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Install & Replace

Covering fireplace opening with cement board

I am putting a direct vent gas insert into my fireplace and I need to reduce the opening at the front of the firebox so the surround can reach an adjacent wall. I am planning on covering the hole and surrounding brick--which used to have a stone veneer over the front of it and is thus very uneven right now--with cement backer board so I can tile the front. What are my options for securing the cement board to the wall? Can I use a combination of mortar and masonry anchors, or do I need to run metal studs of some sort?

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Posted 2011-05-06T21:17:31+0000  by Hamburglar Hamburglar

Hey Hamburglar!


I laughed when I saw your screen name, my old roommate's nickname was 'Grimace' :smileyvery-happy:


Welcome to the community, let's get you that new tile wall.


You are on the right track for approaching this project with either the cement board directly to the veneer or running some sort of structure (metal studs) to frame out the new vent insert.


I would use the latter option ONLY if you are using the vent gas frequently as the new tile wall will need to ventilate and not get hot from the vent. This is because if you use water-based adhesives, such as mastic, you will want the optimum room temperature so the adhesion will not give way, which unfortunately I have seen before.


I have provided pictures below regarding metal wall stud installation as well as an image below that shows the profile of not only the metal wall frame, but as well as the tile being applied as well. Unaltered images are from



With whatever option you do, you will be left with a somewhat (at least to me :smileytongue:) unsightly edges. To alleviate that, you can place decorative edges such as metal or wood trim for tile. I did a previous and in-depth post on the subject of tile trim, it can be found here



As for the other option, you can put wall rated thin-set mortar or pre-mix mastic to adhere on the stone veneer provided:


  • The tiles you are placing aren't natural stone or thicker than 3/8"
  • it is in clean and level shape
  • the stone veneer itself is secure and firm to the frame it is attached
And there you have it, several ways to approach getting you a new tile wall!
Hope this helps you out,


Posted 2011-05-07T13:47:44+0000  by Joseph_HD_ATL

Thanks for the detailed response. It sounds like I should try to attach the backer board directly to the existing surface which is brick and mortar. I'm assuming that to attach the backerboard to the existing surface that I would put thinset over the brick and mortar and use some sort of masonry anchors to attach the 1/2" backer board. Is that correct?

Posted 2011-05-08T06:25:20+0000  by Hamburglar

Actually, you don't have to use masonry anchors as long as you use a high-quality fortified thin-set mortar for the backerboard you'll be fine. In simpler terms, just get a bag of thin-set mortar that is rated for wall applications, such as Custom's Granite and Marble thin-set mortar we sell in 50 lb. bags. You can use anchors, but I would do them in a liberal fashion since the thin-set will give you the proper hold without committing to putting wall masonry screws everywhere. Best of all, we sell all of these materials in our store in-stock.


Any other questions please feel free to contact us again.



Posted 2011-06-17T19:53:48+0000  by Joseph_HD_ATL
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