Shower curb build, concrete slab

Discussion in 'Shower & Bathtub Forum & Blog' started by Rdura, Oct 28, 2020.

  1. Rdura

    Rdura New Member

    Joined:
    Oct 28, 2020
    Location:
    California
    Hello I am new, a senior, and have read and watched everything I can. I have a new shower, as such: rough PVC drain pipe, concrete slab, 32x32 enclosure, hardybacker from ceiling to the slab. For starters, I want to build a curb. I am thinking either cement block thinset to the slab, or, forming & pouring. Cement bricks sound a bit easier than a form/rebar/mix/pour. Please advise. My second question is water ... as the curb will have no wood related expansion/contraction issues, can I tile directly to the brick or concrete curb, or should I redgard it anyway (I will eventually roll redgard on my hardybacker). Third question, if I use bricks, do I need any lath on the top/side? Fourth - if I thinset the bricks to slab, and to each other, do I put a finish coat of thin set over everything as the last step?

    My entire structure - shower, bathroom area, studio area - all one slab.
     
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
    Sep 2, 2004
    Occupation:
    Retired Systems engineer for defense industry.
    Location:
    New England
    Okay, let's back up a bit.

    Yes, concrete pavers are a good way to make a curb on a slab and will work fine.

    Hardieboard is what is called a fiber-cement board, and it cannot be installed in contact with the pan, or embedded in it. What works better in many situations is a real cement board. Because you can't put screws down low, if you use a real cement board, you can lock it to the wall with the top layer of mud.

    Cement is NOT waterproof, and in CA, you'll need a pan. What's common there is a hot mopped pan. Personally, not my favorite. Whatever you run over the sloped pan for a liner needs to go over the curb, too.

    There needs to be a sloped, waterproof layer (called the liner). The liner cannot be laying flat on the floor to meet plumbing codes, which requires it to both hold water (in a flood test), and be sloped so that it will drain.

    Then, on top of the liner, you need something that will allow tile to be installed. Generally, that's a layer of deck mud. The liner needs to be run up at least 2" above the top of your curb, and there can be no penetrations within 3" above the top of the curb.

    Check out www.johnbridge.com for help in building your shower.
     
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  4. Rdura

    Rdura New Member

    Joined:
    Oct 28, 2020
    Location:
    California
    My contractor, since departed, installed the hardiebacker from the ceiling to the slab, all three walls.

    Could I do this: apply redgard to the hardiboard, three thin coats, in order to create a moisture barrier between the pan and the hardiebacker. Or, skim coat hydraulic cement over the lower 6-12 inches of the hardieboard and at the slab/hardie seam. In this scenario, while the hardiebacker is in the pan area, the surface of the hardiebacker has a redgard (or a hrydraulic cement) moisture barrier thus no actual contact with the pan material.

    Once I build the pan with a preslope, which is another question for another time, I was planning to paint redgard over the preslope, and continue up the walls where the pan preslope and wall meet. I would put in the laticrete fabric tape along the seams - change of plane - prior to painting the redgard.

    I suppose another option is to take my angle grinder and cut out the bottom 12 inches of the hardieboard, and replace that section of wall with 12 inches of cement board, i.e. screw in the 12 inches of cement board along the bottom of all three walls. I can do it, but its a bit of a challenge cutting straight with my grinder and of course super dusty. I am not sure where to buy cement board, please advise is this is a must-do (HD?).

    In closing, not to bum people out, but the reality is I, as well as this shower, have maybe 20 years of life expectancy, I pray. I have no doubt someone will demolish my home, and this outdoor structure which has the new shower. I won't use this shower much, it's in a small cottage of no real value.

    My house is old, I'm old, and the so called "new money" has demolished every house on my street which has gone up for sale. It's just a sad reality, the house is nearly 100 years old and beautiful in its own right, but new buyers want everything new. Historic homes mean nothing to them. I'm a DIYer, and due to my advanced age and fixed income, this is my last project before I start giving away my tools and disposing of basically everything else so that I don't leave someone else with a pile of "junk" for an estate sale. I should not have embarked on this project, but I did, and now I need to finish it. Anyone I hire will charge way too much, and probably not do any better than I can do (with the help of this forum and members). I can use most tools, I just need some guidance. I can post photos. I'd really prefer not to take down all of the hardebacker.
     
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
    Sep 2, 2004
    Occupation:
    Retired Systems engineer for defense industry.
    Location:
    New England
    One of the hassles of Hardibacker is that their 'nominal' 1/2" stuff, isn't really 1/2" (it's 0.42" thick), so if you cut out part to then replace it with something else, they will be 1/2", and there will be a bump there. HD carries USG Durrock, which is a 'real' cement board. Hardiebacker is in the class called fiber-cement. The fiber is cellulose (wood fiber up to 14% of the board per their spec sheet) mixed with the cement. The fibers make it stronger, but if the board sits in a conventional pan which gets and stays damp (that's normal), it can be problematic. The Tile Council of North America (TCNA) publishes a handbook annually that is considered the industry bible, and it has two different procedures for conventional shower construction based on the type of cbu used.

    Grinding any cement board will produce silica dust which is carcinogenic...not a great idea without proper protection and dust collection. You could score it and snap it. Hardie calls for pulling it towards the score, which is sort of counter-intuitive, but works.

    So, how well will it all last if you leave it? Can't say. The manufacturer and the TCNA say don't do it for a reason.

