Angela Noah4/5/13WRIT 340Professor Townsend

From Cottage to High-rise: Prefabricated Building Components

Abstract:Though the concept of the prefabricated building has existed since the 1830’s, new technology is allowing complex building components to be prefabricated. Now, with the promise of increasing productivity and decreasing construction waste, many contractors are giving modular building techniques a try.

Bio:Angela Noah is a current junior in pursuit of a Bachelor’s of Science in Civil Engineering and a Master’s of Science in Construction Management. She is very involved on campus in USC-CMAA (a student branch of the Construction Management Association of America) and hopes to enter the construction industry post-graduation.

Blurb:An increasing number of buildings are being built at offsite locations. Find out how prefabricated buildings and building components are revolutionizing the construction industry.

Animation Idea:This animation would show how a prefabricated unit, wheter it be a whole room, a bathroom, or an MEP rack, is created in a factor and then installed onsite. The video would start by showing how the unit is assembled in the factory. Then the unit would be shipped to the jobsite where you would see it being installed in the building.

Introduction

In the 1830’s H. Manning decided to send his son, who was immigrating to Australia, off

with a very special parting gift. Like any logical person would do, Manning decided to send his

offspring away with a house. One that could be built in one location, disassembled into large

pieces, packed into a hull of a ship, and re-assembled upon arrival at its final destination. From

this concept, the idea of the prefabricated house was born [9].

Today, in addition to fully prefabricated, single family homes, commercial and high-rise

buildings, full of prefabricated modules and components, saturate the market. Prefabrication has

the potential to increase on-site productive during a construction project. Because, as the cliché

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goes, time is money, spending less time on site has the potential to positively impact a project’s

bottom line. Through the use of technology, parties involved in the construction processes are

pioneering and perfecting prefabricated and modular construction methods.

What is it?

Buildings are complex structures in which many systems come together to make a sturdy

comfortable shelter. At a very basic level, they are made from a structural support system that

contains walls that house complex electrical and ventilation systems. It is those systems and

even full rooms that have the potential to be made in a controlled factory floor separate from the

construction site.

There is a difference between modular and prefabricated construction. Modular buildings

can be broken apart in such a way that full 3-D rooms can be created as separate parts and pieced

tighter to create a functional building (Fig. 1) [12]. Prefabrication on the other hand, is merely

the off-site creation of building components that can be brought to site and assembled.

Prefabrication and Modularization: Why Now?

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Technological Advances

The proliferation of Building Information Modeling (BIM) technology allows

prefabrication to be used in areas it has never been used before. It allows users to virtually create

a building to ensure that none of the building components intersect, or clash with, each other.

McGraw-Hill Construction found that 78% of the parties using prefab and modular construction

methods use BIM [2]. Digital coordination allows a contractor and its subcontractors to

understand how prefabricated components must be laid out and constructed to that they can

easily be tied into the building’s skeleton. The intimate understanding of how a building’s

systems fit together, allows the building to be broken up into basic building blocks.

One of the most important yet complicated systems in a commercial building are its

mechanical, electrical, and plumbing systems (MEP systems). Made up of various segments of

pipes, ductwork, and conduit, these systems snake through the walls and ceiling of a given

building (Figure 2).

These systems are very

complex, so contractors

and subcontractors who

choose to build

components of MEP

systems in a controlled

factory setting can

often create them

quicker and more

efficiently than could be done on site.

Figure 2: What may be hiding behind above the ceiling in a conference room

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Schedule and Cost Impact

There has always been a huge emphasis on productivity in the construction industry because,

even if no work is happening on a construction site, money is being spent on the basic non-

material items a contractor needs for construction or general conditions (GC’s). Because GC’s

must be paid for throughout the project, the contractors are incentivized shorten project’s

schedules. In a national survey of 809 industry professionals, of 66% firms using prefabrication

and modular methods, 35% of them were able to decrease their project’s schedule by four or

more weeks [2]. So, in order to truncate a project’s schedule, a general contractor may decide to

prefabricate key items.

Modular Construction Schedule

Project Design and Development

Permits and Approvals

Site clearing, grading, and foundations

Installation of Building components

Site Work and Commissioning Time savings

Offsite Building Construction

Traditional Schedule

Project Design and Development

Permits and Approvals

Site clearing, grading, and foundations Building Construction

Site Work and Commissioning

Construction is a semi-linear process in which certain building components must be created

and installed before others can be brought it. Figure 3 [4] shows the main tasks involved in a

Figure 3: Modular construction schedule vs. site build construction schedule

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construction project. With the modular construction schedule, construction on components of the

building can begin offsite while the site is prepared and foundations are poured. Being able to

start building construction while building components are assembles off site, allows the schedule

to be shortened as special pieces of a project are completed in a factory setting.

Where are these methods being used?

Though it is possible to create fully prefabricated modular building units, it is more common

to see manufactured build components. General contractors such as Skanska and Hathaway

Dinwiddie, are taking advantage of the ability to

prefabricate complicated bathroom and MEP racks

(Figure 4) to shorten their schedule and

productivity.

Many mixed-use, healthcare, hospital and

hospitality projects are often made up of many

identical units. Because of this, some of the

projects that fall into this category are using fully

prefabricated bathroom units. These bathrooms,

like all prefabricated components are created in a factory and shipped to the building site. In this

type of setting, sheetrock walls and other components can be created with machines, ensuring

greater precision in the building process and a reduction in human error. Bathroom pods are

completely built, furnished, inspected, and delivered to the project site. Onsite, they are moved

into position and tied into the building’s utilities [5].

