Pbb Posted February 20, 2021 Share Posted February 20, 2021 Hi, We have just had a new underfloor heating system installed and would like some feedback on the quality of work. We have a retrofit installation with insulation panels that has traces in it. Soon there should be a latex screed going down but the company doing the screed has said they cannot do anything until the insulation boards have been stuck down and the edges sealed so the boards don't float up. When the board were put down no adhesive was used, is this normal? Also the boards were not cut to the shape of the rooms and gaps were left. On the advise of the screed company the plumbers were asked to come back and fill them in as a huge amount of screed would be needed to fill them. The guys came back and filled in the gaps with boards they cut in to random piece and put in but again did not fix down. Finally they used some expanding foam around the edges but the board lifted due to not being stuck down. Anyway I have included some pictures to let you see for yourselves. Thanks https://ibb.co/St199JD https://ibb.co/svWfn1T https://ibb.co/7vC4MKv https://ibb.co/xjJmBr0 https://ibb.co/5WBZQgh https://ibb.co/TKhrChX https://ibb.co/hsGkkMB https://ibb.co/fpxDKKd 1 Link to comment Share on other sites More sharing options...
TonyT Posted February 20, 2021 Share Posted February 20, 2021 It’s not good, so cancel the screed until this is resolved. how thick is the insulation? is there any up the sides of the walls on the external walls. have you looked at the manufacturer instructions for the system that’s installed? That will give you specific info to discuss with the ‘plumbers’ Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 20, 2021 Share Posted February 20, 2021 Ouch. That’s shocking. The suppliers are usually able to do a route map when supplying with sections / pipe ways / crossovers all avoided etc so this should have been relatively neat and organised. The boards absolutely must be bonded down, don’t even DREAM of pouring screed over that, it’ll be a train wreck. Pipes will have to come up, boards up, and redo I’m afraid ?. There is no quick fix here. 1 Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 20, 2021 Share Posted February 20, 2021 1 hour ago, TonyT said: is there any up the sides of the walls on the external walls This needs to be set around the perimeter Link to allow the screws to expand and not push directly against the walls. Link to comment Share on other sites More sharing options...
Pbb Posted February 21, 2021 Author Share Posted February 21, 2021 Thank you all for your replies. We had though it would be a case of redoing the job and it is a great help to have it confirmed. @TonyT the board are about 25mm some are against the wall with no perimeter tape/insulation. @NickfromwalesI am pretty sure they had a route map with them when they started the job. I have had a good read up on what is involved and prepared to have a discussion with the plumbers as to what has to be done now. Link to comment Share on other sites More sharing options...
Onoff Posted February 21, 2021 Share Posted February 21, 2021 On 20/02/2021 at 21:30, Nickfromwales said: This needs to be set around the perimeter Link to allow the screws to expand and not push directly against the walls. Screed? Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 22, 2021 Share Posted February 22, 2021 3 hours ago, Onoff said: Screed? Yup. Cheers. Link to comment Share on other sites More sharing options...
Temp Posted February 22, 2021 Share Posted February 22, 2021 Are you tiling over the screed? If so consider forming expansion gaps where two areas of screed meet at doorways. Otherwise there is a chance of getting a curved crack that can propagate through the tile. With a straight expansion gap you can tile upto it or put a cill piece over it. Link to comment Share on other sites More sharing options...
Mr Punter Posted February 22, 2021 Share Posted February 22, 2021 What a waste of materials if it has to come up. They normally start with a perimeter upstand of insulation that slows heat transfer to the walls and allows expansion in the screed. I can see why it will be difficult to liquid screed. Could they use a solid overlay like ScreedBoard 20? It can be tiled and is a dry application that you could even DIY. Link to comment Share on other sites More sharing options...
joth Posted February 22, 2021 Share Posted February 22, 2021 Taking a step back, has there been any heat loss calculations for the system design? It looks like all the pipes are being laid on uninsulated bare floor, with a tiny slither of insulation squashed in around them. I assume this is because of limited height to ceilings, and lack of desire to dig out the floor to reduce depths and do the job properly. The result is going to be 50% of your heating bill going into the ground under your house rather than heating the house itself. Unless that's what you really want, you really should think about abandoning this and using something fit for purpose like a wall hung radiator. (IMHO retrofits designed like this should be illegal under building regs) Link to comment Share on other sites More sharing options...
