Welcome to Construction Physics, a newsletter about the forces shaping the construction industry.

Due to length, this edition has been split into two parts. Part 2 will follow next week.

World War II and Housing

World War 2 era America was a time of massive upheaval in the residential construction industry. During the war, nearly 1 million people migrated to defense areas to work at munitions plants, shipyards, naval bases, and other areas of wartime production. The San Francisco Bay area, responsible for 30% of the ships built during the war, saw it’s population increase by over 50% between 1940 and 1950, and other areas saw population increases of nearly 200%. Huge numbers of houses needed to be built as part of the war effort, and they needed to be built quickly.

And the need didn’t abate when the war was over. During the war, private housing starts (which had just began to recover from depression-era lows) virtually stopped, averaging fewer than 100,000 per year. Simultaneously, marriage and birth rates rose steeply - between 1939 and 1943, the US birthrate rose 27%, to about 24 per 1000 [1]. By 1947, the housing shortage meant that 6.5 million families were living with friends, relatives, or in temporary housing like quonset huts.

Kenneth Jackson talks about the extents of the shortage in “Crabgrass Frontier”:

In Chicago, 250 former trolley cars were sold as homes. In New York City a newly wed couple set up housekeeping for two days in a department store window in hopes that the publicity would help them find an apartment. In Omaha a newspaper advertisement proposed: “Big Ice Box, 7 × 17 feet, could be fixed up to live in.” In Atlanta the city bought 100 trailers for veterans. In North Dakota surplus grain bins were turned into apartments. In brief, the demand for housing was unprecedented.

Unprecedented demand resulted in an unprecedented building boom. From wartime lows, private housing starts rose by a factor of 20, to nearly 1.7 million in 1950 [2].

The scale of both war and post-war housing construction required an entirely new system of construction. Prior to the war the typical home builder built just a few houses a year. But now all over the country houses were needed by thousands, and needed quickly.

Many of the most ambitions attempts at large-scale prefabrication, such as the Lustron House and the British postwar prefabs, stem from this period. But was even conventional construction was reorganized to maximize output. Large “merchant builders” built huge, factory-like homebuilding operations capable of producing dozens of homes a day on housing developments thousands of acres in size. The pent-up demand would take years to satisfy, and these merchant builders would increasingly dominate housing production after the war.

Levittown

Perhaps the most famous of these large developments is Levittown. Built by Levitt and Sons on Long Island between 1947 and 1951, it would ultimately consist of 17,447 homes.

Formed in 1929, prior to the war Levitt and Sons mostly constructed homes for upper middle class families, focusing on custom commissions and small subdivisions. But during the war, Levitt was commissioned to build 2,350 homes for Navy personnel at the Norfolk shipyard [3] in just 18 months.

The low-cost homes were far different than the houses Levitt and Sons had previously built, but the effort allowed the company to perfect rapid, large-scale construction methods. According to William Levitt, the “effort at Norfolk was a nightmare, but we learned how to lay dozens of concrete foundations in a single day and to preassemble uniform walls and roofs”.

After the war, Levitt and Sons continued to build conventional houses, as they acquired the 4000 acres of potato farms [4] on Long Island that would become the largest housing development ever built. Utilizing mass-production techniques and financed by FHA insured mortgages [5], Levitt and Sons began construction on Levittown (then called Island Trees) in spring of 1947.

Levitt aimed to build 350 homes every 20 working days. At its peak, Levittown was adding 30 homes a day. To achieve such rates of production, the entire construction site was turned into a reverse assembly line. According to William Levitt, “The land was our factory. We found it quicker, less expensive, and more efficient to move crews of men in standardized operations over the site than to move the house itself along a factory assembly line.” An article in Time Magazine describes the process:

Every 100 feet the trucks stopped and dumped identical bundles of lumber, pipes, bricks, shingles, and copper tubing, all as neatly packaged as loaves from a bakery. Near the bundles giant machines with an endless chain of buckets ate into the earth just taking 13 minutes to dig a narrow four foot trench around a 25x32 foot rectangle. After the machines came the men. On nearby slabs already dry they worked in crews of two and three, laying bricks, raising studs, nailing lath, painting, sheathing, and shingling. Under the skilled combination of men and machines, new homes rose faster than Jack ever built them and a new house was built every 15 minutes.

Much like factory production, the work was organized to replace skilled work with simple, repetitive tasks. Crews would move from house to house, performing one task at a time. From “Crabgrass Frontier”:

The construction process itself was divided into twenty-seven distinct steps—beginning with laying the foundation and ending with a clean sweep of the new home. Crews were trained to do one job—one day the white-paint men, then the red-paint men, then the tile layers. Every possible part, and especially the most difficult ones, were preassembled in central shops, whereas most builders did it on site. Thus, the Levitts reduced the skilled component to 20–40 percent.

Levittown operations were structured to eliminate all delays. Components such as plumbing trees, copper heating coils, cabinets, and stairways were pre-assembled to minimize installation time. To prevent material shortages, Levitt set up his own supply company. From “Mass Producing the American Dream”:

The North Shore Supply Company ran a half mile along the Long Island Railroad Stop at Roslyn. Its warehouse, always well stocked, contained enough material for the construction of 75 Levittown homes at all times.

