Using prefabricated elements in the
construction of the new Saint Joseph Hospital in Denver — scheduled to open
Dec. 13 — cut 72 workdays off the construction schedule and resulted in $4.3
million in savings, according to a study by University of Colorado Boulder
engineers.
The study, by Matthew Morris and doctoral student Eric
Antillon, both of the Department of Civil, Environmental and Architectural
Engineering, is one of the first to try and quantify the full costs and
benefits of using prefabricated elements in a large-scale construction project.
The study was done in partnership with Mortenson construction, which built the
new 831,000-square-foot Saint Joseph Hospital.
Developers often choose prefabrication to save time on a
project. But because the process of building a unit — like a bathroom or an
exterior wall panel — off site can be more expensive up front, due largely to
the cost of transporting the finished products to the job site, the overall
financial benefits haven’t been well understood.
“The direct cost of the actual units is more
expensive — in this case 6 percent more expensive — but the cost savings come
from indirect costs related to time savings,” said Morris, an instructor of
construction engineering and management. “If you save three months on the
schedule, that’s three months when you don’t have to pay for all the things you
need to run a job site. This reduces your cost of big-ticket items such as
supervision, equipment and your field office.”
For the Saint Joseph Hospital, Mortenson construction
chose to prefabricate the exterior wall panels, the bathroom pods, the
headwalls in patient rooms, and the utilities that run above hospital corridors
by bundling them into prebuilt racks.
Prefabrication is an especially efficient
technique in hospitals or any large building where the same type of unit has to
be built over and over again, such as dorms or barracks, Morris said.
At the Saint Joseph hospital, the need to have hospital rooms with standard
equipment and private bathrooms allowed Mortenson to prefabricate 440 bathroom
units and 376 patient room headwalls.
“This isn’t the solution for every project,” Morris said.
“It takes a particular type of project with repetitive work and an owner and a
design team that are willing to be completely onboard.”
Aside from allowing a project to be completed more
quickly, prefabricating units offsite can also improve the safety of the job
site by decreasing the number of different tradespeople who need to work in the
building at any one time, reducing elevated work and providing a controlled
environment.
For example, when utilities are traditionally installed
in hospital corridors, a number of different subcontractors have to install
cables, air ducts, piping and drywall overhead. Aside from the difficulty of
working above your head, this causes congestion in heavily used hallways that
can lead to accidents. In all, Morris and Antillon calculated that
using prefabricated utility racks in the corridors along with other
prefabricated units avoided seven safety incidents on the job site.
Even with the impressive cost benefits
calculated in the study, Morris said it may be possible for builders like
Mortenson to save even more time in the future by perfecting the sequence of
work. In the case of the Saint Joseph Hospital, some prefabricated elements
moved the project forward so quickly, that the workers responsible for the next
phase of the project weren’t always ready to immediately get started.
It may also make sense in the future to only partially
prefabricate some units before installation, which could help the workflow,
Morris said.
“Fine-tuning is the next step,” he said.
“Now we know that prefabrication saves time and money and increases quality and
safety. The next steps include developing best practices, training project
teams and continuing to drive out inefficiencies.”
Source: University
of Colorado Boulder
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