R-Value for a course of brick and mortar on a slab?

[Linux_Tyro]

Hello,

Already purchased my Hearthstone homestead model 8750H with the four inch legs. Noticed the required R-Value of 6.6 under the stove but assumed that brick hearth had that covered. Now I'm learning that may not be the case. So the question is. "What exactly is the R-Value of one course of brick and mortar that is built on a slab?"

The painful part of this story is that my brick hearth has to be cut down three courses in order to fit the homestead regardless of leg height. Maybe four. The lintel height is 20in. but my ZC firebox closes down to 17in. I don't want to cut out anything other than the eight inch round flue in order to install the insulated liner to clean out tee. There are also rows of ventilation holes on each side of the firebox that can't be covered. My plan is to fabricate something to seal off the firebox but not the ventilation holes and brick.

May have been better off purchasing the homestead in freestanding configuration with six inch legs

Yes, I know that the mantel and trim will be too close as well as the carpet. For now let's concentrate on making room for the stove and meeting R-Values. Firebox to edge of hearth is 23in. Hearth to trim is 32.5in. Width brick to brick is 36in. Width of firebox is 29.75in. Height of firebox is 17in. This is what necessitates lowering the hearth to meet either 22-24in lintel height.

 

[fossil]

A course of masonry only has an R-value of something like 0.6...masonry in general is a poor insulator. You say "on a slab"...does that mean that below the carpet is a concrete slab on grade? If that's the case, and there is no combustible material beneath the hearth/stove location, then you needn't worry about R-value. Shortening that raised hearth is gonna be a miserable job...are you sure you don't want to just cut the carpet, extend the hearth and install the stove in front of the masonry structure with its own connector pipe & chimney going stright up through the ceiling/attic/roof? Then you could just brick in/seal off the old fireplace and forget about it. Just a thought. Rick

 

[Linux_Tyro]

A course of masonry only has an R-value of something like 0.6...masonry in general is a poor insulator. You say "on a slab"...does that mean that below the carpet is a concrete slab on grade? If that's the case, and there is no combustible material beneath the hearth/stove location, then you needn't worry about R-value. Shortening that raised hearth is gonna be a miserable job...are you sure you don't want to just cut the carpet, extend the hearth and install the stove in front of the masonry structure with its own connector pipe & chimney going stright up through the ceiling/attic/roof? Then you could just brick in/seal off the old fireplace and forget about it. Just a thought. Rick

Whole house is slab on grade. The brick mason that I called in for a quote thinks that the hearth is all brick and mortar without a wood form. However I may find sand and crushed brick one or two courses down as a filler. He should be able clean it up with no problem after I knock it out with air tools.

I'd rather use the existing fireplace rather than extending it to 41in X 41in. and going straight up. I'll make a hearth extension later. Thinks for the idea.

 

[fossil]

Yeah, a good deal of it inside of what you see is likely filled with rubble of some sort, but if you knock out what you don't want, then a competent mason can make it look like it was always meant to be that way, pretty much. With slab on grade, you've no worries about hearth R-values, and for an eventual hearth extension you can just cut back the carpet and put down some attractive tile of your choice on the slab around the hearth...as simple as red quarry tile, or something more decorative to trim it out nicely. Keep us apprised of your progress with the project. Have fun! Rick