connick159 Posted June 17, 2021 Share Posted June 17, 2021 Hi all, Building an extension to old cottage and just had the in screed UFH system installed to the new extension and now have a difference of around 60mm between the new extension and the cottage (extension is higher). We are putting an overfloor UFH system in the old cottage which will make up approx 20mm which leaves around 40mm diff. My idea was to add around 20mm of insulation onto the existing cottage slab and then put down self leveler to bring it all up to 20mm below the new extension floor and then the UFH system can go down. Once that's done both floor levels will match ready for tiling. Just wondering if anyone has experience with doing something similar. 20mm is not much in terms of insulation so I'm wondering if its even worth it or should i save money on both the insulation and self leveler and just pour a 40mm topping slab and be done with it? Anu other options or ideas. (besides digging up the existing cottage floor and doing a full slab pour) Hope that makes sense and would welcome any ideas. Thanks Link to comment Share on other sites More sharing options...
PeterW Posted June 17, 2021 Share Posted June 17, 2021 What over floor UFH are you using ..? Will it take tiles directly ..? And how is it linked / separated from the extension ..?? I would go with 40mm of insulation and then final floor over the UFH if the system allows. Link to comment Share on other sites More sharing options...
markc Posted June 17, 2021 Share Posted June 17, 2021 (edited) As you say, 20mm of Insulation isnt much and 20mm of self leveller over that is likely to break up. +1 to Peter`s idea Edited June 17, 2021 by markc Link to comment Share on other sites More sharing options...
connick159 Posted June 17, 2021 Author Share Posted June 17, 2021 3 hours ago, PeterW said: What over floor UFH are you using ..? Will it take tiles directly ..? And how is it linked / separated from the extension ..?? I would go with 40mm of insulation and then final floor over the UFH if the system allows. This one https://www.theunderfloorheatingstore.com/prowarm-trade-warm-panel-800x600x18mm Link to comment Share on other sites More sharing options...
PeterW Posted June 18, 2021 Share Posted June 18, 2021 What are you planning on laying on top ..? I’d want 40mm of insulation under those but you will need to bond the insulation down and the panels may need screwing to the sub floor through the insulation. Link to comment Share on other sites More sharing options...
connick159 Posted June 18, 2021 Author Share Posted June 18, 2021 (edited) 1 hour ago, PeterW said: What are you planning on laying on top ..? I’d want 40mm of insulation under those but you will need to bond the insulation down and the panels may need screwing to the sub floor through the insulation. Hi Peter, thanks for the info so far. We are planning in tiling directly on top of those. The challenge is the the previous owners had vinyl as a floor covering and now I know why as there are high and low spots across the floor with differences of up to 45mm. There doesn't seem to be a uniform fall either. One part of a hall could take 40mm pir first but then another only 20 and yet another, the highest spot, would not need any before those ufh panels are laid. I don't think I could get a level floor but would like to try for a flat one. (Does that make sense). I've priced up self leveler but that is expensive when considering the floors area. I was leaning towards bonding the pir to the floor but with the differing levels it would be a little bit like patchwork. We have planned to mechanically bond the ufh panels into the slab anyways so maybe that will offset the risks with movement in the pir after tiles are installed. We could just screed it I spose but I'm trying to eek out any insulative value but... It may not me worth it for such a little amount. Thanks again! Edited June 18, 2021 by connick159 Link to comment Share on other sites More sharing options...
James Newport Posted June 18, 2021 Share Posted June 18, 2021 I have an old concrete slab I need to raise by 30mm or so. A couple of products I've found which I'm considering - an insulating floor screed: https://proofshield.co.uk/products/insulating-floor-screed/ - some kind of magic stuff called Bondacryl, sold by property repairs systems that allows you to lay very thin screeds: https://www.epoxy-info.co.uk/BondAcryl_data_sheet_front.pdf Link to comment Share on other sites More sharing options...
Mr Punter Posted June 18, 2021 Share Posted June 18, 2021 Any chance of breaking out the old floor so you can get it properly level and insulated? Link to comment Share on other sites More sharing options...
wozza Posted June 18, 2021 Share Posted June 18, 2021 36 minutes ago, Mr Punter said: Any chance of breaking out the old floor so you can get it properly level and insulated? Do this ^^^ On our extension we took out a large area of the existing floor so we could insulate in properly - the hall has the old uninsulated floor - the difference is night and day. Link to comment Share on other sites More sharing options...
connick159 Posted August 20, 2021 Author Share Posted August 20, 2021 On 18/06/2021 at 14:56, James Newport said: I have an old concrete slab I need to raise by 30mm or so. A couple of products I've found which I'm considering - an insulating floor screed: https://proofshield.co.uk/products/insulating-floor-screed/ - some kind of magic stuff called Bondacryl, sold by property repairs systems that allows you to lay very thin screeds: https://www.epoxy-info.co.uk/BondAcryl_data_sheet_front.pdf Hi James, Did you end up doing this slab work? If so, how did it go? Thanks Link to comment Share on other sites More sharing options...
James Newport Posted August 20, 2021 Share Posted August 20, 2021 I haven't done it yet. Link to comment Share on other sites More sharing options...
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