We often forget that Thomas Alva Edison was responsible for patenting the light bulb and phonograph. While these were two of his 1,093 patented inventions, today we primarily remember “the Wizard” of New Jersey as the inventor of the single pour concrete house.¹ Casting an entire home — from cellar to the roof, through the mantels and bathtubs, to the optional piano and refrigerator — in one go, Edison's invention proved decisive in pivoting the mass production of U.S. home construction from wood to concrete. Prior to the patent's approval in 1917, most people in the United States, and indeed large swaths of the world, dwelled in buildings made from an assemblage of wood, stone, or brick. Not only were these structures prone to rotting, chipping, and disintegrating, but bathtubs and sinks, as well as their countertops, were all separately manufactured and replaced at great cost. In contrast, a home made from concrete is easy to scrub with soap and water, never requires replacing siding or shingles, and is simple to paint. Unless we visit a house preserved from the period preceding the ubiquity of concrete buildings, we struggle to imagine such levels of domestic insalubrity.

But we do well to remember that the global success of Edison's concrete house was anything but a foregone conclusion. Filed on August 13, 1908, it took nearly nine years for approval from the U.S. Patent Office. It appears a disgruntled former employee of Edison's, Walter Milcom, submitted a nearly identical patent. While waiting for the authorship of the patent to be adjudicated, two of Edison's longtime associates and fellow patentees, Frank Lewis Dyer and Thomas Commerford Martin, published Edison: His Life and Inventions. A nine-hundred-page hagiography of Edison's achievements in art and industry, chapters 20 and 29 of Edison celebrated his ongoing experiments with concrete. Whereas all of the other inventions profiled in the book either founded new forms of arts and industry or significantly added to existing fields, the nascent single pour concrete house was “on the threshold of an entirely new and undeveloped art of such boundless possibilities that its ultimate extent can only be a matter of conjecture.”² What was once conjecture is now our concrete reality.

In looking back at Edison's patent, how might we retrieve that sense of “such boundless possibilities” of the single pour concrete house in the early twentieth century? What can this blueprint of the future tell us about housing, health, and Edison's desire to create a dwelling that is “practically indestructible and is perfectly sanitary”?³ On the anniversary of Edison's 175th birthday, my talk today attempts to retrieve the circumstances surrounding the inventor's most important design. The historian cannot help but situate Edison's work within a context of concern about the availability of lumber, affordable housing, and health. We know that during this period most housing in the United States was built out of wood using a method known as balloon framing. Christened so in the nineteenth century because many carpenters believed it might fly away with a strong gust of wind, the system proved relatively sturdy and resistant to tornadoes. While historians have debated who authored the system, it was developed between 1831–32 along the Chicago River.⁴ Made of standard, dimensional lumber like 2x4s and 2x6s and held together with nails as opposed to elaborate wooden joinery, the system required considerably less expertise than other forms of house framing. It also cost significantly less to build, could be finished in a matter of days, and made use of North America's abundant forests.

By the turn of the century, this all began to change. With much of the forests of the American South and Pacific Northwest felled for housing, not only did concerns over the future of timber reserves lead to the conservation movement and establishment of the U.S. Forest Service in 1905, but they also created an economic incentive for alternative building materials like concrete. In New York City, where Edison led the city's electrification, the municipality had reached a population of 3.4 million people. An estimated 2.3 million lived in 80,000 squalid tenements. These brick buildings, largely inhabited by working class immigrants, rarely had running water, included no more than a few shared hallway toilets, and contained interior windows with almost no ventilation. Plagued by fires and the spread of disease, these insalubrious building practices were finally halted by the Tenement House Act of 1901.

Fortuitously, 1901 was the year Edison entered the cement business. And by 1907, he was operating one of the nation's largest production plants. After patenting rotary kilns, cement mixes, and forty-seven additional related (original) inventions, Edison went on to build most of the new worker neighborhoods in the Bronx and Queens. A combination of single-family homes and apartment complexes, these buildings reshaped the city's urban landscape. Edison and his lawyers and engineers claimed the single pour house was motivated by altruism for the “wage-earner”. If mass produced, houses could rent for $10 per month, and might even lead to workers purchasing their homes as opposed to renting. Although some newspapers, most notably the New York Times, scoffed at Edison's concrete house ambition, many others from across the country boasted of its potentials.

