Under floor heating (wet) liquid screed

[arfurrrr]

Hi ,

I`ve had a couple of ideas thrown at me from some other tradesmen , non of which are tilers .

One has said , just tile onto the screed (liquid version) and the other has said , there is a mat you can buy which you tile onto and then if the screed cracks the tiles don`t

but what is the experience of you guys n girls who tile ? and what is this mat thingy called ?

TIA

 

[Karis]

One has said, just tile onto the screed (liquid version)

All screeds start of liquid but I think he's talking about a self levelling screed (SLC). But you wouldn't normally use it as the main heating screed & it doesn't remain liquid for very long. If he's talking about an SLC Although not essential, a very good idea when tiling over an electric cable/mat system but not necessary if you’re tiling over a wet system screed. This is usually an anhydrite (Gypsum based) screed used for it's resistenace to cracking under thermal shock; can you confirm.

and the other has said , there is a mat you can buy which you tile onto and then if the screed cracks the tiles don`t

He’s a reasonably informed guy.

but what is the experience of you guys n girls who tile ? and what is this mat thingy called ?

“Mat thingy” is an uncoupling membrane http://www.schluter.com/6_1_ditra.aspx
& you would be silly not to have one with a wet UFH system.

 

[tpt]

i'd echo what karis is saying.

If it is anhydrite with wet UFH you really need at least an s1 flexible adhesive, but you should consider and s2. uncoupling membrane best but if you go onto the screed you MUST have a moisture test done, remove the fine talcy stuff and then use neat acrylic primer first to stop the gypsum reacting with the cement based addy.