Technology Assessment 

of Automation Trends 

in the Modular Home 

Industry

Phil Mitchell

Robert Russell Hurst III

United States

Department of

Agriculture

Forest Service

Forest

Products

Laboratory

General

Technical

Report

FPL–GTR–188
November 2009

Mitchell, Phil; Hurst, Robert Russell III. 2009. Technology assessment of 

automation trends in the modular home industry. General Technical Report 

FPL-GTR-188. Madison, WI: U.S. Department of Agriculture, 

Forest Service, Forest Products Laboratory. 51 p.

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Contents

Page

Introduction.......................................................................1

 Objectives .....................................................................1

 Methods.........................................................................1

Overview of American Modular Home Construction 

Industry .............................................................................2

 Manufacturing Process..................................................2

 Technology Assessment ................................................2

Overview of the German Prefabricated Home Industry ...2

 Manufacturing Process..................................................3

 Classifying Levels of Automation ................................3

 German Wood Frame Homes........................................4

Summary...........................................................................5

Future Challenges and Direction ......................................5

Literature Cited .................................................................6

Appendix A—Trip Reports Summarizing U.S. Modular 

Home Plants......................................................................7

 Plant A...........................................................................7

 Plant B...........................................................................9

 Plant C...........................................................................12

 Plant D ..........................................................................15

 Plant E...........................................................................17

 Plant F...........................................................................18

 Plant G ..........................................................................21

 Plant H ..........................................................................21

 Plant I............................................................................22

Appendix B—Technology Assessment of U.S. Modular 

Home Plants......................................................................23

Appendix C—Trip Reports Summarizing German 

Modular Home Plants.......................................................25

 Plant GA........................................................................25

 Plant GB........................................................................30

 Plant GC........................................................................31

 Plant GD........................................................................34

 Plant GE........................................................................37

 Plant GF ........................................................................40

 Plant GG........................................................................43

 Plant GH........................................................................47

 Plant GI.........................................................................50

 Plant GJ.........................................................................51

Abstract

This report provides an assessment of technology used in 

manufacturing modular homes in the United States, and that 

used in the German prefabricated wooden home industry. 

It is the first step toward identifying the research needs in 

automation and manufacturing methods that will facilitate 

mass customization in the home manufacturing industry. 

Within the United States, a relatively low level of technology was found in domestic modular home manufacturers. 

Raw material transportation was mostly manual; manually 

operated saws sized raw materials; cranes were used to 

move subassemblies, and modules were pushed by hand or 

with a battery-powered pusher. German prefabricated home 

manufacturers used closed panels to construct walls, roofs, 

and floors rather than modular construction. Three levels of 

automation were identified: manual, semi-automated, and 

fully automated. Manual production methods were similar 

to those found in the United States. In semi-automated factories, automated machinery was used, but an operator was 

required to manually load, unload, and start the machine. 

The fully automated factories had equipment capable of machining and transferring panel components and placing and 

fastening components together. Such investment in automation is risky in the cyclic housing industry. The modular 

factory has elevated homebuilding from a craft to mass production, but flexibility is reduced and significant customization is difficult. Future research should examine the cost effectiveness of using high levels of automation, software, and 

equipment in the U.S. homebuilding industry and whether it 

can profitably provide the manufacturing flexibility for mass 

customization. Alternatively, the use of lean manufacturing 

in modular home factories to realize the same benefits needs 

to be examined. 

