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Installing Hardiebacker on concrete slab?

sagevue | Posted in General Questions on

We are redoing a small 5′ x 8′ guest bath. The tub was removed and the new pan was poured for a curbless shower. But because the rest of the concrete slab was not at the proper level to match the height of the new tile throughout the house, the licensed tile contractor installed Hardiebacker cement board (with thinset) to raise the slab in prep for tiling.

I thought that cement board directly on a slab is not the proper way to raise the slab? The contractor has assured me he has been doing it this way for years and guarantees his work.

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  1. GBA Editor
    Martin Holladay | | #1

    HardiBacker is appropriate for use on floors, so your contractor's decision was fine. For more information, see the HardieBacker installation instructions.

  2. sagevue | | #2

    Thanks, Martin, for the link to Hardiebacker. I read their installation instructions which indicate that it should be laid on a plywood subfloor and secured with thinset and screws.

    Ours was used directly on the concrete slab. But only thinset was used and the bond has already broken. So there are hollow sounds when stepped on.

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