Tiling 25mm flagstone over chipboard - Tile Advice

[Chris303]

Hi all.

This isn’t a sob story, just an unfortunate truth I have stretched myself to in inch of my life after my divorce to get my own place for me and the kids so truth is I’m absolutely skint so I’m going to have to try and do some of these jobs myself.

I’m learning as I go so please bare with me

I want to tile my kitchen / dining / hall with 25mm flagstones.

The floor is currently 22mm caberfloor chipboard over 400mm spaced joists.

There appears to be little movement currently on the floor, the joist spacing I feel helps with that and I’ve just boarded the loft space with the same. There doesn’t seem to me like much area for deflection with the spacing that I can see.

The flagstone supplier seemed to indicate their installers have installed it directly to chipboard using a bed of flexible adhesive and matching flexible grout.

Do I need 6mm backer board still?

Do I need Schluter decoupling membrane?

Can I use the membrane on its own without the backing board?

Happy to hear thoughts and I’ve searched but many of the posts about chipboards are over a decade old so not sure where the tech is now.

Hope to hear back.

Thanks all.

 

[Kastar UK]

6mm cement board screwed down every 200mm will help stiffen it up plus tile and adhesive .
A bouncy tiled floor will be a problem
They sprout flexible but really we are aiming for as rigid as possible , using materials that potentially do flex
Loft timbers and Suspended timber floors cant really compare tbh
Depends how bad the movement is ??
Take up the 22mm boards to see what s going on ?
Are they fixed down securely to begin ?
Why is it moving ?

 

[Chris303]

6mm cement board screwed down every 200mm will help stiffen it up plus tile and adhesive .
A bouncy tiled floor will be a problem
They sprout flexible but really we are aiming for as rigid as possible , using materials that potentially do flex
Loft timbers and Suspended timber floors cant really compare tbh
Depends how bad the movement is ??
Take up the 22mm boards to see what s going on ?
Are they fixed down securely to begin ?
Why is it moving ?

I think the movement there is because they’ve cut hatches in a few places to access the crawl space after the floor was laid during construction. It’s a new build.