Keywords: stick-built, automation trends, modular home 

industry, wood-frame housing, factory built housing, home 

prefabrication, closed-wall panels, systems-built housing

Joint Venture Agreement 04-JV-11111133-096

Forest Service Project 5-23767
Technology Assessment of Automation 

Trends in the Modular Home Industry

Phil Mitchell, Associate Professor

Robert Russell Hurst III,* Graduate Student

North Carolina State University, Department of Wood and Paper Science, Raleigh, North Carolina

Introduction

Traditionally, American homes have been constructed on 

site in a method known as “stick built,” meaning that components are connected at the location where the house will 

remain. In contrast, modular homes have major components 

built in a factory and are transported to the building site and 

then assembled into the final house. In 2008, Automated 

Builder reported that approximately 200 modular home 

manufacturers in the United States make assembled sections 

of housing (Traynor 2009). Modular units are constructed in 

factories and produced in complete, box-like sections that 

are delivered to the home site. Multiple-section units and 

stack-on units are also commonly produced. Modular homes 

are 80% to 95% complete when they leave the factory.

Potential advantages of modular home construction 

compared with conventional site built homes include the 

following:

•	 Builders are currently experiencing a shortage of skilled 

workers, and population demographics suggest that the 

labor pool of available construction workers will likely 

shrink even more.

•	 Modular home construction takes place in a controlled 

environment under a factory roof, which prevents weather 

damage.

•	 Results are of better quality, as labor is performed in a 

comfortable environment, and modular manufacturers are 

more likely to have a quality-control program.

•	 Building can continue without weather interruptions.

•	 Reduced construction time results in a shorter period of 

capital outlay for the builder.

•	 Materials can be used more efficiently with the help of 

computerized optimization.

•	 Different components can be manufactured concurrently.

•	 Use of specialized equipment is possible in the factory.

•	 Inventory can be controlled and materials managed better.

Traynor (2009) estimated that of the industrial housing industry (which accounts for 95% of new home production), 

the modular home industry has provided between 6.2% and 

7.6% of new home construction during 2004–2008. Future 

projections range from a high of 90% within a decade to a 

more conservative estimate of 90% in 20 years (O’Connell 

2003, Coates and others 1996). Regardless of which projection is correct, this industry has successfully become a force 

in the homebuilding industry and appears poised to grow.

Objectives

Our long-term goal is to develop a program that will investigate applicable technologies, methods, and approaches 

to factory home production. Future research needs related 

to industrial home manufacturing include applications of 

automation and optimization equipment and manufacturing 

methods that will facilitate mass customization and examining new wood-based materials specifically developed for 

factory-built homes. The first step is to conduct a technology 

assessment of the processes and equipment currently used in 

modular home construction. 

The purpose of the study is to provide an assessment of 

technology used in the production of modular homes. As 

objectives, this assessment will address questions such as 

the following:

•	 What components (which will define the organization 

framework used in this study) of modular housing are 

typically constructed as stand-alone fabrication? 

•	 For each component, what equipment (and process) is 

available and used in its construction?

•	 For major process tasks, what is the state of the technology of major equipment items compared to competing 

technologies?

Methods

Our approach was to examine the modular home industry 

primarily through plant site visits to (1) identify major 

processes in modular home construction; (2) identify 

equipment, supply vendors, and manufacturers used in 

each process; (3) understand the use, application, and 

*Currently Senior Manufacturing Engineer, Elkay Southern 

Corporation, Lumberton, North Carolina.
General Technical Report FPL–GTR–188

2

capabilities of equipment supplied or available to the modular home industry. Seven domestic modular manufacturers 

and two component manufacturers were visited. Because 

we anticipated that the implementation of technology and 

equipment used in factory home manufacturing would be 

more advanced in European countries, we visited 10 German factory home manufacturers. 

This paper summarizes our observations from modular 

home plant visits and visits and consultations with equipment manufacturers.

Overview of American Modular 

Home Construction Industry

This section of the paper summarizes our assessment of the 

current level of technology implementation in the American 

modular home industry relevant to the utilization and processing of wood or wood components. This section presents 

an overview of technology in the modular home industry as 

found in our plant visits during summer 2004. 

Trip reports summarizing visits to American plants can be 

found in Appendix A.

