INSULATION UNDER SCREED

[ITSJONBOYOK]

I am about to put 120mm kingspan under ufh under 60mm of screed,
I have seen somewhere I should also put insulation around outside wall- if so how high and is this general practise?

 

[freddiemercurystwin]

Yes you should, it is common practice and required to comply with regs, to minimize the cold bridge where the screed touches the inner skin. Normally about 25mm up to the top of the screed.

http://www.insulation.kingspan.com/uk/pdf/tf70.pdf page 5 specifically

 

[^woody^]

Is 60mm screed enough?

 

[noseall]

Is 60mm screed enough?

The very thought of laying screed on top of insulation makes me nervous.

However i would be more reassured if i was sitting something weightier on top, like say 100mm thick.

 

[theoldun]

We only ever use celotex.
Unless you have a very long external perimeter, giving a high P/A ratio, it would appear that your thickness of insulation is way over the top. Would suggest you check your P/A ratio.
To achieve 0.20W/m2k, 80mm of Celotex FF4000 would suffice for a P/A ratio of 0.50. Just had quick look at Kingspan and they are the same.
As said Fred 25mm insulation round perimeters
Your pushing your luck at 60mm screed. Good practice is 75mm thick reinforced with fibre. We go 80mm if we can get it. You will have no problems then.
Do not forget your fibre.
oldun.