Russ P Posted July 22, 2017 Share Posted July 22, 2017 Hi all complete newbie so advice needed. Bought a late 1800's cottage and want to underfloor heat the kitchen! its currently a soil sub structure so the current plan was dig it out and do a new floor build up as follows 50mm liquid screed or 10mm gravel concrete 100mm celotex with ufh clipped 150mm spacing 100mm concrete base slab does that look about right? Also is it ok to use 10mm gravel concrete? My thinking on that is I work for a concrete company so can get it slightly cheaper. Unfortunately we don't do screed ? Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 22, 2017 Share Posted July 22, 2017 Dig a bit deeper and put 150mm of insulation in. 100mm is just scraping past current regs, and current regs are shite on a good day . I put 200mm down under the last job ( summer room / conservatory ) and the customers were chuffed. The difference between the floor in the new space vs the concrete 60's slab in the bungalow was huge, and that was with the Ufh OFF. If you can go to 200mm insulation then that would be much better, and then you can go 100mm eps and 100mm PIR ( kingspan / celotex / similar ) as you'll want something tidy to push the Ufh pipe clips into. The best job of all would be do away with the sub slab, and go... Sand blinding. 25mm eps, to protect the DPM. DPM. 150mm PIR insulation. 100mm concrete slab with reinforcing mesh, Ufh pipes zip tied to the mesh. Remeber that liquid screed is a real pita to get anything ( like tiles ) to stick to. I'd go for concrete or screed if tiling. ? Link to comment Share on other sites More sharing options...
Russ P Posted July 22, 2017 Author Share Posted July 22, 2017 14 minutes ago, Nickfromwales said: Dig a bit deeper and put 150mm of insulation in. 100mm is just scraping past current regs, and current regs are shite on a good day . I put 200mm down under the last job ( summer room / conservatory ) and the customers were chuffed. The difference between the floor in the new space vs the concrete 60's slab in the bungalow was huge, and that was with the Ufh OFF. If you can go to 200mm insulation then that would be much better, and then you can go 100mm eps and 100mm PIR ( kings pan / celotex / similar ) as you'll want something tidy to push the Ufh pile clips into. The best job of all would be do away with the sub slab, and go... Sand blinding. 25mm eps, to protect the DPM. DPM. 150mm PIR insulation. 100mm concrete slab with reinforcing mesh, Ufh pipes zip tied to the mesh. Remeber that hat liquid screed is a real pita to get anything ( like tiles ) to stick to. I'd go for concrete or screed if tiling. ? Thanks for that. When you say sand blinding do you mean MOT topped with a layer of sand whackered? (Sorry for the dumbness) you'd think I'd know when I deliver concrete for a living ? Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 22, 2017 Share Posted July 22, 2017 Always ask mate Type one down and whacked is the norm. Most then put a sand blind down and chuck the DPM straight onto that. I prefer to put 25mm of eps down to better protect the DPM. That method also means you don't have to go nuts on the type one and sand layer getting it perfect. Link to comment Share on other sites More sharing options...
Russ P Posted July 22, 2017 Author Share Posted July 22, 2017 Ok thanks. My concern about s the property is that old there is no footings? So majorly concerned about digging down to far. Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 22, 2017 Share Posted July 22, 2017 A simple test dig in two or three locations will put that to bed . Link to comment Share on other sites More sharing options...
Russ P Posted July 22, 2017 Author Share Posted July 22, 2017 I know there's isn't any. I've already dug in a corner for a new water feed as was originally on a shared lead feed. Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 22, 2017 Share Posted July 22, 2017 Ok. What ground is it sat on? You say soil, do you mean no clay found? Link to comment Share on other sites More sharing options...
Russ P Posted July 22, 2017 Author Share Posted July 22, 2017 Yeah I seem to remember hitting a bit of clay Link to comment Share on other sites More sharing options...
Russ P Posted July 23, 2017 Author Share Posted July 23, 2017 Just out of curiosity is it building regs requirement for a 100mm slab to finish off or could I do a 50mm slab to finish. I only ask because I was told that if it's lights screed 50mm is fine. Surely concrete is stronger Link to comment Share on other sites More sharing options...
