Anyone Familiar With Code Concerning Kiva Fireplaces?

[Frank Williams]

I'm attempting to adapt a vintage masonry Kiva fireplace design to meet modern fireplace building code, and have a question pertaining to the requirement that the smoke shelf (throat) be 8 inches above the fireplace opening. My question is: Is the very top of the arched opening used for this measurement, or can a point further down the arch be used - due to the fact that the width of the opening curves narrower toward the top? Does anyone have experience with interpreting this particular dimension?

Thank in advance,
Frank Williams

 

[webby3650]

The smoke shelf is typically above the highest part of the opening by 8" or so. I have never heard of a code that limits the smoke shelf to a certain height. The smoke shelf is different than the throat. The throat is where the smoke chamber meets the flue, the smoke shelf is just above the fireback, at the damper area.

 

[Frank Williams]

In this case, the damper is much further up the chimney, so the reference point would be the shelf itself. Not concerned with the overall height of the smoke shelf, just it's height from the top of the fireplace opening. Just need to know whether the top of the arched opening of the kiva fireplace has to be used since it is tapered. Pics included to show what I'm asking.