Building Fast and Slow: The Empire State Building and the World Trade Center (Part I)
The Empire State Building was completed in 1931. At a height of 1250 feet , it was the world's tallest building, exceeding the recently completed Chrysler building by 202 feet. It would hold that title for the next 39 years, until 1970 when it was surpassed in height by another New York skyscraper, the under-construction World Trade Center, which would reach a height of 1368 feet on the North Tower. The World Trade Center would hold that title for just 3 years, after which it would be surpassed by the 1451 foot Sears (now Willis) Tower, already under construction when the World Trade Center was being built. 
The Empire State Building and the World Trade Center make for an interesting comparison. In many ways, they’re similar. They’re both iconic Manhattan skyscrapers (they were built just 3 miles apart) that sit right next to each other in the sequence of “world’s tallest building”. Both started out as projects aimed at creating (among other things) a large amount of commercial office space, and were later nudged by their owners into becoming the world’s tallest building. Both were completed in the midst of a severe economic downturn (the Great Depression and the 1973 Oil Shock, respectively), and took many years to be fully occupied. The Empire State Building would be only partially occupied through the 1930s (making money largely from visitors to the observation deck), and the owners were only saved from bankruptcy because the lender (MetLife) didn’t want the building. It wouldn’t start to turn a profit until after WWII. Similarly, the World Trade Center didn’t reach full occupancy in 1980. In both cases the building owners had to coerce government agencies to use much of the available space.
They also share an architectural genealogy - the architect of the World Trade Center, Minoru Yamasaki, had worked for several years at Shreve, Lamb, and Harmon, the architectural firm that designed the Empire State Building.
But in many ways they’re different. The Empire State Building is often the first example reached for by those nostalgic for an America that builds. Not only was it built impossibly fast by modern standards (less than a year from setting the first column to being completed), but it came in under budget, with its design becoming a widely praised example of Art Deco architecture.
The World Trade Center, on the other hand, was continuously mired in controversy and difficulty. It was slowed by lawsuits from displaced residents, political opposition from both New York and New Jersey, difficult site conditions, union strikes, and novel building systems and construction methods. From its conception in 1961 (and arguably even earlier) the project took more than 10 years to complete, going far over its planned schedule and budget. Its architecture would be widely criticized (or at best ignored), as would the urban renewal concept at work behind the project - the World Trade Center has been described as representing the opposite of Jane Jacobs’ worldview, which has since become ascendent in urbanist thinking.
This isn't quite a contradiction (building projects are high variance), but it's an interesting contrast - what made two seemingly similar projects develop so differently? Why did building the Empire State Building go so smoothly, and the World Trade Center struggle? What can we learn by comparing the two projects? Let's take a look.
The Empire State Building
The Empire State Building was the brainchild of two men, John Raskob and Al Smith. Raskob was a wealthy businessman who had started his career as Pierre DuPont’s secretary, eventually working his way up to being an executive for DuPont and General Motors. Smith was a 4-time governor of New York and a friend of Raskob. When Smith ran for president in 1928, Raskob resigned his position at GM to serve as his campaign manager. After losing the election to Hebert Hoover, the two men were looking for a new project.
At the same time, a real estate deal to tear down the Waldorf-Astoria hotel and construct a 50-story commercial office building had fallen through when the developer couldn’t secure secondary financing. Smith became aware of the deal through his position on the board of MetLife (which had supplied the initial financing), and saw it as a prime opportunity - not only could the property be obtained for cheap, but the Waldorf sat on an enormous lot, 425 feet long by 198 feet wide. New York’s zoning code at the time restricted building height by way of requiring step backs from the street, but allowed a tower of unlimited height on 25% of the lot. A lot the size of the Waldorf’s (which were rare, and difficult to assemble) would allow the construction of a truly enormous building.
Neither Raskob nor Smith had any experience in real estate development, and it’s arguable whether the site was suitable for a large commercial building - on the one hand, it was near one of the busiest intersections in the world, the intersection of Broadway and 6th Avenue at 34th street, which was crossed by 6 different sets of train tracks. On the other hand, it wasn’t in an office district, or directly on any train lines. The tallest nearby building was the Internal Combustion Building, a mere 28 stories. Regardless, Raskob and Smith, along with some of Raskob’s wealthy associates (including Pierre DuPont) formed the Empire State Building Corporation, and acquired the property. On August 29th, 1929, they announced they planned to build an 80-story, 1000-foot-high skyscraper on the site.
