Once a buzzword and only a possibility, prefabrication [or prefab] is
now common practice on most construction projects. At GLY, we believe
prefab, a Lean practice, to be an inherently sustainable, efficient, and
responsible way to approach our work. However, prefab is not a
one-size-fits-all solution. Establishing a prefab plan on each project
starts long before design and requires input from the entire team:
owner, architect, general contractor, and key subcontractors and their
From mass timber panels
and MEP pipe rack modules to full exam rooms and automated parking
garages, prefabrication opportunities are endless. To identify the most
effective application on a project, the general contractor, architect,
and client must evaluate options and prioritize the drivers for prefab together during design and permitting. Questions addressed during this time include:
- Where can we conserve use of resources?
- How do prefabricated items meet permit inspections and sign-off requirements?
- Where are prefabricated items built?
- How are they transported to the site?
- Are there labor savings to prefab items?
- How many people will be on site at any given time?
- Can we push boundaries and try something new?
In answering these questions, the team takes into account the impacts
on cost, schedule, and quality and develops a final plan—one that
maximizes the appropriate prefab opportunities instead of selecting
options that inadvertently hinder the project’s progress and bottom
Many projects these days use prefabbed components by assembling
repetitive building elements offsite and incorporating them into the
structure at the right time. But what about an entire building? When
does it make sense to prefabricate full building modules with the
majority of on site work limited to site and foundation prep?
To answer these questions, let’s look at a recent example. GLY recently collaborated with ZGF Architects, Modular Resources,
and many others on a one-story, 2,300 square foot prefabricated
building to house a Seattle-based healthcare provider’s MRI services as
their larger facility expansion is built. While the new tower expansion
will feature four new MRI rooms to better serve patients, the client
communicated the need for at least one additional MRI sooner than the
tower’s completion date.
As Modular Resources assembled four separate building modules in Tennessee, GLY prepped the site and foundation in Seattle, Washington. In June 2021, the modules arrived at the healthcare campus. Crews carefully set them into place in the early morning hours and mechanically fastened and welded the pieces together within 5-10 minutes. Modules were prebuilt with nurse stations, changing rooms, a waiting area, medical supply room, and most importantly, Radio frequency [RF] shielding for the MRI equipment. A built-in roof hatch simplified the MRI equipment drop-in. All that remained for on-site work was typical exterior and interior finishes.
The process sounds simple enough—and provides obvious benefits.
However, as with any major decision, there are several considerations to
talk through before choosing to pursue a full modular building.
To Prefab or Not to Prefab?
Do you need it NOW?
In some cases, the need for a specialized service or environment—often a component of a much larger project—is so great that waiting several years for completion of a ground-up building simply isn’t an option. If you have limited existing space to renovate and have access to adjacent land, a complete modular building might be the best solution.
Is the building temporary?
The structural composition and installation of stand-alone prefab structures allows for easy removal when no longer needed. Owners can either deconstruct the modular facility and restore the site to its original configuration, donate or repurpose the building, or even move it to a different location. If choosing this route, be sure to consider costs associated with deconstruction.
Are you looking for speed?
99.9% of the time, the answer is YES. Prefab’s two key benefits, speed and efficiency [and associated cost savings], are precisely what makes it so ideal. In a nutshell, prefab will save you time and money because:
- The building site/footprint and structure are built concurrently verses consecutively.
- Constructing the modules in a controlled environment offsite allows projects to continue full speed ahead throughout the winter months or in rainy, temperamental climates like Seattle.
- Reducing construction performed on site means fewer workers, less travel, and ultimately fewer expenses related to housing out-of-state workers. Regional subcontractors can build components close to home, greatly improving production cycles and reducing overall costs.
- The benefits listed above also pave the way for safer working environments.
Plan Ahead to Prevent Roadblocks
Once the decision is made to proceed with a modular building, start the planning process immediately as the requirements differ from a traditional construction approach.*
Permitting Gray Areas
Permitting a prefabricated modular building, in theory, is more straightforward than the permitting required of traditional on site construction. However, a modular building is technically a piece of equipment, which puts it under the jurisdiction of Labor & Industries [L&I]. Instead of spending a significant amount of time acquiring multiple permits [building, plumbing, mechanical, electrical, fire alarm, etc.], a modular building requires a single permit. It is important to incorporate and plan for the associated gray areas into your schedule.
In the case of the modular building for the Seattle-based healthcare provider, GLY took care of the foundation and site utility permits while L&I covered permitting for the building [remember, a module is considered equipment]. These two key components become one when the modules are lifted into place, which requires special inspections.
We recommend hiring a reliable third-party inspector to observe the module placement and provide reports to help satisfy both L&I and Seattle Department of Construction & Inspections’ requirements regarding special inspections permit. This satisfies both the general contractor’s permits and the module building manufacturer’s permits. A well-coordinated inspection process prevents approval delays and keeps the project schedule on track.
Understandably, L&I will want to inspect the modules before shipment to the site to ensure the building will meet State and local codes. These ship-to-site inspections require several visits and must occur where the modules are constructed. If your modules are prefabricated out of state, build L&I travel time and costs into your schedule. For perspective, the MRI modular building, a four-piece, 2,300 square foot building built in Tennessee, required five of these inspections.
Once the modules are placed on site, L&I will perform another inspection before anyone commences work inside the building. This is another critical activity to incorporate into the schedule well in advance. This inspection takes place 12–48 hours after modules are set. If you experience a waiting period, ask L&I for permission to weather in the exterior to prevent water damage while you wait for inspection.
City Code + Protocol Limitations
Is your project site in a congested, urban location? If so, your City’s Code will likely mandate an off-hours module placement. In Seattle, due to the size of the MRI building modules, the team needed to place all four pieces between midnight and 4:30 am. Each module took about one hour to stage, rig, pick, set, and weld. This entire process—crane on site, modules lined-up, crane pick, welding, and clearing the streets by 4:30 am—requires significant coordination with the local department of transportation, L&I, and Commercial Vehicle Enforcement [CVE]. Most importantly, it requires strong relationships with City officials to achieve a safe, smooth, and successful module installation.
*Specific requirements may vary by state and jurisdiction.
Interested in learning more about this project or prefabrication in general? We’re ready to help! Reach out to Project Manager Josh Lewis or Principal Jim Elliott on LinkedIn.