Installing Cement Backer Board

12 responses

  1. anthony
    April 2, 2012

    im going to be tiling ceramic trying to make 2 rooms into one first has wood subfloor other was an addition at one time has concrete floors i was thinking about putting backerboard over entire floor before tile do you think i can scew down backer boards to the concrete with the proper screws this way my floors will be level

    • Tim Carter
      May 23, 2012


      Way too much to type. You need my 15-Minute Consult.

  2. Chad
    July 13, 2012

    The top of my tub has a flange on it. This flange curves into the top of the tub and therefore is not perfectly straight. When you say "I always leave a 1/4-inch gap between the top of the tub and the bottom edge of the backer board." does this mean leave a gap between the backer board and the top of the tub or leave the gap between the backer board and the top of the flange? I am afraid of going over the flange because I want to put shower doors in and need this to be as square as possible.

    • Tim Carter
      January 11, 2013

      Chad, you need to schedule a 15-Minute call with me. There's simply too much to talk about and type.

  3. Marco
    November 7, 2012

    Hello everyone. I have a quick question. I'm remodeling my shower and the contractor I hired decided to add a paper sheet called Aquabar B ( is a moisture vapor retarder ) on the stud walls. After that he put a cement layer on it, and he 'll finish with other 2 coats of cement and then tiles. In my opinion ( but I'm not a contractor ) I think a cement backer board is necessary between paper and the cement for the tiles. Does anybody have advice? Thank you so much

    • Tim Carter
      January 6, 2013

      Marco, your question requires lots of typing, plus I have some questions for you so I can give you the correct answer(s). I only do pithy answers here in the comment section. If you want to protect the investment you have in your house and not waste time or money *hoping* you make the right decision, you should talk to me on the phone for just 15 minutes. It'll be the best investment you've ever made in your home!

  4. Charles Stephens
    October 18, 2013

    Can I glue cement board to a concrete floor to cover old adhesive?

  5. Lori
    December 4, 2013

    I have installed cement board over metal studs to tile around a fireplace. But my concern is that the cement board seems to have flex to it. Do I need to remove the cement board and sturdy up the framing somehow or does cement board have natural flex? If I need to sturdy up the wall, what would be the best way?

  6. Cody Steadman
    June 19, 2014

    We are replacing the tile in our bathroom. It is on the 2nd floor so it is over wood flooring. We are removing the old mortar and planned to use cement boards. Do we need to pull the wire mesh before we lay down the cement board or can we lay them down over the wire mesh?

    • Tim Carter
      June 19, 2014

      The cement board must be on a solid surface in the same plane. Read ALL of my cement board columns please.

  7. TJ
    February 7, 2015

    This site is very informative.

    Yet I have an unusual question about re-applying some tile over a new piece of cement board I put in place of a section of old backer-board I cut out because it was rotted about half a foot up the wall near the back-end of my tub. The new piece of cement board I installed is 30" wide all the way to the corner of my shower wall. I removed four rows of 4"x4" tile upward from the back wall of my shower.

    I must admit, that I never intended for this job to become what it is now, since initially, I wanted to remove and replace the old moldy caulking from around the edge of where my tub meets the tile wall, however, once I noticed the rot behind the tile and tugged at it only a little bit, it started coming loose. That is why I cut-out the tile and old backer-board about a foot and a half up the wall, because I thought it would be useless to simply apply new caulking, only to have the same problem again down the road.

    To be fair, I know that a bathroom this old, should probably be completely re-done, however I just don't have the money to invest in that right now, but now that I come this far, I'm just hoping to make this smaller repair as complete as possible until that time comes.

    I've already attached the new cement board to the studs (making sure of course that there is about a 1/4" space at the bottom between the board and tub), however, I've noticed a rather unique thing-------that part of the wall has bowed outward in the middle (not a whole lot, but enough that where the new seams meet (between the old backer board and the new board I installed), the old backer-board protrudes about an 1/8" of an inch past the new board underneath it. This protrusion spans about one foot horizontally across this seam.

    My question is this:

    Could I simply place a couple of layers of seam-tape over the top section of the new cement board near where it meets the old backer board to make up for this small difference, or is that not a good idea? Would it cause integrity problems with the tile adhesive by double-layering the tape on this small section of the board?

    FYI: (I'm not talking about taping over a seam, but across the top section of the new cement board where it meets the old board but un-evenly.)

    Any insight would be much appreciated.

  8. Jeff
    August 31, 2015

    August 31, 2015
    Hi…I have installed the hardibacker in my stand up shower (it is embedded 1/2 inch into deck mud..sorry…I know this no longer recommended but I used an outdated diagram from Oatley (slope is great though). However, my plumbing fixture comes out almost 1/2 inch too far, so the handle piece will not press close enough to the cover plate once it is tiled (my fault). Can I add a second layer of 1/4 inch backer board to that wall using longer backer on screws? I guess my other options would be to remove the board (which is embedded…ugh) and add furring strips to studs and redo..or last resort change the plumbing. Recommendation would be greatly appreciated! Thanks

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