    When using Redgard over Hardie, they call for diluting the material with water for the first coat to help prevent it from drying out before it can set properly. Hardiebacker is VERY thirsty...it will absorb LOTS of moisture. Diluting the first coat of Redgard provides enough extra moisture so that that coat can actually work...then, you need two full-depth, coats. If you use it, pick up a wet film thickness gauge and have someone show you how to use it properly (it's not hard, basically, you hold it horizontal to the surface, press it down into the wet film, pick it straight up, look for where the steps stop being covered with the material. The depth is between the one that is wet, and the one next to it that is dry. They're marked. A gauge is cheap. It's a lot harder to get the required thickness than just selecting the recommended roller as how often you go over it, how wet the roller was when you started, and how hard you're pressing can radically change the actual coverage. It must be between the min/max. Extra coats is not good, either.

    I again suggest you check out www.johnbridge.com where the whole site specializes in tiling things, and especially tiled showers. Lots of pros there that participate.
     
  6. Rdura

    Rdura New Member

    Joined:
    Oct 28, 2020
    Location:
    California
    Thank you for your input. One thought I had was to apply redgard to the hardibacker in three opposing direction coats, for the first six inches up from the slab. My thinking is that although the hardi substrate is embedded in the pan (or at least one side of the hardi wall is embedded in the pan) the hardi face is shielded from the moisture of the pan by the redgard moisture barrier membrane between the two materials - the two materials being the wet/saturated pan material, and the thirsty/porous hardibacker material. A poor analogy would be putting a gloved hand into a bucket of water ... the porous skin stays dry thanks to the glove membrane.

    Because my entire structure (a very small studio with a 30 inch wide bathroom) is built on a slab, I'm trying to figure out where the water might go if it escapes. I'm thinking that a mortar preslope with redgard applied over the preslope surface (and the curb and the walls) will hopefully contain all downward migrating water at the shower floor level and channel it to the drain. If some water manages to get past that redgard barrier and into the preslope itself, I'm thinking the preslope itself carries that water toward the drain as the water would rather travel via capillary action with the slope angle than try to go straight down to the slab. In other words follow the path of least resistance as the water absorbs in the preslope. If the redgard is working, only a tiny amount of water ever gets this far.

    But if water does make it down to the slab, it can go any direction as the slab itself is flat, so before I put in my preslope, I was thinking of applying laticrete felt at all of the slab -to- hardiback wall changes of plane, and paint the felt with redgard. This would not control puddling at the slab level, but it would seem to prevent the water from getting to, or worse, under the hardibacker and toward the anchored wall plates behind the hardibacker. The wallplates are PT. Assuming there is puddling at the slab level, the water will have to do something, thus I'm thinking that perhaps the slab absorbs it.

    Sadly, when my slabs were poured, they forgot to slope the shower floors toward the ABS pipe running up and out of the pour. Such a wasted opportunity.
     
    Last edited: Oct 30, 2020
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
    Sep 2, 2004
    Occupation:
    Retired Systems engineer for defense industry.
    Location:
    New England
    Waterproof and vapor proof are two different things...think of something like Goretex. Once the moisture is through, it can diffuse anywhere. Temperature variations can cause condensation. You're plan will slow the progress, not stop it. THen, assuming you have a pvc liner, a mud bed, then put Redgard on top of it, now you have created a moisture sandwich. Admittedly, not a huge amount of water will get through, but what does, won't escape. When building a shower, it's best to choose one listed method, do it right, and not try to reinvent the wheel.

    FWIW, it's not common to slope your slab in a shower. The normal material used is deck mud, or a very lean mixture of sand:cement in about a 5:1 ratio with only enough water to make it hold together if you grab a handful and try to form it like a snowball...it should hold together when you let go, and not drip. It ends up strong in compression , but still relatively weak, and porous so water can flow through it. Because it doesn't flow, it's much easier to shape into the required sloped pan. It's more like wet beach sand than wet concrete.
     
  8. Rdura

    Rdura New Member

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    Oct 28, 2020
    Location:
    California
    Hi Jim, I was hoping to avoid the pvc liner altogether. Thus starting at the slab: build my preslope with mortar, using the proper slope from the wall to the cast iron flange. The shower is only 32x32 so not much slope involved there. Once my mortar bed is dry, apply diluted 4:1 redgard primer over this bed and up the walls. When that primer dries, use redgard and laticrete felt at all seams where the bed meets the walls. I was planning on three coats of redgard, a day apart for each application of the redgard. After my third membrane coat cures, screw in my drain to the proper height, and float with deck mud.

    Why no pvc liner. My walls were installed floor to ceiling. I'd have to cut away the bottom 12 inches, put some blocking between the studs, then do the liner, affix the liner, and then put back my hardiboard. I was hoping to avoid cutting the hardibacker and installing the liner as I think my wall cuts wouldn't be very good, and I'm not so sure I can do the liner hospital folds and the corner dams properly. Thus is where age is not a friend.
     
  9. Rdura

    Rdura New Member

    Joined:
    Oct 28, 2020
    Location:
    California
    I mounted a Steibel Electron DHC-E heater on my exterior wall. Dimensions are approx 14 high, 8 wide, 4.25 deep. I'd like to cover this heater to help it handle the weather, and, to keep curious eyes next door from looking at it. Looking for advice. I can build a box out of redwood, but am wondering if an off the shelf metal box might work.
     
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