Putting it all back together - shower drain in concrete slab.

Discussion in 'Shower & Bathtub Forum & Blog' started by Cactus_King, Jun 10, 2021.

  1. Cactus_King

    Cactus_King New Member

    Jun 1, 2021
    With the old drain removed from the concrete slab I have a 1 ' diameter hole and an 18" x 6" trench leading back to the drainpipe. It's about a foot deep, half concrete slab and half dirt below it. I have all the plumbing I need to put it back together but I have a few questions;
    • Once the plumbing is reinstalled, do I fill the hole with concrete or should I backfill with dirt up to the slab level and then fill with concrete?
    • Do I use concrete patch or just regular concrete to prevent the repair spot from settling or cracking?
    • I had to cut out some plastic sheeting between the slab and dirt during removal, do I just set new sheeting in the bottom of the hole and make sure it overlaps the existing sheeting around the edge of the hole before I pour the concrete or do I need to somehow attach it to the existing sheeting?
    • Do I set the bottom piece of the shower drain flange so the top of it is level with the slab or so the bottom of the lip is level with the top of the slab?
  2. WorthFlorida

    WorthFlorida The wife is still training me.

    Oct 28, 2009
    Orlando, Florida
    For tiling questions and how go's, this is about the best forum. https://www.johnbridge.com/

    1) it depends on the shower base to be used. I would fill most of it with the dirt and pack it down. Then level it off with a few inches of concrete. If tile is going to be installed on top of the water proofing, you might want to go a 3-4 inches of concrete. If you use a base then it doesn't matter

    2) if it is premix concrete patch from a bucket, it can take days to harden. If you mix it with water, it does not matter.

    3) The plastic sheeting is a vapor barrier. Concrete slabs for homes always crack. The plastic help minimize moisture from getting under the finished floor. As you know Florida gets extreme down pours and all that water can work itself under the slab. When you chopped the hole, did you notice the dirt at the top was very hard. Before the plastic is put down, the sand is treated for termite protection. If the drain is close to an exterior wall, get a bottle of boric acid powder and mix it in the dirt to help insect proof it. Ants will find incredible ways to enter a home. https://www.homedepot.com/p/Hot-Sho...g-Powder-with-Boric-Acid-HG-96023-1/203005193

    ) get the drain you'll use and set the level so it levels off at the top of the tile including the thickness of the thin set. Go by the instructions for the drain to know where to cut the 2" drain pipe. The square piece sitting on the 2x4 is the top part of the drain.
    This is my bathroom that was done by a licensed plumber.
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  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    A pan liner over a bench can be really difficult to properly waterproof, as you can't tile directly to the liner. So, some screw cement board to it, then try to add waterproofing on top of it again (maybe RedGard or similar), but that doesn't work well.

    The liner should be installed on top of a presloped bed, as the liner is the waterproofing, not the tile. Obviously, the top surface with the tile is also sloped to the drain to direct the vast majority of the water into the drain, but there WILL be some that gets beneath, and that must be directed into the drain via the weep holes.

    My preference is to use a tileable waterproofing membrane such as Kerdi...that also makes the shower simpler, since you only need one sloped layer, then the membrane, and you can then tile directly on top of it.
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