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Is this OK? Concrete floor install.

Discussion in 'Building' started by mrbiscuit, 11 Jul 2021.

  1. Notch7

    Notch7

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    It sounds like the builder had some 120mm Celetex left from another job - I’ve cut down the odd bit in the past, but only a total muppet would try to cut boards in half for the whole floor -anyway the building inspector would never accept that. I’m not even sure 60mm would be thick enough.


    Preparing a floor for a new slab is pretty basic stuff, how could he get it so wrong.
     
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  3. Scarlet Pimpernel

    Scarlet Pimpernel

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    If you are DIYing it, and you want to make it really easy for yourself, assuming it'll be a pour straight in, you can order self-levelling concrete, It's a decent bit more expensive, but if there's only one of you, it's worth it.
     
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  4. mrbiscuit

    mrbiscuit

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    That's really good to know. Thanks.
     
  5. mrbiscuit

    mrbiscuit

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    Hi All.
    I will be terminating my contract with the builder.
    I'm getting some independent opinion on the cost of work so far, but I would appreciate it if someone could chime in with a ball park figure for the following work, not including cost of materials, which I have receipts for:
    1. Removal of about 10 square metres of suspended wood floor (boards and joists). These were moved into my garden, not taken away.
    2. Installation of a culvert and drain. This involved one portable mixer full of concrete, approx 30 bricks and 10 metres of drain pipe, haunched in at either end. This drain was completely within the walls of the house, and involved just being laid on the ground and set with a little dry mix.
    3. Barrowing in and err, 'leveling' of 5 dumpy bags of MOT type 1 and 1 dumpy of sand.
    In total, I estimate from my records about 5 or 6 hours work.
    I understand it's very hard to gauge, but just a ball park figure would help me with my approach to things today, before I get opinion from people with 'eyes on' the situation.
    As ever, many thanks.
     
  6. mrbiscuit

    mrbiscuit

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    @Notch7 I'm just pricing up the materials left on site. Can you tell from the pictures if it is really Celotex, and if so which of their products it is?
    From a search it looks like it's maybe TC3120, which is specified as flat roofing insulation.
    The packaged boards have no markings other than 120mm with the code 417470...
     
    Last edited: 13 Jul 2021
  7. mrbiscuit

    mrbiscuit

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    Quick update.
    Had Building Control in today. They were very unhappy with what the builder has done, as expected.
    On the bright side though, they were also super helpful, and I got a lot of useful information from them. I'm embarking on the work myself, which will consist of removing a lot of the daft stuff that the cowboys stuck in.
    I'll make use of the hardcore and sand, level it properly and blind it with a proper layer of sand. I've agreed with building control to drain the incoming water from the wall directly through the front wall and into a land drain that will run along the front of the house. Seems to be a far more reasonable thing to do - get the water out of the house as quickly as possible.

    Anyone have any opinions on insulation types and position? I'm wondering if there are any advantages to having the insulation on top of the concrete slab and screeding over that. It seems to make much more sense to me to have the insulation above the slab - easier heating and all.

    Thanks,
    Rich.
     
  8. Mr Chibs

    Mr Chibs

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    Sounds good with BCO.

    You will wonder why you bothered with the cowboys when you’ve done it yourself.

    Insulation above the slab Is meant to heat more quickly than when it’s below the slab.

    You will be needing 60mm-75mm of screed. presume you’ll be screeding conventionally as opposed to liquid pumped?
     
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  10. sxturbo

    sxturbo

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    Good to hear you have a way forward.

    Insulation ontop of slab,
     
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  11. Scarlet Pimpernel

    Scarlet Pimpernel

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    With conventional heating, (i.e. carbon fuel boilers) insulation is more usually placed on top of slab, as others have said, it provides a shorter heating up period.
    But putting insulation below the slab, although requiring a longer heating up period (something like 4 hours as compared to something like 2 hours) it does provide a greater latent heat situation.

    With the move towards alternative heating systems, e.g. air or ground source heat pumps, the longer periods, and greater latent heat potential may provide benefits, and potential future proofing, for changes to the other heating systems.
    Here in France, there are now government grants for such changes to heat sources. But, apparently, it is of greater benefit to more modern homes, (insulation, draught free, etc).

    As others have said, insulation above the slab may require a slightly deeper screed layer.
     
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  12. mrbiscuit

    mrbiscuit

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    There's currently only about 140mm between the top of the sand and the bottom of the skirting boards.
    I might gain a little extra when it's compacted, but I'm guessing not much, considering I'll have to add a bit more to blind.
    Considering that some of that would be the finish flooring, I don't have much room to spare do I?
    Just taking a nominal 20mm for the final flooring, would give me 120mm for the slab, insulation, dpms and screed.
    It's not enough is it?
     
  13. sxturbo

    sxturbo

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  14. Mr Chibs

    Mr Chibs

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    Think you may struggle but there will be a bright spark along, I’m sure With a solution.

    from dpm layer, I had 100mm slab, 100mm insulation, 65mm screed and 20-25mm floor covering = 300mm approx.

    I’m sure regs will insist on 100mm minimum insulation.
     
  15. cdbe

    cdbe

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    Ask your bco, I believe the minimum may be 75mm, forget the screed, and 100mm slab on top. You may get away with trimming the door bottoms a bit, your limiting factor will be the bottom step of your stairs. Don't forget your perimeter insulation.

    The reality is, you'll probably have to live in the house for a hundred years to get any payback in terms of energy saving so just try and do the minimum. I understand your reason for involving building control but you'd have been better with just a dpm, slab and some self leveling on top.
     
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