Jeremy Harris Posted July 23, 2017 Share Posted July 23, 2017 1 hour ago, Russ P said: Just out of curiosity is it building regs requirement for a 100mm slab to finish off or could I do a 50mm slab to finish. I only ask because I was told that if it's lights screed 50mm is fine. Surely concrete is stronger Nothing in building regs apart from the general provisions in Part A with regard to the foundation/slab being designed to take the load. This can be shown either by using a standard detail that's accepted by building control, or by getting an SE to sign off the design. I doubt a 50mm slab, would be OK, as it couldn't be reinforced (not enough cover for the steel fabric), and most probably wouldn't be able to take standard floor loads. My gut feeling is that 100mm with reinforcement is probably about the minimum, largely because you need around 40mm cover either side of the steel fabric Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 23, 2017 Share Posted July 23, 2017 +1 to what JSH says. Imo the prehistoric 100mm slab / 100mm insulation / 50-80mm screed method is the poorest performing solution. As you'll be paying the heating bill, best to consider things properly before moving forward. Firstly, what is the insulation like in the building now, and what is the ventilation heat loss like? Pointless going away from radiators if UFH is going to struggle to perform adequately / in line with your occupancy pattern. A thicker slab = longer to warm up ( but longer to cool down too ) so won't be anywhere near as responsive as radiators, and prob half as responsive as UFH in 50mm of liquid screed. Heating pattern for a retro fitted UFH setup in a house that's not designed for it would typically be :- 05:30 "on" @ 21oC morning comfort 07:00 "off" @ 16oC daytime off 14:30 "on" @ 20.5oC evening comfort 22:30 "off" @ 18.5-19oC night tick-over Morning comfort is to get the house toasty warn for the morning. Daytime off is basically setting the temp one degree colder than the room idles at on a typical day. That way the heating will only come on if it's bitterly cold. Evening comfort is slightly cooler than the morning and can be adjusted ( manual override ) if required to find the sweet spot. Nighttime tick-over is the coldest you'll accept the house to drop to over night. This means the slab won't go 'cold' so it will keep the chill off and not take so long to heat up for the morning event. Note that even though these look like on and off events they are not. With any heating system that takes a long time to heat up or cool down, this needs to a a "how hot and when" setup known as "set-back" control. For eg, if you want morning heating from 06:00 to 08:00, and it's a UFH slab, you'll typically set it on at 05:00 and off at 07:00, fine tuned according to how the house actually reacts. Link to comment Share on other sites More sharing options...
Onoff Posted July 23, 2017 Share Posted July 23, 2017 If you're REALLY bored / lost the will to live, wade through my 1259 photos here: https://flic.kr/s/aHsk23FYzd When I started I hadn't a clue but with the advice of the collective here I rebuilt my floor in the bathroom. - Clay - Home made Type 1 - hardcore graded thru a 40mm mesh - Sharp sand blind - 25mm EPS - DPM - 150mm Celotex - Polypipe panels - 16mm Pex-Al-Pex - 100mm wet concrete (I forgot the fibres) Link to comment Share on other sites More sharing options...
bassanclan Posted July 23, 2017 Share Posted July 23, 2017 You can get away with around 65mm of liquid screed with reinforced fibres, but you will need to hire a machine to scrabble the "wax" which forms on the top (unless you are laying carpet, then really what's the point of ufh) This is what I did, but didn't take the laitance off for a few months which proved to be a right pita. Tarmac topflow. Link to comment Share on other sites More sharing options...
Russ P Posted July 23, 2017 Author Share Posted July 23, 2017 Cheers guys I'm going to do as you've all advised. blinding dpm 100mm eps 100mm PIR 100mm slab with pipes tied to mesh with 150mm or 100mm spaces! been told by a mate although it's 1 room I'll need to run it as 2 zones for best results as I have 200m pipe in the kit Link to comment Share on other sites More sharing options...
bassanclan Posted July 23, 2017 Share Posted July 23, 2017 Not necessarily two zones, unless you wanted different temperatures in different rooms, but definitely two circuits/loops, you wouldn't want 200m in one loop Link to comment Share on other sites More sharing options...
