Hearth extension

[Da Slug]

Hello all, I am having a new Hearthstone Homestead stove installed on my old gas heater hearth (the flue is going to be relined) and I have been reading your posts on building an extension. My hearth is tile and is only deep enough to hold the stove and so I was going to either build up for my extension, or cut down to the subfloor like a few others did. At the time my focus was trying to match the old tile or otherwise make it look not too off. The old tile on the floor of the hearth was cracked in a few places and some ceramic was missing. I decided to just tear the old floor out so then at least the floor would match the extension. After starting on the tiles with a big hammer and chisel, I switched to an electric hammer chipper which made short work of the job, the only problem now is evidently the tile (1920s) was laid directly on a bed of mortar (I guess) and so the surface is not too smooth since it has taken on the surface of the bottom of the tiles which was 3/8" grooves. Plus the mortar is cracked in a couple of places (thus the cracked tiles, I suppose). The base is pretty thick, from what I can tell and I did not want to have to tear it out since my stove is due to be installed on the 30th of this month. I know this is a fire place forum and not a tile forum, but you all seem to have been down a few DIY roads and so I thought maybe someone would have a suggestion. Would a skim coat of mortar over the old base work do you think? Also, now I may have trouble making the extension match the level of the old hearth.... It seemed like a good idea at the time. I forgot to mention, the old hearth floor was level with my hardwood floor and it measures 5' x 19".
Oh, while I have your attention, I did not buy the steel surround which was going to cost another $250. Should I have one?
Thanks...

 

[Harley]

Welcome, Slug

If I read that right... the tiles were level with the wood floor, so now the concrete base is 3/8-1/2" or so below that now (after removing the tile). How thick is the flooring? Once you have a layout planned for the extension, you'd probably be cutting out the wood floor down to the sub-floor, so that would bring you a lot closer (but still "off"). This is pure speculation on my part, but what I'm picturing is the concrete being only about 1/4" or so higer than the sub-floor. Could you make up that distance (or very close to it with some 1/4 hardibacker board (the extension)? On to of that, you could probably skim coat and level the whole area with mortar (after patching the cracks, replacing loose mortar). Then covering with a few layers of durock, etc to get the right R-value needed. This is assuming you'd be OK with raising the hearth a bit. You are going to need some heat protection in the extension. I don't know if your floor has enough room to cut out and build back up to be level with the original wood floor.

On the surround... you don't "need" it. I'm assuming they will be installing a block off plate at the damper. After I installed my heritage in front of the fireplace - I kind of made a sheet metal surround just to cover up the opening to "clean it up" a bit.

 

[Da Slug]

Harley,
The tile that I removed was about 3/8" thick, I would say and my flooring if I removed one layer is 3/4". What I had planned on doing, if the old tile came up nice and clean, was to use 1/2" durrock over the subfloor and the 1/4" tile would bring me up to where I figured I would be with tile on the old mortar....Does that make sense? It did when I was tearing up the old tile...Anyway, I guess job one would be to get the surface ready to tile where the stove is going to sit and then figure out how to make the extension match. From what I have been reading, the half inch cement board and quarter inch tile should be plenty of R factor for an extension. I could be wrong though.

 

[Harley]

I think we are pretty much thinking the same thing... sounds like that would work... assuming the layers of durock on the extension would give you the R-value needed. Just a suggestion, though (tough to really picture the whole project from here. I think rather than prepping the hearth area for tile, and building up the extension to match it.... you might want to consider building them both up level at the same time, and covering the whole area with a layer of cement board, so you are certain that everything is flush. Not sure if I really explained it right, or if that makes sense in your situation.

 

[Da Slug]

Harley,
Yes, I know what you are saying, I am just a little disappointed in the fact that I may not be able to make everything, floor, extension, & hearth, all level. I should say, though, that initially I was figuring on having the extension on top of the floor and so having a 3/4" high hearth. I guess if I can get to just a quarter or half an inch I will be ahead of the game...

 

[Harley]

Harley,
Yes, I know what you are saying, I am just a little disappointed in the fact that I may not be able to make everything, floor, extension, & hearth, all level. I should say, though, that initially I was figuring on having the extension on top of the floor and so having a 3/4" high hearth. I guess if I can get to just a quarter or half an inch I will be ahead of the game...

Its really going to depend on the flooring and support you have out there in front of the extisting hearth. It sounds like you want the height to be as small as possible. Is the height of the hearth above the floor limited because you don't want it sticking up too high, or because the hearth can only go up a little bit to get the stove connected in the existing opening?

 

[Gooserider]

Well there is a tile forum that I've used and found offered good advice - John Bridge - Tile your World it may not hurt to run things by them as well.

A few thoughts - it may be possible to clean up some of that old concrete by tackling it with an angle grinder and a masonry wheel - wear lots of dust protection, it will be messy!

The John Bridge folks also talked some times about using stuff they called "deck mud" to level out floors, either to get rid of slopes or even out irregularities.

If you are going to put down Durock to give you an even working surface, you will need to put it on a thick enough layer of thinset or other mortar type adhesive to fill any voids so that the Durock is fully supported - the screws hold the Durock DOWN, but the mortar holds it UP, and you need both.

I would agree with Harley that you should work on getting the entire floor where the extension will be level when putting down the Durock. If possible it is best if you have one continuous sheet making up the entire top layer. If that isn't you at least want the joints to be flat.

Gooserider

 

[bcnu]

I put in a Homestead this summer and also wanted to keep the hearth flush with our new wood floor. Started out below grade and could have done it, but could not come up with any Micore 300. Used Micore 160 and Durock - and ended up with a hearth about 1" above the rest of the floor. I'm happy enough with it but would have been nice to have kept it flush.