Whats supporting this old fireplace?

[branimal]

I'm renovating a 100-year old 3-family building in Brooklyn. Each floor has 3 old fireplaces - that I'm guessing they were used to burn coal or wood. They've been covered up with plaster & lathe at some point.

My plan is to cover the fireplaces up with studs and sheetrock. I'd like to make the hearth area part of the finished flooring. I need to get some blocking nailed to the nearby joists to give the floor support. I've done this on the floor above without issue.

I started digging out the hearth and the bricks below it and it seems the fireplace is barely supported underneath. The fireplaces on the floor above had bricks directly underneath providing support. Like one continuous stack of fireplaces. I didn't pull out any bricks from underneath the fireplace - only bricks under the hearth area.

How is this being supported? I'm a bit concerned on proceeding.


Pics to help explain the issue attached.

 

[Uncle murph]

I'm renovating a 100-year old 3-family building in Brooklyn. Each floor has 3 old fireplaces - that I'm guessing they were used to burn coal or wood. They've been covered up with plaster & lathe at some point.

My plan is to cover the fireplaces up with studs and sheetrock. I'd like to make the hearth area part of the finished flooring. I need to get some blocking nailed to the nearby joists to give the floor support. I've done this on the floor above without issue.

I started digging out the hearth and the bricks below it and it seems the fireplace is barely supported underneath. The fireplaces on the floor above had bricks directly underneath providing support. Like one continuous stack of fireplaces. I didn't pull out any bricks from underneath the fireplace - only bricks under the hearth area.

How is this being supported? I'm a bit concerned on proceeding.


Pics to help explain the issue attached.

There’s probably something to either side,I’m curious as to why it looks like more flue under there complete with smoke stain.Footings as we know them are a relatively modern thing,most older houses and barns have walls literally laid up on dirt.I’d be darn careful digging any more until you do know what’s supporting it,don’t let your renovation turn into a search and rescue.

 

[branimal]

There’s probably something to either side,I’m curious as to why it looks like more flue under there complete with smoke stain.Footings as we know them are a relatively modern thing,most older houses and barns have walls literally laid up on dirt.I’d be darn careful digging any more until you do know what’s supporting it,don’t let your renovation turn into a search and rescue.

Yeah as soon as I saw the void I thought about all those bricks tumbling down on me. I'll try to get some better pictures of the support structure underneath.

 

[wrenchguy]

All 3 fireplaces the bricks are finger jointed/tied to the brick bearing wall behind it.
Show photo of inside corners.
How thick is the back wall? Could be angle iron supported from it.

 

[My Old Tools]

Looks like the hearth and facing are just sitting on framing and only the flue itself is continous. The sand and rubble is the "insulation" for the framing. The flue appears to be behind the visible "fireplace". I think those were there to provide a safe spot for a cast iron stove, not a fireplace.

 

[branimal]

I pulled out all the bricks I need to. There does seem to be some type of support under the firebox. Like bricks tied into the back wall with a staggered pattern. The wall behind is one layer of brick like rest of the building.

I didn't want to stick my hand in there to feel around for a piece of metal angle.

Looks like magic to me.

 

[Zeke]

I'd be in a hurry to fill that void with concrete. You don't say where this is (so many don't and in cases like this it's a hinderance) but there are earthquakes in regions not known for quakes. Just like every once in a long while there's a tornado in CA.