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All-concrete bathroom ideas?

CloudHidden | Posted in Construction Techniques on June 9, 2003 12:24pm

Houses I design are all concrete–shotcrete walls and poured floors. Client wants to explore making the bathroom all-concrete. Actually, several clients do. They figure that since the builder’s already in there with the pump and rebar, etc, might as well form curved shower walls with rebar and a mesh or sheet-foam backer, spray it, trowel it, seal it, etc.

There are a lot of options, and I’m trying with this thread to weed out the good from the bad. The finish coat, for example, needs to be something that won’t be stained by soaps or cleaners, and won’t easily grow mold or mildew. The methods used can’t be prone to leaks, of course. FHB 3/02 p 102 has an article on Making a Concrete Tub that shows the tub in a room with cast concrete walls and a concrete sink. Inside the tub they used an epoxy primer and paint designed for swimming pools. I know of a house with stucco walls for a shower. I’ve shotcreted a hot tub and trowelled swimming pool plaster as the finish coat.

I’ve read a bunch about creating a proper base for a tile shower floor, but am wondering if there’s a way to make a slab work as a shower floor without the membrane, but with sealers.

So, if you were the builder of one of my designs, and it specified concrete sink base/counter, and curved shotcrete shower with concrete no-curb shower floor, and concrete tub…..after you hunted me down and broke my fingers so I couldn’t type such things ever again, how would we procede to make it work? What would your concerns be? How would you recommend to seal the surfaces and avoid both stains and leaks?

I don’t know many other people to talk this over with, so I’m trying to get a handle on it here first. Thanks for humoring me.

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  1. Jamie_Buxton | Jun 09, 2003 01:31am | #1

    If your house is entirely concrete, why are you putting a waterproof membrane underneath the shower?   In conventional wood-framed houses, that membrane is required to keep water off the wood.   In your house, there's no wood to deteriorate. 

    1. User avater
      JeffBuck | Jun 09, 2003 02:14am | #3

      Because concrete isn't waterproof...

      and the concrete would spall then disintergrate over time.

      Cloud....one quick thought from a sometimes tile guy that makes my own shower pans custom fit for each job....

      how about a 2 part pour?

      Lay the rough out stubs...pour the whole floor...

      then for a shower.....make sure the forms were done so the shower floor has the right pitch towards the drain....and pour it right along with everything else.

      Let that set as per a regular pan.....lay the membrane ontop of the preslope...

      then dry pack the top layer...as per usual....

      if you left some mesh sticking out just tie to shower pour to the original...

      or plan on an expansion joint and call it a day.

      I'd broom a finish so no one trips....

      They see one big mass of concrete....but U know there's a membrane under there tied into a 2 part clamping drain.

      Then I'd still try to seal the hell outta it so it lasts a bit longer.

      Now..when that water does get thru the concrete....it's got a way to find the drain like it's supposed to.

      That's just a rough draft off the top of my head.....don't warrenty that quite yet!

      JeffBuck Construction   Pittsburgh,PA

       Fine Carpentery.....While U Waite                  

      1. Jamie_Buxton | Jun 10, 2003 03:00am | #8

        Jeff --

          "and the concrete would spall then disintegrate over time"?   I must be missing something here.  Are you saying that concrete disintegrates because it gets wet?   How come folks build roads and dams and bridges and houses with the stuff?

           Jamie

        1. User avater
          CloudHidden | Jun 12, 2003 04:11pm | #9

          I'm curious on this, too. Not doubting it, just looking to achieve a better understanding of all the factors.

        2. kostello | Jun 12, 2003 04:32pm | #10

          i was under the impression that it spalls because the rebar gets wet, then rusts and the rust expanding causes the spalling???

          also water in cracks in cold weather would cause cracks and crumbling (just like bricks i imagine)

          aleks

          1. Jamie_Buxton | Jun 12, 2003 06:42pm | #11

            Yes, when rebar gets wet enough to rust, bad things happen to the concrete near it.  That's why concrete guys use dobies and such to ensure that the steel does not penetrate the surface of the concrete.   The concrete protects the steel so that it does not rust.

