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Replacing concrete floor and installing UFH

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#1 sturtm


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Posted 05 November 2009 - 01:27 PM


We are currently purchasing a 1917 detached house. The existing floors are concrete and we want to install a wet system due to the long term costs of dry.

Someone has suggested that 75mm is needed to fit it and the existing floor will probably have to be dug up and replaced, with the new concrete floor incorparting the pipes.

Alternatively, we could put it on the existing floor but will lose 75-100mm of height in the room and the associated problems with existing doors etc that we want to avoid.

The floor space is about 72m2.

Can anyone give an indication of:
Cost of digging up floor (is this something I can realistically do myself with Kango hire?)
Laying of new floor
Installation of wet UFH

Any help or guidance here will be gratefully received!


#2 Jill4287


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Posted 06 January 2014 - 03:08 AM

The problem with laying it on top of the existing concrete I would imagine is that you don't know what's underneath by way of insulation etc. you want the heat to be directed upwards and not simply absorbed by the material beneath. We had all the old concrete floors of our barn conversion taken up by necessary as we needed to install new drains etc and I saw what went down afterwards. We had the ceiling night to super insulate and our builder put a layer of 'kingspan' on top of all the other layers (DPC , etc). We had about a 100m2 to cover and opted for a wet system of UFH. We used a company called Xpert Energy for all out heating and hot water system and we have been thrilled to bits with them. They installed a wet system upstairs and down, using a plastic coated aluminium pipe system, very strong and durable, the manifolds are a thing of beauty, fantastic bit of engineering. Each room has its own zone and can be separately controlled by an easy to use wall mounted thermostat control. That section of the whole job came in at about £ 4000 fully installed. We laid repro farm house flags on top and they are fantastic conductors of heat. Better than the engineered wood we have upstairs. The pipes down stairs were covered in a 50mm screed which took a while to dry out, allow a minimum of a day per mm. You can run the UF to force dry it a little quicker but don't rush to lay your finished flooring before this has been dried completely or you will trap moisture. Not sure what heating system you have overall or what the rest of your homes insulation is like but do your research. UF heating works best if you are well insulated, this includes walls and roof, as air tight as you can reasonably manage and you allow it to run constantly so once your house is up to temperature it stays that way. The water in the wet system only needs to be at around 35 degrees, much lower than in a radiator, and it will bring a room up to a very comfortable warmth. If you try and run it like a conventional heating system i.e twice a day etc it's not as efficient. I am no expert, just a 'self builder' who has just finished a big barn conversion. Two floors, 228 m2 , underfloor throughout, PV, solar thermal, ASHP, log burner with back boiler and two 300 ltr tanks. We have been able to have constant domestic hot water without compromise to the heating, never been cold (moved in 2 months ago and have had a full house over Xmas. Cost a lot of money but so far I would spend it all again. We are all electric with a lot of tech, 3 adults live full time here as we work from home and my old mum lives with us. With the heating running constantly, two kitchens, TVs, computers, a biodisc sewage treatment plant and mechanical heat vent recovery running constantly I am monitoring our power usage and calculate it's costing us about £7 a day to run this house ( thanks to the PV and the insulation).

#3 Penni123


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Posted 30 January 2015 - 04:32 PM

Hi. Just read your post. Hope you are enjoying the barn. It sounds lovely. I am currently renovation 200 yr old cottage. I must be mad. My husband really wants underfloor heating, but I cannot dig down into the subsoil too much as I only have a foundation of 3 bricks deep. I was interested to see that your screed was only 50mm. Please could you tell me what materials and depth you laid under the screed. Many thanks. Sara

#4 Onoff


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Posted 30 January 2015 - 06:05 PM

There's a specific section here on UFH have a good read of some of the threads:


#5 temp


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Posted 31 January 2015 - 09:42 AM


Alternatively, we could put it on the existing floor but will lose 75-100mm of height in the room and the associated problems with existing doors etc that we want to avoid

You would probable loose more than that. Most people recommend at least 100mm of insulation and the minimum for normal screed is 65mm. The thinnest I would recommend is a system using 80mm of insulation between 80mm deep battens with 20mm engineered wood (eg oak) floor on top. That would total 100mm and give you an oak or similar floor finish not carpet. It assumes the house is reasonably well insulated.

If you can't accept thw 100mm loss of headroom or want carpet then either take the floor up or fit rads.

#6 Nickfromwales


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Posted 31 January 2015 - 10:20 AM

Plus one on that.
Instead of screed you use aluminium spreader plates
Then as said just finished flooring over that or ply then tiles ;)
No delays or drying time then too :)
Regards, Nick.

Edited by Nickfromwales, 31 January 2015 - 10:21 AM.