Mr Punter Posted February 22, 2021 Share Posted February 22, 2021 18 minutes ago, joth said: (IMHO retrofits designed like this should be illegal under building regs) I agree. I think that this should be covered in the regs and some minimum standard applied. I know several people who get a new kitchen, a bit of building work (like chimney out) and underfloor heating with little / no insulation. The problem is the hassle and expense of taking up an existing floor, which neither the builder nor the householder wants to do. If it costs an extra hundred a year to heat, they may never get their money back. Link to comment Share on other sites More sharing options...
Big Jimbo Posted February 22, 2021 Share Posted February 22, 2021 I don't believe that any of these overlay systems are worth a toss. The only way i would consider any overlay would be floorboards up, 100mm pir between joists, floorboards back, then 20mm pir over floorboards, glued down. pipes layed on top, and then 40mm screed. Even then i doubt it would be great. I would be going for either modern rads, or trad rads, depending on the style of house. In my opinion, with what you have got there you are going to need the heat on 24 hours a day to get a decent amount of heat into the house. Sorry, but i'd be scrapping that. I think you are heading for a big disappointment. Link to comment Share on other sites More sharing options...
Onoff Posted February 22, 2021 Share Posted February 22, 2021 (edited) Get digging! Edited February 22, 2021 by Onoff 1 Link to comment Share on other sites More sharing options...
Pbb Posted February 22, 2021 Author Share Posted February 22, 2021 @TempWe have an engineered oak floor going down over most of it and tile in the kitchen. @jothAs far as we know all the calculation have been done to qualify for the RHI. We don't know why the areas were left where the pipe was put directly on the floor? The only reason we can come up with was they were too lazy to cut the boards properly. If I had done the job myself I could easily have made all the boards fit the area without the need for anything to touch the ground. As far as digging out the floor, we did that ourselves before the plumbers even got started. The house heats up very well with this system in and retains a lot of the heat. Link to comment Share on other sites More sharing options...
Onoff Posted February 22, 2021 Share Posted February 22, 2021 33 minutes ago, Pbb said: The house heats up very well with this system in and retains a lot of the heat. Nobody is suggesting it won't heat up. Just that it would likely heat up quicker and retain more heat, as well as using less fuel if there was more insulation in the floor. Underfoot I'm sure it feels lovely. Similarly your "boiler" might last longer if it's working less. Link to comment Share on other sites More sharing options...
Dave Jones Posted February 22, 2021 Share Posted February 22, 2021 as others have said, you need really 150mm of insulation and 75mm of screed on top of that to do the job properly or to building regs. This additional 225mm would mean you would hit your heads when walking through internal doors which is why the floor has to come out first. Honestly you will be better off with rads. Link to comment Share on other sites More sharing options...
joth Posted February 22, 2021 Share Posted February 22, 2021 2 hours ago, Pbb said: @jothAs far as we know all the calculation have been done to qualify for the RHI. This maybe the problem, unfortunately this doesn't actually mean anything for UFH. RHI has no minimum requirement for insulation below ground floor, only for loft and cavity walls. Moreover, the worse the EPC, the higher the RHI payments, creating an absurd reverse incentive to insulate as little as legally possible. Which is all well and good until the RHI payments finish and then the customer is left with a needlessly expensive to run system. Link to comment Share on other sites More sharing options...
