Multiple sub-floor levels...best way of getting FFL?

[Rod Evans]

Hi all,

We are needing to complete work on our old place, as my better half is battling with Parkinsons and mobility could become an issue. Therefor I'm looking at floor levels.

We're looking to lay Karndean and Tiles in the kitchen area which is a suspended floor, and I'd like to have the FFL at the same height in case theres the need for wheelchairs etc.

I'm installing celotex and then wet UFH between joists, then adding 18mm T&G ply..then another 6mm of ply (to satisfy Kanrndean warranties) ...then 3mm of Karndeanan. This means a total thickness of 27mm above joists excluding the Karndean adhesive.

Any ideas on how I could add floor tiles into the same same floor area / thickness?

Many thanks

 

[Dumbo]

6mm Hardie backer to strengthen floor prior to tiling on top of ply 3-4mm adhesive say 10mm for tile equals 19-20mm above ply therefore you need 18mm ply on top of existing ply to come close .

 

[Rod Evans]

Thanks JCR

Just checking I've understood.
From joist...

18mm T&G ply for structural element
6mm Hardie backer
4mm adhesive
10mm tile

total floor = 38mm above Karndean

That correct?

Is Hardie board OK with UFH?

 

[Dumbo]

No
38 above joist
Therefore you need thicker ply under karndean

 

[Dumbo]

Also your chosen tile may be 12 mm which would alter calcs .

 

[Dumbo]

Sorry forgot about ufh
Hardie is better than ply .
36 mm of ply would be an issue

 

[Rod Evans]

Sorry...I meant to say 38 above joist !!
So that would be 10mm above the Karndean level, which may not be too bad if she really wants tiles around the wet areas and cooker etc.

How would the join between the two work?

 

[Boggs]

What about 22mm t&g No More Ply in place of 18mm ply and 6mm Hardie.
That could get you down another 4mm.

 

[Waluigi]

22mm NMP on the whole area.

Then tile directly on top of the NMP. Let’s say that takes you up 15mm above the NMP

So we have to get the LVT area up to the tiles;

Add some 6mm cement tile backer board glued and screwed on top of the NMP, that’s another 8/9mm up. Then 3mm of Karndean

That’s 8/9mm + 3mm = 11/12mm so just 3/4mm to make up which can easily be done with the Vinyl fitters latex and will comply with Karndean installation instructions. A bit of feather finish might be needed .

 

[Just Rizzle]

id use karndean through out will be easier to maintain than tiles and due to its flexability will be easier to lay especially if your using wheel chairs

 

[Rod Evans]

Thanks for your help with this gents..

I'm with you on Karndean throughout as that was the original plan, but my significantly better half looked lovingly at some tiles, and I'd love to be able to sort that out for her!

I think i forgot to mention tvst tbete are three otber rooms linking to the kitchen which I'll also be levelling to. Karndean worked out OK across all of it.

Basically I was thinking to put an 'L' shape area of tiles around the sink...dishwasher ...cooker area and I reckon 5ish mm of level change would be OK. My concern would be the join breaking up over time...is that likely?

 

[Rod Evans]

Forgot to say that I was looking to keep the matetial level above tbe UFH as small as possible to maintain thermal efguciency etc....maybe that's not possible?

I was told ply is better than chip and 22mm Ply will take MUCH longer to warm up than 18mm...surely it can only be approx 25% ish more....unless 22mm ply become an insulator with tog levels etc?

 

[Just Rizzle]

if you want it level you could reduce down rather than build up take up t and g put in extra noggins and and over lay with hardy backer 2 layers of 12 mm board to get your levels even.

 

[Rod Evans]

Thanks Ray

Would 2 layers of 12mm... cross bonded..be regarded as a structural floor and equivalent to 18mm t&g?

 

[Just Rizzle]

just read your post again could you not use t and g and use hardy backer boards 2 layers of 12mm bonded together with fiberous adhesive and screewed this will give you a better heat transfer than putting insulator down ie wood for l v t and tiles you can screed over the backer board for smooth surface to put karndean down