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Chipboard over wet UFH?

Discussion in 'Plumbing and Central Heating' started by sealed, 16 Oct 2021.

  1. sealed

    sealed

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    Hi,

    Midway through refurb with some heating concerns.

    I’ve had UFH put in. Part of downstairs is concrete, insulation with screed over UFH. Nice and hot.

    However, 75% of downstairs is joisted. I was worried by builder and plumbers plans to put UFH in here. They’ve put insulation between joists. Then UFH pipes onto insulation. Then screed. Then 25mm chipboard. Barely feels warm.

    What can be done to fix this?
     
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  3. muggles

    muggles

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    Is it the floor that isn't warm, or the room that isn't warm? The floor doesn't need to feel warm if the room is warm. That being said, 25mm chipboard isn't going to help. 18mm would normally be used. Did they install aluminum spreader plates, or just throw the pipes onto the insulation? Or was it rigid insulation with channels routed into it for the pipes?
     
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  4. sealed

    sealed

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    hi, the room is warm but I can’t tell yet whether much of this heat is coming from the screed. Maybe I’m paying too much attention to the feel of the floor but it still has 15mm engineered wood floor to go over the top.

    no spreader plates. Standard PIR with pipes clipped into the top. No channels.
     
  5. Mr Chibs

    Mr Chibs

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    You don’t want a really hot floor for wet ufh. As it’s built to be heated low and slow.

    How thick is the screed is in the joisted section ?

    Also wood is not the best floor covering to get best from ufh. As it’s and insulator, which is not what you want... Tile or stone is better suited.

    Might have been better to remove the chipboard and replace with screed, then float the floor??

    Think about it you will have nearly 40/50mm of wood on top of screed.

    if the room is warm enough, why worry?
     
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  7. sealed

    sealed

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    hard to say how thick the screed is but I think at least 50mm.

    A new builder came round today to quote to finish off last builders work and freaked out about the chipboard.

    He wants to rip out chipboard and screed! I can’t afford the labour or the time but think that it should be left alone or maybe there’s another solution out there.

    The reason for the chipboard was to spread the weight that the screed and PIR would be bearing between the joists. The floorboards will be running parallel with the joists. Is there any other way to support the floorboards or support the screed??
     
  8. Madrab

    Madrab

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    I'd be checking the floor temp on the chipboard, if the system is set up properly then there shouldn't be an issue. Wooden flooring isn't the best thermal conductor though so it may not feel super hot, that and a wooden floor wouldn't normally exceed around 28Deg otherwise the wood flooring may have problems.

    As suggested though 25mm is excessive, 18mm at a max will provide plenty of support and ideally the pipes would be in a biscuit mix rather than a screed when infilling joists for UFH to minimise expansion issues.

    Measure the temp of the flooring as it is, if a target room temp is around a normal 21Deg then if the floor is around 28Deg, there won't be an issue, you just need to run it properly to maintain the air temp. i.e. correct manifold temp output, flow settings and durations.
     
    Last edited: 7 Nov 2021
  9. Exedon

    Exedon

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    If you work on basis you have a screed system as that's what it is basically if you use maximum flow temperature 55c with minimal pipe centers say 100mm maximum floor temperature you can achieve is around 28.5c but that's on top of screed .
    If pipe centers wider or flow temperature less = less output
    Ideally screed should be 65/70 mm.
     
  10. muggles

    muggles

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    Have to say I agree with the builder about the chipboard, it needs to come out. Can't the floorboards run perpendicular to the joists to solve the problem?
     
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