By September 9th, the architect was brought on board - Shreve, Lamb and Harmon, the firm that had been engaged to design the previously planned 50 story building. Two weeks later, the general contractor, Starrett Brothers and Eken, was chosen. By October several design schemes had been floated, with the seventeenth version (Scheme K) chosen.
Like most “tallest building in the world” projects, the size of the Empire State Building was partly an exercise in building economics, and partly the result of a desire to build the tallest building. An expensive piece of real estate is a large fixed cost (it’s estimated that even at a discount, the property cost $16-17 million, or nearly $300 million in 2022 dollars), and the more rentable area you can spread that cost over, the better. But when building tall, each story is proportionally more costly to build - building taller means a heavier structure, more complicated mechanical systems, more elevators, etc. Adding more stories to a building increases the return on investment only up to a point, which is typically much less than the height it’s physically possible to build.
Economic analysis showed that the maximum rate of return for the Waldorf lot was achieved with a 63-story building, but the developers (largely Raskob) wanted to build even taller. Partly this was out of a belief that the publicity from building the tallest building in the world would be worth the lower returns, and partly it was due to a rivalry with Chrysler. A deal where Raskob would go and work for Chrysler had previously fallen through, and Raskob wanted his building to eclipse Chrysler’s new building, which was under construction at the time. To exceed the announced 1000-foot height of the Empire State Building (as well as the height of the Bank of Manhattan building), Chrysler added a large steel spire, surreptitiously assembled within the building, and bringing it to 1048 feet. In response, Raskob told the designers to go back and design a building taller than Chrysler’s. The building would ultimately be 85 stories, with an added mooring mast that would bring its height to 1250 feet.
In addition to the height requirements, the shape of the building was largely a reflection of its various design constraints. Since better lit spaces could be rented for more than poorly lit ones, the architects opted for a maximum of 28 feet from window to corridor. For elevator service, in lieu of more complex designs, the architects opted for a large number of elevators on the ground floor, that would reduce (along with the size of the floor plate) as you went up, creating a “pyramid of rentable space surrounding a pyramid of non-rentable space.”
The other major design constraint on the building was the time to build it. At the time, New York had two days, May 1st and October 1st, where leases expired. A building completed after one of those dates would sit empty until the next lease expiration day. The developers thus set a date of May 1st, 1931, for completion, giving just 21 months to design and build it. This was an aggressive construction schedule (especially given the size of the building), but it wasn’t unheard of. The Chrysler Building would take just 20 months to build, and Starrett Brothers and Eken had been chosen partially because of their experience building quickly - at the time the Empire State Building was announced the Starrett Brothers were building the 70 story Bank of Manhattan, which they would complete in less than a year.
According to the architects, the design of the building was largely a reflection of these design requirements:
The program was short enough - a fixed budget, no space more than 28 feet from window to corridor, as many stories of such space as possible, an exterior of limestone, and completion by May 1, 1931, which meant a year and six months from the beginning of sketches. The first three of these requirements produced the mass of the building and the latter two the characteristics of its design” - William Lamb in Architectural Forum
Lamb later stated that “the adaptation of the design to conditions of use, construction and speed of erection has been kept to the fore throughout the development of the drawings of Empire State. Whatever “style” it may be is the result of a logical and simple answer to the problems set by the economic and technical demands of this unprecedented program.”
Design and Construction Speed
The rapid construction schedule ended up shaping almost every aspect of the building. Primarily, this meant the design of the building needed to be as simple and repetitive as possible.
This simplicity manifested in a few ways. One was the use of well-vetted, well understood building systems wherever possible. The building was supported by a structural steel skeleton made from Carnegie sections. The floor is a cinder-slab concrete floor, which consists of draped layers of steel mesh which are then covered in concrete. For fire protection, the steel frame was covered in concrete or clad in brick masonry. The exterior cladding of the building consisted of panels of limestone and aluminum with stainless steel accents, and steel windows.
These, and the other building systems used, were all standard practice of the day. In his analysis of the design of the building, Donald Friedman has noted that “no element was exceptional. The steel frame, the floor slab, and mechanical systems were all similar to other buildings”. John Tauranac similarly noted in his history of the building that “'to the greatest extent possible, they [the architects] opted for the tried and true”.
This sentiment is echoed by the designers themselves who variously described the systems chosen as “nothing unusual” (the building floor system), “"a standard type without special features of design” (the windows), and “no experiments and no non-standard manufacture” (the method of window support).