Manufacturing Process

Modular home factories are generally designed in one of 

two basic flow patterns. In side-saddle flow factories, the 

modules move through sideways in a single line. In contrast, 

modules are arranged end-to-end with dual lines in the typical shotgun-flow pattern. Both flow patterns are most often 

in a straight line, although other configurations have advantages and disadvantages. Other variations include the use of 

mezzanines and the spacing provided between dual lines.

Modular home construction involves many processes outside the realm of wood construction. However, focusing on 

those processes that involve wood products, the major steps 

are as follows:

 Floor framing

↓

 Floor decking

↓

Wall framing

↓

Wall set

↓

Wall sheathing

↓

Roof framing

↓

Roof set

↓

Roof decking

Our study is focused on the major structural ingredients of 

home building: floor, walls, and roof. Other major steps in 

the modular home factory include installation of electrical 

and plumbing systems, insulation, interior dry wall, siding, 

painting, and more. 

Technology Assessment

Our technology assessment goal focused mainly on the 

movement of materials, the sizing of components, and how 

components were connected. We asked four questions at 

each of the processes that primarily used wood:

1. How is the raw material transported?

2. How is the raw material sized?

3. How are the components fastened?

4. How is the finished product moved?

As shown in Table 1, the level of technology found throughout our representative sample of factory visits was basic. 

We did not find the advanced levels of automation that we 

thought might exist (at least in some factories). Raw material transportation was manual in almost all cases with a joist 

transport cart (sometimes called a joist dealer) occasionally 

assisting. Similarly, raw material sizing of studs, joists, and 

sheathing was generally done with a manually operated circular, cut-off, or panel saw. Manual nail guns and pneumatic 

screw drivers were prevalent throughout these factories. 

Cranes were often used to move subassemblies, while the 

in-process modules were pushed by either a battery-powered 

line pusher or human hands, assisted by rollers, tracks, or air 

pads. 

A more detailed table listing technologies found in each of 

the seven domestic modular home factories visited can be 

found in Appendix B.

Overview of the German 

Prefabricated Home Industry

Wooden homes account for approximately 14% of new 

homes built in Germany; 84% of these wooden homes are 

prefabricated off-site as closed-wall panels and then transported to the home site where the panels are assembled 

to construct the house (Personal communication between 

Russell Hurst and Oswald Alexander of the Bundesverband 

Deutscher Fertigbau on March 21, 2007). 

In June 2005, we toured 10 prefabricated home manufacturers in Germany. This report provides an overview of the 

German method of home manufacturing, including the automation levels employed at the factories we toured.

The German method of closed-panel prefabrication differs 

greatly from most present-day American methods of home 

prefabrication. In German home prefabrication, the wall 

panels typically have doors, windows, insulation, and conduits for electrical wiring, moisture barriers, OSB (oriented 

strandboard), and drywall already installed when they leave 

the factory. Exterior siding is also often installed on the wall 

panels. At some factories, interior finishes are even applied 

to the panel. 

On-site construction of these closed-wall panels requires 

setting the panels with a crane, fastening the panels to one 
Technology Assessment of Automation Trends in the Modular Home Industry

3

another, connecting the electrical wiring between panels, 

and installing plumbing lines. Middle floors (the floor between the first and second story) and roofs are also built 

as panels in the German prefabricated method. These floor 

panels are typically built with OSB decking on one side of 

the joists, insulation installed between joists, moisture barriers installed on both sides of the floor panel, and furring 

strips nailed to the bottom of the floor element. The ceiling 

drywall is hung onto these furring strips once the home has 

been wired in the field. The roof panels are comparable to 

the floor panels except the furring strips are on the outside 

of the panel and OSB and drywall are on the inside. 

For increased energy efficiency, moisture barriers are installed on both sides of the wall, floor, and roof panels. 

Manufacturers told us that with such airtight construction, homes had to be manually or mechanically vented to 

prevent moisture build-up. None of the manufacturers we 

toured, however, installed air-conditioning in their homes.

