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Unread 09-08-2013, 07:22 PM   #1
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Join Date: Sep 2013
Posts: 7
Backsplash Guidance Needed

I'll be as brief as I can:

I am a DIY guy, fairly proficient. I have some experience setting tile and more with thin brick. I need to install a tile kitchen backsplash 6 1/2" high, 20' long (runs of 12' and 8'). The existing countertop is new 3cm. granite butted up to old, moderately damaged-in-the-course-of-demo wallboard. The studs are roughly (the original construction is not precise) 14" o.c. I have the tiles on hand. They are 5/16" thick. They are fired and glazed (of course) but they are Mexican and the body material is, as you may expect, quite porous.

I plan to remove a horizontal strip of the wallboard approximately 6 1/2" high and to replace it with 1/2" cement board (without advice to the contrary, I would do that regardless of the condition of the wall board), probably using a Hardie product, furring as needed to correct a major wow in the wall, and to set the tile with thinset. I can mud the remaining wallboard above the furred portion to achieve a plane parallel to that of the tiles' surface. Assuming my basic idea is OK--and I am certainly willing to listen to alternatives--I have the following questions.

1. Is horizontal blocking necessary (toed in) to back up either the upper or lower edge of the cement board or the wallboard? I guess there will enough strength and rigidity at both edges without blocking, but I am not sure (and please see Question 3).

2. What fasteners should I use? They will be set in awkward places and I am more reliable with a drill-driver than with a hammer, so my bias is toward screws rather than HD roofing nails. Also, pounding tends to shake up old work nearby in unexpected ways.

3. How do I handle the joint between the granite and the tiles to keep water away from both the cement board and the drywall? Ideally, the granite would run back to the studs but that is no longer possible. Blocking would provide a backstop for backer rod, which would in turn enable me to caulk the joint the way I would like to. I could as an alternative leave a small gap above the wallboard and below the cement board. That might be adequate to contain and control the back of the backer rod without blocking. Is there a better way? I have in mind to make a 3/16" joint at the bottom of the tile and to caulk that joint with a Sika product. Are there caulks of equal quality that have a better choice of colors? Assuming that blockless approach is correct, what diameter ought the backer rod or maybe parallel backer rods be?

4. What sort of waterproofing membrane should I use and how can I avoid buying too much of it? I am totally inexperienced with this product. I assume it goes on the face of the cement board with thinset, and that the same the same thinset is used to set the tile on it. The detailing of the membrane at the bottom seems also to relate to Question 3.

New here, I hope that my post is not too long and that I am not asking too much. Thank you.
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