A fireplace in a circa 1900 mansion.
The floors are terra cotta tile arches supported on steel beams. The fill layer that runs over the arches has been temporarily removed during the current construction, leaving the tops of the beams standing proud above the terra cotta surface. The beams are supported by brick bearing walls.
The firebox has a brick arch in front rather than a lintel, which is a straightforward and old-fashioned way to deal with the heat. The firebox itself appears to be common brick except for the bottom, which is hard-burned yellow brick.
The NYC code (and pre-comprehensive-code regulations) requirements for fireplaces barely changed from the mid-1800s through 2008, when the city adopted a locally-edited version of the International Building Code. And really, even the post-2008 codes are fairly close to the old requirements. There are few code sections that have gone so long with so few changes, for the simple reason that the mid-1800s requirements worked.. They kept the fire and smoke where they belonged, which is another way of saying they led to workable fireplaces that didn’t set buildings on fire. Those fireplaces, of course, became less and less important over time as stoves, gas lights, steam heat, and electric lights were added to the expectations for new buildings.
Having the steel beam running straight into the base of the fireplace feels wrong. Most of the buildings with this type of fireplace have wood-joist floors, and the joists are supported by a header just outside of the hearth, so that there’s no flammable material at the hearth. In this case – and in other buildings with fire-resistant floors – the fire-rated floor is as heat-resistant as the fireplace itself, so there’s no reason that the floor can’t simply run to the wall and directly support the hearth.
We’ve got a fireplace that would not have been out of place hundreds of years ago, sitting (safely) on a steel and terra cotta floor that was new technology when this building was built. A nice mix, and one that shows the way that new eras slip in as old ones ease out.