Ditra And Underfloor Heating

[jonnyc]

Had an interesting point come up this week.i was trying to put architect off using anhydrite screed and suggested that I could fix ditra on sand cement screed after approx 5 days. I know you could do earlier. Architect then asked how long you need to leave screed before putting on underfloor heating even though stone fixed after a week. Good point . What do you reckon?

 

[J Sid]

Hi Jonny
Wet ufh?
Floor area?
Sure Ditra would say No.
If you are happy to have a go I think it would depend on how much control / trust you have in the plumber with the floor temp / ramp up temp, when it is turned on.
Yes, I have done it, and was fine. Floor went on after about 8 weeks and was ramped up over 2 weeks slowly. I know and trusted the plumber and he went to site every other day to check temp.
I sure there will be a many you will slate me for doing it....... But in the real world sometimes you can't go by the book.

 

[jonnyc]

Been laying on ditra without heating commissioned for 25 years.schluter aren't bothered if heating not commissioned if when heating put on done do slowly over many days .they won't say how long you should wait. I know what I do but interested in what others rrvommend

 

[Time's Ran Out]

If the heating has been pressure tested then it will be fine to tile on the Ditra as you've suggested and also for the commissioning to be done slowly.
However what guarantee do you have that the client won't increase the temperature if the weather turns cold.
And as there is only word of mouth documentation that the zones have been set out with the correct insulation , how can you be confident of an even distribution of heat! Had a stone floor a couple of years ago showing 32 degrees in the middle and 12 degrees a metre from an outside wall.
We rarely get the right information prior to being asked to tile a screed. There needs to be regulation and a technical sheet provided down the line.
'It's a cement screed and wet underfloor heating ' - just doesn't work anymore.

 

[J Sid]

Yes John, as I said, you need to trust the plumber on jobs like this to lay it correctly and commission it slowly.
As above all keep the customer away from the controller.

 

[Dougs Third Go]

4 weeks, then 2 degC above ambient temp on thermostat for 24 hours then off for 24 hours, then on again raising temp by another 2 deg C more etc,,,,tbh, I think that's all we can ask for customer to do.