The Status of Modular Construction Standards

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The advantages of repetition and working in a factory environment for constructing buildings has been a topic of heightened discussion the past few years. According to Guardian Booth in 2020, some notable builders using modular construction processes at the time included: Bechtel, Fluor, Katerra, Prescient, Skanska, Turner Corp, and William Scotsman. The Modular Home Builders Association (MHBA) member directory lists 42 builders that build modular homes for consumers and 20 companies that manufacture modular buildings for sale, lease or rent through dealers to consumers.

Modular construction; image: AIAContracts.org

Outlook

The Q4 2019 Commercial Construction Index assessed the outlook for construction industry growth as positive, with significant increases in the modular building industry. A BigThink article in mid-2021 likened the modular process to “building with Legos but on an industrial scale” and related that the market is projected to be worth $114-billion by 2028.  

Builders benefit from modular processes by being able to reuse designs, reduce labor costs and get a faster return on investments. MHBA describes the modern benefits to homeowners as variety, custom design options, expedited process, energy efficiency and sustainability, and attention to codes and standards.

Codes and Standards

Typically, modular construction adheres to the same building codes and standards as conventional structures. In the US, the International Building Code (IBC) published by the International Code Council (ICC) is updated every three years. Each state adopts its own version of the base-model code, resulting in regional variances and even differences from county to county. In Canada, the National Building Code of Canada (NBC) is adopted by most provinces and is updated every five years.

On its blog, modular space and storage supplier WillScot explains that, since building codes can vary depending on the area where the building site is located, builders have to consult with local authorities about area-specific modular building codes. For years modular companies have expressed concern about these regional benchmarks versus national codes for modular construction.  

With a business model that requires construction in a central factory with shipments to distant construction sites, regional and local differences in regulations can introduce an unwelcome element of “custom” engineering and administration. This can impair modular builders’ efficiency.


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Modular in transport; image: ClaytonHomes.com

The Modular Building Institute (MBI) explains the industry has developed its own administrative rules and regulations, in addition to guidelines and standards, that augment the IBC or NBC. As of 2017, MBI was cooperating with ICC to work on guidelines and standards for the industry. An example of a standard that’s been cited as needed is transport sizes, including width.

According to an AIA Contract Documents blog article, the ICC and MBI approved a set of first edition standards in late 2021 – ICC/MBI Standards 1200 and 1205. Multiple states are adopting modular construction rules and regulations and entering into reciprocity agreements with adjacent states. The Interstate Industrialized Buildings Commission has also been formed to make the certification and inspection processes more efficient.  

Attempts have been made to add American National Standards for planning, design, fabrication, and assembly to the IBC for modular construction. However, as of the 2022 World of Modular convention and tradeshow in April, they have been unsuccessful. Estimates are that it may be 2027 before offsite construction standards are added to IBC.