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Rick
Rick, General Contractor
Category: Home Improvement
Satisfied Customers: 21797
Experience:  Licensed construction supervisor with 35+ yrs. experience.
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I have 15 porcelain shower wall tiles around the single knob

Customer Question

Good morning. I have 15 porcelain shower wall tiles around the single knob hot/cold water valve to install. I have mudded in the two layer thick green board and am ready to tile. When laying the tile on the, 4 are slightly higher. Can I sand down the green board to ensure a straight fit prior to using the mortar adhesive?
Submitted: 1 year ago.
Category: Home Improvement
Expert:  Rick replied 1 year ago.

Welcome to Just Answer, my name is ***** ***** I will do my best to help you with your issue. If my initial response doesn’t answer your question then let me know and we can continue our conversation.
I'm sorry to be the bearer of bad news but you can't use thinset on "green board" and you really should have used tile backer (Durock, Denshield, etc) not MR sheetrock in a shower. You can sand down the wall board but sand more than you need then coat the exposed gypsum with 5 minute EasySand (< click on the link) mastic doesn't bond well to gypsum. You also need to use ceramic tie mastic
http://www.homedepot.com/p/Custom-Building-Products-AcrylPro-1-Gal-Ceramic-Tile-Adhesive-ARL40001/100015587

If you decide to stay with the MR sheet rock.

Customer: replied 1 year ago.
I used the green board for the 21"x13" replacement area because it was what I took out. I have AcrylPro Ceramic Tile Adhesive and Versabond thin set mortar ready to go once I get the green boarded wall ready to hold the tile evenly and level. I have been using USG All Purpose Sheetrock joint compound to fill and holes, gaps, and bound to the existing green board. Are recommending using the AcrylPro Ceramic Tile Adhesive and sanding the green board down further to ensure a good tile fit?
Expert:  Rick replied 1 year ago.

Yes you must use the AcrylPro not the thinset on MR wallboard. And yes you'll need to sand down the high spots if you want the tile to set flat. But the mastic won't bond well to the gypsum under the paper so that why I said you should coat the gypsum. You can use joint compound it just takes a lot longer to dry then EasySand 5

Expert:  Rick replied 1 year ago.

Do you have any more questions?