Figure 4: Factory Assembly of Prefabricated MEP Racks [3]

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Completed in November 2010, one of the biggest hospital prefabrication efforts to date

manifested itself in the Miami Valley Hospital Southeast Addition. Skanska Shook, a joint

venture between Skanska and Shook Construction, acted on the general contractor on this

484,000 square foot hospital in Dayton, Ohio, and was the party that suggested using this

construction method on the project. After getting the green light from the project’s owner,

Skanska Shook used prefabrication to help put together its 178 patient rooms and 120 overhead

MEP utitlity racks that comprised the project [3]. The identical structure of the patient rooms and

corridors, made this project well suited for prefabrication.

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For this project, being able to

start building the complicated MEP

systems for the hospital before the

decks for the various floors were

poured saved a massive amount of

time [6]. Typically construction on

the corridors of a given project can

only begin after the walls and roof of

a project are completed. However,

this hospital job, construction on the

five containing prefabricated units

began before those floors physically

existed [3] (Figure 5). So, when the steel was erected and the concrete was poured for those

floors that the prefab units could be hoisted into the building and construction could begin on the

rest of those floors.

Why Isn’t It Everywhere?

Constructing a building with a fully modular system requires, not only technical expertise

from a given contractor, but it also requires the build to be designed in a way that allows for

construction of individual pods. There are only a limited number of architects who are willing to

subject their artistic expressions to a conglomeration of shoe boxes that can be arranged to make

a structure [10].

In addition to layout limitations, there are also physical restrictions on how big a given

module can be. Modals must not only conform to the Department of Transportation’s guideline

Figure 5: Real Schedule Impact of Prefabricated Building Components is Shown in Yellow [3]

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that limit the size of cargo a flatbed truck can carry, but modules also must be light enough to be

hoisted into place a jobsite. Because of these size restrictions, architects designing fully modular

systems would constantly need to consider the bulkiness of the materials they specify.

Limitations of prefabricated building components may be restricted by some local

building codes. The Los Angeles Municipal Code, for example, requires certain prefabrication

building components to be reviewed by a testing agency to examine how items perform from an

engineer standpoint [12]. This process doesn’t typically take less than 8 week and it can be

costly.

Though prefabrication building components are becoming increasingly more common,

costs associated with the rental of warehouse facilities for a prefabrication effort can become

costly. Also, the hoisting required for a large modular construction project may add costs that

the increase of productivity helped to reduce. Until, fully modular prefabrication in the US

become more mainstream and buildings allow for it, do not expect to see a huge increase in

massive modular construction projects any time soon.

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References

[1] R. Kaysen. “SQUARE FEET: Squeezing Costs, Builders Take New Look at Prefab.” The New York Times, Jun. 15,2011. [Online], Available: nytimes.com. [Accessed: Feb. 24, 2013].

[2] McGraw-Hill Construction. “Prefabrication and Modularization: Increase Productivity in the Construction Industry,” McGraw-Hill Construction. [Online]. Available: construction.com. [Accessed: Feb. 24, 2013].

[3] N. M. Post. “Racking Up Big Points for Prefab.” ENR.com, Sep. 8, 2010. [Online]. Available: http://enr.construction.com/buildings/construction_methods/2010/0908-prefabpotential-1.asp. [Accessed Feb. 24, 2013].

[4] Modular Building Institute. “Why Build Modular?.” Modular Building Institute. [Online]. Available: http://www.modular.org/HtmlPage.aspx?name=why_modular. [Accessed Feb. 24, 2013].

[5] EggrockModular. “Manufacturing & Installing Eggrock’s Factory-Built Bathrooms.” YouTube.com. [Online] Available: http://www.youtube.com/watch?v=jlct4U_ImkE. [Accessed Feb. 24, 2013].

[6] cmhopper. “Skanska_Multitrade Prefabrication_ Miami Valley Hospital.” YouTube.com, May 29,2012. [Online] Available: http://www.youtube.com/watch?v=rEgjRUsB8jM. [Accessed Feb. 24, 2013].

[7] C. V. Bagli. “At Atlantic Yards, Ready to Test Plans for Prefab Tower.” The New York Times, Nov. 27, 2012. [Online] Available: http://www.nytimes.com/2012/11/28/nyregion/groundbreaking-soon-at-atlantic-yards-on-prefabricated-tower.html?pagewanted=1&_r=0. [Accessed Feb 25, 2013].

[8] R. Maloney. “Modular High-Rise Breaks Ground in Brooklyn.” Arup.com, Dec. 21, 2012. [Online] Available: http://www.arup.com/Home/News/2012_12_December/21_Dec_Modular_highrise_at_Atlantic_Yards_breaks_ground.aspx. [Accessed Feb 26, 2013].

[9] J. Zarroli. “Prefab: From Utilitarian Home to Design Icon.” NPR.org, Sept. 15, 2008. [Online] Available: http://www.npr.org/templates/story/story.php?storyId=94119708. [Accessed Feb. 25, 2013].

[10] V. Cowles, IV. Interview, Topic: “The use of prefabrication in construction.” Civil and Environmental Engineering Department, University of Southern California, CA, Apr. 3, 2013.

[11] Modular Building Institute. “Permanent Modular Construction 2012 Annual Report.” Modular Building Institute. [Online]. Available: http://www.modular.org/documents/2012-PMC-Annual-Report.pdf. [Accessed Apr. 3, 2013].

[12] The City of Los Angeles. “Official City of Los Angeles Municipal Code.” The City of Los Angles. [Online]. Available: http://www.amlegal.com/nxt/gateway.dll/?f=templates&fn=default.htm. [Accessed Apr. 3, 2013]