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Thread: UFH in screed or not in new extension - advice needed

  1. #1

    UFH in screed or not in new extension - advice needed

    Hi, have a question for the builders/plumbers or anyone else here that I could really use some advice on please. My builder has moved on to another job whilst we waited for the doors to be fitted to our extension and now he seems in no rush to come back at all. He is happy if we finish it up with other trades if we can get them in. In summary we need to finish off some boxing in, small amount of plaster-boarding, the plastering, flooring, 2nd fix electrics and any heating options.

    It’s 36sqm, flat roof and has a fair amount of glass on two of the three external walls. It has a concrete slab floor with 100mm celotex on top. The plan was (and there is still space) for a 60mm screed and then an engineered wooden floor on top.

    We were intending to have a wet ufh system installed in the screed. This is looking like an expensive option at around £4K, and then there is the flowscreed cost at around £1.9k

    I am now questioning if this is a good spend or if we should look at other options. So I googled ‘do I need to screed’ and it seems you don’t. So could I put down another 40mm celotex on top of the 100mm (or replace with 140mm celotex),then lay down tongue and groove chipboard, and then lay the final wooden floor on top of that. Obviously we’d need to fit radiators if we didn’t have ufh, probably two radiators to heat the space.

    I think this option would cost around £750 for the additional insulation and chipboard, and maybe another £500 for decent radiators. It’s It’s not all about cost though, to get ufh would involve most of the floors in the hall being lifted to get the 22mm pipes back to the boiler which is around 10m away in the garage. Then accommodate the manifold somewhere nearby. I’m also told ufh manifolds/pumps can be noisy, is this true?

    I’m also feeling that the ufh is only likely to be needed for the coldest of months as this has been built to modern insulation standards. But what I obviously have no idea about is just how cold this room will be in these coldest months. Could I end up regretting not having ufh. The flip side is I do want rugs down and therefore once sofas are there and furniture, I may only see or feel 40% of the floor anyway.

    So I don’t know what to do for the best. Will any option that other than screed leave us disappointed and cold? I don’t like bouncy floors, would this be likely with a non-screed solution. I’d really appreciate any thoughts. Thanks

  2. #2
    Grand Master snowman's Avatar
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    What do you have in the rest of the house?

    Obviously, UFH gives you that nice, warm underfoot feeling, but if you're used to radiators in the rest of the property I don't imagine you'll feel the room is cold without it, presuming you fit big/enough radiators.

    Just my tuppence worth.

    M
    Breitling Cosmonaute 809 - What's not to like?

  3. #3
    Master
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    Give Pitch3110 a shout

    Resident expert for such things

    Jim

  4. #4
    Grand Master Chris_in_the_UK's Avatar
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    We went the UFH route - it gives you more usable space without radiators.

    If I was at this stage it would be screed 100%.
    When you look long into an abyss, the abyss looks long into you.........

  5. #5
    Master ~dadam02~'s Avatar
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    My neighbour and I built identical extensions to the back of our houses, big open plan kitchen/diners. I put in underfloor heating, he did not. I love mine as it's toasty warm whenever I want it, he hates his as it's constantly cold. You pays your money.

  6. #6
    Grand Master Dave+63's Avatar
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    We have wet UFH in the kitchen extension but electric UFH in both bathrooms, the utility and the conservatory.

    Electric works well and isn’t particularly expensive to run, the conservatory being only 2kw (200w/m2 and 10m2). It’s not on constantly but switches on and off on a thermostat in the floor (as does wet).

    There’s nothing quite like the warm feeling on your feet to make you feel warm and no unsightly radiators to worry about.

  7. #7
    Master
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    I had this in our old extension. Next refit here and it's going in again. Have a look:

    https://www.discreteheat.com/

  8. #8
    I wouldn't be without UFH now. I'd go for a wet system but don't forget you need somewhere to keep the balancing manifold at the terminals.. maybe in a kitchen cupboard or something.

  9. #9
    Grand Master oldoakknives's Avatar
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    Had electric underfloor heating in a large hardwood conservatory/orangery. Wouldn't recommend it unless you have your own wind farm.