According to Levitt “We wouldn’t let ourselves be stopped by shortages. When cement was unavailable in this country we chartered a boat and brought it in from Europe. When lumber was in short supply, we bought a forest in California and built a mill. When nails were hard to come by, we set up a factory in our backyard and made them ourselves.”

Like most early efforts at mass production, the houses had little variety. Floor plans were essentially identical (though they would see an updated design in 1949), and have little exterior variation beyond paint color.

The houses were initially priced at $6,990 (later raised to $7,990), and demand was enormous [6]. The first 2,000 would sell out before foundations were poured. By 1949 the demand was so great that all advertising was stopped. Hundreds of people waited in line to fill out an application to buy one.

Levitt and Sons would build a second Levittown in Pennsylvania in 1951, and a third in New Jersey. By then, sales had begun to slow - pent up wartime demand had been satisfied and people were beginning to desire greater variety in their homes than the Levittowns offered.

Homasote Houses

Similar feats of construction were required during the war, to house the thousands of factory workers, shipbuilders, and servicemen that were moving to defense areas. These were built by a variety of different builders and building systems, and were often constructed even faster than Levittown. In terms of pure speed and scale, some of the most impressive were the “Homasote House” developments.

Homasote is a fiberboard made from wood pulp, newspaper, and resin. Originally developed for car roofs under the name “Agasote”, the company developed a wallboard product for use in buildings. The product proved so successful that the company changed it’s name and began hunting for new uses of it [7]. In trying to find new markets, the company developed a prefabricated building system, named “Precision Built”. The system was a stressed skin wall panel system, consisting of 2x2 wall studs with a layer of Homasote on either side.

This system was used in some of the most rapidly-built wartime housing developments. A 1941 project in Carquinez Heights, California, consisting of 992 Homasote houses and 690 plywood houses, was built in 73 days, an average of 23 houses per day. A development for the Norfolk navy yard consisting of 5000 Homasote houses was built in just 154 days. At its peak, houses were being built at the Norfolk development at the rate of 56 per day, nearly twice as fast as Levittown.

The Homasote House was a fully prefabricated system. Panels would be made at a central location and then trucked to the jobsite, where they’d be put together one house at a time. At Carquinez Heights:

Central fabricating plants produced walls and partitions that were made section by section and trucked to the desired location. Because of the flat roof design, it was possible to build both ceiling and roof at the same time. Wall sections were installed in tandem with prefab plumbing, and then after the roof sections were placed by crane, the unit was ready for paint or wallpaper.

Normally prefabrication took place at a Homasote franchise location that was set up to build the panels. At Norfolk, the pace of construction was such that a purpose-built factory was created near the site:

To handle this impressive assignment, Barret & Halp moved bodily across the continent and set up a local factory in a converted fertilizer plant, 12 miles from the sites. Lumber is unloaded from railroad sidings and fed into a line of 18 power saws ringing the plant where it is cut to proper length; five jig tables are operated to construct floor panels; wall sections are built on 24 other jigs.

Like the Levittown houses, the Homasote houses were all essentially identical. And like Levittown, site production proceeded in a staggered, reverse assembly line fashion. Crews would put the wall panels into place in just 15 minutes, then move on to the next house, while workers coming behind would install the plumbing, roof, electricity, etc.

Homasote Houses under construction at Carquinez Heights

The Homasote houses were extremely successful during the war years. They could be erected incredibly quickly, and at extremely low-cost (the Carquinez Heights houses were just over $2800, less than the budgeted amount). Homasote’s materials (old newspaper) were easily attained in a time of rationing. The houses were well-built enough that at least some were still standing over 50 years later.

But after the war, the system failed to catch on. Like other prefab building systems, it never managed to capture more than a tiny fraction of the housing market. And though Homasote is still sold today, it’s no longer used for prefab houses.

This concludes Part 1. This edition will wrap up next week with Part 2!

[1] The current birthrate is just under 12 per 1000.

[2] Current housing starts in the US are just under 1.2 million per year, though 2021 population is over twice that of 1950s US.

[3] Norfolk increased in population from 144,000 in 1940 to 213,000 in 1950.

[4] One factor that aided the construction of huge housing developments was that the rise of agribusiness, combined with war migration, combined with depression-era foreclosures, meant that large swaths of farmland were available at low cost.

[5] From “Mass Producing The American Dream” - Levitt and other builders could benefit twice from government programs. Not only did the new laws create customer demand, they also allowed the builder to obtain easy financing for his projects. Builders were able to obtain a FHA commitment o insure a mortgage up to 90%…Arguments have been made that the real credit for the creation of Levittown should go to the federal government.

[6] Racist FHA mortgage policy meant that the first Levittown homes were only available to whites. Though overturned by the supreme court in 1950, it would be 10 more years until African Americans were allowed to purchase houses in Levittown.

Construction Physics

WW2 Era Mass-Produced Housing (Part 1)