Flexi or not for tiling over screedboard on top of wet floating ufh

[deedee]

Hi Gang,

I have just had a wet floating ufh system installed - underneath it is the concrete slab and a 3mm layer of latex self levelling. On top of it I am going to lay Cellecta Screedboard 20mm, and I have been given conflicting advice about flexible adhesive and grout. Some are saying I need to use flexi because the screedboard will expand and contract when heated or not, and others day the substrate is rigid so there is no need. Please tell me what you have done and what you recommend!

By the way the tiles I am planning to use are 600x600mm polished porcelain.

Thanks,

Dee

 

[Ajax123]

Re: Flexi or not for tiling over screedboard on top of wet floating uf

Screed baord is a gypsum based material like a very dense plasterboard so in terms of thermal expansion and contraction relatively low. However it is a composite structure with loads of joints I.e. Between boards and is usually on timber which will move and flex. I am not sure on adhesives but my gut feeling says flexible is the way to go.

 

[cam_low]

Re: Flexi or not for tiling over screedboard on top of wet floating uf

if in doubt flexi it out !

 

[Chalker]

Re: Flexi or not for tiling over screedboard on top of wet floating uf

Why take any chances.
just use flexible, belt and braces.

 

[deedee]

Re: Flexi or not for tiling over screedboard on top of wet floating uf

Thanks for the advice. The screedboard people tell me that we have to leave a 5mm expansion gap around the room so they believe that there will be some movement horizontally. I guess there is no harm in flexi?

 

[mike1979]

Re: Flexi or not for tiling over screedboard on top of wet floating uf

What they said ^^^^

 

[Brian the Tile]

Re: Flexi or not for tiling over screedboard on top of wet floating uf

Flexible or even two part flexible plus flexi grout