't try and correct it with building up the tile adhesive as it's a pain and it's not the right way of going about it.

 

[Waluigi]

If the chipboard is coming up then bolt some timber to your existing joists.

Often when doing a bathroom, you need to adjust pipe work below the floor so the chipboard would have to be partially taken up anyway and chipboard doesn’t lend itself well to being taken up in pieces here and there.

The only thing you sometimes need to consider is that you hope there is a joist running under your walls. Had this plenty of times. One false move and the partition wall is in the kitchen

 

[On one]

Over what distance is it 20mm and 12mm out?
Over the length of the radiator it actually won't be 'out' that much will it?
Wall mounted units would also take out the floor, not being level out of the equation.
Trying to level that floor might mean quite a step into the room(if the floor runs up from the door)

 

[Waluigi]

Yeah, usually Bathroom Furnitire has a plinth. The plinth is scribed to the floor.

 

[David Bingham]

It’s 20mm from left to right and 12mm from back wall to door , luckily the carpet is quite high tho as they had a thick laminate floor in before .
Unfortunately the level would show as it has ornate plinths etc on it also it’s a roll top bath with claw legs so ideally got to be bang on .

It’s looking like hardiebacker down and self levelling is gonna be the best option.

 

[LM]

It’s 20mm from left to right and 12mm from back wall to door , luckily the carpet is quite high tho as they had a thick laminate floor in before .
Unfortunately the level would show as it has ornate plinths etc on it also it’s a roll top bath with claw legs so ideally got to be bang on .

It’s looking like hardiebacker down and self levelling is gonna be the best option.

With Mapei eco prime grip and renovation screed you won’t need Hardie backer.

 

[David Bingham]

Awesome I’ll look into that
Thanks for everyone’s replies, has been a big help

 

[Solidfixpro]

I would cut the chipboard on the centre of the joist nearest the airing cupboard wall, then remove the rest. Pack the joists level with plenty of plastic packers (stick them on with hot melt glue or gripfill) and then screw down 18 or 25 plywood really well. Use a strip of thin plywood to make up the bit by the problem wall, packed level and gripfilled and screwed in place. Boom a nice level floor without getting wet!

 

[David Bingham]

Sounds like a good option! Have already bought the hardiebacker etc now and I’m doing it today ,sounds like a good option for next time tho! And just feel it will be the strongest option with the bath sitting on it and and gives me more workability on the tiles I’m laying.
Thanks for the reply !