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How best to dry a ufh screed


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My 55mm screed went down March 11th, approx 80 days ago but it's still showing circa 90%rh with no movement downwards

 

I've had the laitance sanded off about 20 days ago and the heating was switched on around 15 days ago - currently running at around 21degree floor temperature. 

 

The period since the screed going down has been very dry and I've had the windows and doors open with lots of through draft.

 

What else can I do to speed up the drying process? And how hot should I take the floor temperature?

 

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My understanding is that laitance inhibits the process. Might be worth comparing readings between an area with high traffic (hence laitance would have worn off earlier) vs. an area with no traffic.

 

I would expect 80 days to be sufficient, especially over the relatively dry spring we have had.

 

I came across an interesting internet article that said air flow was a key factor, in our case I ran the MVHR to do this. I will see if I can find the link.

 

Ufh flow of 21C is not much higher than ambient. Have you asked your screed supplier what temperature they recommend?

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From my screed supplier:

"Force drying of a Liquid Screed can begin as early as 7 days following installation of the screed by various methods. Commissioning (heating & cooling procedure) of under floor heating systems. Set flow temperature to 20-25ºC, maintain for a minimum of 3 days and then gradually increase the temperature in Max 5ºC increments to maximum operating temperature. This should be maintained for a further 7 days (water temperature should not exceed 55ºC for screeds), prior to returning to ambient temperature again in Max 5oC increments"

 

Though I would check with your supplier first. And it would make for an uncomfortably hot build site!

Edited by ragg987
typo
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