Porthole Posted January 17, 2022 Share Posted January 17, 2022 Hi there We are putting underfloor heating down on an existing part of the house and the builder is suggesting 20mm celotex with 16mm pipes on top, then 55 mm sand and cement screed with fibres in it on top of the celotex so 39mm minimum above the pipes (there will be more screed in other areas but this is the minimum it will be). Is 39mm sand and cement screed with fibres ok or is it a bit too thin. On top of that there will dietramat and porcelain tiles which are 6mm thick (long planks). Thank you very much Link to comment Share on other sites More sharing options...
Mr Punter Posted January 17, 2022 Share Posted January 17, 2022 I often see traditional screed specified at 75mm and liquid screed at 50mm. I guess you could shave 10-15mm off these but any more may be risky. Link to comment Share on other sites More sharing options...
BenP Posted January 17, 2022 Share Posted January 17, 2022 Min 65mm, usually designed at 75mm. This is helpful: https://www.labcwarranty.co.uk/blog/floor-screeds-and-underfloor-heating-a-best-practice-guide/ Not sure about the option for fibres - I've heard mixed opinions! Link to comment Share on other sites More sharing options...
nod Posted January 17, 2022 Share Posted January 17, 2022 55 mil will be fine Link to comment Share on other sites More sharing options...
bassanclan Posted January 17, 2022 Share Posted January 17, 2022 20mm celotex is not a lot! Is there any other insulation under that? Link to comment Share on other sites More sharing options...
saveasteading Posted January 17, 2022 Share Posted January 17, 2022 Presumably there is already a floor, hence keeping it all thin. If it is a concrete floor then it won't go anywhere and you should be ok with a thin screed. I have been happy with fibres. It looks strange with hairs sticking out but they rub off, and it can't do any harm in holding the screed together. 20mm celotex to persuade the heat to go up and not down? isn't a lot, but if it is a small area or comfort rather than efficiency then perhaps this is justifiable. If it is central (not exposed) then that helps too. I put an electric mat down on an existing concrete shower-room floor, with only 10mm insulation (then tiled) It loses a lot pf heat of course but is only on for short peiods and the floor is cosy then. So not ideal but it works. Link to comment Share on other sites More sharing options...
Mr Punter Posted January 18, 2022 Share Posted January 18, 2022 Just re-read and 20mm of insulation is pathetic, especially as you intend to heat the floor. This would only be acceptable in, say a bathroom. In a larger room it is stupid. 15 years ago we were doing 75mm floor insulation. Link to comment Share on other sites More sharing options...
SteamyTea Posted January 18, 2022 Share Posted January 18, 2022 7 hours ago, Mr Punter said: Just re-read and 20mm of insulation is pathetic, The Daily Mail will like it as it is going to save us all. https://www.dailymail.co.uk/sciencetech/article-10410911/Geology-Earths-interior-cooling-faster-expected-study-suggests.html Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now