wet underfloor heating problem

[Perfect Tiling]

Morning all. I have got a floor to tile that has a few issues. The tiles on it just now have been down for a few years but a lot are loose or cracked. The sub floor is constructed of joists with ufh pipes between them on osb above glasswool. The pipes are then flushed off to the top of the joists with dry sand and cement. The problem is that on top of this is 2 15mm layers of ply which is glued and screwed down. Surely this is insulating the ufh...customer says floor not that warm. I feel that the pipes are so hot that the ply is distorting and cracking the tiles and adhesive. Is there a better base than ply I can use. Plan would be to remove ply and lay something similar to hardibacker that passes heat, is strong and wont distort. Only other option is to advise against tiling and go for something like amtico etc. Floor around 18 sq mtrs.

 

[One Day]

Painful floor construction! Only thing I can think MIGHT be strong enough would be Hardi's new floor boards. http://www.jameshardie.co.uk/hardiefloor
Normal hardi would be too weak.

 

[jonnyc]

Painful floor construction! Only thing I can think MIGHT be strong enough would be Hardi's new floor boards. http://www.jameshardie.co.uk/hardiefloor
Normal hardi would be too weak.

i spoke with hardie about the new board they do for same make up and this seesm to suit the job.
have yet to try it though

 

[Diggy]

Carpet

Diggy :0)

 

[J Sid]

I've tiled a few floor over the year with a similar construction. Instead of the dry sand and cement the builder use clay balls about the size of peas. Can't remember what the product was called but held the heat and disrupted it very well. Again 2 layers of ply, joins staggered, uncoupling membrane then stone. Worked very well. Hope this helps

 

[Chalker]

Lay fermacell on top. It is made for this, works well with underfloor and you can tile straight onto it.

 

[Perfect Tiling]

Many thanks to all so far. Is fermacell similar to hardiebacker. Ive just been on the hardibacker site and seen their hardiefloor product. It seems a good solution to remove the ply as some is delaminated anyway and replace with the hardiefloor which will transfer the heat and stay stable. Just like hardibacker it is tiled onto directly.

 

[Chalker]

Fermacell
http://www.fermacell.co.uk/mobile/en/content/2421.php