Bringing Wood Fireplace Hearth Extension up to Code

[DigbyDog]

Hi all. We recently bought a 1958 home with a great Indiana limestone faced wood burning fireplace (that was painted white... and we stripped the paint!). The fireplace has been inspected and confirmed it is working order/chimney is clean, unfortunately the hearth was out of code and due to some close calls with family/ friends and wood burning fireplaces we wanted to bring this up to code. The original hearth extension was only 10" straight out from the inner hearth/firebox, but it was already 8" from on the sides. When we had the hardwood floors refinished, we had the floor cut to current code (16" straight out). Since our hearth extension is flush to the ground, we need to the 2" of concrete or masonry supported by non-combustible materials.

Now for the question: what are the best options to support and add the additional 47.5"x6"x2" hearth extension?
I assume we will need to redo the floor joists and box out the area. From there, I am not sure which is the best option. Some contractors have suggested adding concrete backer board supported by angle iron. I thought a metal decking might be easiest to get the noncombustible material and structural support needed. But I am looking for your input!
Thanks.

Some extra info:
We plan to have a tile placed in the area once we have the support completed.
Joists are 2x8s
From top of hardwood floor to sub-floor is ~7/8" (sub-floor depth is 3/4")
From top of hardwood floor to existing hearth concrete is ~1-1/4" (it sits a bit above the floor joists)
All utilities/HVAC in conflict are easy to re-route, so no issues there.
Record stand and wire will be moved before we burn...

 

[bholler]

Hi all. We recently bought a 1958 home with a great Indiana limestone faced wood burning fireplace (that was painted white... and we stripped the paint!). The fireplace has been inspected and confirmed it is working order/chimney is clean, unfortunately the hearth was out of code and due to some close calls with family/ friends and wood burning fireplaces we wanted to bring this up to code. The original hearth extension was only 10" straight out from the inner hearth/firebox, but it was already 8" from on the sides. When we had the hardwood floors refinished, we had the floor cut to current code (16" straight out). Since our hearth extension is flush to the ground, we need to the 2" of concrete or masonry supported by non-combustible materials.

Now for the question: what are the best options to support and add the additional 47.5"x6"x2" hearth extension?
I assume we will need to redo the floor joists and box out the area. From there, I am not sure which is the best option. Some contractors have suggested adding concrete backer board supported by angle iron. I thought a metal decking might be easiest to get the noncombustible material and structural support needed. But I am looking for your input!
Thanks.

Some extra info:
We plan to have a tile placed in the area once we have the support completed.
Joists are 2x8s
From top of hardwood floor to sub-floor is ~7/8" (sub-floor depth is 3/4")
From top of hardwood floor to existing hearth concrete is ~1-1/4" (it sits a bit above the floor joists)
All utilities/HVAC in conflict are easy to re-route, so no issues there.
Record stand and wire will be moved before we burn...

View attachment 301525View attachment 301527

That framing sucks to deal with. You are going to have to support the floor joist on both sides cut it out reframe. Then make a sheet metal pan form drill for rebar at opposing angles into the existing slab and pour the extension.