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RenovatingFlooringDIY
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Levelling the subfloor by breaking the concerete

Lev
2 years ago
last modified: 2 years ago

Hello,

The concrete subfloor is too high in one corner of the room causing a bad gap between the flooring and skirting board.

We already tried evening out the room with two layers of self-levelling compound, but it's still too high about 1~2 cm in this particular spot.

Can I go ahead and start breaking the concrete using a hammer drill then topping up with the self-levelling compound?

My builder is concerned about moisture coming up from the ground if cracks appear in the concrete.

This is a ground floor flat with no basement.

Any ideas welcome.

Many thanks.



Comments (4)

  • PRO
    Kingfisher Designs
    2 years ago

    I'd listen to your builder, you cannot be certain what's down there and breaking a slab will always make it weaker and prone to moisture.


    If you're very careful you could chip away at the top to level it off, but it would be more like a stone mason dressing a block with a fine chisel and maul rather than a baluster and sledgehammer job.

  • Lev
    Original Author
    2 years ago
    last modified: 2 years ago

    Well another builder said this "There should be a damp proof membrane under the concrete to stop rising damp. If you're worried you can put in a vapour barrier before the flooring".


    Many thanks for your suggestion, I'll try the chisel+maul.

  • arc3d
    2 years ago

    Your second builder is right.


    Concrete, cracked or otherwise, doesn't prevent moisture coming up. There will be a damp proof membrane under the concrete. If you damage the DPM in the process you can just glue in a small section.


    You can remove as much of the concrete as you like.

  • PRO
    Inner Space Flooring
    2 years ago

    If the house is built post 1960, it will have a damp proof course due to building regulations. Removing 10-20mm should be fine, if you do happen to reach the damp proof layer, we would advice a liquid DPM being applied. What floor covering are you going for?

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