CotswoldDoItUpper Posted September 11, 2021 Share Posted September 11, 2021 Evenin’ all! The plan is to fit UFH in 2 downstairs carpeted rooms, the floor will be - 100mm pir (max we can get whilst maintaining 50mm air gap) between joists - 18mm chipboard - 20mm foiled eps with UFH pipes routed in - ??? - underlay (0.7 - 1tog) - carpet (1 - 1.5tog) the question is what (if anything) needs to go in between the eps and the underlay? Thanks! Link to comment Share on other sites More sharing options...
Onoff Posted September 11, 2021 Share Posted September 11, 2021 Wouldn't you put routed chipboard on top of the EPS? Then underlay and carpet atop the chipboard? Link to comment Share on other sites More sharing options...
CotswoldDoItUpper Posted September 11, 2021 Author Share Posted September 11, 2021 (edited) 32 minutes ago, Onoff said: Wouldn't you put routed chipboard on top of the EPS? Then underlay and carpet atop the chipboard? Didn’t know such a thing existed! yup will do that. Do the ‘empty’ bits of routed chipboard need filling with anything? Or would you feel the uneven surface of chipboard and pipes through the carpet and underlay? I guess you could always also use pir over joists for better results then the eps? Or are either not strong enough to take the further floor make up? Edited September 11, 2021 by CotswoldDoItUpper Link to comment Share on other sites More sharing options...
Onoff Posted September 11, 2021 Share Posted September 11, 2021 (edited) I'm a bit lost as to where the 50mm air gap is? Is this a suspended timber floor? How deep are the existing joists? Cleverer people will be along shortly. Just Google "routed chipboard UFH" and go Images. Use btw 22mm boards not 18mm. Putting underlay then carpet direct onto foiled EPS is a bad idea btw. Edited September 11, 2021 by Onoff 1 Link to comment Share on other sites More sharing options...
CotswoldDoItUpper Posted September 12, 2021 Author Share Posted September 12, 2021 12 hours ago, Onoff said: I'm a bit lost as to where the 50mm air gap is? Is this a suspended timber floor? How deep are the existing joists? Cleverer people will be along shortly. Just Google "routed chipboard UFH" and go Images. Use btw 22mm boards not 18mm. Putting underlay then carpet direct onto foiled EPS is a bad idea btw. - air gap under joists (yes suspended floor) - joist depth 100mm on 400 centres - I wasn’t planning on putting underlay directly onto the eps, Im trying to establish what I should put between them. google images here I come! Link to comment Share on other sites More sharing options...
CotswoldDoItUpper Posted September 12, 2021 Author Share Posted September 12, 2021 Any idea what should go between UFH pipes and carpet underlay? surely if you lay routed chipboard there will still have to be a covering so you can’t feel the empty bits where there are no pipes? Link to comment Share on other sites More sharing options...
Temp Posted September 12, 2021 Share Posted September 12, 2021 (edited) I think you have two options something like.. Carpet Underlay 18mm OSB or Flooring grade chipboard Routed and foiled EPS with UFH pipe between joists Insulation between joists Carpet Underlay Metal Heat spreader plates (just flat sheets) Routed Chipboard and UFH pipe 18mm OSB or Flooring grade chipboard Insulation between joists I don't think 18mm Routed Chipboard is strong enough on its own over joists. I believe its intended for use over concrete floors or similar. Edited September 12, 2021 by Temp Link to comment Share on other sites More sharing options...
Onoff Posted September 12, 2021 Share Posted September 12, 2021 It can be a pig to get pir to fit tightly between floor joists. Some people cut them boards 5-10mm short on the width then fill with expanding foam. An option is using mineral wool instead. @Ferdinand did similar I think with his Little Brown Bungalow refit? A few pointers here. https://www.ecologicalbuildingsystems.com/post/best-practice-approach-insulating-suspended-timber-floors Whatever you decide or get told, post up here. Someone will have seen it before and likewise comment as to good/bad. Link to comment Share on other sites More sharing options...
RHayes Posted September 13, 2021 Share Posted September 13, 2021 Routed chipboard should be strong enough for joisted floor providing the routed grooves are laid perpendicular to the direction of the joists. A 3mm ply or even 1.5mm aluminium sheet on top of groved chipboard would be sufficient to prevent feeling the empty grooves. Or just fill the grooves that don't have pipe in with an adhesive, but most grooves will have pipe and this should be flush with the top of the chipboard and won't be felt though the carpet and underlay. Take care on the thermal resistance of your carpet. Kind of goes without saying but a carpet will hold the heat back. Link to comment Share on other sites More sharing options...
Ferdinand Posted September 13, 2021 Share Posted September 13, 2021 LBB th 14 hours ago, Onoff said: It can be a pig to get pir to fit tightly between floor joists. Some people cut them boards 5-10mm short on the width then fill with expanding foam. An option is using mineral wool instead. @Ferdinand did similar I think with his Little Brown Bungalow refit? Thread: The detail I used for my existing suspended floors. Note this is wall rads not ufh. For UFH I would want more insulation - probably 75mm not 25mm PIR over the floor. Given that my final restriction was being able to trim internal doors enough (limit was about 60mm), I might be forced to go PIR between the joists if I was not able to do things to doorframes. Calculate the u-values. The other option is to seal the void to moisture and fill it with polystyrene beads. May cause BCO to have kittens. Calculate your u-values against what you need. Further discussion on this Boffin's Corner thread about the build up: Ferdinand 1 Link to comment Share on other sites More sharing options...
vala Posted September 13, 2021 Share Posted September 13, 2021 (edited) @CotswoldDoItUpper I'm in the process of installing UFH to the first floor in my home which will predominantly have carpet on top. I came across this underlay which may also be of use to yourself, https://wilsons-underlays.co.uk/thermalstream.html Edited September 13, 2021 by vala Link to comment Share on other sites More sharing options...
CotswoldDoItUpper Posted September 13, 2021 Author Share Posted September 13, 2021 3 hours ago, vala said: @CotswoldDoItUpper I'm in the process of installing UFH to the first floor in my home which will predominantly have carpet on top. I came across this underlay which may also be of use to yourself, https://wilsons-underlays.co.uk/thermalstream.html That’s a great suggestion thanks! Did you install anything between the pipes abs the underlay to ‘level’ the floor, and if not, can you feel the pipes through it? Link to comment Share on other sites More sharing options...
vala Posted September 13, 2021 Share Posted September 13, 2021 27 minutes ago, CotswoldDoItUpper said: That’s a great suggestion thanks! Did you install anything between the pipes abs the underlay to ‘level’ the floor, and if not, can you feel the pipes through it? I'm having a different system to yourself. I'm going for a pug screed system, so on top of my joist at present I'll have chipboard T&G boards first, then the underlay, then carpet. However I've asked my structural engineer if I could use cement T&G boards as these should make the system more efficient. However they are much heavier. I'm a good 1-2 months away from potentially evening running the system....still doing the prep work!! 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