Undertile Heating - When to Switch On?

[Nick777VVV]

Can you advise whether I'm safe to turn my undertile heating on?

Screed was laid before Christmas. Then, two weeks ago, Marmox boards, the mats and self-levelling compound was added and limestone tiles were laid.

Can I press the button and switch on...or do I need to wait any longer. Maybe I'm being too cautious but I don't want to risk any tiles cracking etc!

Thanks
Nick

 

[Gazzer]

Bit more detail needed....How deep was screed? What type of screed was it? what was the date it was laid?
Were the heating mats self levelled over or tiled to direct ?

 

[Nick777VVV]

There's a concrete base over which has been laid a 600mm Celotex insulation layer. I can't tell you what the screed mix was but it would have been about 300-400mm above the Celotex. This was laid around the 18th Dec, so getting on for two months.

The heating mats were self-levelled before tiling.

Hope this helps.

Nick

 

[Gazzer]

300-400mm ??? so thats over a year drying time ?????
1 day per mm

 

[Nick777VVV]

Did I say 300-400mm?! Should've read 30-40mmm!

So is that the Golden Rule? Allow 1 day for each 1mm of screed?

 

[Gazzer]

Thats pretty much a rule of thumb but err on the plus side.

Was any decoupling matting used before tiling with Limestone. A lot of tilers insist on this when using stone and UFH.

Anyway the heating can be turned on slowly after 2 weeks following the tiling and grouting being finished. The heating should be turned on slowly and increased daily by a few degrees until full working temperature is achieved.

 

[Nick777VVV]

No, no decoupling matting. I was advised that Marmox would do the job of both insulating and decoupling (the insulation boards cross three substrates: the screed, quarry tiles and ply).

 

[White Room]

Marmox as a decoupling, new one on me...I thought the screed laid over insulation boards was 65mm minimum.

 

[Nick777VVV]

Ah. I was told that the Marmox boards would serve to counter any movement in the substrates and that no matting was needed... It's all down now so too late to go back...

 

[Gazzer]

All you can do now is turn on slowly as I stated and hope all is well.