Viewing 22 posts - 1 through 22 (of 22 total)
  • Wet underfloor heating – advice please!
  • alibongo001
    Full Member

    Hello all

    I am having my kitchen refurbed which is involving a large amount of work – plaster off – new electrics / gas etc

    I would like to have wet type underfloor heating and wondered if anyone has done this before or could point me in the direction of any good online resources.

    The job is to dig up Yorkshire stone floor- then prepare for the heating – insulation etc

    So far there are 2 methods discussed:

    1 dig down around 6″ and insulate with kingspan / lay heating on top then screed & tile on top.

    2, dig down, lay joists to form false floow / insulate then heating with tiles on top

    Any help or direction you could offer would be very welcome

    Cheers
    Alastair

    wrightyson
    Free Member

    Wooden floors don’t work that well with underfloor heating. Digging 6 inch won’t be enough I’m afraid, you’ll be pissing money away.

    alibongo001
    Full Member

    I am easy on the prep – what would you recommend?

    I know the top layer needs to be tiles – the rest is up for decision

    Do you think the screed / insulation method is better?

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    5thElefant
    Free Member

    I’ve had option 1 in a new build.

    It took several weeks to dry the screed with the heating on (I was going to say months, but maybe it just felt like that). You can’t put your top layer of floor on until the screed is dry and you’ll have a room like a sauna until it’s done.

    wobbliscott
    Free Member

    Like 5th elefant I had it in a new extension. I’m sure the depth was about 18 inches below floor level – definitely more than 6 inches. Damp proof membrane, then thick insulation and the plastic piping pegged into the insulation and quite close to the floor level. I had 2 coiled circuits, then the screed over the top. Pretty simple really and works great.

    My brother installed it himself on a wooden joisted floor, so again he had the space below the floor level, insulation between the joists, notched the joists to lay the piping over the whole area then a dry biscuit screed. Works fine for him, very efficient.

    Why are you only digging down 6 inches? Can you go deeper?

    alibongo001
    Full Member

    I could go down deeper – looking for a balance between cost of doing the job and efficiency of the finished work

    Would 8 to 12 inches with 6 inch of insulation be good?

    lesgrandepotato
    Full Member

    It’s more than six inches, we’ve done it in our refurb. Took out the old slab, then the old Mot base. Dug down 6 additional inches, relayed the Mot, visqueen and then kingspan with pipes on top. Then a fibre screed of 40mm on that. Whole floor is about 18″ thick in total

    tomlevell
    Full Member

    “Best” solution is in screed.
    You need flat base, insulation say 50mm minimum, screed on top of about 65mm. You’ll probably need to dig deeper to get the flat base sorted out.

    Screed will take a couple of months to dry and you don’t do it with the heating system as you’ll crack the screed. Switch at a very low temperature after screed down for a certain period then ramp up.

    “Other” solutions are trays on joist or insulated panels with flooring on top. Got to be careful with levels.

    Simplest option is heat with rads and stick some electric tile heating in.

    blurty
    Full Member

    Can’t advise on the heating, but screed naturally dries out at 1mm per day, assuming it doesn’t get re-wetted. This can be sped-up with dehumidifiers

    A liquid DPM can be painted on top if there isn’t time to let it dry before a timber floor is laid.

    If it’s ceramic tiles (have you seen the posh ones that look like wood?) then use a cement adhesive

    alibongo001
    Full Member

    The wood ones do look great – I think we have chosen some limestone tumbled ones that appear similar to the Yorkshire stone we were hoping would be underneath!

    They do some different sizes so that it looks more original – I think they call it modular!

    petefromearth
    Full Member

    We had the exact same thing done in our kitchen last year

    Think they dug down about a foot, no more

    Then it was a layer of hardcore, DPM then concrete (wheelbarrowed through the house and raked level)
    Then 4″ kingspan, with the UFH pipes clipped on top
    Finally a fibre reinforced screed which was hand trowelled on

    To finish we wanted half the room tiled and the other half oak laminate. We were advised the slate tiles could go on after about a week but should wait a couple of months to do the oak.

    very happy with the end result, so comfortable when it’s on

    Only gripe is a couple of cold spots. Make sure your builders are more precise than ours where they lay the pipes Vs your kitchen layout, and get the spacing consistent.

