I'm helping my parents with their new bathroom tiling project, and I ran into a bit of an issue. The crew that installed the Duroc cement board for the bathtub surround mistakenly applied sheetrock joint tape and mud over the cement board joints. Now, I'm looking at the best way to waterproof it with Redgard before I tile on top. My main concern is whether this installation will be viable in the long run if I proceed as is, or if I should just take the time to grind off the sheetrock tape and mud and replace it with alkali-resistant tape instead. Also, will grinding out the existing mud potentially damage the cement board?
1 Answer
You should definitely try to scrape off the tape and mud as thoroughly as possible. Use a mud blade to scrape, then a wire brush for any remaining bits. Finish it off with a sponge and some hot water to clean it up. Leaving the sheetrock tape and mud could lead to headaches later on, trust me!
Yeah, you really want to make sure all that debris is gone. I've read that if you leave any sheetrock materials under the Redgard, it can compromise the water barrier. Plus, cement and gypsum can create weak spots at the joints.