Designing housing has never been an easy task. Now, with the advent of more prefabricated housing, the workflow is changing, and with those changes, the design element because more urgent and more critical.

In order to address the importance of these changes, the Modular Building Institute published the 2018 Permanent Modular Construction Report, which notes four stages to modular construction:

  1. Design approval by stakeholders and any regulating authorities;
  2. Assembly of components in factory;
  3. Transportation to the site; and
  4. Erection of modular components to create a finished building.

Those stages differ from the conventional model, ultimately shaving 30% to 50% of time off the schedule, mostly from the efficiencies of dual paths in the workflow, but, at the same time, highlighting the importance of proper design.

Modular Building Institute

John Westrum, chairman, founder and CEO of Westrum Development Co., has been using modular construction for more than a decade, shifting from single-family conventional construction, and admits the transition to modular was messy.

Westrum says it took his group nearly that entire time to make the transition from conventional to modular, starting with single-family homes and progressing to townhouses. Westrum was a pioneer in the field, saying there weren't resources to tap into or best practices in place at the time, and for that he paid the consequences.

“We made tons of mistakes, then we got good at it,” he says. “We hired more progressive builders and went through three modular companies until we found the one that we work with now. Lots of expensive learning. [I paid] lots of dumb tax paid, but it was worth it.”

Other groups, like PrefabLogic in Idaho, have made a similar journey. Curtis Fletcher, co-founder and CEO of PrefabLogic, created his company to address the issues in the transition of workflow, mainly the disconnect between architect, developer, and manufacturer.

“Manufacturing groups are new to it and don’t have infrastructure to deal with training an architect on how it all works,” Fletcher says. “It has been part of our challenge to educate the architect on best practices, how to develop plans to work with manufacturing, how MEP is going to work and how it can be transported. We have project managers who attend regular meetings and help drive everyone to the efficiency point that modular demands.”

And, with a background in manufacturing, PrefabLogic understands the angles. Plus, the company now has experience building thousands of units and the challenges that come through the cycles of what works and what doesn’t work.

What PrefabLogic and Westrum also both discovered is that it’s about the right design. In this short video, Westrum shares his journey and the value of learning the process.

In the decade of trial and error, Westrum has evolved to nearly production line capacity with his operations.

“We know how to design the product so that it comes off the line and goes to the site in the way that it is assembled,” Westrum says. “We didn't originally do that and it slowed the process. We build our products now just like Legos with extensive instructions. If one thing is wrong or in the wrong place, the product may not go together and then there is tons of time, money and effort to rip it apart and fix it. Huge learning curve.”

PrefabLogic also learned the benefits for seamless connections. Fletcher explains that being able to design and build modules that result in seamless connections is really meaningful in the process. At a volume level, the way the MEP connections work will create consistency, then subcontractors and contractors can get in a rhythm and more easily price, which means that there aren’t bidding or execution challenges.

In order to manage that consistency and the specificity of the design, PrefabLogic uses Revit models and BIM that allows the manufacturing floor to put together framing and MEP.

“It’s a challenging piece,” Fletcher says. “In a normal site built area of construction, the designer for MEP and everything, is a little looser because you think you have the opportunity to deal with things on the fly. But with manufacturing you don’t have that chance. It has to be right. It’s a major challenge.”

With best practices like what the Modular Building Institute just published, designers now have the opportunity to be ahead of the curve. According to the Institute’s 2018 report, designing for manufactured construction should factor in the following:

  • Three-dimensional modules have widths typically 8, 10, 12, 14 and 16 feet, with 12 and 14 feet being the most common.
  • Framing dimensions are typically 2 inches less than nominal size.
  • Module lengths are up to 70 feet.
  • Module heights can vary between 11 feet, 6 inches to 13 feet.
  • Wood-frame construction is the most common; however, manufacturers also build with steel and concrete.
  • Multistory modular buildings can be built up to heights allowed by code, some exceeding 32 stories.
  • Modular buildings can be put together with various sized modules.
  • Design elements, like paint color, need to be determined earlier in the process.

The success and popularity of modular is driving the need for these types of guidelines, and helping in the success of both Westrum and PrefabLogic. PrefabLogic is currently in the process of adding four manufacturing facilities in Idaho and Westrum between 2,000 to 2,500 units in the pipeline for the next couple years.