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Clarification needed on seams for cement backer board for wall tile

801 Views 9 Replies 4 Participants Last post by  Old Thomas
I'm getting ready to tile my master bathroom. I used permabase cement board. I can't seem to find any really good information about what type of thin-set to use in order to fill over the mesh tape once I put it on the seams. I'm using glass tile as my final product. I also can't seem to find any information that is Dependable about whether you are supposed to fill in around outside and inside corners on the cement board. I have a couple areas where the cement board wraps around and I've seen a couple videos where it looks like they are filling in the gaps and then a couple of others where they say don't fill in the gaps but put a skim coat of thin-set on over the mesh. Does anybody have a good answer for this?
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You should be using alkaline resistant mesh tape and modified thinset for the seams. They all need to be covered, even more neatly with glass tile. As an aside, be sure to buy more glass tile blades than you anticipate as glass is tough on blades.
You should be using alkaline resistant mesh tape and modified thinset for the seams. They all need to be covered, even more neatly with glass tile. As an aside, be sure to buy more glass tile blades than you anticipate as glass is tough on blades.
I have the fibatape for cement boards. Ang specific modified thinset? I have a bag by Mapei for porcelain tile left over. Using a different one for the glass. And do I fill the corner seams with mortar or leave it to allow for expansion?
Why not use the same thin set you will be setting the tiles with?
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Why not use the same thin set you will be setting the tiles with?
I don't trust that I have enough and the tile place is closed right now. I have some extra porcelain tile mortar so just curious if it's okay to use it. And also do you use it at the outside and inside corners?
If the thinset isn't crumbly or hard, you can use it. You seem to have a reluctance to do the corners. Why? You need to do all corners using the mesh tape and thinset.
If the thinset isn't crumbly or hard, you can use it. You seem to have a reluctance to do the corners. Why? You need to do all corners using the mesh tape and thinset.
Thank you. The reluctance is explained in my initial question and post. I have seen opposing posts on the internet that are not clear on whether you should do corners or not. Some say you need to not fill the corners but just thin-set the mesh tape down because you have to allow for expansion. Others say different. Just looking for clarification.
The mesh keeps the corners from breaking due to the expansion. I would be fearful more of allowing moisture to enter behind the tile and grout and penetrating to wall structure. Grout is not waterproof.
The mesh keeps the corners from breaking due to the expansion. I would be fearful more of allowing moisture to enter behind the tile and grout and penetrating to wall structure. Grout is not waterproof.
Excellent point. Thank you!
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Latex modified thin set mortar.
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