Bathroom Chipboard floors - what do you do??

[SteveyJ]

Hi all

For years now, I've been over plying chipboard floors in bathrooms, and never had any failures (to my knowledge ) and all is good, but recently customers have been talking to me about the raised height level etc, especially if I then overlay 4mm marmox board to repel the UFH cable heat upwards to the tile then SLC etc. So really just wondered what you all regularly do, alot of the time removing existing chipboard floor isn't cost or time effectiove especially if its tongue and groove and runs under partition walls.

So what thickness WPB do you use for overplying?
Never used it on timber but will a de-coupling membrane work well on existing chipboard?
Can I use a thinner ply if I lay a de-coupling membrane over the top?

Thanks Steve

 

[Gazzer]

Why not cement backer boards ? 6mm.

 

[SteveyJ]

Why not cement backer boards ? 6mm.

I was told ages ago that you cant just use backer boards alone as a over-plying method??? By Marmox (i'm sure but definitely by my tile shop)???

And if you mean like Hardi-board - never used it before - can this be used is it very different to Marmox/Wedi etc?

 

[AliGage]

Current project i'm on i couldn't cut much of the floor out. Managed to get out where the wet tray was going, but the rest was pretty sound so i glued and screwed 12mm hardie. 6mm shallower than putting 18mm ply over and the floor is as solid as a rock!

 

[Gazzer]

The original floor has to be solid and deflection free , backer boards can then be used, They do not IMHO add any strength to the floor.

 

[Rookery]

Hi all

For years now, I've been over plying chipboard floors in bathrooms, and never had any failures (to my knowledge ) and all is good, but recently customers have been talking to me about the raised height level etc, especially if I then overlay 4mm marmox board to repel the UFH cable heat upwards to the tile then SLC etc. So really just wondered what you all regularly do, alot of the time removing existing chipboard floor isn't cost or time effectiove especially if its tongue and groove and runs under partition walls.

So what thickness WPB do you use for overplying?
Never used it on timber but will a de-coupling membrane work well on existing chipboard?
Can I use a thinner ply if I lay a de-coupling membrane over the top?

Thanks Steve

What thickness ply have you been using up to now?

 

[Marksmithtiling]

6mm Hardie glued with spf and screwed ,after making sure floor is deflection free, seems to work for me.

 

[Rookery]

6mm Hardie glued with spf and screwed ,after making sure floor is deflection free, seems to work for me.

Thats generally my approach too.

 

[SteveyJ]

Sorry to re-ignite this but posted then had computer issues and now all back and running now so will re-comment if ok?!?!

So is that the route you guys all go - 6mm hardi, but if its going over existing timber tongue and groove for example or even chipboard you cant use an SPF to stick it can you???

Could I use say a thin overply, then self-level if required then some ditra??

Steve

 

[macten]

Yes you can mate, the adhesive is there simply to fill any voids, it's the screws that do the sticking!
I use Hardi 250 or No More Ply and use No More Ply's mega strength glue to stick em down with and then use their screws.
Don't use screws over 25mm or you risk hitting pipes, 25mm turbo gold from screwfix are a cheaper alternative.

 

[Alan.P]

As a wise man I worked with once asked me, what's the point of using a flexi addy and then screwing the sheets down ???

 

[AliGage]

As a wise man I worked with once asked me, what's the point of using a flexi addy and then screwing the sheets down ???

Because you'll never make a wooden floor 100% deflection free. You also need to allow for the natural expansion and contraction of the timber.

 

[Concrete guy]

I always used to fit 12mm Aquapanel glued and screwed then tape the joints. But most of my work was stone so I wouldn't consider 6mm.

The idea of using SPF is not only to deal with shear loads but also vibration and deflection.

More often than not I would get oak thresholds made to the thickness of the door to take up and height issues, either flat or sloped to take up any height issues.

 

[Two-Trowels]

Bit confused here - you have a bathroom floor that is boarded with plain floor boards, or even T&G - it's pretty solid but there will be at least some movement, so you decide to overlay with a cement board of some kind and laid on a bed of SPF to take up undulations and also enable you to flatten and level the floor at the same time, handy bonus.

Why do you screw it down too? anything that comes into contact with SPF is usually stuck fast :smilewinkgrin:

I think I've worked out that SPF actually means single part flexible :hurray: I usually use Mapei Pro Flexible, I wouldn't want to try and take up cement boards stuck down with this stuff - are screws really necessary?

 

[kilty55]

hi there yes the screws are needed

 

[macten]

The adhesive is there just to fill the voids.