Fireplace Hearth, Tile, and Ditra

[BillGriggs]

Hi all! New here, but I'm hoping someone can help me out with a project.

I'm working on replacing a hearth. My home is built with a 2"x6" tongue-and-groove subfloor. On top of that was laid 1/2 particleboard.

In front of my fireplace was a 2'x6' section of 8x8 tiles. I popped these up and found they were adhered to 1/2 fiberboard. The area for this was cut out of the plywood underlayment, so the fiberboard was nailed directly into the plank subfloor. There was also a metal ember strip under this board.

My plan had been to replace the fiberboard with 1/2 ply, and then do a ditra installation (1/4" modified thinset, ditra, 1/4" unmodified thinset) for some 12"x12" porcelain tiles (3/8" thick).

My fireplace is a Superior brand, model number b1038. This was likely all installed in the early 80s.

I want to make sure I'm on the right track and won't burn my house down. Any advice you can give would be great! Thanks!

 

[webby3650]

Your plan sounds fine, just leave that ember strip there.

 

[BillGriggs]

Your plan sounds fine, just leave that ember strip there.

I've had some other people say this isn't the way I should go because it would mean putting a combustible (ply) between the tile and the ember strip. This setup would also have the ply touching the fireplace.

I don't think it's a huge deal, but someone else said they've done remodels and discovered ply in this position all burned and charcoaled.

 

[webby3650]

I've had some other people say this isn't the way I should go because it would mean putting a combustible (ply) between the tile and the ember strip. This setup would also have the ply touching the fireplace.

I don't think it's a huge deal, but someone else said they've done remodels and discovered ply in this position all burned and charcoaled.

It's a zero clearance fireplace. Meaning combustibles can touch it in certain places, that varies. But what does not vary is that it can sit on a combustible floor. The only requirement is that there is ember protection out front. 24" is plenty for most. Your ember strip would go on top of the plywood, under the tile. The unit will never get hot under the opening, you just need to make sure a coal can't make its way in between the fireplace and the non-combustible ember protection.

 

[BillGriggs]

It's a zero clearance fireplace. Meaning combustibles can touch it in certain places, that varies. But what does not vary is that it can sit on a combustible floor. The only requirement is that there is ember protection out front. 24" is plenty for most. Your ember strip would go on top of the plywood, under the tile. The unit will never get hot under the opening, you just need to make sure a coal can't make its way in between the fireplace and the non-combustible ember protection.

Thanks! I'll take a look when I get home. I think the ember strip is pretty much stuck where it is (since it's half under the unit and half over the plank subfloor). Would it work to get some sort of a second ember strip and put it under the thinset and tile (and right above the ply)?

 

[webby3650]

If in doubt, skip the ditra and just use cement board instead. It's cheaper anyway.

 

[BillGriggs]

If in doubt, skip the ditra and just use cement board instead. It's cheaper anyway.

That's where I'm running into trouble. One option is replacing the ply entirely with cement board, but I don't want to lay that in mortar because putting that right on the planks sounds like a nightmare either now or later if we ever redo this area. I'm trying to determine if just affixing the cementboard to the planks would be ok.

Otherwise I would put cement on the ply…but that gets back to the original problem of having a layer of ply above the ember plate.

 

[webby3650]

That ember strip means nothing, ignore it. It's just a 4"x 40" strip of sheet metal, add another one where needed.

 

[WoodyIsGoody]

That's where I'm running into trouble. One option is replacing the ply entirely with cement board, but I don't want to lay that in mortar because putting that right on the planks sounds like a nightmare either now or later if we ever redo this area. I'm trying to determine if just affixing the cementboard to the planks would be ok.

Otherwise I would put cement on the ply…but that gets back to the original problem of having a layer of ply above the ember plate.

You can screw the cement board to the sub-floor, it doesn't need to be bedded in mortar. Use lot's of screws.

 

[webby3650]

You can screw the cement board to the sub-floor, it doesn't need to be bedded in mortar. Use lot's of screws.

It's recommended to bed it in thinset and then screw it on a 4"x4" grid.