How to know Hearth is all brick?

[sdlxcoupe]

Here is my question.

I am installing a fireplace insert in my existing masonry fireplace/chimney.
I am trying to figure out if the hearth in front of my firebox is all brick or some frame covered with brick.
This is a question/concern as part of the insert will be on the hearth and the insert requires specific R/K values for transferring heat.
My house was built in the late seventies. When in the basement under the fireplace I see that there is floor/framing reinforcement.
There is also mortar that has seeped through probably during construction which is leading me to believe that it is all brick.

Anyone with any help on this would be appreciated.

picture of fireplace attached.

 

[jotul8e2]

What you describe is common brick over framing. It is not a true masonry hearth for code purposes. If it were there would be masonry or concrete going all the way down to dirt.

 

[sdlxcoupe]

I guess the question would be then.
Is it a framed out box with bricks mortared to the box or is it all brick stacked up sitting on the subfloor?
Not sure if this can be seem by looking at it.
If it is all brick then the k and r values i am trying to achieve will be far exceeded because it would literally be 1 foot of brick, but if it is just a box covered in brick it would be cutting it close as only being 1 brick on its side.