            As to "cracks in cold weather", I think you're thinking about water freezing to ice and expanding.  If the poster's bathroom gets to the point that water freezes, the homeowners probably have bigger problems to concern them.  <G>

          2. kostello | Jun 12, 2003 07:18pm | #13

            i agree that rebar shouldn't cause problems in concrete if done correctly.

            i do know that some high rise apartment buildings have had to be demolished due the concrete fatigue or some thing like that.

            i also agree that bathrooms should be above freezing.

          3. User avater
            CloudHidden | Jun 12, 2003 06:49pm | #12

            My porch has rebar and get's as wet as a shower and nothing's happening to the concrete. And Jamie was right re temp. We freeze the bathroom and spalling concrete wouldn't be our biggest problem! (Plus, my driveway gets wet and freezes all the time with no obvious problem.)

          4. IanDG | Jun 12, 2003 08:54pm | #14

            With water-retaining/restraining concrete structures it's normal practice to use a high-strength concrete vibrated thoroughly and with rubber "dumbbell" water stops cast into the construction joints. Waterproofing additives by themselves aren't a lot of good because they have a limited life and with good practice they aren't necessary anyway.If I understand you correctly, you don't want to apply a coating to the concrete, although there are silicone treatments that leave a natural finish. On the rebar/rusting problem, the cover to the rebar is normally increased for water-retaining concrete.I would think your greatest problem is going to be avoiding entrapped air bubbles when casting the inside of the tub and getting a smooth enough finish without patching after -- have you considered grinding the concrete a la terrazo?Interesting concept anyway.

            IanDG

          5. User avater
            CloudHidden | Jun 12, 2003 09:08pm | #15

            Thanks Ian. I'm absorbing all that people are suggesting.

          6. ak373 | Jun 12, 2003 09:09pm | #16

            As the father of 8 and 6 year old boys who are lousy aims I want an all concrete bathroom.  And I want a drain in the floor and some kind of high pressure water sprinklers in the ceiling and a UV disinfecting lamp. 

            When it's time to clean the bathroom, remove the towels, shut the door and push a button.  The sprinklers wash it down, the UV kills the bugs...

            Design me one Cloud...

          7. kostello | Jun 13, 2003 12:22am | #19

            send them to the compost heap!!!

            t doesn't matter if they miss then

            aleks

    2. User avater
      CloudHidden | Jun 09, 2003 02:16am | #4

      That notion probably came from seeing it done once in an article on tile. And I recall asking about no-curb shower here once and the answers included recessing the slab a few inches and for a foot or two beyond the shower, and then using a membrane and mud. I always figured that with concrete being able to crack, water, soap, etc could seep out through the crack. Never addressed that (false?) assumption in detail till now.

      So, are there any leakage issues with a bathroom slab?

      Edit: Jeff's answer posted as I was typing mine.

      Edited 6/8/2003 7:18:16 PM ET by Cloud Hidden

      1. edwardh1 | Jun 09, 2003 02:29am | #5

        Some motels in the Carribean have concrete floor bathrooms with a side curtained area for a shower area, and a floor drain in the middle.

        Not air conditioned like the bedroom.

        Rgular fixtures though.

      2. Gabe | Jun 09, 2003 02:52am | #6

        You could use the same sealers that we use for tank containment. It's a 2 part epoxy paint that seals permanently. When we install diesel tanks inside buildings, we have to place it inside a concrete containment structure that can hold the same volume as the tank itself in case of rupture. If it can take the punishment of commercial cleaners and fuels, I'm sure it would do the job for a shower base.

        Gabe

        1. User avater
          JeffBuck | Jun 09, 2003 03:15am | #7

          the problem I see with a paint on sealer is getting the stuff to flow down the drain..not around it.

          that's the whole reason for a 2 pt clamping shower drain.