    Of the two I always prefer radiators to underfloor. Underfloor seems to take so long to come through.
    Started out with nothing. Still have most of it left.

  10. #10
    Grand Master oldoakknives's Avatar
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    Quote Originally Posted by Jubal View Post
    I had this in our old extension. Next refit here and it's going in again. Have a look:

    https://www.discreteheat.com/
    That is interesting, first time I've heard of it!
    Started out with nothing. Still have most of it left.

  11. #11
    Master Pitch3110's Avatar
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    Quote Originally Posted by Jimmcb View Post
    Give Pitch3110 a shout

    Resident expert for such things

    Jim
    Bloody hell never been called that Jimbo hehehehe.

    I would 100% go under floor it would be a simple job with its separate zone. Massive ? On flowscreed!!!!!! It’s a pig to dry plus latents to remove if you decide anything different to wood floor. 60mm screed seems a bit light, 75mm would be preferred

    Pitch

  12. #12
    Craftsman
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    You could always look at a dry screedboard and UFH solution. Have a look at Fermacell to see a possible alternate approach to traditional wet screed. I have used this successfully in commercial buildings in the past.

  13. #13
    Master
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    Quote Originally Posted by Pitch3110 View Post
    Bloody hell never been called that Jimbo hehehehe.

    I would 100% go under floor it would be a simple job with its separate zone. Massive ? On flowscreed!!!!!! It’s a pig to dry plus latents to remove if you decide anything different to wood floor. 60mm screed seems a bit light, 75mm would be preferred

    Pitch
    LOL

    Knew you’d know you know. Know what I mean??

  14. #14
    The only reason I can see that underfloor heating would be ideal in your extension is if wall space is a challenge. As you are using engineered timber, and not stone or ceramic tiles, the floor won’t feel cold underfoot. Do you see any issues with finishing up the build? Has the project been inspected and signed off so far?

  15. #15
    Thanks for the comments guys. We had always intended to go wet ufh in a screed and there is space for it in the floor build up to align to existing floors. It’s slightly tighter than I would have liked, there is about 80mm, and the floor we like is a 20mm engineered oak, so only 60mm to play with. Flowscreed will be fine they tell me at 60mm, however traditional screed it may be too thin?

    Happy with the build and it’s been inspected throughout. Spoke to building control last week, and just plaster finish, 2nd fix electrics and Fascias/soffits/gutters to complete for them to donfinal Sign off. He wasn’t concerned about floor finish or screed.

    We are tight on wall space. It’s a 3 sided room, two of which are mainly glass. So the skirting heaters are interesting. Possible to combine them with an radiator perhaps.

    As with all these things, if money was no object we’d probably just do it but it’s already over budget and still more spending to go. Also we like floors with large rugs and there will be sofas etc so just starting to question if ufh and screed is £6k well spent.

  16. #16
    Craftsman
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    If it's an area of the house you are going to use often and you intend staying at that house for a while, it is definitely money well spent. Got a wet system on my ground floor of house I self built. So many +ves. The heat is just different so much that I don't like the feeling of radiator heat anymore. No hassles with furniture being managed around radiators on walls. Like you, I moaned at the start at the Mrs for putting down rugs etc but it doesn't seem to have any effect on heating up the room. Sounds like you are up to speed on need for engineered flooring, thickness etc. As said earlier, it is an investment up front but I don't know anyone with UFH that would want to change and go back to radiators.

  17. #17
    Master
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    As many others have said, go with the wet UFH. We have it throughout the ground floor (only 32 SQM) but it makes the house so comfortable in winter. Plus it is more efficient. After a while you will probably find that you'll want it in the rest of the house so you might want to better a bigger manifold to future proof.

    One thing I would do is to get some more quotes. I am certain we didn't pay much more than half of what you have been quoted. We had standard screed not flowscreed so I don't know if that is making the difference.

  18. #18
    Master
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    Have you considered ceramic tiles? We were in a similar position and we don’t regret it. They never need refinishing and look great. I think they cost more than wood but worth it IMHO. We also went for a vertical rad with UFH


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