Trip reports summarizing visits to German plants can be 

found in Appendix C.

Manufacturing Process

Because walls, floors, and roofs are all constructed as 

panels, the manufacturing processes were very similar for 

these components. The first process in panel construction 

was sizing the OSB panels, drywall panels, and studs and 

joists used in the wall, floor, or roof panels. After sizing, 

elements for a panel are transferred to a jig table where the 

individual wall, floor, or roof panel is built. After framing, 

exterior sheathing is installed and the panel flipped. Insulation, conduit, and moisture barriers are then installed and 

the interior of the panel sheathed. Closed panels are then 

hung vertically for installing exterior and interior finishes. 

Windows and doors are installed at either station, depending 

on manufacturer preference. Panels are then loaded onto a 

trailer for transport to the home site; at none of the toured 

German factories did we see large inventories of finished 

panels (houses) waiting to be delivered.

Classifying Levels of Automation

We observed three distinct levels of automation in production, which we classified as manual, semi-automated, or 

fully automated. The manual German plants processed their 

components in similar fashion to American methods. In 

semi-automated factories, automated machinery is used at 

some workstations. These workstations, however, are not 

inter-connected and require an operator to manually load, 

unload, and start the machine. The fully automated factories 

we visited had equipment capable of machining almost all 

components for the panels, transferring the cut components 

to other machinery, and inserting or placing and fastening 

the components onto the panel. The fully automated factories did have operators on the production floor, although 

Table 1—Summary of wood processing technology found in modular home industry in floor wall and roof build 

processes 

Technology used 

 Raw material transportation Raw material sizing Component fastening 

Finished product 

transportation 

Floor framing Manual Cut off saw Manual nail gun Crane 

 Manual w/ joist dealer Precision-end 

trim saw 

Crane to track 

Rollers 

Floor decking Manual Circular saw Manual nail gun Crane to track 

 Crane to rollers 

 Air pads 

Wall framing Manual Cut off saw Manual nail gun Crane 

Wall sheathing Manual Circular saw Manual nail gun Not applicable 

Wall set Crane Not applicable Manual pneumatic 

 screwdriver 

Not applicable 

Roof framing --------------------------------Outside purchase of trussesa

------------------------------------ 

 Manual Cut off saw Manually connected Manual to cart 

 Pressed plate 

Roof assembly Manual Not applicable Manual nail gun Crane 

Roof decking Manual Circular saw Manual nail gun Not applicable 

Roof set Crane Not applicable Manual pneumatic 

screwdriver 

Not applicable 

 a Some plants purchase roof trusses from outside sources. 
4

these operators were typically there to clear any errors in the 

machinery and to manually insert components such as insulation, doors, windows, and exterior/interior finishes into the 

panels.

Although each factory toured had a unique production setup, Table 2 summarizes typical machine capabilities for 

each of the three levels of automation.

In semi-automated manufacturing, we saw a variety of 

computer-numerical-controlled (CNC) routers used for 

panel sizing; these CNC routers were typically wired into 

the factory’s network, allowing the operator to download 

the program onto the router without leaving the workstation. Almost all factories used CNC saw/joinery machinery 

to cut the beam or joist to length, drill holes through which 

cables or plumbing would be run, and notch the beam or 

joist where necessary. This machinery consistently produced 

accurate cuts and appeared to be significantly faster than 

comparable manual operations. The fully automated factory 

we toured was truly impressive with its extensive automated 

machinery, material handling systems, and capacity to produce 1,000 homes annually. In this factory, after being sized, 

elements of the wall panel were transferred onto a conveyor 

system that temporarily stored them in a queuing rack until 

the elements were needed by other machinery. As impressive as the automated factory was, it was only producing at 

approximately one-third of its capacity, leading us to question the practicality of such a large capital investment given 

the dependence of future profitability upon the typically 

cyclic housing market.

