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The New Multifamily Modular


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Image: OxBlue Construction Cameras

By Yes Duffy, AIA, LEED AP

This is a shared resource for developers, architects, contractors, and consultants. It’s part of an ongoing effort to collectively build on our latest modular endeavors.

At DBA, now more than ever, we get asked, “What does it take to go modular?” The time­-saving and cost­-saving appeal of “going modular” varies broadly and depends on a variety of factors, which can make or break the potential benefits. Should modular be appropriate for your project needs, here's an unpacking of the specifics of “going modular” into a set of working strategies that DBA has developed over the years as an innovator of multifamily modular technologies.

DBA has designed over 1,000 units of multifamily modular buildings in a variety of project types and construction types, and our approach is constantly evolving as the industry and technologies mature. The following working strategies were born from our experience in the Bay Area housing market, yet may apply nationally as well.

The Union Flats pairs with Station Center Family Housing to bring a wide range of housing options to the emerging neighborhood. Another modular development is currently in design for the site to the north. Image: David Baker Architects

Scaffolding is about to come down on this corner of the Union Flats, modular housing in Union City. Image: David Baker Architects

The Union Flats is the largest multifamily modular development in Northern California. At right, Union Flats Construction Timeline video by Guerdon Enterprises.

First, Learn from the Past

Factory-built housing has fascinated architects for nearly a century, despite the fact that very few projects were ever realized. The few that were—such as Habitat 67 by Moshe Safdie in 1967—served as aspirational prototypes, but they were unable to fulfill the promises of cost­-effectiveness and faster delivery. Forty years later, a handful of developers and contractors have taken on the risks associated with this “new” product delivery method, with mixed results.

Despite the absence of any modular “silver­ bullet” outcomes, high­-cost construction markets have forced continued interest in pursuing more multifamily modular prototypes across the US, in an effort to circumvent high construction costs and make up for local labor shortages. The lessons gleaned from these new experiments have collectively “moved the needle” closer and closer to making multifamily modular a cost­-effective reality—at least in the hot housing markets of Los Angeles, the Bay Area, and New York City today.

Image: David Baker Architects

Quantify and Prioritize Tradeoffs of Modular to Your Specific Project Needs

Each project is different. The modular industry touts a long list of tantalizing advantages, yet few of these assumptions have been widely tested and the results vary greatly. However, the factory­-built approach offers advantages, some of which may not only be beneficial, but may even be necessary.

In one example, DBA designed the 243-­unit modular Union Flats in 2015 for Windflower Properties, and according to developer Fei Tsen, the schedule was so tight that going modular was the only way to realize the project, because it provided a significant time savings over the conventional construction approach.

Other purported advantages of modular can include more predictable scheduling, less disturbance to the neighborhood, greater labor consistency and predictability, reduction of waste, and increased job site safety. According to the industry, if all benefits are taken into account, in hot markets, construction costs can be decreased by 20 to 50% by going the modular route today. 

Color-coded details coordinate scope between factory and site-built contractor. Image: David Baker Architects

Begin with an Experienced Team with a Collaborative and Innovative Mindset

Interdisciplinary team collaboration and innovation are has been critical for our projects. A conventional construction job typically has only one of each consultant, each progressing with the entire development of the project, each relying on decades of industry standards.

However, with modular, you have essentially two separate contractors (the factory contractor and the site­-built contractor) and potentially twice the number of consultants. To accommodate for this, the modular design process front­loads the schedule with a lot of early architect-­led design decision making and team collaborations between the factory contractor, the site­-built contractor, and the structural, mechanical, electrical, plumbing, and civil engineers.

After delivering the mods, the modular team hands the project over to the site­-built team. Coordinating this effort in terms of individualized scope, assembly sequencing, and detailing takes an all­-team effort and a collaborative mindset in the early phases of the design.

It’s important to allow for flexibility, innovation, and team learning in the early stages, as there are a lot of moving parts and a relatively unconventional team structure early on. Contracts, bidding, financing, and scheduling are atypical and require more upfront investment and resolution.

