Comissioning of wet UFH

[kaharrison9]

Good Evening.

I'm sure it will have been covered but have spent 1 hour looking.

Soon have a wet UFH system on an anhydrite screed coming up and would like to know the plan for the comissioning of the heating system.

At what temperature i start at,over how many days,what the maximum temp i go to.how long it's then turned off.etc.

Many Thanks

Kev

 

[bugs183]

This will be a post worth watching as its very relevant at the moment.

 

[Ajax123]

Start at approx 20 to 25 degrees for three days. Then increase by max 5 degrees per day up to maximum of 55 degrees. Leave at this for minimum three days (no maximum) and then reduce by maximum five grees per day down to 20 to 25 degrees (some systemss dont allow below 25) then switch off for three days and then moisture test. If dry, prime and tile assuming prep done to remove construction detritis from screed.

 

[bugs183]

Hi Ajax.
Good to have someone here that knows about poured screeds, and is help in high regarg by all the members/
When you say start at 20-25 degrees, how long after the screed has been poured can you start this?
And in your opinion what is the best methods/methods to moisture test?
Cheers.

 

[Ajax123]

You can comission after 7 days. If you are using the heating to force dry the screed as well you should leave it up at its highest temperature for a week to ten days and make certain it is well ventilated to remove the moisture from the air above it.

Moisture testing is best done with a flooring hygrometer. Cost approx £80 but well worth the cash. This test takes about 48 to 72 hours to do properly.

What coverings are you putting down?

 

[kaharrison9]

That's great Ajax.

So valuable this sort of advice.

When we say degrees i take it that it's the atmosphere temperature not the screed?

I am looking at a digital floor hygrometer at £97 at www.yorksurvey.co.uk which is local.

Would this be fine?

The screed was poured in December,sanding tomorrow,5-1 lightly primed with N+C primer,ditra down with N+C gypfix,then an S1 cement adhesive between the Ditra and tile.

Can you see any flaws?

Many Thanks

Kevin

 

[Ajax123]

Flow temperature of heatin system. This is usuall set either at the boiler or he manifold and the room stats will nedd to be over ridden or tuned up full.

 

[Ajax123]

And the loor hygrometer is perfect.

 

[kaharrison9]

Much appreciated.

Kevin

 

[bugs183]

Cheers.Really helpful advise that.
I'll be getting an hydrometer asap, as poured screeds are taking off around here.
Any tips on using one of those whilst we're picking your brain????

 

[Del W]

"The screed was poured in December,sanding tomorrow,5-1 lightly primed with N+C primer,ditra down with N+C gypfix,then an S1 cement adhesive between the Ditra and tile."

I thought with gypfix you didnt have to prime ?

 

[Ajax123]

Depends on how porous the substrate is but generally you dont.

 

[Del W]

Some times you prime.some times you dont,a little more info on this sometimes difficult topic for us all.Gypfix.

Not directed at you Ajax,cause your the man when it comes to this subject,youve helped me and no dought many others.

http://www.ncdirect.co.uk/pdf/gypfix.pdf

 

[Ajax123]

I guess the key here would have to be if in doubt prime but seek gidancefrom the manufacturers if you can. A very simple test to do would be thewer drop tet. If you put a drop of water........not a bucketful, just a drop, on the screed surface and if it just sits there the screed is not porous. If itsoaks in quickly and disappears then it is porous. Generally speaking the low laitance screeds will not be particularly porous. Hope this helps

 

[bugs183]

I knew anhydrite screeds had their issues but having followed this and other threads then there are a few questions i must ask you Ajax, as i've never known anyone so knowledgeable about this stuff!
Right, As a tiler i have turned up at a job to measure, and i find its an anhydrite screed. I guess i need to ask:
What make of screed?
How long has it been down?
What thickness is it?
Does it have underfloor heating?
Now comes the tricky parts.
Would you advise i go to the manufacturer and gather ideal drying times and moisture content before laying?
If a floor had no underfloor heating, so can't be forced dried, i take it the customer has to wait until the screed is deemed dry enough (from moisture test), this could take over a year, from what i read.
And if the screed has underfloor heating i take it it is recommended that the heating is fully commissioned (as above), before laying any tiles?
Many customers have the floor screeded whether it be sand and cement or poured, and want the tiling done asap, way before the plumber gets to commission, what are the screed manufacturers opinions on this?
Sorry for asking so many questions, but these screeds are appearing everywhere and i have a good reputation that i want to uphold.