Waterproof membrane over Hardiboard needed on walls around tub?

diy77June 4, 2009

I'm in the middle of a bathroom remodel. It's a simple small bathroom. I installed 1/4" Hardibacker on the floor, including underneath the tub. On the back wall above the tub, (which is an "outside" wall), I installed poly behind 1/2" Hardibacker. Currently the other two walls around the tub just have 1/2" Hardibacker w/o any poly behind them.

In order to ensure it is waterproof and so I use a consistent method, could I just remove the Hardibacker from the two side walls, put up poly, recover the side tub walls with the Hardibacker, then tape the seams (and of course cover the seams with thinset), then tile?


should I remove the polly from the "back" tub wall, put the Hardibacker back up, tape the seams, and use a sheet membrane or Redgard on top of the 1/2" Hardibacker?

Also, IF you recommend using a sheet membrane, is there anywhere to get Kerdi fast? The quickest turnaround I've seen is "we can get it to you in 8-10 days". If I need to get it, I'd like it asap.

Lastly, I'm also going to be tiling the floor. Do I also need to put a waterproof membrane on top of the 1/4" Hardibacker I have on the floor?

I'm a newbie to bathroom remodeling, so I want to make sure that I do this right.

Thank you for reporting this comment. Undo

Bill or any other experts? please help

    Bookmark   June 4, 2009 at 8:02PM
Thank you for reporting this comment. Undo

If they don't see this, I believe the correct answer is either/or, but not both. You can do a more traditional vapor barrier behind the CBU, OR you can use a membrane. On the floor, if you want it to be waterproof (but that is "extra") you could use Ditra, but the CBU is a good enough tile backer without anything else (if it is over a proper sub floor). Waterproofing aside, Ditra over CBU is overkill.

If you choose to use the Kerdi, tile-experts.com is a great resource, you can call and talk to them about your time limitations, I am sure they would be able to help you out!

Below is a link to a great Kerdi link created by MOngo and saved by weedyacres--- scroll to the bottom for the tub surround pic.

Here is a link that might be useful: Mongo's Tutorial

    Bookmark   June 4, 2009 at 9:36PM
Thank you for reporting this comment. Undo

Thanks Pepperidge Farm I appreciate it.

    Bookmark   June 4, 2009 at 9:58PM
Thank you for reporting this comment. Undo

If they don't see this, I believe the correct answer is either/or, but not both.

Yup. The problem is that the vapor barrier should be continuous, meaning all three walls should come down and redo the vapor barrier all the way around.

    Bookmark   June 4, 2009 at 11:20PM
Sign Up to comment
More Discussions
Did anyone buy a Venetian dual system tub from Costco?
I just came across this tub, looks good on paper. It...
Finished Conestoga cabs bathroom
This wasn't our usual full DIY, we paid for the tile...
Trying to reconfigure master bath to include washer dryer
How does this layout look? how could I make this space...
Quality Pocket Door Frames?
(Please accept my apology for the duplicate post -...
Ikea Lillangen - can it be used as vessel sink?
Hi, We are redo-ing our children's bathroom & purchased...
People viewed this after searching for:
© 2015 Houzz Inc. Houzz® The new way to design your home™