    Our UFH system was from Wunda and I would use them again in future

    Spud
    Full Member

    When our kitchen was done, it was down to base, concrete, 150mm Celotex, poly, pipework, screed (45mm – ideally should be more) and then tiled. Works great. I didn’t do it however, all done as part of a large extension. As above pumped screed was a ‘mare to get dry and then it needs scuffing for the treatment and grout etc to stick. It took I think ~5 weeks and that was pushing it with dehumidifiers etc. It was November/ December mind.

    petefromearth
    Full Member

    A liquid DPM can be painted on top if there isn’t time to let it dry before a timber floor is laid

    That’s actually what we ended up with because we couldn’t be arsed to wait any longer.

    peterno51
    Full Member

    Have a little looky at this…

    Retrofit cheating…

    alibongo001
    Full Member

    Have you used the stuff on your link Peter?

    Looks interesting!

    Thanks for all the input so far!

    Screed seems the difficult bit – I am sure OH would like to get to the point where we have some kitchen units sometime this year!

    chiefgrooveguru
    Full Member

    Are you doing the whole house or whole storey with underfloor?

    I looked into wet underfloor heating for the living room bit of the extension we’ve built but ended up going electric because the rest of the house is on radiators and it was a complication too far, with the double whammy of the slower response time and the required lower working temperature.

    chickenman
    Full Member

    I fitted UFH into a suspended timber floor in a new build conservatory. Upped the joist size a couple of inches to take the extra weight, built trays between the joist to take 50mm insulation, clipped the 15mm plastic pipe to it (notched over joists near their ends so as not to weaken them) then poured 50mm of concrete on top. 12mm engineered hardwood flooring forms the floor surface. Obviously not very efficient having timber on top or even having it heat the sky during long winter evenings but it has made the conservatory the favourite place to hang out in the house all year round. Was self build and on a tight budget. Been running fine since 2001; the joists have shrunk about 5% with the heat so the floor has dropped a bit!

    alibongo001
    Full Member

    Hi Chief – just a kitchen, but might make it into the utility room depending on difficulty – main thoughts were around keeping the wall space for kitchen units as the room is a bit of a strange shape to it.

    The room will also have a wood burner (true to STW type) which will provide most of the heat when on – but it wont always be on!

    Room is about 25m2 so quite large

    metalheart
    Free Member

    In a commercial situation I’d spec 75mm insulation/75mm screed/pipes but there would be additional insulation under the 200mm concrete slab.

    I’ve had 4-5 UFH jobs and none of them have gone well, the installers don’t really care and it’s never set up properly.

    If that wasn’t bad enough underfloor heating needs the slab to be kept up to temp as it has a slow response time (to heat up or cool down) and will need to operate at different times from your radiator circuits so your heating system will need to run longer. Takes at least a day to come back up to temp after being switched off.

    Screed takes forever to dry/cure and it limits what kind of floor covering you can put down too. Max output you’ll be able to achieve is 80w/m2 gross 100W/m2 net floor area. If you fancy wanting to change your kitchen layout tough, the heating is fixed.

    You may just get the inkling that I’m not a fan…. 😀

    hamishthecat
    Full Member

    Chiefgg makes a good point. We have wet UFH in a dining room extension plus I installed it myself in a study which had a big step down into it. Both run off a normal rad circuit. The study works pretty well as it is a small room but the dining room needs to have the boiler on all day to get it going. I’d think hard about having it for one room off a normal circuit.

    slightreturn
    Free Member

    I have Velta/upanor wet system. Superb investment. I have mine under York stone flags, which act as massive storage slabs. The heat output is lovely.
    I dug down the appropriate depth. Layed DPC then concreted over that. Kingspan type insulation on top then pipe work layed into four zones coving all downstairs in my house. Liquid screed to cover pipes. Then I relayed the York stone flags using a solid bed of sand and cement.( do not spot lay, as the heat cannot transfer through stone)
    Cleaned and sealed my flags with LTP mattstone (superb sealant).
    Enjoyed it since. Especially the cat

    Pp

    peterno51
    Full Member

    Ours is a mixture of rads and wufh.
    1st floor all wufh using NuHeats older system of kingspan laid between the joists and then shaped 12mm foam with metal trays that the pipe work clips in, laid on top of the kingspan.

    Ground floor is a same idea but with pipework laid in 11mm screed on top of kingspan within the joists instead. There is one room still on rads.

    This is in a 1890’s Victorian villa type thing.

    We use Honeywell EvoHome to make it all the right temperature using its room heating profile woowoo and it all just works.

    Ymmv.

    (Would probably have gone for the new NuHeat lay it on top system I linked to earlier, but for that you ideally need to set a datum floor height through out that floor to make it seamless floor levels)

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