D
Dumbo
Does anybody how long s and c screed has to down before ufh can be commissioned or is it moisture dependent.
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O
Old Mod
Although there may be still moisture present, I think Portland cement takes 21-28 days to cure.
I’m fairly confident you need to wait 21 days.
Hopefully someone else can confirm, or not as the case may be.
I’m fairly confident you need to wait 21 days.
Hopefully someone else can confirm, or not as the case may be.
The general rule we've always been told is 1 day per 1mm of screed, but as the system is used for the first time, the mixing valve must be set to the minimum setting to let the moisture in the
screed to dry out. The temperature should be increased by 2 degrees every day until the mixing valve is set at 45°C.
screed to dry out. The temperature should be increased by 2 degrees every day until the mixing valve is set at 45°C.
O
Old Mod
Yes that’s correct 1mm per day to 40mm,
1mm per 2 days over that, are the standard drying times for a s/c screed
And 2 degrees a day increase in temp from min is what we advise, but quite often ufh is used to speed things along a little.
My understanding is that you must wait a minimum of 21 days before the ufh can be turned on for this process.
Jerry is looking for confirmation on that.
Are you able to help with that @Uheat - Jake please?
From my understanding it's at the end of the screed curing process as if you input any heat into it before its cured it can cause cracks in the screed.
O
Old Mod
Thanks Jake.
H
hmtiling
It's my understanding that screed drying and curing are different things completely. I've always thought heating of traditional screeds can be commissioned after 28 days lowest setting up 2 degrees a day as above. A 70mm screed with ufh would be 100 days before heating can go on otherwise
D
Dumbo
.
Last edited by a moderator:
Cement Based screed should not be commissioned before 21 days from curing but should be cured for 7 days after installation under polythene so if done correctly would be 28 days
Anhydrite screed UFH can be commissioned after 7 days
the process is always a debate as different standards suggest different methods however my advice is treat them both the same
switch on after above periods of time at minimum manifold temperature. usually 35 degrees C and leave for 3 days. then increase by 5 derees per day up to a maximum of 55 degrees and leave at this for 3 days. then reverse the process.
To commission the heating properly the flow temperature should not be limited by room stats i.e. make sure the stats are disconnected ad operate the temperatures manually via the manifold mixing valve or at the boiler.
Anhydrite screed UFH can be commissioned after 7 days
the process is always a debate as different standards suggest different methods however my advice is treat them both the same
switch on after above periods of time at minimum manifold temperature. usually 35 degrees C and leave for 3 days. then increase by 5 derees per day up to a maximum of 55 degrees and leave at this for 3 days. then reverse the process.
To commission the heating properly the flow temperature should not be limited by room stats i.e. make sure the stats are disconnected ad operate the temperatures manually via the manifold mixing valve or at the boiler.
O
Old Mod
Thanks Alan.
D
Dumbo
Thanks
Much appreciated
H
hmtiling
I was right
J
Jimcub
As a diyer who put his own UFH in I can vouch for the above with a cement based screen. I used some lads from Bolton who laid 33sq mts for me with a laser and it was within 1mm according to the tiler.
Let it dry and cure slowly I waited till after the 21 days, then from a low heat did increase it 2 deg each day then had the tiles put down when it was cold. Keep the pressure in the pipes whilst cold I was told and did just that.
Result is a flat warm conservatory 21 deg all winter, heat loss was minimal and it was kept on 24/7. Not seen a great deal of difference in gas use as we didn't have to use the central heating as the UFH warmed the already warm house.
Let it dry and cure slowly I waited till after the 21 days, then from a low heat did increase it 2 deg each day then had the tiles put down when it was cold. Keep the pressure in the pipes whilst cold I was told and did just that.
Result is a flat warm conservatory 21 deg all winter, heat loss was minimal and it was kept on 24/7. Not seen a great deal of difference in gas use as we didn't have to use the central heating as the UFH warmed the already warm house.
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