waterproofing before tile

Discussion in 'Remodel Forum & Blog' started by rrekih, Jan 12, 2010.

  1. rrekih

    rrekih New Member

    Messages:
    46
    Location:
    Canada
    I am redoing my front porch.
    It is approx. 8ft by 3ft.
    I have put down 3/4in ply. with joists spaced at 14in, the short way.
    I want to put down tile, what is my best way to waterproof the ply. before I lay the tile?
    I have thought of using a membrane type of product.
    Does what you lay have to have some roughness for the mortar to take.
  2. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    Best advice....see our friends on the tile forum, johnbridge.com

    From my personal experience, there are couple of products you might use:

    A few companies make membranes. They are intended and designed for direct application of the tiles. There is also a paint-on coating called RedGard which also works well.

    Most importantly, tile needs to be on a very rigid substrate. Any flex will cause tile cracks. Generally, a 1" minimum thickness of subfloor is recommended.
  3. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,022
    Location:
    New England
    Look at www.schluter.com for waterproofing. Laticrete and Noble also make some good products. Ditra is an anti-fracture membrane that could be applied to the plywood. Since it comes in 1M wide sheets, you wouldn't need any seams. You'd probably want to use some Kerdiband and waterproof up the house side wall and a drip edge at the outside edges. If there's living space underneath the porch, you should consider other stuff. Schluter makes all of those as well.

    If the tile is natural stone, you need a second layer of ply, at least 3/8", offset from the first layer, otherwise, the 3/4" should be fine for porcelain if the footers are solid and there is adequate support for the outer ledger board.
  4. lajoe

    lajoe FlooringSupply

    Messages:
    4
    Location:
    Los Angeles CA
  5. dtherrien

    dtherrien Licensed Building Contractor

    Messages:
    13
    Location:
    Massachusetts
    rrekih.....install the 1/2" water proof hardi backer board on top of the plywood. I would cement it down with karabond mixed with karalastic with a few screws so it doesnt move. Install your tiles with the same cement of karabond/karalastic......grout with epoxy grout.......make sure you use a good quality tile as this will not come apart easily.
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,022
    Location:
    New England
    A common misconception is that stuff like Hardibacker or any cbu is waterproof - WRONG! In this instance you need waterproof to keep the ply intact for the long-term. All cbu's are not damaged by moisture, but that in contact with the ply over time is not a good idea.

    One thing I like about Ditra is that it is waterproof, a great decoupling membrane, and has channels in it that allows the substrate to breath, which is a great side benefit.
  7. dtherrien

    dtherrien Licensed Building Contractor

    Messages:
    13
    Location:
    Massachusetts
    I'll put my methods.....most of which are traditional....against any. If done right, you dont need all this new crap that they have out there today.
    i have never had a call back from a tile job.
  8. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

    Messages:
    4,173
    Location:
    North Vancouver, BC
    Some other points to consider

    Post(s) deleted by John Whipple
    Last edited: Mar 18, 2014
  9. GabeS

    GabeS Remodel Contractor

    Messages:
    294
    Location:
    Brooklyn NY

    I would advise that you do some research on these new products since they can make your life a lot easier. It wouldn't hurt you to give some of them a try. It's just a matter of getting comfortable with them. You're only comfortable with your current methods because that's what you are used to.

    And as Jim stated, hardibacker is NOT waterproof. It's resistant to crumbling from exposure to water. That's it. To effectively waterproof a floor, you need a waterproof membrane like kerdi, or Ditra with the seams kerdibanded, or similiar membrane. There are other methods like a few coats of redguard or mesh and asphalt which I myself are less familiar with.

    But just hardibacker on a floor will not cut it. This is not a traditional method for waterproofing. I'm all for traditional methods, they work great, but must be done properly.
  10. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,022
    Location:
    New England
    Not all cbu products are recommended by the manufacturer for outdoor use. It's been awhile since it read that on Hardie, but I think it is one not recommended for exterior use.
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