First floor ufh - problems

[Reetster]

Morning everyone

Our house build is progressing nicely and we have recently had the ufh installed both downstairs in the traditional way (stapled to insulation, screed on top) and also on the first floor, in 25mm in between batons etc.

We then screwed and glued 6mm ply to the batons to protect the screed and provide a sound surface for tiling/flooring.

Although the dry screed was swept and hoovered before the ply was laid The problem we are now finding is a 'crunching' noise when you walk around, between the ply and the screed.

Has anyone who has used this system experienced similar problems? Does it go in time? I don't want to get to a position of getting carpets etc down and still hearing the annoying crunch.

Any advice/experience gratefully received.

Many thanks

[ProDave]

6mm ply WILL bend, it is not a structural floor.  You would need at least 18mm to be self supporting between the battens.

 

Often the screed between battens is a weak dry mix laid as a heat spreader and not expected to take any load.  What is under the screed?  That might only be thin ply or OSB not expecting it to take any load.

 

A similar floor make up here but we used 20mm engineered oak floor planks that are self supporting and place no load on the screed.

 

EDIT: If you are planning carpets then put chipboard flooring down, 18mm if the joist spacing is 400mm or if joists spaced 600mm then you will need 22mm.

[Reetster]

Thanks for your reply Dave.

The screed is laid on 22mm chipboard on 600mm spaced easy joists (253mm depth)

I guess the thinking was although the ply is only fixed to the battens, as they are flush with the screed I didn't expect the movement we are seeing.

I have heard some people lay underlay then carpet straight on the dry screed.

The positive thing is that we haven't laid the flooring yet, so worst case could rip the ply up before we do.

[Temp]

I sometimes think that companies like Hardi (makers of Hardi tile backer board) are missing a trick. Isn't there a market for a cement board that..

 

* Is strong enough to be used over joists (or battens)

* Rigid enough (over joists) to take tiles.

* Conducts heat well enough for UFH. 

* Water resistant for wet rooms.

 

Or is it just not possible to make one?

 

 

[Temp]

How about this stuff..

 

https://www.tilingsuppliesdirect.co.uk/product/no-more-ply-tongue-groove-board-18mm-22mm#.YF50wMinw1I

 

 "No More Ply Tongue & Groove Board is a thicker version of the standard No More Ply Tile Backer Board. It is a fibre cement board with a tongue and groove connection that is designed to directly replace floorboards on joists."

 

Does it conduct better than plywood?

[PeterW]

8 hours ago, Temp said:

I sometimes think that companies like Hardi (makers of Hardi tile backer board) are missing a trick. Isn't there a market for a cement board that..

 

* Is strong enough to be used over joists (or battens)

* Rigid enough (over joists) to take tiles.

* Conducts heat well enough for UFH. 

* Water resistant for wet rooms.

 

Or is it just not possible to make one?

 

 

12mm CemBoard or MagPly would do that overlay with support from the battens but it’s going to be eye watering in price. The NoMorePly product can replace the whole floor and it’s good but again it’s expensive. 
 

6mm ply won’t work in the way it’s been used by the OP as it’s far too flexible.