Let us take a moment to look at the patent itself, and to read it within this wider context. Of the nine drawings submitted, the last is the most revealing. We see here, drawn in vertical section, all the aspects of Edison's invention come together. On the left-hand side, a Portland Cement mixer churns the concrete. Made from crushed stone, quartz, or a similar material, and then mixed with water, sand, and Portland cement, the concrete must reach a consistency that is neither too thick nor too soupy. Next, the gelatinous concrete is put in an agitator before being delivered by a bucket conveyor to the peak of the roof's formwork. It is then dumped into the patented double wall structure, where the wet concrete mix slowly settles down to the bottom.

The double mold on the right is, in effect, a precise inversion of the classic American balloon frame. Edison's swerve on the nineteenth century structure is made from a “double-wall mold formed of removably connected sections including wall and floor portions”. Created from cast iron and patented in 1915, these molds were reusable for many more homes. They typically came in segments no larger than two feet by four feet. The portions for lintels and stairs were far more intricate. Inside the double walls one can see a thin black line drawn in the middle of the void: these are steel ties to make the concrete as strong in tension as it is in compression. Stairs, windows, interior walls, doorways, mantels, and bathtubs were all part of the double mold. (The optional piano and refrigerator, each of which added significant costs, were specially made sections for the living room and kitchen.) Air can easily get trapped in what Edison referred to as the “tortuous channels” of the mold, most notably in the floors and stairs. To guard against these traps, Edison inserted air vents, along with modern conveniences like plumbing and conduits for electricity. Given how thoroughly thought-through the house's construction was, it should come as no surprise that the inventor believed a properly poured concrete house would require no insurance or expenditures for repair.⁵ It was indestructible, non-combustible, affordable, and healthy.

And yet, for all his concern with air vents and indestructibility, Edison's drawings envisioned an ideal state. Most patent drawings, to be fair, live in an ideal state, where, until they are made concrete, their future is a matter of conjecture. Edison's drawing did not anticipate a common occurrence with a hard object susceptible to freezing and thawing: cracks. After pouring twenty-five houses in Phillipsburg, New Jersey, fractures began to appear in each building. These cracks often originated at the seams of the house, where a wall met the floor, or at a corner. If left unattended, the cracks would have surely been the end of the concrete house. However, shortly thereafter, a rubber expansion joint was patented, which subdivided the structure into smaller sections so that the concrete might expand and contract without fracturing. This small innovation, patented by Goodyear, not only salvaged Edison's reputation and design, but also led to the Edison Portland Cement Company becoming one of the largest construction companies in North America.

Along with receiving major commissions, like Yankee Stadium in New York City in 1922, the company also built millions of affordable homes across the country. Notable neighborhoods include Winterhaven in Tucson, Arizona, and Sea Ranch in Sonoma County, California. Although both communities were built using Edison's patents, houses in Winterhaven are climatically suited to the extreme changes in temperature in the Sonoran Desert. Similarly, the houses at Sea Ranch take advantage of the slopes and views of the site along the Pacific Ocean. Both neighborhoods received top prizes for their thoughtful use of concrete by the American Institute of Architects (AIA) and the Association for Affordable Dwellings (AAD). In the span of a decade, Edison's design proved effective in meeting the demands of affordable housing as well as conserving and enlarging forests in the U.S. and abroad. Shortly before Edison passed away in 1931, there were signs that the zeal for concrete was producing unintended outcomes. Newspapers and newsreels ran stories about the state of air quality and the growing number of gravel pits marking the landscape like craters on the moon. Forests were recovering, but the shift within the construction industry from the vegetal kingdom to the mineral kingdom led to unprecedented mining.

Decades before climate scientists showed that the manufacture of 1kg of cement produces 0.9kg of carbon dioxide, did Thomas Alva Edison have a sense of how concrete was changing the quality of air? By all accounts, he did not. And if he did, would he have reversed all that he had done to advance the acceptance of concrete to combat insalubrious housing and make homes more affordable? Given the avalanche of subsequent patents that have attempted to minimize the environmental impacts of cement manufacture, we might assume that Edison would be at once joyful and perplexed. Joyful no doubt because his forty-nine patents laid the groundwork for our architectural future; perplexed because so few of the patent drawings project the quality and space of new homes and neighborhoods constructed with concrete. If, for Edison, concrete housing was about the quality of life these spaces sustain, then, for engineers, it is about the metrics of this building technology. The architectural conventions of plans and sections, with their attention to living rooms and windows, have been supplanted by equations and diagrams with little concern for what Edison sought to revolutionize: how we build to live together.