Design of Modular Manufacturing
In 2019, MBI worked with the American
Institute of Architects to help develop a
new guideline called “Modular and Off-Site
Construction Guide.” This Guide serves
as a primer on the modular approach for
architects and includes:
Value and opportunities of modular design
Pitfalls designers should be wary of
Case studies that exemplify successes
In general, the architect’s role in a construction project is critical to its overall success. The decision to utilize modular construction should be made prior to design and should factor in the following considerations:
• Three-dimensional modules have widths that are typically nominal eight, 10, 12, 14, and 16 feet, with 12 and 14 feet being the most common. Framing dimensions are typically two inches less than nominal size.
• Module lengths are up to 70 feet, usually in two feet increments.
• Module heights vary from approximately 11 feet, six inches to 13 feet, not including the height of the unit’s transport trailer or frame.
• Wood-frame construction is the most common type of construction; however, manufacturers also build with steel and concrete and can meet the requirements for Type-I, -II, and -III construction.
• Multi-story modular buildings can be built up to the maximum stories allowed by code. While most modular buildings are one- to four-stories, a growing number of projects have exceeded 10-stories in recent years, including a 32-story project in New York.
• Restroom areas should be designed so that a module “marriage line” does not split the space.
• Multiple roof-framing styles are available. Some can be completed in the factory, and some may require the installation of trusses on-site.
• Modular buildings can be configured using modules of various lengths and widths.
• Design elements need to be decided earlier in the process (paint color, for example) as the off-site construction process begins and is completed more quickly.
Thirty-five states in the U.S. and one Canadian Province (Alberta) have some form of administrative agency that oversees and regulates the modular construction industry. While the terminology sometimes differs, the general procedures for building inspection and approval are similar. In the states where no agency exists, the local Authority Having Jurisdiction (or AHJ) is responsible for the inspection and approval process.
The administrative rules of each agency provide for safety standards and inspection procedures for industrialized building construction, design, and manufacture. Buildings and building components are either inspected and approved directly by the agency staff or by a third-party inspection agency (TPIA) or engineering firm acting on behalf of the agency.
Buildings constructed using modular methods must comply with all applicable building code requirements including wind, snow, and seismic conditions. Because most elements of the building – including electrical and plumbing – are completed off-site at the modular manufacturing facility, the inspection protocols must be clear and concise. Local code officials must be assured that the building has been inspected and will meet all requirements.
Once inspected and approved, modular/industrialized building components are deemed to have met all the applicable code requirements and a modular program label or insignia will be affixed to the module (see image below of sample state insignia).
Once the modules are delivered to the final site, other requirements are subject to approval at the local level. These requirements may include land use and zoning, local fire zones, site development, building setback, side and rear yard requirements, property line requirements, subdivision regulations, subdivision control, review and regulation of architectural and aesthetic requirements, foundation design, utility, and module connections.