Help! Fireplace Hearth Support?

Hey folks, I found this under a house I recently inspected and I am having trouble finding the proper verbiage regarding what it is and how it’s supposed to look. This is beneath a masonry hearth. These steel components are held up by non-cantilevered 2x4s nailed upwards into the joists. If this is considered to be structural to the masonry fireplace, I want to call this out. However, I am having trouble finding what this is referred to as. I need to be able to educate myself on it and give a proper recommendation to my client. Any advice or information would be greatly appreciated!

is this under the firebox itself or just the hearth extension?

It appeared to be just under the hearth extension, I couldn’t quite get my head up there in a position to see just how far back that steel goes. The nailed 2x4s stop at the sill plate.

They were meant to be removed after the concrete was cured.


That’s an expensive way to do something very simple. Obviously it’s the formwork for the hearth extension. I would hope that no one would construct an elevated hearth extension without internal reinforcement, but there’s no way to tell. Normally the form is wood plank or plywood, and left in place. Here we have some interesting steel work. Crazy.

I call things like this an “ad hoc construction method.” There’s no way to tell why they did it this way. But, a home inspection is not a code inspection. Report what you see, and if you have a concern, refer it to the guy that signed off on the permit, or to an engineer. I have my own way of assessing these things, but it’s on a case by case basis.

If it is just under the hearth extension I see no problem other than maybe a bit of overkill in the way it was done…

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Typically, the means and the methods are left to the contractor as they see fit to achieve the same outcome, but a DIY is most likely to achieve it in mysterious ways and not always done right. LOL
As long as the minimum thickness of the hearth extension is at least 2" on non-combustible material, chances are it is alright.
What you should check that we don’t see is above the floor.
The extension vs. the fireplace, opening if that is what it is.

The hearth extension must extend at least 16" from the front of the fireplace and 8" on the sides for smaller fireplaces. When the opening of the fireplace is at least 6 square feet, the hearth extension needs to extend at least 20" from the front of the fireplace, and 12" on the sides.


Thanks Scott!

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Hey Darren, I greatly appreciate your insight! My main concern with this is that the 2x4s are essentially being used as a ledger board. When we see this kind of nailing pattern in a ledger board we call it out for a qualified decking contractor. In this case, I’m trying to figure out if this needs to be referred to a fireplace contractor or to a structural engineer.

Hey Marcel, I appreciate your input! As far as the fireplace itself, clearances, etc. everything looked fine. This is really the only concern I had with it.

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