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tile shower stall

I am retiling my shower stall and want to know how much of a gap is placed between the cement board and the white plastic shower floor? I know it doesn't sit down on it just dont know how far up it should be.

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Posted 2012-02-23T14:12:40+0000  by cfarley cfarley

Hey there cfarley,


Thanks for joining our community!~ = )


You will indeed need to allow a small gap between your shower base and the cement board before you tile. It's actually a commonly missed step for DIY showers, so kudos for catching it!


As displayed in this diagram from the Durock installation guide, a 1/4" gap is the recommended gap size for this job. Be sure however, to remember to seal the area with caulking so that water doesn't seep into it and cause costly damage down the line.




Hope that helps answer your question!~ Feel free to reply back if you need any more input on the matter. Also, be sure to keep us posted on how the job turns out-- we'd love to see pictures of the finished product!~ = )


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Posted 2012-02-23T16:25:48+0000  by Jay_HD_CHI

What about rolling on a waterproofing membrane or adhering a sheet-type waterproofing product over the cement board before installing the tile.  I watch Mike Holmes' programs, and he always emphasizes this.  However, he doesn't give any detail.  I am remodeling my bathroom tub surround and floor, and have the cement board installed.  I figure my next step is to tape and mud it.  On the floor I will need to pour on a floor leveler.  I also have a heat matt to install.  So, where and when do I put the waterproofing, if at all?


I'd appreciate any advice you can give me.


Sharon Staples

Posted 2012-03-02T16:07:46+0000  by staples47

Hey there staples47,


Welcome to our community!~


Good to also hear from another Holmes fan! The man is a genius of DIY and has taught me quite a bit more than I ever knew I could learn = )


The products that he likes to use on most of his jobs are made by Schluter, and include both the DITRA and KERDI.


It's relatively easy to use once you have the right products and the right materials; plus it comes out completely waterproof at the end!


In most cases I have seen him install it directly over new cement board, but I believe they were all gypsum style boards, such as DUROCK. We do sell a cement board in our stores called, Hardibacker which is also completely water-proof as well. If you've already put up this style of backerboard, then the Schluter system may be a bit of an overkill for you.


For setting this material, you'll need a thin-set. Do not use a pre-mixed thin-set, it must be a dry mix. Since you mentioned that you're working with radiant heat, you'll want to make sure with the manufacturer of the heat mat that you're able to put a waterproofing barrier ontop of it, and that it can accept being covered in thinset. Most will, but I can't tell you for certain that yours will. In most cases however, you'll apply your thinset layer directly atop your radiant heat mat and then apply the DITRA layer.


Your type of thinset is key however, so i'll cover that first before anything else. For laying tiles on to the DITRA or KERDI system, you must use and un-modified thinset, such as CustomBlend. In most tile jobs, I would always recommend a modified thinset, but since those styles need to air dry you'll be out of luck when placing it between two impervious surfaces like KERDI and porcelain let's say and it would take weeks to start drying. I would also use the same un-modified thinset for when applying your DITRA layer to the floor and your KERDI to the walls.


You'll be starting the the corners first and working your way from there. You'll apply the KERDI-BAND on to the wall in your corners to water-proof them. This step is very similar to applying tape into the corners of drywall. Mortar on the wall, apply the band, and then use your clean trowel to go back over the band to remove any air bubble or excess mortar. When finishing off the bottom corners where the KERDI-BAND meets the base, you'll apply a thin sheet of KERDI-KEREC, which comes pre-cut for making corners, or cut sections of KERDI-BAND and is laid similarly to the band. Once those are set, you'll add another BAND layer to the bottom of the walls where they meet up with the shower base.


Trowel out onto the wall itself now, and apply the KERDI. Overlap your BAND layers and cover those seems with a thin layer of thinset. As you set the wall, make sure to again go over the KERDI with your dry trowel and remove any air bubbles. You'll need more than 1 sheet for the job, so make sure that you overlap the seams of two KERDI's by about 2" so that you keep them waterproof.


The DITRA is applied similarly to the flooring, atop a layer of your thinset. However unlike with the KERDI, you only butt the edges of two sheets up, as your thinset layer will act as a waterproofer between them. Again, make sure to remove any air bubbles with your dry trowel before letting the product set.


Hopefully this explains it all a bit better. If you need me to go into more detail, just let me know!~ Best of luck with the project and be sure to post up pictures if possible...we'd love to see how it's going!


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Posted 2012-03-02T19:48:46+0000  by Jay_HD_CHI

Hi Mr. Jay,


Thank you for your friendly and succinct reply.  A big relief to me because I did use your Hardibacker.  I own rental properties, and the rest of your reply gave me needed options for when I have to redo a bathroom.


Not to take too much advantage of your knowledge, but, I went into a local Home Depot last week (geez, I hope it wasn't Lowe's lol) just to look at the Ditra and Kerdi membranes.  There was a bevy of gentlemen employees in the tile isle, and they all had slightly different opinions about waterproofing products and installation.  I ended up buying Redguard Waterproofing and Crack Prevention Membrane in a ready-to-use bucket and it rolls on.  (Then I received your reply.)  Okay, would you consider that overkill to apply it to the Hardibacker?  I'd like to return it if I don't need it.


Thank you,

Sharon Staples

Posted 2012-03-08T14:55:59+0000  by staples47

Not a problem Sharon, glad I could help!~ = )


My personal opinion on your RedGard dilemma would be that seems a bit excessive. Now that isn't to say that you can't use the RedGard on top of the HardiBacker, because you certainly can and I can go more into detail about the proper application method if you would like as well.


My rationale behind why it seems to be a bit much is simple. While I'm an ardent supporter of "do it right the first time," I also prefer to save people money that they don't necessarily need to spend. You've already purchased a substrate that's impervious to water, and kudos to you for doing so. The RedGard is great if you're going over a gypsum based cement board that isn't waterproof already, but it isn't going to have as stellar results with your current set up. I'd hate to see you waste the money on something that isn't going to make the job significantly better. Again, that's my opinion at least.


Let me know what you think and we can go from there = )


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Posted 2012-03-08T17:35:27+0000  by Jay_HD_CHI
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