Contradicting contractor recommendations

Discussion in 'Subfloor Preparation' started by Brombeer, Sep 15, 2020.

  1. Brombeer

    Brombeer Member

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    Hi all,

    New poster though I've read a fair bit on here and it's been very useful (thanks!).

    I've had contradictory advice from flooring contractors regarding subfloor preparation and I was hoping to get some advice on here:
    We've got a '50s semi, it's not bad for damp issues given that we live in a quite coastal position in the SW. There's no DPM (confirmed during recent renovations) and we would ideally like to put an engineered wood floor in. I've had two flooring contractors around, both seem to be reputable and have good reviews/come recommended but their advice is quite contradictory:
    - Contractor 1 recommended a SLC/surface DPM/SLC sandwich and glued floor (seems to be quite commonly advised on here) as that would solve all moisture coming in through the floor.
    - Contractor 2 said to go with an SLC, then underlay with built-in DPM (not so popular?) and some form of locking joint for the planks as a surface DPM would just shift the moisture problem into the walls.

    Flooring contractors are few and far between around here so I was hoping to get some opinions on this from forum members.. Based on what I've read on this forum I was leaning towards the SLC/DPM sandwich, but having spoken to the neighbours, they had this done and have had no end of trouble with damp getting into the walls. Ultimately they had to tank the walls up to 1.5m high, which they described it as 'living in a swimming pool' for the next six months and generally it seems to have made their damp issues worse (they certainly suffer a lot more from it than we do!). Am I right in thinking contractor 2 his proposed method would not preclude doing the SLC/DPM/SLC sandwich at a later date if it turns out to not work?
     
  2. Brombeer

    Brombeer Member

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    Forgot to say it's all blockwork downstairs with a very loose/sandy scratchcoat and plastered+wallpapered.
     
  3. merit

    merit Well-Known Member

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    They must have a lot of damp for that to happen. I’ve only seen it when there is water trying to push up through the subfloor ie a leaking pipe or a serious moisture issue.


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  4. Brombeer

    Brombeer Member

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    I see your point, it's a bit hard to get much reliable detail from them regarding their damp issues (i.e. what's real and what's exaggeration).

    For what it's worth, the party wall seems fine with regards to moisture and I can't see how the issue would suddenly stop there when the houses are otherwise each others mirror image? Also, the scratch coat underneath the plaster is dry/crumbly all the way to the floor so it's not exactly sopping wet.

    Contractor 2 used a wood moisture meter to quickly assess damp, and whilst I know these are notoriously unreliable for concrete/plaster, they did definitely show much higher readings up to approx. 300mm up the wall so there was a trend there.
     
  5. merit

    merit Well-Known Member

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    The simple solution is to put a hygrometer down and get a reading. You can then speak to Ardex about the subfloor and readings and get a specification from them


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