German Wood Frame Homes

German wooden houses had few major differences compared with wooden houses in the United States. On average, 

German homes are smaller than American homes. Germans 

seem to place greater emphasis on design and quality of the 

home than size. As more than one German manufacturer 

told us, homes (both wood and brick) in Germany are “built 

for more than one generation.” Most German home manufacturers offered significantly longer performance guarantees on their new prefabricated home compared with new 

homes in the United States. Typically, the wooden homes 

had a 30-year structural guarantee (including roof leakage). 

One key selling point of wooden homes in Germany is their 

high insulation value. This focus on energy efficiency is due 

to higher energy costs, public emphasis on and perception 

about energy efficiency and conservation, and tax deductions available for low-energy homes.

We did not see trusses being used in construction of singlefamily residential houses. Rafters are still favored, and attic space is typically used as living space in the home. The 

home manufacturers we toured sheathed walls with OSB or 

plywood on both the inside and outside of the wall, again 

emphasizing energy efficiency. Drywall was installed over 

the interior OSB. Vapor barriers were installed on all sides 

of walls, ceiling and floors, and roofs. With such air-tight 

construction, we were told that homes had to be manually or 

mechanically vented to prevent moisture build-up. None 

of the manufacturers we toured, however, installed airconditioning in their homes. 

Table 2—Average machine capabilities for three levels of automation 

Machines used 

Job Manual production Semi-automated production 

Fully automated 

production 

Sizing OSBa

 and drywall Table saw Table saw or CNCb router CNC router 

Sizing studs and joists Saw CNC saw/joinery machine CNC saw/joinery machine

Transferring sized 

components

Carts Carts Conveyor system 

Affixing studs or joists to 

frame panel 

Manual nailgun Manual or CNC nailgun Multi-function CNC 

machine 

Placing OSB and drywall 

onto panel 

Manual Manual Multi-function CNC 

machine 

Nailing OSB and drywall 

onto panel 

Manual nailgun Manual or nailgun bridge Multi-function CNC 

machine 

Flipping panel Butterfly table or crane Butterfly table Butterfly table 

Inserting components 

into panel 

Manual Manual Mostly manual 

Manufacturing stairs Manual or CNC router CNC router CNC router 

a

Oriented strandboard. 

b Computer numerical controlled. 

General Technical Report FPL–GTR–188
5

German basements were typically pre-cast concrete panels. 

The basement floor is poured on site after the wall panels 

have been set. Wood is used to make floor, wall, and roof 

elements. Some manufacturers reinforced floor sections 

with steel I-beams for large spans. We did not see the use 

of engineered wood products such as wooden I-beam floor 

joists, truss floor joists, or roof trusses. We also did not see 

glulam beams. Typical wood products used were OSB for 

inside and outside wall sheathing and fingerjointed wooden 

posts for walls, floors/ceilings, and rafters. We were very 

impressed with the quality of lumber we saw being used. 

German manufacturers typically marketed and produced 

three classes of homes: completely custom, semi-custom, 

and standardized. The completely custom homes were designed specifically for the client by either an independent or 

in-house architect and had very few limitations on design. 

Manufacturers also offered their semi-custom homes. These 

were homes designed by the manufacturer (the plans belonged to the manufacturer) that customers could customize to fit their needs. We called these homes “Dell homes” 

because customers could add features for set prices, similar 

to how a customer specifies options when purchasing a Dell 

computer (Dell, Inc., Round Rock, Texas). Typically, this 

line of home had one or two base floor plans. Often, one or 

two walls were (re)movable. Bay windows or built-in (winter) gardens are common additions to the floor plans. These 

semi-custom model homes had specific options for flooring 

(limited selection), doors, wall treatments, window types 

(wooden or vinyl), and heating equipment. Extra insulation 

and exterior siding were also options. We found the options 

presented in this line of homes very comparable with tractbuilt homes in the United States. 

