Arup

David Farnsworth

In my 20 years as a structural engineer with Arup, I’ve been lucky to work on a range of projects that challenge construction industry conventions. In 2009, I was asked to join one such project. A developer had hired a team to design a volumetric modular system suitable for implementation on an unprecedentedly large-scale, fora 32-story apartment tower in Brooklyn, New York. Despite encountering some challenges along the way, the viability of the systems used on that project eventually proved out. I’ve been a true believer in the potential of volumetric modular ever since.

In my opinion, no technique has more potential than volu­metric modular to bring the efficiencies of the manufacturing sector to the construction industry. Deployed at scale, it could help answer some of the most pressing challenges our cities face, from shortages in affordable housing, to the scarcity of skilled construction labor and the resulting escalation in con­ventional construction costs for large urban projects.

When we started the Brooklyn tower ten years ago, our team assumed, as many still do, that the biggest challenges we’d face with volumetric modular would be technical. How could we make a modular system withstand hurricane force winds in a high-rise configuration? How could we develop fire protec­tion strategies that met code compliance standards without UL listed assemblies? How could we connect modules together on site without ruining the finishes that had been so painstak­ingly completed in the factory? All these technical challenges were actually solved with relative ease. We found that the real obstacles to more widespread adoption of volumetric modular are not technical. Instead, they have to do with the scalability of production capacity and the incompatibility of standard procurement processes with the needs of modular.

Modular manufacturers are currently well set up to deliver single family homes, 2-5 story student housing, workforce housing, military barracks, and other relatively small-scale projects. Many of these projects lend themselves to the use of dimensioned lumber structural modules. However, lumber modules aren’t code compliant for projects over six stories or those with specialized program types that necessitate the use of non-combustible construction materials.

You might assume then that the higher cost of steel modules is the main obstacle to adoption of modular techniques for larger urban projects, but, in fact, we found that the costs of producing and erecting a steel modular structural system were comparable to the costs of a site-built concrete flat slab system. Instead, it is the constrained production capacity of manufacturers that limits the size of projects considered viable for modular.

Consider that a single crane can easily set 10 or more modules a day, and 100 modules in a matter of weeks, while most modular fit out factories are set up to produce only 2-4 steel-framed modules per week. The current level of output is fine on a smaller job (<~40,000sf), because the factory can be­gin producing modules about the time site work starts and have them all ready within 4-6 months by the time the foundations and plinth are complete. But when projects get significantly above 40,000f2/100 modules, most modular suppliers start to encounter difficulties. The number of modules steeply increas­es, but the time required to complete foundations and site work stays roughly the same. Given sufficient lead time, modular manufacturers could, of course, produce the required number of units, but this approach undercuts one of the main economic benefits of modular construction: shorter schedules. This leaves only one real solution: to meet the needs of large urban projects, manufacturers need to scale up their production rate by an order of magnitude.

Scaling up production is no small task and will clearly en­tail significant time and investment, but there are real benefits to be gained by doing soon both the fabricator’s side and the client’s. For example, design and shop drawing-level detailing tend to eat up a substantial amount of a modular supplier’s man­agement team. While the number of details requiring attention on a 15,000f2 project is fewer than those on a 150,000f2 proj­ect, the time spent in coordination and detail development is not directly related to area—or as my colleagues say, “the brain damage is about the same.”

Consequently, bigger modular jobs have lower overhead / design costs per area than smaller ones. Therefore, those modular manufacturers who can scale up their production rate to keep up with the crane, by refining their techniques, growing labor forces, or making investments in automa­tion, will reap substantially more value from their pre-construction efforts. But to justify the expense of scaling up produc­tion capacity, most manufacturers need a reliable pipeline of future projects. It’s a classic problem of what comes first – the chicken or the egg?

The second major barrier to more widespread adoption of modular for larger dense urban markets is owners’ perceptions of procurement process risk and value. Currently, design bid build is the most common approach to procuring conventional multi-family housing. 

Most developers believe that the best value is achieved by bidding complete design packages to a wide bidding pool of capable contractors. This is difficult for modular projects. Modular suppliers and design professionals are often asked if we can “modularize” conventional designs that are close to completion. This rarely works, be­cause each modular manufacturer has their own preferences for structural systems, bathroom layouts, MEP strategies, levels of finish, façade systems, etc. Part of the man­ufacturer’s efficiency (and profit) comes from being able to deploy the same proven systems on the modules they build. The economic and schedule benefits of modular construction can be easily undercut by the time and money it takes to reconcile the cli­ent’s pre-existing design with the modular manufacturer’s system preferences. 

Unfortunately, going modular from the start and hiring a design team to develop a contract package also doesn’t guarantee a smooth procurement process. Even in these instances, it’s not uncommon for the bidder pool equipped to deliver the final design to have shrunk down to one manufac­turer, or even none. If the client tries to open the field to other bidders, they often find that every modular manufac­turer suggests different design changes, based on their own system preferences. This leaves the developer in the position of trying to compare apples to oranges. The way to overcome these difficulties is to adopt a design build or IPD ap­proach, where the modular manufactur­er is part of the design process from the start and the team can tailor the design to the preferred system. This approach works best when there is a pipeline of repeat projects—a critical factor in pro­moting fair behavior of contractors and owners in a design build scenario.

There is much investment flowing into construction technology these days. Many modular startups are focused on trying to invent better mousetraps and claim space through patents. But advancements in technology aren’t the key to the broad adoption of modular prefabrication. Patents are, in fact, a barrier. Real progress can only be achieved by scaling up production capacity and taking a more strategic approach to procurement. Modular manufacturers looking to break into the arena of large urban projects would be wise to invest now in forging long-term relationships with owners who can help them justify investments in scaling-up by providing a reliable pipeline of work. They should also go into this process with reasonable expectations about how long it will take them to scale up and optimize their process. The first project of any new venture is rarely easy. Scaling up production capacities will require process repetition and incre­mental improvements. If these issues of production capacity and procurement perceptions can be solved, I believe that volumetric modular can deliver the cost savings and productivity gains required to help the construction industry to meet the challenges we face today.