Cast Iron

New Mixed With Old

by Don Friedman on April 12, 2018


That picture, of the 157th Street Station on the 1 train, shows the unevenness of adoption of new technology. It’s right there, can’t you see it?

Here’s a close-up with the contrast cranked up high:



You see that thing in line with the column and below the platform lip? That’s cast iron. That’s the metal technology that New York embraced in the 1850s and only abandoned after several disasters showed that it was ill-suited to structures with dynamic loading, which is to say bridges and buildings. But it’s okay here…

The original line of the Interborough Rapid Transit ran from the now-closed City Hall station to 145th Street. It was always meant to grow beyond that, and 157th Street was the first new station added, in November 1904. This station was designed as part of the original system, so the engineering took place around 1900 or 1901, before cast iron was completely abandoned. We’re seeing two main pieces: a round column and a column base. Starting at the top of the close-up, we’ve got a masonry column enclosure covered with tile, then the edge of the concrete platform (with the yellow warning stripe), a beam supporting that edge, running below it and covered with dirt, a seated connection for that beam in line with the column (in the form of a T, with the actual seat as the T crossbar and a stiffener as the T stem), a short stretch of circular cast-iron column, a column splice (in the form of two horizontal-plane circular plates) and then the column base proper, which has a bunch of sloped vertical plates leading down to a base plate. The seated connection is cast iron and integral with the column, the top plate of the two that make up the splice is integral with the column, and the bottom splice plate is integral with the base. You can build up a base like that from steel plate but that requires welding technology that wasn’t ready for use in 1904; I’ve only ever seen this particular geometry in cast iron. I used to think of them as cast-iron spiders because there are eight vertical plates.

The load on this column is overwhelmingly dead load: the weight of the soil above the station, the weight of the station roof, and the weight of the platform. The live load of people on the platform and even traffic on the street is small by comparison; the street load is also spread out from having to travel though some six to ten feet of soil before It gets to the station roof. Cast-iron columns are at their best when subjected to static or mostly static loading, which is the situation here.

Why didn’t the IRT’s engineers use steel, the modern technology they were so successful with so many other places? Value engineering. Cast-iron columns are cheaper than steel and so were a good idea where they could be safely used: in stations, where train speeds were slower in stations and therefore there was less dynamic loading. The future was here, but unevenly distributed.

No Expiration Date

March 29, 2018

This is the third and last post on what I called a “rather boring” building. That very geometric picture is a roll-down door on the left, a pier in the middle, and a window on the right. Here’s the thing that caught my eye: That’s a cast-iron column, rectangular in cross-section, with openings on the […]

Read the full article →

Design At Different Scales

February 1, 2018

Rain Noe gives a nice summary of cast-iron vault lights here: Urban Design Observation: Why SoHo Has 19th Century Glass Sidewalks and Stoops. Noe is approaching vault lights from an industrial design perspective, which is obviously different from my background. The nice thing about design discussions is that one perspective isn’t necessarily more right than another: […]

Read the full article →

An Iron Appendix

January 16, 2018

That’s a photo of an areaway in London. The wall on the right is the building and I’m standing at the corner of the areaway. The black coping along the left is on top of the curb that’s an extension of the areaway’s outboard wall, extending above the sidewalk. If I had to guess, I’d […]

Read the full article →

You Can’t Not See It

January 3, 2018

There’s a fairly well-known phenomenon by which once you’re aware of something you start to see it all over. This isn’t the result of inanimate objects in the natural world conspiring against us but rather the result of sensitization. We can look at something for years and not see it because we don’t think about […]

Read the full article →

Analyzing a Historical Anecdote

December 18, 2017

That’s my close-up of the top of one of the fence posts at Bowling Green. (Yes, it is on my walk to work. Thanks for asking.) As you can see, the top of the post is quite rough. In one of the more famous acts of vandalism in New York history, the Sons of Liberty […]

Read the full article →

The Machine Aesthetic

December 1, 2017

In one sense, all building materials are artificial. Even the wood we use as lumber is shaped into geometries not seen in nature: rectangular in cross-section, straight, and identical from one piece to the next. But somehow metal seems artificial in a way that masonry and wood do not. You can see artists struggling with […]

Read the full article →

Expounding on a Neat Trick

October 30, 2017

I talked a bit about this type of detail recently but I was surprised to learn that I hadn’t posted these pictures. This is a middle-third of the 1800s tenement in Hell’s Kitchen that was built with retail space on the first floor. The wood joists of the floors and roof span left to right, […]

Read the full article →

Partially Hidden, A Neat Trick

October 26, 2017

I thought I had talked about this type of structure before, but maybe not. How do you create a storefront when it’s the 1840s or the 1860s? How do you support a masonry wall over a glass void? Affordable steel beams are decades away and wrought iron beams are untried and new technology. The answer […]

Read the full article →

Labor Day Weekend 1

September 2, 2017

Workers erecting cast-iron columns.

Read the full article →