The Many Advantages of Modular Construction

by Jeff Shaw

Use of light gauge structural frame (LGSF) panels helps maximize efficiency, reduce project costs and shorten construction timelines.

By Sean Fowler, Project Executive, DPR Construction

The MonteCedro Senior Living Center, by Episcopal Communities & Services (ECS), is a continuing care retirement community in Altadena, Calif. ECS, the project’s developer, hired DPR Construction to build the 331,350-square-foot facility based on successful completion of two previous projects for ECS.

DPR Construction set out to try something new and different, the project will be the largest prefabricated modular construction project for DPR Southern California to date.

Scheduled for completion by the end of this year, the plans for MonteCedro include 186 living units, a 90,000-square-foot subterranean cast-in-place parking garage, and four standalone buildings with a cocktail lounge, an art studio, chapel, movie theater, business center, library, performing arts/multipurpose auditorium, fitness center and pool.

Striking a balance between safety, comfort

Typical for Southern California residences, the architect originally conceived the construction as a wood-frame structure.  But a recent update to the California Building Code stated that if combustible building materials were used — given the building height and nature of the occupancy — then the number of non-ambulatory and/or bedridden residents were restricted to the lower two levels.

MonteCedro’s owners didn’t want to impose these constraints on their residents. The goal was to provide a true “aging in place” environment, such that residents could choose to remain in their apartments and not have to move if they required more care and staff support.

Fortunately, there was a provision in the code. If MonteCedro opted to use noncombustible building materials instead, then non-ambulatory residentscould reside on any floor, adding flexibility and maximizing the duration of use for each unit.

DPR, the owners, and the architect got together to brainstorm ideas. Traditional choices such as cast-in-place concrete and structural steel were excluded due to their higher cost per square foot. Alternative building materials came under consideration.

The decision was made to use light gauge structural frame (LGSF) panels, which are nonflammable. Although LGSF panels cost more per square foot than wood framing, LGSF still costs 22 percent less per square foot than structural steel and cast-in-place concrete systems. And by using metal building materials, this project is environmentally sustainable.

Rise of BIM Method

Panel prefabrication added great efficiencies to the putting the LGSF system in place. By first building the project virtually using building integrated modeling (BIM), DPR coordinated closely with a team that included the architect, mechanical designer, plumbing designer and electrical designer.

DPR played a large part early in the design of joist spanning, stud gauges, headers, and most importantly in the details that enable the panels to be prefabricated, shipped and erected.  It was key that the open-minded structural engineer understood how to run out of the normal calculations to back up the design and still meet the prefabrication requirements.

When the panel designs were ready for the prefabrication subcontractor, the BIM method accurately accommodated the eventual placement of pipes, ducts and fan coil units.

The prefabrication of panels offsite provided several advantages.

First and foremost, prefabrication is a manufacturing type of environment. There are a lot of repetitive processes and efficiencies. Within this controlled environment, the prefabrication process has greater precision and quality versus building the panels in the field. Therefore, the quality, trueness and accuracy (the straightness of the walls) results in a fit and finish that is much better than a wood job.

As a bonus, one of the subcontractors employed war veterans. It turned out to be a great program for the vets as it provided them a way to get involved with the LGSF industry. The offsite prefabrication schedule only required seven months and 63,246 hours, whereas onsite stick framing methods would have required approximately 10 months and 175,000 hours.

Highly efficient installation process

The LGSF panels were delivered by 284 trucks. More than 3,200 wall panels and 1,300 floor panels (as well as the 2,000-plus trusses) were erected by two 65-ton rough terrain mobile cranes.

The light gauge structural frame panels are not as heavy as red iron. Weighing less than 2,000 pounds each, the panels are uniform in shape and size. The installation of the panels was highly efficient.

In the end, using the prefabricated LGSF system proved to save $4 million and shave four months from the schedule when compared to a non-prefabricated metal stud system.

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