From Brian Potter's Construction Physics substack, July 22:
When we left off, over a few short years mobile home manufacturing had grown into a massive industry, and was supplying an increasingly large fraction of the US’s housing. In 1973, 580,000 mobile homes were shipped, just over 50% of the number of single family home starts that year (1.1 million), and 22% of total housing units produced that year (including single family, multifamily, and mobile homes.) The Department of Commerce predicted that mobile home shipments would be between 750,000 and 850,000 by 1980.
The HUD Code
As a result of the increasing size and importance of the mobile home industry, and growing concern about mobile home safety [0], in 1974 Congress passed the Mobile Home Safety Standards Act, which placed mobile home regulation under the purview of HUD. HUD then began the process of developing a set of safety standards for mobile homes.The industry hoped that HUD would simply adopt the ANSI A119.1 standard, which by then had been in use for over a decade and had been adopted in some form by over 40 states. Of the 1000+ responses received by HUD regarding new standards, over 800 of them were requests that ANSI A119.1 be adopted.
HUD opted not to do this - the explanation given was that they were reluctant to effectively hand regulation authority over to a third party. The HUD Code was ultimately based on A119.1, but it was modified based on the results of several studies of mobile home performance (for instance, HUD analyzed the problems encountered on 4000 mobile homes that they had purchased as emergency housing for Hurricane Agnes relief, and the National Bureau of Standards (now NIST) performed several studies on mobile home fire performance.)
The HUD Code went into effect in 1976. HUD estimated that the new, stricter regulations added approximately $380 to the cost of a mobile home, while the average dealer estimate was closer to $500 (or about 4% of the cost of a typical singlewide at the time.) Much of this increased cost seems to have been due to increased administrative requirements, rather than physical changes.
The stricter HUD code seems to have had its intended effects. The rate of fire death in mobile homes, for instance, had been 3 times higher than in conventional homes prior to the HUD code, a difference that was eliminated after the HUD provisions took effect:
Collapse and decline1974 also saw the collapse of the US housing market, following the energy crisis-induced recession. Total housing starts (including mobile home shipments) fell by over 50%, from 2.9 million in 1972 to 1.3 million in 1975.
The mobile home industry was hit especially hard. While single family and multifamily housing starts declined by approximately 50%, mobile home shipments declined by 63% (from 580,000 in 1973 to 213,000 in 1975.) 40% of mobile home manufacturers went out of business. And while the conventional housing industry bounced back (to some extent - 1972 would ultimately be the peak of conventional housing construction as well as mobile home construction), the mobile home industry never quite did. Conventional single family and multifamily starts had recovered to 85% of their previous high by 1979, but mobile home shipments were only 45% of their previous high. Rather than exceeding 800,000 units per year as predicted, mobile home shipments have never since exceeded 400,000 units per year and, outside a six-year window in the early 1990s, have never passed 300,000 units per year. In 2021 manufactured home shipments (they officially changed from “mobile homes” to “manufactured homes” in 1980) were just 106,000 units, approximately 6% of total housing units built that year.
Why didn’t the mobile home industry bounce back? What stopped it from continuing to take a larger share of the housing market in a Clay Christensen-style low end disruption? Why aren’t we all living in mobile homes?
The HUD Code theory of industry decline....
....MUCH MORE
Quite amazing that 1972 was the peak year for home construction.
Here's the first part:
The Rise and Fall of the Manufactured Home - Part I
- "The Science of Production"
- "How much do construction costs matter? Some factors that affect the price of housing"
- Construction Physics: Where Are The Robotic Bricklayers? (plus: planning your dynasty)
- "Real Estate, Property Rights, and Negotiation"
- "Why did agriculture mechanize and not construction?""Construction Costs Around the World: How Does the US Compare?"
- Why Is It So Difficult To Automate Construction? "Construction, Efficiency, and Production Systems"