Russ P Posted July 23, 2017 Author Share Posted July 23, 2017 The kit I've ordered has a 2 port manifold so I presume he meant to run half on 1 port and the other half on the second port! I just assumed each port was a zone Link to comment Share on other sites More sharing options...
Russ P Posted July 23, 2017 Author Share Posted July 23, 2017 So The final thing I never mentioned has my final finish isn't the normal finish like most people have tiles or wood!! It's going to be a golden fossil paving slab 1 Link to comment Share on other sites More sharing options...
Onoff Posted July 23, 2017 Share Posted July 23, 2017 Go on, what's a golden fossil? 1 Link to comment Share on other sites More sharing options...
PeterW Posted July 23, 2017 Share Posted July 23, 2017 2 hours ago, Russ P said: The kit I've ordered has a 2 port manifold so I presune he meant to run half on 1 port and the other half on the second port! I just assumed each port was a zone You don't need any zones - or actuators for that matter. Just pipe it as two equal loops and leave the actuators off, link the stat to the pump and set the mixing valve as low as you dare ... 1 Link to comment Share on other sites More sharing options...
Russ P Posted July 23, 2017 Author Share Posted July 23, 2017 2 minutes ago, PeterW said: You don't need any zones - or actuators for that matter. Just pipe it as two equal loops and leave the actuators off, link the stat to the pump and set the mixing valve as low as you dare ... I won't be doing the plumbing lol. I was happy doing my bathroom but with this I think I'll lay the pipe and then get my cousin to do the rest when he connects to the boiler Link to comment Share on other sites More sharing options...
Russ P Posted July 23, 2017 Author Share Posted July 23, 2017 6 minutes ago, Onoff said: Go on, what's a golden fossil? They are the paving slabs that I have used on my patio but the boss (wife) thinks they will keep a nice cottage feel if we continue them through the Kitchen. Which I strangely agree with her on Link to comment Share on other sites More sharing options...
PeterW Posted July 23, 2017 Share Posted July 23, 2017 You need to seal that sandstone very well if you use it indoors as it stains very easily. It may even be worth sealing it with one coat before laying and then add another over the grout and slabs when it's done. You will have to watch carefully if you are linking direct to a boiler with the UFH as the time for it to warm through will be quite a lag from when you put heat in - mixed UFH and trad rads can mean issues where the rads overheat as the floor hasn't reached temperature. Plan carefully ..! Link to comment Share on other sites More sharing options...
Russ P Posted July 23, 2017 Author Share Posted July 23, 2017 1 minute ago, PeterW said: You need to seal that sandstone very well if you use it indoors as it stains very easily. It may even be worth sealing it with one coat before laying and then add another over the grout and slabs when it's done. You will have to watch carefully if you are linking direct to a boiler with the UFH as the time for it to warm through will be quite a lag from when you put heat in - mixed UFH and trad rads can mean issues where the rads overheat as the floor hasn't reached temperature. Plan carefully ..! Was planning on putting a few coats of sealant over it! The idea was the underfloor heating would have its own independent thermostat so run a separate heating program to the rest of the house. I have no where to install a traditional rad in the new kitchen since removing the walls hence the ufh plan. Link to comment Share on other sites More sharing options...
Onoff Posted July 23, 2017 Share Posted July 23, 2017 1 hour ago, Russ P said: Which I strangely agree with her on Slippery slope mate! Btw, I'm not sure I'd go with the Polypipe panels again though a doddle to lay pipe with them (and the home made de-coiler): When I knock thru the lounge / diner (and how all on here are looking forward to that ) I may just put a membrane (to separate foil from concrete) atop the foil face of the Celotex (PIR), staple the pipe and concrete. Why, you may ask when the panels make it so easy! Basically for a more solid sounding slab. As Duke Ellington said; If it ain't got that ring etc. The way the Polypipe panels are formed means there are 30mm deep x 90mm dia areas on a 200mm pitch that are "hollows" formed by the panels giving only 70mm cover on a 100mm slab. Maybe I'm doing it a disservice and the ease, as per the video will sway me! Link to comment Share on other sites More sharing options...
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