No announcement yet.

hardiboard prep

  • Filter
  • Time
  • Show
Clear All
new posts

  • hardiboard prep

    I am confused with the mixed messages regarding hardiboard.

    I am redoing the area around our bathtub. It's Originally a 1966 vintage home that had drywall and mold! Today I plan to install porcelain tile.

    I removed all the old drywall and mold! Then I installed 1/2" hardiboard. I used stainless steel flat head screws to secure the stuff. I then taped and used thin-set to cover the screws and joints.

    At the tile store they said I need a latex modified mortar and you're golden! I then read and heard not true....You still need to seal the hardiboard with redgard or similar!

    This is a guest bathroom with minimal usage. I live in AZ and the exterior walls are uninsulated slump block!

    So..tile directly over hardiboard? -or- or apply a coat of redgard and then tile using modified mortar and never mastic?

    I looked at the Johnbridge tile reflector but I never did find the black and white answer of yes or no!

    Cactus Man
    Last edited by cactusman; 05-08-2008, 08:47 AM.

  • #2
    Re: hardiboard prep

    I myself self have never sealed the board before tile. Have done and seen plenty of baths with the board and they also were not sealed. My tile counters were done 4 years ago with Hardiboard and have had no problems.

    I don't know if it is something new with Hardiboard but it might not hurt to go to their website and check it out. You could always send them a email about it to be sure.

    Good luck, shup.


    • #3
      Re: hardiboard prep

      Heres what is going on. Perfecting something never seems to stop, someone will always try to better any situation. Redgard is an elastic water proof membrane. Which will stop water from getting threw. Should you use it, I think so. Now that it has been use for a good period of time and w/success.

      Hardyboard and Durock will still allow water to get through, even after tiling, the tiling doesn't stop water, but it does deflect it to a major degree. Steps, vapor barrier, then some people like to add another backer like 1/4" plywood for more durability, then Hardy or Durock, prep with thinset, getting all seams, then redgard, then your typical way of tiling, then a sealant. Then I run a bead of 100% micro bacterial silicone on all seam areas, where it meets the tub and inside corners going up, around shower doors. You might find matching silicone to the grout color, or clear.

      I have had no problems with just vapor barrier and hardy or Durock, prep walls with thinset, tile it, seal it. And last step as mentioned above, silicone it. I have had zero failures and no call backs, can I say for certain, moisture is not getting into those walls, no I can't. But if it is, its a small degree of moisture.

      I do now recommend any elastic membrane to be applied, this way your 99.9% moisture free inside your walls. You must use this, if you have pockets or stools build in......

      I'm not a pro with Redgard, I have just started to use it myself, but I have done a lot of research and its a terrific product. There are other brands out there too...
      Great Link for a Construction Owner/Tradesmen, and just say Garager sent you....

      A good climbing rope will last you 3 to 5 years, a bad climbing rope will last you a life time !!!


      • #4
        Re: hardiboard prep

        And I should add, that more people will be adding on tips and techniques, so you might want to stay focused here for a while.

        When one wall is done and you should bring your next tile up tight, to the finished wall and still pack grout into it, then when everything is done, caulk it. I don't leave a gap, for grout at inside corners. The caulking (hopefully matching color w/grout) will be your grout look.
        Great Link for a Construction Owner/Tradesmen, and just say Garager sent you....

        A good climbing rope will last you 3 to 5 years, a bad climbing rope will last you a life time !!!


        • #5
          Re: hardiboard prep

          Garager is pretty much right on. I dont use the redgaurd stuff though. I have only used it on a few jobs, but personally, sometimes I wonder if "to-tight" is a good thing. Stuff that cant breath can give you problems.

          But, I do use a rubber membrane on Steamshowers.

          Hardi-board, I usually roll on the primer you usually use for doing self-leveling. I used the stuff on all floors and walls when ever thinset is going to be used. By rolling the stuff on, it slightly seals the surface your puting it on, but also makes it tacky. The biggest advantage to it is that it will slow down somewhat how fast the Hardi sucks the water out of your thinset. One issue I have with any fiber cement backer is that your thinset will dry VERY fast on you. Also, this primer will also encapulate and adhere any dust you didnt get off by vacuuming or wiping down with a sponge.

          Hardi is great stuff, and I use it for everything, I dont touch Durock anymore... HATE THAT STUFF! But, be careful and try the best you can to not breath in the dust from the stuff, its not good for ya at all.

          Last tip, if you do a bench in a shower, I have found that something like "Shulter Kerdi" is a great product for water proofing them! That or "Noble Seal" basicly the same stuff, different brand. Its much easier to work with than the rubber membrane.


          • #6
            Re: hardiboard prep

            I appreciate the quality replies so far....

            I do have a call to Hardiboard tech support ugh! voice mail!

            I understand that so far there is no steadfast rule about sealing hardiboard or similar.

            Again, this is for your typical tub area, the sides are 30" wide and the long wall is about 60"
            I plan to go from the edge of the tub to the ceiling or about 83"

            This is the guest bathroom so it will not get daily use.

            The plan is to have 1/8" grout lines, I'll be using sanded grout and will seal them once dry.
            The tiles I'll be using is porcelain

            I also have caulk coming the same color as the grout for the inside corners and between the tub and tile. I already caulked between the hardiboard and the tub [about 3/16" space]

            I will report back what I hear from hardiboard

            Cactus Man