This desire for simplicity extended to many of the design details. For instance, the conventional method for supporting stone cladding was with shelf angles and brackets attached to the main structural frame. This added complexity to the steel framing (which would have slowed down fabrication) and slowed down the construction of the facade - fitting the stone to the angles often required significant adjustment and cutting of stone on-site. In lieu of this, the stone cladding and its brick backing was instead supported on an “extra” steel spandrel beam mounted outside the rest of the steel frame, which simplified both the steelwork and the erection process, as well as allowing fabrication to begin on the steel while the design of the cladding was still being finalized. Similarly, the windows were designed to sit flush with the stone cladding instead of the more conventional method of having them inset several inches. This allowed the stone to be much thinner, reducing the weight on the building, as well as the weight that had to be moved by the workers building it - the Empire State Building used perhaps 25% of the stone per cubic foot of building that a typical stone-clad building did. This window placement also meant that the sides of the stone weren’t visible in the final condition (they were covered by stainless steel trim), and thus didn’t need to be finished, which made the stone cheaper and easier to fabricate.
Similarly, the stone cladding isn’t continuous, but consists of vertical “piers” between the windows, with the windows having aluminum panels above and below them. This greatly simplified the stonework (since it didn’t have to attach to any headers or sills), minimized the amount of stone cutting on-site required, and allowed the design to consist of many identical pieces of stone. The stonework panels were sized so that they could be easily moved on interior material hoists.
There were many other examples of this sort of simplification. Though there were 5704 aluminum spandrels on the exterior, there were only 18 different variations. The floor beams were set low so that electrical cables could run over the top of them without needing to be bent (saving the labor for bending them and making it easier to pull the wire through). The interior marble finishes chosen were ones that could be obtained quickly in the necessary quantities - the originally specified marble was in fact switched out when the quarry said they couldn’t meet the construction schedule. Ultimately an entire quarry in Germany was purchased, which supplied a Rose Formosa marble.
There were some notable deviations from standard practice. In addition to the novel outboard spandrel beam, the building used a stronger structural steel than the code had previously allowed (18,000 vs 16,000 psi). The developers lobbied the mayor directly for the change (which was already common in most other American cities), who signed it into law in May of 1930, just as steel erection commenced. Similarly, the building was designed for elevators with a speed faster than allowed by code (1200 feet per minute vs 700 feet per minute). After completion, the building spent six weeks with the elevators set at 700 feet per minute until another code change (partially the result of advocacy by the builders) allowed them to operate at their full speed.
The building was designed to also avoid, to the extent possible, interdependency between the different building systems. Shreve noted that “special study was given to eliminate as far as possible material interdependence, to provide in every way for entire independence of manufacture and erection, and, where the elements were necessarily interrelated, to arrange so that the placing of any one group, once started, might proceed freely without being held up by another.” Friedman notes that “trades move at different speeds, have special requirements, and may view the same detail in entirely different ways. By eliminating as much of the contact between trades as was possible, the builders reduced the risk of cascading delays.” To the extent possible, hand-fitting on-site was eliminated.
This design for maximum speed of assembly wasn’t achieved by the designers working in isolation. Shreve describes the process of design and construction as one of collaboration, where a “board of directors” consisting of the owners, the architects, the general contractor, the engineers, and any other participants deemed necessary collectively worked through the design and construction issues:
The group engaged in such an important operation should constitute a Board of Directors upon which should sit the owner supported by his bankers and real estate agents, the architect in company with his structural and mechanical engineers, and the builder whose subcontracting and material supply associates from time to time assist in the discussion of special problems. It is under such direction that the Empire State Building is being designed and constructed.
It was only by way of this close coordination that the speed of construction was achievable:
“In November, 1929…demolition of buildings on the site was proceeding, and a program had to be prepared for placing foundations in February and setting steel in March, four months being allowed for the completion of architects’ information, the preparation of steel designs by the engineers, the bidding and award of contract for the steel, and the fabrication, delivery, and placing of the first structural shapes. Only the most careful planning and thorough cooperation made this result possible.
Fred Brutchy, the plumbing engineer, similarly noted that the successful cooperation of the “board” was a major factor in the successful design of the building. And Paul Starrett likewise noted in his memoirs that “general simplicity in the design of the whole was underlaid by innumerable simplicities and economies in detail, which the architects worked out in collaboration with us.” (Diligent readers will note that this is exactly the method used by some homebuilders to build cheaply and efficiently.)
