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Screeds vs Leveling Compounds for Floor Construction with UFH when laying engineered wood

Discussion in 'Floors, Stairs and Lofts' started by Cej238, 12 Dec 2018.

  1. Cej238

    Cej238

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    We are currently building an extension and have poured concrete in the new area. We are about to have under-floor heating installed and the builder is proposing pouring a screed on top of this. I've discussed this with builders, floor suppliers, potential fitters etc, I'm between language barriers, my lack of knowledge and the fact we are never in the same place - I'm a bit confused about the best approach.

    We are going to fit a 10mm thick, herringbone (with non-bevelled edges), engineered oak floor. We want the wood floor to be glued down. I believe this means adding primer to the top concrete surface, then gluing each block down. The fact that the wood blocks are unbevelled means it is vital that the underlying floor is perfectly flat otherwise it will look/feel naff.

    I sense that when pouring screeds you only get one chance, it would be a nightmare trying to make it less if you pour too much, or of the wrong type. Would be really grateful for adivce on the best way to proceed.

    Is it just a case of laying the UFH, then pouring "screed"? If so, precisely what sort of screed? How thick? Anything to watch out for?

    Or is it the case that we will want to pour screed, but then add some sort of "self leveling compound" to make it super flat? And if so, what sort of self leveling compound?

    I've been reading about it tonight, and it seems that "screed" covers all sorts of things and there are considerations about thickness, whether it is bonded, risk of curling, etc.

    Thanks.
     
  2. dazlight

    dazlight

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    A poured screed would be ideal.

    I’d post this up on the flooringforum.com for some in-depth answers.

    Moisture control will be very important as well if having wood glued down.
     
  3. Cej238

    Cej238

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    Thanks, I will register there as well and ask the question.
     
  4. crazydaze

    crazydaze

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    Depends on the UFH system, but a base screed followed by a latex screed will be required.

    And then the floor needs to dry, and this is the most critical bit. The floor needs to be absolutely dry before the wood can be fitted, the wood will have its specifications in it's instructions but you will need to test the floor with a protometer and hydrometer to get proper readings, left to dry naturally usually takes a fair amount of time depending on the depths of screeds etc (approx. 4 weeks per inch of depth.)

    Glueing a herringbone floor over underfloor heating is a very tricky business, and even if done perfectly correctly, acclimatised, with the UFH set up correctly you will get gapping in areas at different times of the year as the floor expands and contracts with the heat and humidity of the floor and room temperatures/seasons etc.

    Fitting Herringbone is also a time consuming and specialised job, make sure your installer knows exactly how to fit this type of floor, it's nothing like laying regular Engineered flooring etc.
     
  5. Cej238

    Cej238

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    Crazydaze: Thanks - given the gapping - is that just something you have to put up with if you opt for a herringbone floor? Is there anything that can be done to minimise the gaps, or encourage the gaps to appear in low traffic areas?

    Thanks
     
  6. crazydaze

    crazydaze

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    It’s important to be aware that the gapping is likely to occur in some way with this type of floor fitted over UFH in this manner.
     
  7. DIYnot Local

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