Tiling over wet UFH between joists - Tile Advice

[CJ]

I need to quote for a job, as the title says........over wet UFH between joists. Much the same as the link I've put up.


Insulation, fitted between joists.....pipes laid, maybe with or without spreader plates. (Not sure as yet which way customer is doing this) then the floor would be overlaid with ply.....or maybe something else??? Then I mentioned putting down Ditra/Durabase.

Tiles they mentioned where 450x450 marble?? But not totally sure on that.

I have done this type of floor before, but some years ago and can't remember how I did it.

Any ideas?

 

[Chalker]

Forget the ply etc.
Just fit fermacell gypsum boards onto the joists. Prime and tile.
Make sure they have either used spreader plates or encased the pipe work with a solid mass.

 

[Dumbo]

Personally myself over board with 12mm ply making note of where pipes are then cross bond with 12mm ply glued and screwed at 150 centres then durabase and tile . Reason for ply is to add structure . Reason for two sheets no continuous joint from from joist to top then durabase for lateral movement .

 

[Old Mod]

Schluter will NOT guarantee an installation like this over ply.
As to other materials, I'm afraid I don't know.

 

[Kyle Knowles]

I laid 100m over this kinda system tjis time last year and had no issues as yet and that was 18mm ply over the pipes in trays with ditra then tiles with a s1 adhesive which isn't by the book but you all know what builders are like lol

 

[Kyle Knowles]

I wouldn't advise using 2 layers of 12mm ply it will take forever to heat up ....

 

[Kyle Knowles]

Hardi make hardifloor for this kinda installation

 

[Chalker]

Plywood will insulate. A solid mass is needed to transmit heat.
The primary function of ufh is to heat the room. any surface is just a decoration and should be able to transmit the heat too.
Thre should be a substrate that allows heat to pass through, does not suffer from large expansion and can support the weight that will be applied to the floor

 

[Dumbo]

Let's just bear in mind there are a lot of houses with wet under floor heating 22mm chipboard underlay and carpet . Yes I agree wood is an insulator and doesn't conduct heat as well as some other materials but it not as bad as some of you would make out . Oh and it works fine in my house and also through the engineered oak flooring .

 

[Chalker]

Let's just bear in mind there are a lot of houses with wet under floor heating 22mm chipboard underlay and carpet . Yes I agree wood is an insulator and doesn't conduct heat as well as some other materials but it not as bad as some of you would make out . Oh and it works fine in my house and also through the engineered oak flooring .

Yes it works, but not very efficient.

 

[CJ]

In an ideal world, something like the structural Hardifloor would be perfect as it offers high thermal conductivity with minimal thermal resistance and is also fairly stable with regards to expansion and contraction - So perfect to tile.

Structural bases made out of timber work well too - but as Chalker said it does take longer for the heat to come through initially because the wood does have a higher R value than something like fermacell - but because of this it retains heat into the room better once it is in.

Again, as Chalker has said the pipe is essentially a heating element but because of thermal bridging it will do very little to warm the space without a means of spreading the heat over the whole floor. Don't even think about trying to run the system without the use of a heat diffuser "spreader" plate or (provided the joists are strong enough to take the weight) a screed over the pipes between the joists.

Whichever, install method / material is chosen for the UFH I would advocate a decoupler on top as a matter of course because we all know how fragile any natural stone can be... At least if there is a membrane present the tiler has done everything in their power to protect the top layer.

Thanx for that David.

Have been looking at Hardifloor, but at 37mm thick, plus membrane, and tile, that will raise the floor by quite a horrendous amount. Poss 52mm? Wot else do you suggest?

 

[J Sid]

Thanx for that David.

Have been looking at Hardifloor, but at 37mm thick, plus membrane, and tile, that will raise the floor by quite a horrendous amount. Poss 52mm? Wot else do you suggest?

thought in came in 19mm or 22mm , no?

 

[Old Mod]

It does Julian.

 

[CJ]

Slight size typo........not sure which bit I read.

 

[Dannym80]

HardiFloor is the best way to go, no expansion or flex issues that you'd have with ply as its far more stable. As some have already said, its thermal conductivity is better than ply also. It does come in 19mm or 22 mm so height shouldn't be an issue. With marble going down I personally would fit ditra or durabase everytime over any ufh.