For instance, Shreve describes the process of figuring out the design details for the steel trim on the exterior cladding:
It is intended to use on the exterior of the building a large quantity of chrome-nickel steel. Consideration of this construction feature involved the determination of the length and width of sheets which could be rolled and fabricated; the possibility of forming the sheet on the brake; the method of jointing and of bracing; the relation of the metal form to the exterior wall surfaces, the window heads, sills and jambs, and the spandrel; the means for attaching the metal form to the frame of the structure, as well as the finish and durability of the bright surface.
Neither architects, builders nor subcontractors felt competent to deal with this complicated technical problem of construction without full consultation. Accordingly, after full preliminary discussion, an all-inclusive meeting was called which was attended by representatives of the owner, the architects and builders, the subcontractors rolling the material, the metal workers who were to fabricate and those who were to erect it, and the inspectors who were to test all sheets at the several stages of preparation.
Shreve further notes that “hardly a detail was issued without having been thoroughly analyzed by the builders and their experts and adjusted and changed to meet every foreseen delay.”
The speed of construction had a similarly large impact on the construction methods used. One example is the use of what now would be called “fast track” construction - the sequencing of construction steps so they begin before the design is completed. The demolition of the Waldorf-Astoria began just two days after the general contractor was brought on board, before even the preliminary designs had been completed. Construction on the foundations would similarly start before demolition was completed. When steel erection commenced in April of 1930, the upper floors were still being designed - over the course of the project, each level of structural steel was designed just a month ahead of when the order was due at the mill.
On-site, a variety of methods were employed to maximize speed of erection (and to minimize cost). Four elevators from the Waldorf-Astoria were saved and repurposed as construction elevators in the initial stages of construction (these were later replaced with more conventional construction elevators). For moving material, holes were left in the floors to allow material to be raised up through the building with the use of six electric material hoists. Concrete batch plants were built in the basement to avoid having to truck in concrete, and special brick hoppers were built that allowed bricks to be dumped from the truck and raised to the proper floor without a human hand ever needing to touch them.
To minimize the time workers spent traveling to get food, cafeterias (set up by a local restaurant) were set up on the third, ninth, twenty-fourth, forty-seventh, and sixty-fourth floors.
But the most notable was the narrow-gauge rail track (called the “industrial railroad”) that was installed on each floor, which allowed material to easily be moved to the appropriate location by way of mine carts. Only the enormous size of the building made such a system cost effective.
Beyond these innovations, construction of the building was a case of carefully orchestrating the huge amount of men and material - at its peak, nearly 500 trucks were arriving each day (about one truck a minute), and nearly 3500 men were working on the building at once. Each truck was sequenced - if a truck missed its place in line, it had to come back the next day. Nine cranes were used to lift the steel into place. The builders describe the process as like an assembly line of standard parts, the “purchase, preparation, transport to site, and placing of the same materials over and over again”. But repetitiveness shouldn’t be confused with ease of operation - keeping the project on schedule was monumentally difficult. In his memoirs, Paul Starrett states that “the strain of erecting the Empire State Building in 11 months was too much for me, and I suffered a rather severe nervous breakdown”.
The building was erected at roughly a rate of a floor per day for the upper floors (the larger, lower floors were slower). The structural steel was completed by September, just seven months after installation began. The concrete floors were completed two weeks later, and the exterior stone and aluminum a month after that. Despite the emphasis on speed, work largely took place during the normal workday (only rarely extending into night), and during a normal 5 day week. Nevertheless, every trade completed their work faster than required by the schedule.
The Empire State Building was completed in April of 1931, several weeks before the deadline of May 1, and for approximately $2,000,000 less than the budget. 
This series will continue next week with Part II
 - This is the original height of the building, with the mooring mast for dirigibles. The current height to the tip of the television mast is 1452 feet. In general, there are a variety of different metrics for calculating the height of the building. “Tip height” is the height to the tallest portion of the building, including masts, antennas, etc. “Architectural height” is the height to any architectural elements such as spires, but not technical equipment like masts or antennas. “Occupied height” is the height to any occupied floor. Architectural height is the most common measurement of building height.
 - The Sears Tower would hold the tallest building record until 1998, when it was surpassed by the 1483 foot Petronas Towers, marking the end of the US having the tallest building in the world.
 - The costs of the Empire State Building are somewhat tricky, due to the influence of the depression and the resulting deflation - what had been worth a dollar in 1929 was worth 89 cents in 1931. Raskob’s original estimate was $35 million, Tauranc states that the final estimate was $43 million, but with an actual cost of $24.7 million (which is from Starrett’s records). Starrett claims they built it for $2 million under budget.