Preparing Broken Concrete Hearth Extension for Tile

  • Active since 1995, is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.


New Member
Mar 16, 2021
New York
Hi All,

I am planning to retile my fireplace hearth extension. As I was removing the old tile, the front edge of the concrete bed crumbled away. I presume this was because it was much thinner than the remaining concrete (~1"), and because there was no mesh lathe holding it together. The remaining concrete appears to be ~3 inches thick, based on what I can see from the basement. The remaining concrete is recessed from the wood floor by 3/4", and the tile I plan to use is 3/8" thick.

How should I patch this missing section of concrete so that it is a strong bed for the tile to sit? I need to add about 3/4" to bring it to the same height as the rest of the concrete.

My initial thought was to either use cement board, or float a bed of mortar up to the same level as the existing concrete, and then secure a 1/4" cement board with tapcon concrete screws and thinset to make a uniform surface. This will leave 1/2" left for the thinset and tile. Research has shown that that might not be adequate and that it isn't recommended to use concrete screws on cement board, but I can't tell if that is just because it is tedious to drill all the pilot holes (it's a small area, so I'm not concerned with that) or if there is another reason not to do that.

Any suggestions are greatly appreciated.