Hello, I am new here and my 1st post – I have plans to build a Masonry Fireplace – I am unsure if anyone in this forum can help but I will ask anyway — because, if there are professional masons here, they may be able to help answer my question.
As I said, I will be building a masonry fireplace (a Rumford) 36" wide firebox. It will be built as part of a custom home build in Tennessee. In learning the code for fireplace construction, I find that the Code in Section R1001.9 - “combustible material shall not remain against the underside of the hearths and hearth extensions after construction”. This brings up a question about this underside clearance requirement.
I get it that the Hearth and Hearth “Extension” needs to be at least a 4 inch reinforced concrete slab and that the firebox hearth can be either at floor level or a raised hearth.
With the reinforced slab being a “cantilevered” member – My question is – can that slab be separated on the underside from any materials with an AIR GAP (like a space between the concrete underside and any materials) by some 2 inches or more of gap and non-contact?
As Code R1001.11 Fireplace Clearance states: “Wood beams, joists, studs and other combustible material shall have a clearance of not less than 2 inches (51 mm) from the front faces and sides of masonry fireplaces, and not less than 4 inches (102 mm) from the back faces of masonry fireplaces. The airspace shall not be filled, except to provide fire-blocking in accordance with [Section R1001.12].” I get that this is referring mainly to walls – However, it mentions “joists”.
My point in this – Is there an interpretation which would allow the HEARTH slab to be constructed OVER a floor joist IF AN AIR GAP between the slab and the floor joist is planned so that there is at least a 2-inch, or more, AIR SPACE/Gap provided?
I researched several places – In Scotland they allow a 50MM (2 inch) Gap from the slab underside to any combustible materials. I realize we are not in Scotland – But I still wonder if the gap has been a subject addressed by any masons who regularly build masonry wood burning fireplaces under Chapter 10 of the Code?
Again, I am asking here, as I cannot find other forums or info sites that may be able to provide comment or advise. Thank you i advance – Rich
As I said, I will be building a masonry fireplace (a Rumford) 36" wide firebox. It will be built as part of a custom home build in Tennessee. In learning the code for fireplace construction, I find that the Code in Section R1001.9 - “combustible material shall not remain against the underside of the hearths and hearth extensions after construction”. This brings up a question about this underside clearance requirement.
I get it that the Hearth and Hearth “Extension” needs to be at least a 4 inch reinforced concrete slab and that the firebox hearth can be either at floor level or a raised hearth.
With the reinforced slab being a “cantilevered” member – My question is – can that slab be separated on the underside from any materials with an AIR GAP (like a space between the concrete underside and any materials) by some 2 inches or more of gap and non-contact?
As Code R1001.11 Fireplace Clearance states: “Wood beams, joists, studs and other combustible material shall have a clearance of not less than 2 inches (51 mm) from the front faces and sides of masonry fireplaces, and not less than 4 inches (102 mm) from the back faces of masonry fireplaces. The airspace shall not be filled, except to provide fire-blocking in accordance with [Section R1001.12].” I get that this is referring mainly to walls – However, it mentions “joists”.
My point in this – Is there an interpretation which would allow the HEARTH slab to be constructed OVER a floor joist IF AN AIR GAP between the slab and the floor joist is planned so that there is at least a 2-inch, or more, AIR SPACE/Gap provided?
I researched several places – In Scotland they allow a 50MM (2 inch) Gap from the slab underside to any combustible materials. I realize we are not in Scotland – But I still wonder if the gap has been a subject addressed by any masons who regularly build masonry wood burning fireplaces under Chapter 10 of the Code?
Again, I am asking here, as I cannot find other forums or info sites that may be able to provide comment or advise. Thank you i advance – Rich
