Floating Chimney

[Mike Lamb]

This chimney was added after the house was built. and it serves a manufactured steel fireplace (DESA). It's obviously heavy and is supported by something.

Is this considered a masonry chimney which needs to be supported by solid masonry beneath as per IRC?

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[kurt]

I'm a little mystified; what's holding it up now?

[chrisprickett]

Originally posted by kurt

I'm a little mystified; what's holding it up now?

Magic! Unless there's some hidden super-duper engineering going on, I'd say that homeowner is screwed.

[jon_ran]

There are actually a few things wrong with that set up.

1. No support under chimney, unless it is supported by cantilevered beams ( I don't think cantilevered joists would support the weight). Unless that is an artificial brick such as Z-Brick.

2. Too close to condensing units.

3. Inaccessible hose bib and conduit connections for one condensing unit.

4. Refrigerant lines buried in the concrete waste, which means that they weren't protected from damage.

[Mike Lamb]

There is steel under the brick so I assume a cantilever. My understanding is this chimney has been in place about 8 months and is a standard size brick veneer like the brick laying on the ground. There was no signs of stress that I could see. This is a 2 story chimney.

My IRC 2000 says:

R1001.1.1 Support.

Masonry chimneys shall be supported on foundations of solid masonry or concrete at least 12 inches (305 mm) thick and at least 6 inches (152 mm) beyond each side of the exterior dimensions of the chimney. Footings shall be founded on natural, undisturbed earth below the frostline. In areas not subject to freezing, footings shall be located a minimum of 12 inches (305 mm) below finished grade.

However, if the firebox is not real masonry and the chimney is a veneer, it is not a real masonry chimney, and is not subject to R1001. Right?

[hausdok]

That depends on the weight it's supporting. If it's considered "load bearing" it can't be cantilevered beyond the depth of the joists. That cantilever appears to be about twice the depth of the joists. Most chimney chases wouldn't qualify; however, once you add the weight of all that brick to the outside face?.........

OT - OF!!!

M.

[Bain]

I still don't get it. What did they cantilever it into? An existing 2" x 10" floor system? Even if there are steel beams beneath the chimney, what are they anchored to? And how?

[Jesse]

What are those two small vertical pieces of lumber underneath the chimney? One looks like it's standing on a concrete footing of some kind.

[inspector57]

I very rarely call for a Structural Engineer, but that is the call I would make on this one. Even if it is "just" a chase, it is too heavy to float on air. It does not fit the model building code, so it needs an engineers design and stamp.