Using a Granite Raised Hearth Extension for wood burning fireplace - what materials?

[RenoG]

I have a masonry wood burning fireplace (not prefab) on a concrete slab. We hammered off the ugly 12 inch high brick bench and want to replace with a half-step hearth for (6 inches final height) with a 1 inch granite top. The firebox is raised 12 inches above slab level. I've read fireplace codes for 3 nights days and found we're within dimensions; 12 inches on sides 16 inches in front of firebox. I am at a loss how to construct the support for the granite half-step.

I have few specific questions.

1 - The code 211.10 says hearth extensions shall be constructed of concrete or masonry supported by noncombustible materials. The code does not call out stone as suitable for hearth extension. Can I make a 12 by 60 box framed with metal studs bordered with 1/2 inch Durock, or do I really need to use concrete or brick below my granite slab?

2 - Code 211.10.2 says the minimum thickness of hearth extension is 2 inches. My granite is 1 inch thick; so do I just need to add two 1/2 inch sheets of Durock under it to meet the code requirement of 2 inches thick?

3 - I see a lot of photos of masonry wood burning fireplaces with either a bench seat with wood siding or half-height steps with wood sides; are those all violating the building code? it looks like the answer is yes. I'm not as worried we're going to eliminate wood and use metal studs if possible and granite siding.

Any thoughts, advice would be greatly appreciated! Thanks in advance!

Reno

 

[kennyp2339]

As long as the granite top is resting on the concrete slab and nothing combustible you should be fine. perhaps pics are needed, but from what I gather is that you have a whole floor concrete slab with a masonry fire place built on top (of course with proper footings to support the fireplace and chimney) instead of have one large step from the floor to the firebox level your adding a half step on an existing concrete slab covered by a granite veneer. IMO nothing was gained / nothing was lost since your building on a non combustible floor (your slab) using non combustible materials.

 

[RenoG]

As long as the granite top is resting on the concrete slab and nothing combustible you should be fine. perhaps pics are needed, but from what I gather is that you have a whole floor concrete slab with a masonry fire place built on top (of course with proper footings to support the fireplace and chimney) instead of have one large step from the floor to the firebox level your adding a half step on an existing concrete slab covered by a granite veneer. IMO nothing was gained / nothing was lost since your building on a non combustible floor (your slab) using non combustible materials.

Thank you for the confirmation. I saw a lot of "how to" videos online showing people building the bottom frames with wood, but clearly that is not up to code for masonry fireplaces. We are going with pouring a concrete 4 inch foundation on top of the slab to hold the granite going on top for the half step.

Hopefully this helps others in my situation who do not want a big nasty brick bench in front of their fireplace. Photos coming. This is what we're going for, but the step area will be veneered in granite, not wood.

 

[kennyp2339]

Thank you for the confirmation. I saw a lot of "how to" videos online showing people building the bottom frames with wood, but clearly that is not up to code for masonry fireplaces. We are going with pouring a concrete 4 inch foundation on top of the slab to hold the granite going on top for the half step.

Hopefully this helps others in my situation who do not want a big nasty brick bench in front of their fireplace. Photos coming. This is what we're going for, but the step area will be veneered in granite, not wood.

The only thing that I should mention code wise is that the hearth extension needs to be tied into the masonry fire place it self, so you may need to pin it, but that same code doesn't stipulate the difference with having the hearth on a 2nd floor of a wood rafter home and a hearth sharing the same concrete poured floor.