Drying time for rapid set concrete please - Tile Advice

[wayfoward]

Hi, got a job coming up next week of tiling on a rapid set concrete floor with a pipe based under floor heating system fitted. Large format 600 x 900 x 20 natural stone tiles are being laid on top. Been told by the builder the concrete is being laid on the piping this Friday and I should be able to tile on it the following Monday. This seems too soon to me, especially in this colder weather. It's in a new extension and totals approx 80m squared. No heating till the UFH can be fired up. I'm worried about possible shrinkage problems if I tile on it too soon. Also not sure about possibility of decoupling / using ditra mat over a heating system.

Advice required about how long before starting tiling and should I advise builder they should put a large de humidifier in the room, cheers.

 

[Ajax123]

Sounds like a nightmare in waiting...

 

[Dumbo]

Don't know about the screed but ufh needs to be commissioned before tiling

 

[J Sid]

you need full spec on the concrete being put down, may need the surface sanding. As said, the ufh needs commissioning, and yes Ditra.

 

[Flintstone]

Lots of potential issues here. Need more details on the screed, but whichever screed it is it shouldn't be tiled on until the heating has been commissioned properly.

 

[wayfoward]

Thanks for your replies, a nightmare in waiting is exactly what I want to avoid being associated with. Forgot to mention that, being an extension, half the floor was old concrete (insulation issues?) and half the actual extension when I looked in 2 weeks ago. I see major issues with the floor heating crossing the two. I don't know if its the builder or a specialist who's installing the pipework.
Will advise the builder to zone floor in 2 halves if possible so floor heating is even. I should point out I just tile and know nothing about how building / heating system should be done. Just googled commissioning UFH for an idea of what's done. Came up with this:

Underfloor Heating and Screeding | The RIBA Zone | Flowcrete UK - http://www.flowcrete.co.uk/campaigns/flowcrete-and-riba/underfloor-heating-and-screeding/

Will also advise builder floor needs to be commissioned before I start tiling. Builder / customer won't like that, as I'm basically telling him / them I won't start tiling to the new year. I'm thinking ditra mat for sure now, bearing in mind all the above. Going to stop by the job this morning for a chat as I'd like to think the builder would like to avoid a nightmare in waiting too.

 

[Time's Ran Out]

Unfortunately neither will be interested and will find someone else!