Unitized Facades

by Marcy Marro | November 1, 2021 12:00 am

“Unitized wall assemblies are fabricated and assembled off-site in a shop, but they are installed in the field on a more traditionally built structure,” explains Ryan Rademacher, AIA, director of business development at MG McGrath[1], Maplewood, Minn. “Often the interior finishes won’t start being installed until after the facade is installed and the building is dried-in.”

Project Types

When it comes to deciding whether a specific project is a good candidate for unitized construction, buildings with large exterior surfaces, repetition, simple geometry or even tight construction sites, are all good candidates.

As Peter Babaian, SE, principal at Simpson Gumpertz & Heger[2] (SGH), Chicago, and Christopher Grey, PE, senior project manager, SGH, Boston, explain, “Large, repetitive facades on constrained construction sites or with a condensed construction schedule may find modular wall construction to be advantageous.”

According to Rademacher, unitized construction can work well in most market types across both residential and commercial construction. “Low-rise and mid-rise projects can be well suited to modular,” he says. “Unitized is more flexible overall and can be suited to a wider variety of project types. Large projects with a lot of square footage and tight schedules are well suited, including high-rise construction with unitized curtainwall.”

Chad Showalter, vice president of sales at Metal Design Systems Inc.[3] (MDSI), Cedar Rapids, Iowa, explains the company is promoting and actively fabricating unitized construction in all sorts of projects from hospitals to hotels and schools. “Our customers in the automotive, retail and foodservice industries can especially benefit from the time and labor savings of unitized construction by multiplying those savings over large-scale, multisite facility branding programs.”

Streamlined Benefits

Unitized construction offers owners, designers and contractors another option for the efficient design and construction of exterior wall systems. “Prefabricated exterior wall systems can streamline construction schedules, reduce overall construction costs and improve exterior wall assembly quality,” explain Babaian and Grey. “The use of prefabricated exterior wall systems is especially beneficial on construction sites with limited site access.”

Pre-building exterior wall assemblies in a factory allows contractors and installers to quicky and more efficiently put the walls together on-site. According to Showalter, “Unitized construction can speed up the time it takes to clad the facade or elements of the facade of a building. It allows architects to incorporate more complex angles and curves into the facade, while the structure itself can remain relatively simple. This reduces particular labor costs, as much of the wall and details can be planned and organized during the preconstruction phase of the project, rather than in the field.”

Rademacher adds that unitized construction allows for quality control in a climate-controlled shop. It also lends itself to higher structural, thermal and moisture performance.

Design Challenges

As with any type of construction method, there can be some challenges to using unitized construction. “The engineering and coordination can make the systems themselves more expensive than other approaches,” explain Babaian and Grey. “Coordination between panel and non-panel systems can be difficult and can potentially result in issues on the building. Repairs or modifications after the panels are in place are extremely difficult.”

And, as Rademacher notes, there is more coordination required upfront, which needs to be planned for early on in the design process Also, there can be some limitations with design, such as staggered joints, or irregular patterns for the cladding that can be more challenging or limited with unitized construction. And, since much of the work for unitized construction is done in a factory, it is important for the builders and installers to hold certain dimensions when building in the field. “Typically, there are industry standard dimension tolerances, for example, in the structural steel, so they unitized construction can build from shop drawings,” Showalter adds.

“Not every design aesthetic can be met with prefabricated exterior wall panels,” says Babaian and Grey. “Panel manufacturers may not offer certain cladding systems or may have limited experience with others. Panelized projects work best with highly repetitive facades. And the design needs to cater to the panel constraints in terms of sizes and location of panel joints.”

However, as Showalter notes, unitized construction can actually expand design choices. “This is why we highly recommend that architects engage MDSI early on in schematic design or design development stages of their projects so we can find opportunities to preserve their aesthetic vision by unitizing certain wall elements.”

Growing Demand

Even with taking those points into consideration, Showalter says more and more of their subcontractors are wanting to save labor in the field by unitizing during fabrication. “Our design lab is constantly innovating to find new ways to help our customers unitize, reducing project costs and speeding up construction lead times related to the facade of the project.”

Babaian and Grey say they are also seeing more projects consider and select fabricated modular exterior wall construction across all of SGH’s offices, including unitized curtainwall systems, which have been around for a long time, and prefabricated modular exterior wall systems, which are more recent to the market.

Rademacher agrees, saying, “Each year we see an increase in inquiries and desire to build this way. Along with that, we continue to increase our capabilities and capacity to meet the growing demand.”

Keys to Success

As with all building projects, communication is key. And that communication extends all the way from the owners and architects to the general contractors and builders. As Showalter notes, “It is important to consider unitized wall construction because proper planning can yield significant savings in installation time and labor costs.”

“Early engagement and collaboration are critical to success down the line,” adds Rademacher. “With that, the traditional design-bid-build delivery method and process does not align well with modular construction. The design has to be tailored (through collaboration and negotiation) to the capabilities and processes of the modular fabricator/contractor.”

“For a project to be a success, everything must be thought through and communicated from the beginning,” Showalter continues. “Too many times, we see construction delays where one or more trades are behind schedule—all because of poor or insufficient planning. Unitized construction puts the fabricator and erector in a position to plan, design and engineer, then build. If you select the right fabricator early on, unitized construction can relieve a lot of stress, confusion, missed scopes of work, time, and surprise costs during the actual construction phase of project.”

And, remember, not every project is a fit for prefabricated modular exterior wall construction. The projects that are require early design decisions that cannot be changed without impacting the project budget, stresses Babaian and Grey. “They require early involvement of the contractor and subcontractors, often in the design development stage of the project. The upfront costs for engineering and planning are greater. The wide range of panel manufacturers and designs requires substantial vetting to make sure the panel manufacturer can meet the project requirements—both for performance and for aesthetics.”

Additionally, Babaian and Grey always recommend performing laboratory mockup testing prior to fabrication to verify that the panel will work for the specific project. “Once installed, field testing is critical to confirm performance.”

Source URL: https://www.metalarchitecture.com/articles/unitized-facades/

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