# All-masonry fireplace hearth bears on wood floor structure



## Willin (Nov 10, 2018)

New construction, a large freestanding fireplace with CMU core and fieldstone facing comes up through the wood-framed floor structure of the main floor.  It goes through the basement floor where it bears on a suitably-sized pad.

The fireplace opening is 16 inches above the floor, and the hearth extension, 100 percent masonry, sits atop the floor structure.  It is not connected to the fireplace structure other than with mortar along the joint.  No cantilevered concrete shelf will be built.  This hearth extension has CMU core with fieldstone facing and its top is paved with bluestone.

Code-perfect?


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## cda (Nov 10, 2018)

welcome


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## cda (Nov 10, 2018)

If you can convert the plans or draw a simple plan,

Make it into a web link

Post it would help.

I am not in to structural, but seems like a structural engineer, might should be involved.


So what does the fireplace set on??  a concrete basement floor, or wood basement floor???


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## Willin (Nov 10, 2018)

Don't know what it takes to be able to include an image.  So here is more detail.

A large pier pad is directly beneath the 4" floor slab in the unfinished basement.  Atop this is built, with CMU walls, the fireplace foundation, which rises up and through the wood-framed structural main floor about 8 feet above.  A framed opening in that floor structure is for this fireplace, and the opening comes to all sides of the fireplace foundation, with about 1" clearance.

Above this floor, the CMU is stepped in a distance for the fieldstone cladding thickness.  The fireplace stack rises 16 inches, where the fireplace opening begins with its firebrick floor.  The fireplace opening is thus 16" above the wood-framed floor.

Sitting atop this wood-framed floor and abutting the front of the fireplace is the hearth extension, all-masonry, CMU core, rock faced, 2" bluestone slab atop it, the bluestone slab top elevation same as the fireplace floor which it tightly abuts.

Note we've not built this masonry fireplace with a cantilevered slab below the hearth level, for supporting not just ht the hearth, but any hearth extension.  We have built the extension as a separate masonry mass, sitting atop the wood-framed floor structure.

Code?


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## Willin (Nov 10, 2018)

Sort of like this.  The extension is sitting on the wood-framed floor, and not on the fireplace structure.

http://www.riversidebrick.com/Image...Bucks_County_Dressed_Fieldstone_Fireplace.jpg


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## cda (Nov 10, 2018)

Give  it a few days and there are plenty of people that speak structural that can reply


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## TheCommish (Nov 12, 2018)




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## ADAguy (Nov 13, 2018)

cda said:


> If you can convert the plans or draw a simple plan,
> 
> Make it into a web link
> 
> ...



He already said what it sat on, the hearth is on wood and the FP sits on a footing, a crawl space install.
The concern here is the grout intersection between the hearth and the face of the FP. Hot coals can collect sometimes at this intersection and over time can char the hearth support members.


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## jpranch (Nov 13, 2018)

The living room floor at code minimum would have to have the capacity to support a 40 pound live load and a 10 pound dead load. I would be hard pressed to approve something like this and would require an analysis by a structural engineer. Been inspecting buildings for about 29 years and have never seen anything like this. The hearth extensions that I have seen have always been supported by cantilevered concrete.


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## RJJ (Nov 17, 2018)

I agree with Commish & jpranch.


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## jar546 (Nov 17, 2018)

Willin said:


> New construction, a large freestanding fireplace with CMU core and fieldstone facing comes up through the wood-framed floor structure of the main floor.  It goes through the basement floor where it bears on a suitably-sized pad.
> 
> The fireplace opening is 16 inches above the floor, and the hearth extension, 100 percent masonry, sits atop the floor structure.  It is not connected to the fireplace structure other than with mortar along the joint.  No cantilevered concrete shelf will be built.  This hearth extension has CMU core with fieldstone facing and its top is paved with bluestone.
> 
> Code-perfect?



The framing that supports your hearth needs to be of sufficient design for the loads imposed.  The framing requirements are above and beyond the scope of the prescriptive tables in the IRC, therefore you would need a structural engineer as code inspectors, plan reviewers, etc are limited to enforcing prescriptive methods in the code books.


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## jpranch (Nov 19, 2018)

jar456 said it better than I did. Right on target.


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