          Maybe we start with my idea and paint your stuff on.....I'm getting closer to warrenting this project. I like the industrial line of thinking....

          Jeff

          Buck Construction   Pittsburgh,PA

           Fine Carpentery.....While U Waite                  

  2. Wet_Head | Jun 09, 2003 02:03am | #2

    make sure the seal does not make the shower pan overly slick when wet.  What if you do the whole thing as an open room?

  3. User avater
    CloudHidden | Jun 12, 2003 11:27pm | #17

    Siiiiigh.....I could use a cigarette after that...

  4. skids | Jun 12, 2003 11:36pm | #18

    i have quite a bit of experience with structural concrete, but as a form carpenter i at most usually only assist in the placement of the concrete. with most bridges, warped wing walls, etc. there is a waterstop in the expansion joints. that might help for some of your applications as extra insurance for leakage. a similar material in sheet form (some kinda rubber vinyl mix) for sink basin and tub/shower bottoms and critical areas might be a good idea. you may want to consider burying some of the forms with shotcrete. if you dont have to strip a form you can get more of a monolithic pour or shotcrete application to prevent leaks. i wouldn't mind trying to form something like that up, would not hunt you down. forming with expanded metal would eliminate stripping and provide reinforcement at the same time. have you ever heard of the kiosk public toilets in san francisco? after you use the toilet and leave it locks itself and goes through a cleaning cycle so you never have to clean the bathroom. for the public toilets its an automatic feature but for a private bath i would have it switched so i could remove towels etc. and turn it on only as neccesary. now i think that would be really cool, expensive though. just trying to provide food for thought

    1. User avater
      CloudHidden | Jun 13, 2003 09:26pm | #20

      Hopefully we'll get Jeff back here to continue the discussion of what can happen to concrete under these conditions, and what causes it to spall. Pending that, my concerns include the water carrying organisms and sloughed off skin cells, etc into tiny gaps and cracks where they can breed mold or who know what. Among the many things I'm not, I'm not a micro-biologist, so I don't know what to be concerned about or with what priority.

      1. viliam | Jun 14, 2003 02:27am | #21

        Hi Cloud, Hi Guys!

        I'm Viliam's wife,  (we are new to this site).My name is the Anarchist Gardener/renovator.

        I love concrete!

        I'm obsessed with concrete!

        I dream about a concrete house!

        I love it because you can give it any shape you want, it's natural (I'm a gardener,      I 'm into nature man..........).....and it's indestructable (I have two kids , a dog and I'm a gardener...)...........if it's done right.

        About 6 years ago , in my last house, I put a concrete counter in my kitchen(a horizontal wave going around the kitchen) . I loved it and I miss it very much. It was so cool. I am gong to do it again in this house when I reno this kitchen.

        Anyway, what I would like to add to this discussion is that yes bathrooms are dirty and icky, but guess what guys you clean them! I think it would be much easier to clean a concrete shower than a tile one, especially one made with those gorgeous

        mosaic 1/2 inch tiles, which I would love, but I don't have a maid to clean all those tiny little grout lines! I hate toothbrushing with bleach my 8" tile in my shower as it is!

        I'm going to be renovating my bathroom this summer and I would love to have concrete walls in the shower and outside the stall  as well. Any suggestions on how to do this in an existing house?

        Cloud, I would like to embed river rocks into concrete as the shower floor as well as the rest of the bathroom. I don't think it would be slippery (I hope)  and then your feet can get a massage as you shower. I think in an open bathroom,like the one your describing,  with a solid concrete floor, just embedding river rocks in a very naturalistic pattern in the shower area would be way funky!

        Cheers,

        J.

        The anarchist Gardener(and renovator)

        1. kostello | Jun 14, 2003 01:40pm | #22

          i can't under stand whats natural about concrete???

          i do think that a concrete bathroom could be cleaned with a pressure washer.LOL

          aleks

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