Tiling & electric UFH onto new screed

[stooley]

A 60-70mm deep standard sand/cement screed has just been laid in my new kitchen, sitting on 80mm insulation boards on top of a new concrete slab (laid 6 weeks ago). On the new screed I plan to lay (as soon as possible !) :
1) 10.5mm Econoboard foam insulation boards (stuck down with a suitable adhesive)
2) Thermonet electric UFH matting
3) Flexible latex
4) 600x600mm ceramic tiles (using flexible SPF tile adhesive)

I'm getting conflicting advice over how long I need to wait for the screed to dry before starting the UFH & tiling. My tile shop says "4 to 6 weeks", my builder says "a couple of days should be fine". I suspect the answer lies somewhere in the middle.

I've looked at other threads in this forum that mention "Ditra matting" and "BAL Green adhesive" as ways of shortening the wait, but have a couple of further questions :

1) Will my 10.5mm layer of Econoboard insulation boards achieve essentially the same thing that the Ditra matting is for, presumably being to separate the tiles from the screed so any slight shrinkage on drying doesn't disturb the tiles above ?

2) If the answer to this is Yes, what is the earliest I can go ahead and start to stick down the Econoboards on the new screed ? The room is well ventilated and, given the British summer, the temperature is typically around 20 deg C. If I wait a week, is that sufficient ?

3) Would I be wise to use BAL Green adhesive to stick down the Econoboards to the new screed ? Or is there something else I should use ?

All advice gratefully received !

 

[david campbell]

http://www.thermonet-online.co.uk/images/technical pdfs/Econoboard.pdf

i had a look through this and the only thing i could see was point 1
-make sure the surface is ready for tiling,this i would assume is waiting the neccesary time you could tile onto the surface which is 1mm per day drying time so about 6 weeks is a lot closer thn your builders advice!
i'm not sure how it works with using green screed or similar products and i would suggest phoning or e-mailing there technical dept

ps welcome to the forum

 

[nybor62]

imo i,would give it at least 4 weeks, before attempting to stick the boards on to the screed,

 

[dock]

Screed needs to be at least 3 weeks old (British Standard for tiling) but domestically should be a minimum of 65mm if it is a floating screed (which yours is)
stick your foam boards down with Mapei Keraquick
Secure your heating mat and blind with Mapei Fibreplan
Commission underfloor heating by bringing temperature up to intended working temp. at 5C per day and run for three days then switch off and cool for 24 hours.
Fix your large format ceramic in Keraquick
Grout minimum 3mm joints with Ultracolor Plus
Allow 21 days to dry out following completion of grouting and movement joints
Switch on heating as per commissioning process

The above follows British Standard and National Builduing Specification recommendations

 

[Dan]

"a couple of days should be fine" - Shocking coming from a "builder"!

 

[chris.tiling]

Using Bal Green Screed should allow you to tile a concrete screed a week after laying it, however, you wont be able to turn on the UFH for the full 6 week period to fully allow the screed to properly dry out. This is what BAL technical dept told me a couple of months ago anyway! If you use Mapei Keraquick, you should wait three weeks from screed being laid to start fixing the boards etc as per Dock's post above

And :welcome:
Chris