Tiling Shower Wall Question

dsf767February 5, 2014

Boy am I glad I am on gardenweb.

I am in the middle of my DIY bathroom remodel and am almost to the point of tiling the shower walls.

When I originally bought everything the Lowes flooring "expert" said to use mastic on the shower walls, right over the Hardieboard I already have installed.

After reading another thread here I am glad I didn't do that job yet, as the mastic will be breaking down and mold will eat it if I ever had a grout issue.

So I returned the mastic, picked up some MAPEI Aqua Defense and MAPEI Polymer Modified thin set mortar.

Just wanting to double check I do everything right, I should apply the Aqua Defense let that dry, apply the thinset, then tile?

Again Thanks Gardenweb for saving me a issue down the road!

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"Just wanting to double check I do everything right, I should apply the Aqua Defense let that dry, apply the thinset, then tile?"

Yes, that's the correct order of work. If you haven't already done it, read the Aquadefense pdf.

Take note of seams in your cement board. If the gaps between panels or in the corners are excessive, you can mix up a little thinset and trowel it into the seams. You're not doing drywall, so you don't need to feather it out over the gap. You're just looking to fill the gap. You don't want to create any speedbumps.

The thinset fill is simply to allow the AquaDefense to bridge from one board to another.

So fill the seams if required and make sure there are no thinset speedbumps. If you have any over-driven cement board screws, you can fill those depressions with thinset too.

Let that thinset cure overnight.

Come back the next day and run your hand over the wall. Make sure there are no thinset nibs, or screw heads proud of the cement board. You can wipe the cement board down with a sponge to clean up any dust.

Then AquaDefense it all.

Good luck!

    Bookmark   February 5, 2014 at 7:43PM
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I have already filled in the cement board seems with thinset, I just wanted to note above the hardieboard there is a small area that I used greenboard (6 inches all around the shower) as this was far above the showerhead and not in a direct water contact area I read this was acceptable. does this change the application at all?

Here is a picture for reference:

Please excuse the plastic sheeting, its my only bathroom so it needed to be functional though the remodel so I hung the sheeting as a temporary means so I could still take showers until it is tiled.

    Bookmark   February 5, 2014 at 8:05PM
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I wouldn't worry about that little bit of greenboard.

    Bookmark   February 5, 2014 at 8:24PM
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Are you planning to use a waterproofing membrane at all? In our bathrooms DH used Hydroban by Laticrete on the tub/shower surrounds and ceilings. 3 coats. It rolls and brushes on like paint. Expensive, but easy to apply.

    Bookmark   February 5, 2014 at 8:40PM
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I am using MAPEI Aqua Defense which is a very similar product to Hydroban.

    Bookmark   February 5, 2014 at 8:57PM
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cat-mom, the Aquadefense is the waterproofing membrane. I just finished using that. Easy to apply, we used a brush rather than a roller.

Dsf, we also used alkali resistant mesh tape over the seams and in the corners before we put on the thinset. DH was particularly concerned about keeping all the seams/joints in the shower niche nice and waterproof, but I don't see any niches cut out in your pic so at least you don't have that to worry about!

Let your Aquadefense dry at least overnight. Especially in winter, may take a little longer to dry/cure.

    Bookmark   February 5, 2014 at 8:58PM
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Good. An ounce of prevention and all that. :)

    Bookmark   February 6, 2014 at 12:31AM
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our installer is also using the Mapei Aqua Defense. He appears to be extremely competent thus far, and must prefer this product for whatever reason. He used a brush to apply.

    Bookmark   February 6, 2014 at 1:56PM
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