Shower basin cast into a new slab?

Discussion in 'Shower & Bathtub Forum & Blog' started by idssteve, Oct 15, 2010.

  1. idssteve

    idssteve New Member

    Messages:
    7
    Location:
    Santa Fe NM
    Shower basin cast into a new slab?

    We are planning to build a new home on a slab. The newly poured slab will have embedded multicolored “river gravel” into the surface and then ground flush and polished. We fell in love with examples we’ve seen. I already have the grinder/polisher. ;)

    We are pondering the idea of screeding a 60x60 sloped (1/4” per foot??) shower basin directly into the slab. Then grind and polish like the rest of the floor. I’m wanting a scenario with minimal ledges for the wife’s wheelcair to negotiate.

    I’m envisioning fabricating and brushing a free standing stainless shower stall. Trust me, that part will LOOK nice. Mostly concerned with casting and/or troweling the shower basin. ?? Any suggestions or concerns with this concept?? Moisture into the slab??

    Thanks
    Last edited: Oct 15, 2010
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,354
    Location:
    New England
    While you can have river rock as the floor, industry standards won't allow you to do what you are proposing. They don't consider concrete as a waterproof layer, so you need a liner. That liner must be sloped to a drain with weep holes to drain any moisture that gets beneath the setting layer. You can still have a barrier free shower, but you shouldn't (and it wouldn't pass code if the inspector knows anything).

    So, I'd have them depress the slab where you want the shower to accommodate the barrier free, then build it up 'normally'. This means, preslope, liner, setting bed, then finished surface. Getting the details all right with the walls as you've envisioned might be a little non-standard as well, but doable. Suggest you check out www.johnbridge.com for help on this...they deal exclusively on tiling, showers, etc. and lots of tiling/shower pros to bounce ideas off of.
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,301
    Location:
    Cave Creek, Arizona
    IF you have a "flush" roll in entrance, then there is little sense in having a liner because the water could never accumulate in the shower above the floor level, without also flooding the room. There would also be no way to "conceal/enclose" a liner with a free standing shower wall.
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,354
    Location:
    New England
    Check out Tile Council of North America. They have design diagrams for this sort of thing (haven't looked recently for this situation), and you may need to waterproof most of the floor in the bathroom (and part way up the walls) to accomplish what you want and pass codes and meet industry standards. First step is to see if you can talk to the local inspector, describe what you want, and get his blessing. I'd still check out www.johnbridge.com for their thoughts...they do this sort of thing every day.
  5. Gsalet

    Gsalet George the Plumber

    Messages:
    83
    Location:
    San Francisco
    I have done a couple of these and a liner is required. a nice touch is a trench drain if installed on the outside edge it prevents the water from traveling past the edge of the shower, or if installed next to the wall it provides a more even surface to walk or roll on. and be sure to talk to a good tile person
  6. idssteve

    idssteve New Member

    Messages:
    7
    Location:
    Santa Fe NM
    Hmm, well, looks like there’s a little more to it than simply putting in a “glorified floor drainâ€. ;) My concern with “typical†membrane ADA installations is that the wheelchair itself is difficult or impossible to dry and it will carry and drip significant moisture onto the floor in front of the membrane edge when exiting. How to keep moisture from getting under the membrane from outside of its protected zone? Make the whole room a “shower panâ€?? Hmm… further research needed.

    Thanks guys. Good info.
  7. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,301
    Location:
    Cave Creek, Arizona
    The purpose for a membrane is to contain the water inside the shower basin when the water accumulates faster than it can drain. It has absolutely NO PURPOSE when the water can flow onto the floor of the room since it cannot "accumulate" higher than the floor. Here, they would require a trench drain at the entry, but that is an independent matter from the membrane.
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,354
    Location:
    New England
    Schluter www.schluter.com makes two membranes that can be combined. Check out their website. Kerdi inside of the shower, and Ditra outside will make a totally waterproof area. Use some Kerdi-band on the floor wall junction outside the shower, if you're paranoid. I've used Kerdi and Ditra, and find them easy to use and to work well. They have some new waterproof panels designed for tiling walls, benches, etc. called Kerdi-board that can be used in place of a wall panel, and then the waterproofing. You can tile directly to it, make benches, etc. out of it so there'd be no wood or other stuff in the shower area to waterproof. If you ever got enough water outside of the sloped shower area, it would flow out of the room, but that's another story; normally, it would only be some drips, and may not even need additional waterproofing.
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