Advice requested on levelling concrete sub-floor

Discussion in 'Subfloor Preparation' started by Jon Doe, Jul 14, 2019 at 8:43 AM.

  1. Jon Doe

    Jon Doe New Member

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    Hi,
    Some advice and recommendations on the following would be appreciated. Some photo's of the existing floor are attached for reference. 1.jpg 2.jpg 3.jpg 4.jpg 5.jpg

    We have a concrete sub-floor of around 25 square metres on which we plan to lay some 3mm acoustic silver underlay followed by some 12mm laminate. The house was built in 1969.
    The sub-floor is reasonably flat apart from two sections which are several mm higher than the rest.
    These are near the french doors at one end of the room and then a three foot wide section right in the middle which runs across the width of the room (where a partition wall used to be).
    To my mind, the best approach would be to lower the high points, apply a minimal amount of SLC if necessary (Mapei ultraplan perhaps) and then lay the flooring.
    Levelling everything up on the other hand creates new problems, such as:
    Half the skirting board will end up below the level of the floor (or will have to be replaced);
    The floor will end up close to the top of the level of the threshold of the french doors;
    There will be a more noticeable step down into adjacent rooms (hallway and kitchen);
    The cost of levelling up could be prohibitive.

    One contractor I contacted stated they didn't believe it would be possible to remove the excess near the french doors (no reason given), but would just level up using their preferred ready mixed compound, at a cost of £50 per tub (£30 materials, £20 labour per tub). But with each tub covering just 5 square metres to a depth of 3mm this could get quite expensive.

    Another contractor stated a floor grinder could be used successfully on both of the high spots, but has since indicated he has 'passed the details of the job onto a colleague with more experience', i.e. isn't interested in the job for whatever reason.
    A plasterer up the road indicated he could use his SDS hammer drill to break up and remove the excess, but failed to turn up to an appointment to assess the job more fully.

    I've started taking the old tiles up already and they will be completely removed before work on the new floor starts. These are metric 30cm tiles so apparently do not contain asbestos. They also pop right off with a minimum of effort.

    Any advice on what the best option/tools for the job are would be appreciated, as would any recommendations for a reliable and reasonably priced contractor in the Plymouth area.

    Thanks.
     
  2. Rugmunching

    Rugmunching Well-Known Member

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    Whip them old skirts off
    Long handled scraper to flip the tiles up
    Providing you have no moisture issues (get it tested) then minimal screed coat if it really needs it, lay flooring and fit fresh skirts. Least then you wont have to fit crappy beading
     
  3. Jon Doe

    Jon Doe New Member

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    Thanks for the advice. I've got most of the tiles up now and they came up fairly easily using just a bolster. I don't plan on removing the skirting boards if I can help it though just to keep the costs down a bit and avoid and also because all the walls are concrete the skirts are well nailed in so removing them could result in needing a plasterer as well.
    The floor underneath the tiles is as mentioned pretty level already, it's just the area near the back door and a section across the room in the middle which are somewhat higher.

    How would the pro's go about removing a few mm of (presumably screed) from the high points?
    Is a concrete grinder the best option or a rotary hammer drill with scaling chisel perhaps? Would something like the Titan TTB278SDS SDS Plus be sufficient at 8 joules or is something a little more heavy duty like the Titan TTB280DRH breaker required, which can impact with 45 joules (sorry it won't let me post the links)?
     
  4. merit

    merit Well-Known Member

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    You can hire concrete grinders and planers to remove high spots. Breakers will work but they will damage a large area of the screed most likely


    Sent from my iPhone using Tapatalk
     
  5. dazlight

    dazlight Super Moderator

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    Hire a hand grinder. Take down high spots best you can to try and get it flat over 2m
    Use screeding compound like ardex NA , f ball 1200 pro or tilemaster pro flow.
    Remove any loose adhesive.
     

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