waterproof membrane under tile floor?
Pigsooie
| Posted in Construction Techniques on
Boning up for a tile floor in my bathroom, I read in Renovation 3rd edition that I need a waterproof membrane under the hardibacker. HD doesn’t appear to be hip to this. Is the membrane necessary? If so, what am I looking for and where can I get it?
Thanks
Replies
What type of application is this? Yes Hardibacker is water impervious, but not waterproof! However none of the CBUs are. If you want waterproof, you will need Ditra with a Kerdi band. See Schluter.com.
It is not common to put anything besides thinset under CBU on a bathroom floor. If people are leaving huge amounts of water on the floor all the time then yes water will eventually reach the plywood. If for some reason you want to waterproof the floor you could use something like Laticrete 9235, and HD is nowhere near sophisticated enough to carry that, let alone talk to the sales people about it. Go to a tile store.
Seems like the time to put a membrane down is in a child's bath, 'cause you know they will not keep the water in the tub/shower.
The other question is "how long will you be there?" A membrane is cheap insurance.
Advocate
Edited 2/8/2006 11:54 pm ET by Advocate
Grout with sealer and latex-modified thinset over CBU is very water resistant. I suppose a child's bath might be a place to consider a membrane, but only if you plan to have several children in a row so that it will be a child's bath for many years in a row.
I think the key area is at the base of the tub. Putting down bituthane for 12" back might be one way to address this.
Advocate
As others have noted, only extreme water sports demand a membrane to protect a tile floor over correctly set CBU. One easy way to get a membrane, if you still want one, is to set and tape your CBU's, then roll/brush on two layers of RedGard. HD sells it here in SoCal, $37 a gallon.
Set your tile over the dry membrane with modified thinset, and you are all set. And be sure to caulk the tub apron to the membrane before you tile, since this joint typically sees the most water. Having the membrane on top means that the CBU won't get/stay all wet and wick the water laterally. The screws won't rust, either, and they don't penetrate the membrane.
If your tiles are large, the thinset will take longer to set up, since modified needs to dry as well as cure by hydration, and the RedGard is a vapor barrier, as is the glaze on your tile. All of the excess moisture in the mortar has to exit via the grout joints.
Bill
Thank you, gentlemen.
I'm going to hazard NOT using a membrane on this project after considering all points made.
I appreciate everyone's input.