Understand and Manage the Permitting Process Early

The permitting process for modular construction is different from the process for conventional construction and varies from state to state and from city to city. For example, in California, we produce two different drawing sets, which are approved by two different agencies. We refer to these as the “state set” and the “city set.”

At the state level, the Department of Housing and Community Development reviews and approves only the factory­-built portion of the project. At the local city level, the local jurisdiction approves all site­-built work (the foundation, the podium, the roof, and the exterior building skin). The local jurisdiction also reviews the code compliance of the entire building holistically, although that is typically shown in both sets. The clear coordination and scope delineation of these two separate sets has been critical to pulling permits on time. This documentation effort is one of the “inefficiencies” of drawing production when it comes to modular.

Finished interior, straight from factory. Image: David Baker Architects

Restricting the construction to the corridor.

DBA's interlocking "nested" modular units. Image: David Baker Architects

Focus on Design Innovation from the Inside Out

Multifamily modular buildings are often indistinguishable from their site­-built counterparts, yet the internal systems design and construction detailing are often unconventional. At DBA, we continue to develop design solutions that capitalize on the efficiencies of going modular, from reducing on-site expensive labor inside finished units to streamlining factory production methods to increasing the efficiencies of craning and setting modules.

One example of this approach is to maximize factory­-based work and minimize expensive site­-built work. By minimizing onsite construction to only corridors and exterior walls, modules can arrive with completely finished interiors—from flooring to fixtures and furnishings.

In cases where two modules become connected into one unit, we ensure that mate lines are coordinated and minimally impact the unit interior. On one recent project, we worked with Guerdon Modular to help increase factory efficiencies and save costs by minimizing the number of modular metal frame jigs used in the project. We also cut the shipping costs and crane ­time in half by utilizing the full shipping size of the module (16’W x 12’H x 74’L) and constructing the corridors, stairs, and elevator shafts in the factory. 

A 3D shop drawing from the ZETA Communities factory. Image: ZETA Communities

Prototype the Mods and Critical Connections

Each factory contractor uses a different system for translating architectural drawings to shop drawings and ultimately to the factory floor. As we design for modular efficiency early in the process, we can really reap the benefits of those efficiencies at scale. However, the opposite is also true: an error either in the drawings or on the factory floor, unchecked, can scale to hundreds of costly errors once the mods are delivered.

This increased risk is best mitigated by having the architect and consultants review not only the full­-scale mod prototypes, but also the shop drawings for every mod. Despite the high-risk nature of this critical coordination effort, there is still no standard for how this process is carefully executed.

On the Union Flats, DBA worked with Prefab Logic to manage the translation of architectural drawings to shop drawings on the factory floor. 

Using only two mod widths for entire development makes for an efficient factory build. Image: David Baker Architects

A variety of unit types with a fixed mod width allows for the design to better meet the nuanced needs of market and client. Image: David Baker Architects

A variety of unit types with a fixed mod width allows for the design to better meet the nuanced needs of market and client. Image: David Baker Architects

Once the mods are set, it is extremely important to begin to seal up all mate lines and provide robust weather protection on the entire building, as this is a unusually vulnerable moment for the entire project.

Design the Workflow from Factory to the Freeway to Set and Secure (and Check the Weather!)

Many factors can quickly damage a finished mod once it leaves the factory. Water damage, structural stresses, tight roadway widths, high winds, and human error can easily damage a mod in transit. The need for sensitive coordination from the factory to the final resting place is unique to modular construction.

DBA worked with Cannon to develop a method that minimizes the risks and maximizes the efficiencies of craning a 50,000-­pound, 74-­foot-­long finished mod 85 feet into the air and then sets and secures the mod quickly. Critical stack sequencing, multiple crane positions, temporary waterproofing and protection, and setting and securing of the mods was efficient and safe.  At Union Flats, Cannon was able to stack the entire 243-unit building in three weeks. 

