saveasteading Posted October 31 Share Posted October 31 11 hours ago, Roger440 said: the odd chipped corner. If you are staggering overlaps these don't make much difference as they become air pockets. And consider the proportion of area....negligible. 1 Link to comment Share on other sites More sharing options...
ColdHouse Posted November 6 Share Posted November 6 @Kacha , have you had any quotes yet for how much it'll cost to dig up the existing floor? I'd like to do the same with my house (1990's, ~65m2 ground floor area) as you're planning, but have no idea how much it'll cost. Link to comment Share on other sites More sharing options...
saveasteading Posted November 6 Share Posted November 6 3 minutes ago, ColdHouse said: have no idea how much it'll cost. How long would it take? X £500/ day How many skips? X £200 for clean concrete. L X w X depth in m3. X 1.5 for bulking. Add £500 sundries. That's just a guide. Link to comment Share on other sites More sharing options...
Wil Posted November 11 Share Posted November 11 Hmm spec for my retro fit floor is hardcore and sand 160mm. 200mm PIR. 150 concrete. Pipes in the concrete. Tiles likely on top. Sounds like there are options to cut 50mm off the concrete at least. So useful post. The 200mm was me insisting on exceeding BR, architect and contractor not keen. I have a QS cost for rates of digging I can try and find if useful. Link to comment Share on other sites More sharing options...
saveasteading Posted November 11 Share Posted November 11 20 minutes ago, Wil said: . 150 concrete 150 pir is the pragmatic choice, even 100 if it helps a lot. 100mm concrete is plenty. You can drive forklifts on 150 if the hardcore is good. Link to comment Share on other sites More sharing options...
Wil Posted November 11 Share Posted November 11 I lied- here’s the spec- it’s 125mm concrete and much more hardcore/ blinding: Link to comment Share on other sites More sharing options...
saveasteading Posted November 11 Share Posted November 11 1 hour ago, Wil said: it’s 125mm concrete and much more hardcore/ blinding: OK. what thickness might help you practically? This is a house so nobody is going to break the floor. The weakest layer is of course the insulation. After that the loads are very well spread over the stone below. If the hardcore is good quality , ie not a heap of old bricks, then that can be reduced in thickness. Likewise the sand. The sand is there for adjusting the level so there might be none above the highest point in the stone. so i am suggesting 100mm concrete, on 150 PIR, on 150 of stone and sand (total). that is still 400mm which is a lot to dig out, but a lot less than 500. IFFFFF you do it to a high standard of level control and compaction. Link to comment Share on other sites More sharing options...
Wil Posted November 12 Share Posted November 12 Realistically, every little helps. That’s a useful breakdown, thank you- I’ll discuss with the contractor who’s bidding. A couple of questions if I may? In my spec above it looks like there’s a vapour layer over the insulation with a damp membrane/ radon barrier under. Is this second barrier necessary? I was imagining pinning the UFH pipe to the insulation direct with the concrete and reinforcement poured directly on top (or even follow the spec and tie to the rebar). Does 100mm concrete differ from 100mm screed poured? Link to comment Share on other sites More sharing options...
saveasteading Posted November 12 Share Posted November 12 You only need one layer of plastic. Choose a radon spec and it does the dampness thing too. You need an extra plastic layer on top of the pir as it stops concrete or grout from running into gaps and floating it. I've seen it and isn't fun. Screed or concrete. Either will do. BUT I would say put a thin concrete screed down for the pir to sit on, and then 60mm pumped screed goes on top with the ufh in it. Link to comment Share on other sites More sharing options...
