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    hobbzilla's Avatar
    hobbzilla Posts: 28, Reputation: 2
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    #1

    Apr 29, 2009, 10:32 AM
    Kerdi on Drywall
    I am extending my shower into our closet. (See here). 2 existing walls have a medium knock-down texture and have been primed and painted. Can I install Kerdi on top of that, or is it best to just hang new board?
    Bljack's Avatar
    Bljack Posts: 245, Reputation: 28
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    #2

    Apr 30, 2009, 06:37 AM
    Remove the old sheetrock and install new sheetrock. Don't use greenboard, just regular sheetrock. Don't prime it or paint it. The only thing I do with seams where two pieces of tapered sheetrock edges come together is to use alkali resistant backer tape and thinset to go over that. Not because the joint needs to be finished, but because I don't want the recess in the plane of the wall.

    I am planning on having a bench and recessed niches. What are the specific requirements there? Thanks in advance!
    Well, normally for a niche I would calculate where each row of tile will fall along the wall and frame out the niche to conform with a balance of tile around it, placing blocking between the studs, covering with cbu and painting on a waterproofing membrane such as Hydroban or Redgard, within the niche and 6-8" around the niche over the wall. I always make the bottom a little bit lower so that as I go up the wall with the tile, I can use the tile edge as a screed guide and fill with mud or mortar.

    Pretty simple to do. However, If I were to go to Hell when I pass on, spending eternity wrapping niches is kerdi would be my punsihment so I will suggest to you to use a preformed niche and bring the Kerdi over the face of the niche using "kerdifix" to adhere the Kerdi to the niche. I know of no reason why you couldn't use a waterproofing liquid membrane over the niche as normal and then use Kerdifix to seal the Kerdi to the liquid waterproofer, other than incorporating two different products like that would remove the warrany you'd have from either manufacturer.

    For the bench, you can frame it with 2x's and add plywood and sheetrock to the seat and sheetroc on the face and then cover the entire thing with Kerdi. Works great when it's all clean 90 deg angles. If you want a rounded bench, Noble company makes preformed benches in round, square and neoangle and triangular configurations. You install them once you are done wrapping the shower with kerdi, pick a corner for the bench, pile some mud on a layer of thinset, comb thinset on the back sides of the bench, place it in the mud and press the thinset coated sided against the wall and use Kerdifix between the bench edges and the Kerdi.

    Finally, by far the best method of creating a bench is to use a product from Innovis Corporation called " Betterbench."

    Both Nobel and Innovis make preformed niches as well.

    Noble sells online with $5 flat rate shipping on all orders or you can use the like for a local distributor and Innovis has a Dealer locator link on their site.

    Sheet Membranes & Shower Installation Products for Tile & Stone

    Shower Benches and Shelves - Better-Bench, Better Bench Adjustable Unit, Recess-It by Innovis Corporation

    Good luck with your project.
    hobbzilla's Avatar
    hobbzilla Posts: 28, Reputation: 2
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    #3

    Apr 30, 2009, 08:33 AM

    FYI. I did contact Schluter Systems directly via e-mail and here was their response:

    Kerdi can go over a latex painted drywall with an unmodified thinset.
    Bljack's Avatar
    Bljack Posts: 245, Reputation: 28
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    #4

    Apr 30, 2009, 09:23 AM
    I know it can. But you have textured walls. With that being the case, I'd open up my wallet for $12 worth of sheetrock.
    jfrwhipple's Avatar
    jfrwhipple Posts: 6, Reputation: 1
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    #5

    Mar 28, 2012, 05:56 AM
    Drywall is not allowed in shower use at all. In North America all the tile councils have removed the use of drywall from your shower locations.

    Drywall can be used in places like powder rooms or kitchens but not wet locations.

    Many people are confused by Schluter's acceptance of drywall but if you check with the

    NTCA
    TCNA
    TTMAC
    Or the Gypsum Organazaition you will find that drywall is not an approved backer board.

    If you use Kerdi over drywall you need to make sure that there is no drywall compound or paint of any kind. Non-modified thinset does not stick to either!

    If you must use Kerdi (there are some many better choices) then pick a backer board like Green EBoard, Hardi Board or Wonderboard - but not drywall.

    Best,

    John Whipple
    By Any Design Ltd.

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