City of Palo Alto rejects any drywall in wet areas - suggestions for backing?

Discussion in 'Shower & Bathtub Forum & Blog' started by rap, Mar 21, 2012.

  1. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,268
    Location:
    New England
    A floated wall is the cadilac of walls, just like a mudbed is for flattening a floor prior to tiling. Now, the way it is actually put together can produce something to be proud of, or a piece of junk, depending on how well it is executed for both the car and the wall!
  2. rap

    rap New Member

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    63
    Location:
    california
    LLgetfa, thank you for your reply,
    Obviously, squaring up of CBU can be done by shimming etc, but thats not the point in contention. FWIW: the guys who taught me would one-coat a three wall tub surround - using sticks/screeds - in approx 40 mins. Flat, plumb, square to a perfectly controlled depth.
    I dont understand your difficulties with "humps" etc? Assuming that you have basic plastering skills, then floating sand and cement and lime is the most basic form of skill required. It will pull-out all uneven background. Inside corners are rubbed and cut-in to square with a plastic or wood float.

    cacher, thank you for your post,
    Point is, that floating has not had it's day, it's still widely used, for example, a large, SF Bay Area tile co. that i know of, floated all it's walls and screeded all it's floors and counter tops, no CBU. $10k to $80k jobs.
    A long term, secure, mechanical fixing for the wire or mesh is necessary for floating.
    What method would you propose for fixing metal to CBU?
  3. LLigetfa

    LLigetfa DIYer, not in the trades

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    4,157
    Location:
    NW Ontario, Canada
    The difficulty is not with my ability to not make humps, it is that the humps are already there when I go to tile, hang cabinets, lay countertops, etc..
  4. cacher_chick

    cacher_chick Test, Don't Guess!

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    Land of Cheese
    I have no experience with floating walls, but I know that it has become pretty common to install masonry veneer over CBU. When doing this, the lath or wire is installed with corrosion-resistant screws through the CBU to the studs.

    Whatever you end up doing, post some pictures along the way- we would all enjoy seeing the process.
  5. rap

    rap New Member

    Messages:
    63
    Location:
    california
    LLitgetfa, Things are getting a little confused.
    1. I'm not suggesting that you are creating difficulties for yourself.
    2. A floated bed, vertical or flat, will quickly iron out all the above,existing difficulties.
    3. Perhaps as suggested by "cacher" pics would help if one is not familiar with the process. Unfortunately, among my many faults is computer illiteracy - i'm working on it. There are, however, many pics and diagrams of the process on the web - see above.

    cacher, difficulties occur in your post:
    1. Using CBU and a floating coat is time consuming and more expensive. Definitely a non-starter, especially on tracts, where production speed is the essence.
    2. Exterior fabric backing and interior wet areas are two different animals.
    3 Suppose that i used your suggestion, how many penetrations of the CBU and vapor barrier would take place in a shower or steam room? And at 16"c/c, whereas wire to drywall is stapled on at 4"c/c.
    4. I'm not asking for advice for a particular project, i'm looking for suggestions to my original post.
    5. However, thank you for your contributions.
  6. rap

    rap New Member

    Messages:
    63
    Location:
    california
    Hackney, thank you for that information ref. CI joints. It had certainly never occurred to me before, and i've been a helper around quite a few of poured joints.
  7. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    4,157
    Location:
    NW Ontario, Canada
    You grossly underestimate the potential for poor workmanship. I contend that "the most basic form of skill" is in short supply as is "common sense" which really is not all that common.

    Yes, I could grind down a hump or even grind down the backside of a stone to clear the hump. I could also refloat the whole area if not constrained by overal thickness. I could vary the thickness of the setting mortar to even out the variation if the overall thickness allowed for it. If the designer did not make allowance for corrections, it makes more work for the setter.

    I'm not sure where this is heading. My point was that the installer of CBU should not compound the problem with tolerance stacking. If the wall is true and the corners square before install, skill level (or lack of) should not be a factor except for allowing for the corners. Of course, if the framer left bows and out-of-square corners, the CBU will simply telegraph them without additional stacking.
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