AliG Posted February 23, 2021 Share Posted February 23, 2021 23 hours ago, Big Jimbo said: I don't believe that any of these overlay systems are worth a toss. The only way i would consider any overlay would be floorboards up, 100mm pir between joists, floorboards back, then 20mm pir over floorboards, glued down. pipes layed on top, and then 40mm screed. Even then i doubt it would be great. I had exactly this done and it was still poor. I had to turn the flow up to 60C to heat the room (not a such problem when you have radiators running that hot anyway)and loads of the tiles cracked. Personally I think the problem is that suspended timber floors with air blowing under them are not a great starting point for a UFH system. 1 Link to comment Share on other sites More sharing options...
Newbuilder20202 Posted April 24, 2021 Share Posted April 24, 2021 Would really appreciate guys feedback on this I’m currently doing a self build and by accident instead of putting 500 gauge plastic on top of insulation and then putting down the underfloor hearing pipes we put the pipes directly on the insulation and then the 500 gauge plastic and then 75mm screed could you please tell me if this will cause problems thank you for taking the time to read this.I’m just worried the 500 gauge plastic will stop the screed from heating. Link to comment Share on other sites More sharing options...
SteamyTea Posted April 24, 2021 Share Posted April 24, 2021 You may have a problem as there could be air trapped between the pipes and the insulation. This will increase the thermal resistance, in effect, giving you less power delivery. Link to comment Share on other sites More sharing options...
Declan52 Posted April 24, 2021 Share Posted April 24, 2021 3 hours ago, Newbuilder20202 said: Would really appreciate guys feedback on this I’m currently doing a self build and by accident instead of putting 500 gauge plastic on top of insulation and then putting down the underfloor hearing pipes we put the pipes directly on the insulation and then the 500 gauge plastic and then 75mm screed could you please tell me if this will cause problems thank you for taking the time to read this.I’m just worried the 500 gauge plastic will stop the screed from heating. Is the screed sand and cement or a lightweight flow type screed. Link to comment Share on other sites More sharing options...
Newbuilder20202 Posted April 24, 2021 Share Posted April 24, 2021 (edited) It is sand and cement self leveling but the guy who lays it has a very good name and says the 500 gauge plastic won’t be a problem but if it was heavier it would be. this is more information on it . The screed arrives on-site pre-mixed and is pumped to the area rendered inaccessible to traditional screed methods. The product is levelled off to give a smooth levelled finish. Once installed the product is cured with and appropriate curing agent. Edited April 24, 2021 by Newbuilder20202 Link to comment Share on other sites More sharing options...
Newbuilder20202 Posted April 24, 2021 Share Posted April 24, 2021 6 hours ago, SteamyTea said: You may have a problem as there could be air trapped between the pipes and the insulation. This will increase the thermal resistance, in effect, giving you less power delivery. Sorry if I didn’t make myself clear there is 6inch slabs of kingspan then the pipes for underfloor heating then the light 500 gauge plastic the ln 75mm of self leveling screed Link to comment Share on other sites More sharing options...
Declan52 Posted April 24, 2021 Share Posted April 24, 2021 The extra layer of polythene is just there to stop the screed getting into the joins of the insulation and lifting them. I would remove the polythene and tape the joins as good as you can. Sand cement screed doesn't be no where near as wet as a flow type screed so much less of a chance of lifting the insulation. Link to comment Share on other sites More sharing options...
Newbuilder20202 Posted April 24, 2021 Share Posted April 24, 2021 11 minutes ago, Declan52 said: The extra layer of polythene is just there to stop the screed getting into the joins of the insulation and lifting them. I would remove the polythene and tape the joins as good as you can. Sand cement screed doesn't be no where near as wet as a flow type screed so much less of a chance of lifting the insulation. Declan thanks so much for coming back to me the problem is the screed is poured now and the floor set I was just asking with this cause issues long term.since I put up post a energy expert and flooring expert said it wouldn’t I was just asking if anyone else had this happen them. Thanks Link to comment Share on other sites More sharing options...
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