Wil Posted November 13 Share Posted November 13 So that would be 100ish hardcore, sand, concrete(how much?), 150mm insulation, plastic membrane, 60mm screed with UFH pipes? Link to comment Share on other sites More sharing options...
saveasteading Posted November 13 Share Posted November 13 This is becoming non standard but then so is ( to me) having insulation straight on stone. So I'm going to say, stone as thick as you like...but at least 100, laid really flat and with 0 to 10mm max sand blinding but zero if you can. Dpm, to radon spec if necessary. Then a concrete screed about 75mm, hand tamped and nicely level. A light mesh (A142) would be a nice touch. Shop around. 150mm insulation Dpm, taped, any spec as it is only to close the joints. Ufh pipes pegged to the pir. 60mm pumped screed. I like the level control in this, so the thicknesses are controlled. Plus having the lower screed keeps it all clean and the pir laid solid. BUT it depends who is doing it. Link to comment Share on other sites More sharing options...
Wil Posted November 14 Share Posted November 14 Thank you for the advice, much appreciated. I’ll discuss with the contractor tomorrow if they can give assurance on the quality control. Link to comment Share on other sites More sharing options...
ColdHouse Posted November 15 Share Posted November 15 On 11/11/2024 at 16:23, Wil said: I have a QS cost for rates of digging I can try and find if useful. If you could, that'd be very helpful. Thank you 👍 Link to comment Share on other sites More sharing options...
Clark Kent Posted November 15 Share Posted November 15 On 31/10/2024 at 08:51, IGP said: Might be worth taking a look at to see how they did underfloor heating as well. About 5 mins in. This is really interesting, I’m doing a similar refurb but cannot dig out the ground floor. This guy isn’t either and adding no insulation at all and yet reckons his heating bills are £80 a month? Link to comment Share on other sites More sharing options...
IGP Posted November 15 Share Posted November 15 10 minutes ago, Clark Kent said: This is really interesting, I’m doing a similar refurb but cannot dig out the ground floor. This guy isn’t either and adding no insulation at all and yet reckons his heating bills are £80 a month? The system is visible on https://heatpumpmonitor.org/system/view?id=139 so make of it what you will but it looks impressive to me. Link to comment Share on other sites More sharing options...
IGP Posted November 15 Share Posted November 15 It looks like he’s gone for what he’s losing in actual heat loss, making up (and possibly more) with efficiency of the system. Link to comment Share on other sites More sharing options...
keyser Posted Sunday at 21:37 Share Posted Sunday at 21:37 On 15/11/2024 at 11:56, IGP said: It looks like he’s gone for what he’s losing in actual heat loss, making up (and possibly more) with efficiency of the system. I saw this video and thought it was surprising he didn't go with extra floor insulation. But I take it he installed this some time ago and we can now see the data for the past year? COP 4.9 292 days of data. Winter is coming so might take a small dip. That's without floor insulation, sooo that's interesting. Future thoughts abound for my 1960s ground floor flat with concrete floor Link to comment Share on other sites More sharing options...
alfaTom Posted 15 hours ago Share Posted 15 hours ago Thought might be worth adding to this since we are renovating a 1950s house and digging out the floors to add UFH... Our buildup is: 150mm MOT sand blinding DPM 170mm PIR Plastic sheet 75mm reinforced screed with UFH at 150mm Total dig out was around 425mm. You need to be careful you don't undermine the foundations and also fill it back in as soon as reasonably possible. If you're digging out the floors it's worth thinking about any cabling or drains you may need to put in - we've put a 40mm waste pipe for cabling to the kitchen island and also had to fit the shower drain run prior to the floor buildup. Link to comment Share on other sites More sharing options...
Roger440 Posted 12 hours ago Share Posted 12 hours ago On 17/11/2024 at 21:37, keyser said: I saw this video and thought it was surprising he didn't go with extra floor insulation. But I take it he installed this some time ago and we can now see the data for the past year? COP 4.9 292 days of data. Winter is coming so might take a small dip. That's without floor insulation, sooo that's interesting. Future thoughts abound for my 1960s ground floor flat with concrete floor Indeed. Good info, as ive zero intention of digging up my floor to install insulation. Based on my calcs, it will never pay for itself while im alive. If i achieved something like this, it pushes payback even further into the future. Link to comment Share on other sites More sharing options...
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