Alternative firebox base materials

[Ross Neag]

Was wondering if there is anything else that satisfies CSIA or NFPA guidelines for firebox base material, such as 1" soapstone, similar heat resistant natural stone, specialty steel, etc. Is there a published list of acceptable alternatives? Any info would be much appreciated, thanks.

[Bob Harper]

Was wondering if there is anything else that satisfies CSIA or NFPA guidelines for firebox base material, such as 1" soapstone, similar heat resistant natural stone, specialty steel, etc. Is there a published list of acceptable alternatives? Any info would be much appreciated, thanks.

Are you talking about a factory built fireplace or a site constructed masonry fireplace?

CSIA does not promulgate standards, codes or guidelines--they are chimney sweeps.

NFPA 211 is the nationally recognized standard for fireplaces, chimneys, vents and solid fuel burning appliances. You local building code may or may not expressly refer to 211. For instance, the IRC refers to 211 for chimneys and venting for heating appliances but not fireplaces.

[Ross Neag]

Let's suspend technicalities if we can for a moment, Bob. Masonry (ie, old) WBFP with smaller opening, 24" wide 30" high and 16" deep with 8 x 8" chimney. Client is going to line it. Base of firebox is durock waiting for finishing with 7/8" lip to existing floor finish level (yes, firebox is lower than floor). They want to know if they can use 1" soapstone instead of fire brick. I know soapstone is used for wood stoves and surrounds--is it suitable as a base?

[Bob Harper]

Let's suspend technicalities if we can for a moment, Bob. Masonry (ie, old) WBFP with smaller opening, 24" wide 30" high and 16" deep with 8 x 8" chimney. Client is going to line it. Base of firebox is durock waiting for finishing with 7/8" lip to existing floor finish level (yes, firebox is lower than floor). They want to know if they can use 1" soapstone instead of fire brick. I know soapstone is used for wood stoves and surrounds--is it suitable as a base?

Sure, if you install about a 5" thick slab. That's about what it would take to make an 8" round liner legal for that size opening fireplace. As for materials, the code recognizes two choices: firebrick and all other forms of solid masonry units. If you use firebrick, you can reduce the firebox thickness requirements by 2". Otherwise, 12" firebox walls. The codes generally don't get too specific on the hearth. Soapstone is a great material for firebox construction due to its high specific heat. Are there any combustibles under this hearth or hearth extension? Why the Durock?

[Ross Neag]

Unknown as to Durock but firebrick is what I will recommend. Its a 100 yr old frame here in the city but no access to any of the framing around the fireplace. Zero.

I did a search for soapstone firebrick and boy would that be fun to construct a Rumford with a soapstone firebox, hearth and surround. Thanks for the assist.