Marmox board directly on top of Celotex/Kingspan?

[FresnoBob]

Potentially a silly question which I haven't thought through, but my head is absolutely killing today lol.

If the subfloor is completely level (just humour me here lol), and there's Celotex/Kingspan already laid (no screed), is there any reason why Marmox board (or other tile backer board) couldn't be laid directly on top of this instead of plywood?

 

[geraint]

Potentially a silly question which I haven't thought through, but my head is absolutely killing today lol.

If the subfloor is completely level (just humour me here lol), and there's Celotex/Kingspan already laid (no screed), is there any reason why Marmox board (or other tile backer board) couldn't be laid directly on top of this instead of plywood?

Yes....

 

[FresnoBob]

Potentially a silly question which I haven't thought through, but my head is absolutely killing today lol.

If the subfloor is completely level (just humour me here lol), and there's Celotex/Kingspan already laid (no screed), is there any reason why Marmox board (or other tile backer board) couldn't be laid directly on top of this instead of plywood?

Yes....

yes there's reasons? indulge me lol

 

[Richard C]

The floor will not be stable enough....

No doubt the dick will be along soon to lecture you about all and sundry about tiling..... yawn yawn...

Amazingly, the geriatric is not spouting his usual inaccurate troll drivel but it’s rather difficult to troll if no one else has posted & I’ve been busy today . He eventually got there & I actually find myself agreeing with at least a part of his post; you are basically constructing a “floating floor” & it doesn’t really matter if it’s ply or backer board. This needn’t necessarily be a problem, it depends very much on what type of floor your proposing but will have restrictions.

 

[^woody^]

I can't see why it can't be used, subject to properly installing it as with other boards

 

[diggerjones]

done this loads of times, concrete base, visqueen, kingspan or celotex. then we have put flooring boards down cant remember what you call them. anyway boards down glued together and tile on top of that.

 

[Richard C]

Thank you for quoting me.... Thought I was losing the plot....Mr mod is following me tonight... Even deleting my posts that answer a question....

How sad is he......

I have no problem with recognising or quoting accurate & good advice but that’s not what you’re about. The majority of your posts are insulting, disruptive & mostly inaccurate; although you never admit so even when presented with hard facts. I don’t think you’ve lost the plot at all, just that the plot you choose to follow is always disruptive & has no bearing on fact &, for that, I’m totally behind the mods; if disruption is all you ever intend then the sooner your rid of, the better.

 

[FresnoBob]

Oh dear, what have I walked into lol

The idea came to me purely because we have limited depth to work with....it's very very borderline whether we could fit in insulation and screed and get it all level....it's more likely we'll end up with the finished floor height exceeding the front door step.

....the original floor set up was an uneven subfloor, polystyrene and chipboard, which was about as level as the sea.

I figured Celotex and Plywood would be a more stable upgrade to the original polystyrene/chipboard setup (if not ideal)....this got me thinking if Marmox would be both more insulating and more rigid than the plywood....along with not having the expansion problems of wood.

We're hoping to lay ceramic tiles (I appreciate a floating floor isn't an ideal base), but I'm hoping the combination of a very level subfloor, upgraded insulation, more rigid base for the tiles, along with flexible adhesives and the like will result in minimal problems (emphasis on hope lol).

The rooms themselves aren't massive (small hall 3sqm, new downstairs toilet 5sqm, and a kitchen 12sqm).

Edit: I'd also be looking to tape all the insulation and backer board at the joints