Once the mods are set, it is extremely important to begin to seal up all mate lines and provide robust weather protection on the entire building, as this is a unusually vulnerable moment for the entire project.

 

Many thanks to all of our collaborators in this effort thus far:
 

Holliday Development
Factory OS
Guerdon Modular
Fei Tsen, Windflower Properties
Larry Pace, Cannon Constructors
Carol Galante, Terner Center for Housing Innovation
BRIDGE Housing
Tipping Structural
Murphy Burr Curry
SDE-DCI
FARD
Emerald City
Envision Housing
180 Santa Cruz

 

 

Looking into the Future

There have been very few innovations to the way we produce housing since steel framing was introduced nearly 100 years ago. The rest of our economy has evolved significantly, yet the construction model has remained relatively unchanged, until now. The latest innovative efforts to pursue modular multifamily housing have proven that progress and promise in this arena is positive, despite a significant amount of early investment in testing new technology.

As more cities, architects, factory contractors, site contractors, and engineers work together to establish best practices for financing, permitting, and construction, we may begin to see the relative risk level of modular become comparable to conventional construction, or even surpass it as the process becomes more predictable.

We may also see more predictable pricing, predictable scheduling, and predictable contractor performance as more projects come online nationally, however, this is still conjecture at this point. As architects, we drive the design, yet we also aim to streamline consultant coordination and the documentation process from our desk to the factory floor, where ideally, our 3D BIM model becomes the shop drawings, gaining new efficiencies and minimizing costly coordination errors.

We also seek to better capitalize on the unique assets of each factory to a point where we are not just building conventionally in a factory setting to save money. We are invested in using the factory setting to innovate new methods for making better performing, better designed buildings, and perhaps even new factory­optimized building typologies.

David Baker is the Chief Design Officer at the new Factory OS modular, right here in our backyard on Mare Island. DBA currently has more than 1,000 units in design in a variety of project types, from high­-tech micro-hoteling to market-­rate apartments to single ­room occupancy residences for homeless populations.

Image: Anne Hamersky

An Associate at DBA, Yes Duffy, AIA, LEED AP, is an architect, fabricator, educator, and urban-interventionist. His work combines contemporary fabrication methods with traditional architectural wisdom to achieve collaborative, place-based innovations focusing on democratic design for everyday people. You can contact him at yesduffy@dbarchitect.com.

Image: OxBlue Construction Cameras

The Union Flats pairs with Station Center Family Housing to bring a wide range of housing options to the emerging neighborhood. Another modular development is currently in design for the site to the north. Image: David Baker Architects

Scaffolding is about to come down on this corner of the Union Flats, modular housing in Union City. Image: David Baker Architects

Image: David Baker Architects

Color-coded details coordinate scope between factory and site-built contractor. Image: David Baker Architects

DBA's interlocking "nested" modular units. Image: David Baker Architects

Finished interior, straight from factory. Image: David Baker Architects

Restricting the construction to the corridor.

Using only two mod widths for entire development makes for an efficient factory build. Image: David Baker Architects

A variety of unit types with a fixed mod width allows for the design to better meet the nuanced needs of market and client. Image: David Baker Architects

A variety of unit types with a fixed mod width allows for the design to better meet the nuanced needs of market and client. Image: David Baker Architects

A 3D shop drawing from the ZETA Communities factory. Image: ZETA Communities

DBA worked with Guerdon Modular to use a waterproof membrane on the top of mods for shipping, which later becomes part of the floor assembly.

Staging mods is a critical site-sequencing issue.

Once the mods are set, it is extremely important to begin to seal up all mate lines and provide robust weather protection on the entire building, as this is a unusually vulnerable moment for the entire project.

Once the mods are set, it is extremely important to begin to seal up all mate lines and provide robust weather protection on the entire building, as this is a unusually vulnerable moment for the entire project.

Image: Anne Hamersky