Hearth Extension Modification/Construction

[NYSB]

I have a Regency CI2600 insert (which we love) and I wanted an opinion on my method of extending the pre-existing hearth extension. In our original masonry fireplace, the hearth extended about 18" beyond the front edge of the firebox. The Regency is pretty much flush, but it does push the front of the firebox outward about 2", so I wanted to extend the hearth a little bit. The existing hearth was the usual cement slab and had a piece of bluestone over it. There was also a brick surround. Before installing the new stove I wanted to lay ceramic tile over the pre-existing brick surround and cement hearth. I removed the bluestone and used some concrete mix to smooth out the surface of the existing concrete hearth. I then layed some 5/8 wonderboard around the existing concrete hearth over the wood floor about 2" in the front and on the sides. Over that is about an inch of medium-set mortar to make it even with the concrete hearth. Next I put another 1/2" of medium-set mortar over both the concrete and wonderboard sections of the new extended hearth and put another layer of wonderboard on top of the that, to make it one monolithic surface. Then, using thin-set mortar, I layed the ceramic tiles. So now I have a ceramic tile hearth extension which is even with the front of the existing masonry firebox and measures 2" thick above the floor level. Out to 16" in front of the new fireplace door it is tile on top of wonderboard on top of concrete. From 16" to 18" in front of the fire box it is ceramic tile on top of two layers of wonderboard/medium-set mortar sandwhich. The full width of the hearth is 5.5 feet. Over the brick surround I used the thinner wonderboard and tiled over that. Does tall his pass muster?

Thanks for all the help!

 

[Ashful]

Sounds good, for an ember-only hearth extension. I like that you laid a second layer of board over existing hearth to tie in extension.

 

[begreen]

This insert has a high R value requirement of 2.13. The last 2" are not up to that insulation value though it sounds like you're OK for the 16" US requirement in front of the stove door. Can you post a picture?

 

[NYSB]

This insert has a high R value requirement of 2.13. The last 2" are not up to that insulation value though it sounds like you're OK for the 16" US requirement in front of the stove door. Can you post a picture?

Here are some stills of the before and after.

 

[NYSB]

Obviously I have not built the mantle yet...

 

[NYSB]

...The brick surround on the wall has been covered with wonderboard, thinset, and the tiles. The fireplace lintel is about 10 inchest above the actual stove and about 3 inches above the stove's steel surround. I didn't want to use the extra-large backing plate for this stove, so I brought down the bottom edge of the wonderboard over the top such that the edge of the tile extends about 1" below the top edge of the stove's steel surround - behind it is just the wonderboard and behind that is just the open masonry firebox. So the first combustable material is about 18" above the stove, and about 14" to either side - so I am well beyond the Regency manual specs there. Out of curiosity I have been taking note of various temps with a surface thermometer. The dry wall above the center tiles on the top of the surround gets to around 87 degrees, and that's after a week of running the stove continuously. The wood floor in front of the hearth is about 90, with a room temp in the low 80's.

So here's the question - I know I am within the "letter of the law" on the current hearth, but is it worth the effort to go beyond the minimum at this point? If I were to do this again knowing what I know now I would have removed the 3-4" of hardwood and subfloor underneath the new heart extension and added layers to increase the R-value. Do I want to go in now and remove the wood and subfloor from underneath the hearth extension and replace it with greater R value material? This would be more difficult now, but certainly do-able.

Thoughts?

 

[begreen]

So far it sounds ok. The minimums are the tested safe limits.