Manufacturers also typically offered their line of standardized homes. This line of homes had very few choices for the 

customer to make. The advantage for the customer was the 

lower cost per square meter of the home. Options in this category would be door color (wooden or white for example) 

and exterior home color. 

German manufacturers often offer their homes at various 

levels of completeness. The majority of homes are built 

“turn-key,” although it is not uncommon for the home 

manufacturer to close in the home and leave finishing to the 

customer. This is entirely based on customer demand. One 

of the largest manufacturers we toured offered an interesting 

line of semi-custom homes. In this line of homes, the customer selected the options for their home (windows, doors, 

siding, floor-plan, roof style) from a list of options, and then 

selected one of the five levels of completion: turn-key and 

levels one through four. Each successive level offered more 

steps for the customer to finish. 

Summary

We were surprised (and somewhat disappointed) at the relatively low level of technology found in domestic modular 

home manufacturers. Although factory home manufacturing 

offers many potential benefits, too often these were not being taken advantage of or were overridden by other issues. 

For example, although the potential for cut-up optimization 

exists because equipment systems are available in the 

factory that would improve material efficiency, modular 

homes actually consume more wood than stick-built in order 

to resist racking forces when modules are lifted by cranes.

Our trip to Germany and tour of 10 wooden-home prefabrication factories did provide us with a firsthand look at how 

automation can be incorporated into factory home production. Whereas all the manufacturers we toured were producing high-quality homes, it became apparent that the home 

manufacturers using CNC automation were more consistently producing accurately sized and squared components 

resulting in homes that fit together easily and tightly. But we 

also realized the risk of spending too much on automation 

in an industry dependent on the cyclic nature of the housing market. In the United States, such a high investment by 

private companies in the face of a market downturn would 

likely prove ruinous and we therefore reject this option as a 

prohibitive risk.

Future Challenges and Direction

The domestic modular home factory of today resembles 

Henry Ford’s early automobile assembly lines. Whereas the 

modular factory is elevating homebuilding from a craft to 

mass production as did Ford’s early assembly lines, flexibility is reduced and significant customization is difficult. The 

challenge facing the modular industry is to develop those 

processes and techniques that will allow easy and economical customization to occur along the production line.

The issues and challenges that the factory-built home industry faces also define future research needs of factory-built 

housing research programs: 

•	 Would a home-producing factory using high levels of 

automation, software, and equipment technology be costeffective in the United States and provide the manufacturing flexibility required for mass customization?

•	 Can lean manufacturing strategies be incorporated effectively into current modular home factories, and would the 

change dramatically improve flexibility and profitability?

•	 What are the appropriate levels of outsourced subcomponents compared with building them in-house?

Technology Assessment of Automation Trends in the Modular Home Industry
6

Literature Cited

Coates, J.F.; Mahaffie, J.B.; Hines, A. 1996. 2025: Scenarios 

of U.S. and global society reshaped by science and technology. Greensboro, NC: Oakhill Press. 508 p.

O’Connell, John. 2003. Modular home construction may 

become industry norm—these are not your father’s prefabricated buildings. The Peoria Journal Star. October 18, 2003.

Oswald, Alexander. 2007. Personal communication 

between Mr. Russell Hurst and Mr. Oswald Alexander of 

the Bundesverband Deutscher Fertigbau on March 21, 

2007. Mr. Oswald referenced “Entwicklung der 

Baugenehmigungszahlen im Ein- und Zweifamilienhausbau 

nach Bauweise in 2005” (“Development Analysis of Building Permits issued for Single and Double Family Homes in 

2005”), published October 27, 2006.

Traynor, Terry. 2009. State of the industry report for 2008. 

Automated Builder. Automated Builder 451: 8–10. 

General Technical Report FPL–GTR–188
7

Appendix A—Trip Reports 

Summarizing U.S. Modular Home 

Plants

Plant A

Contact: Sales Manager

June 2, 2004

Key Points

•	 Plant A will produce custom homes.

•	 The company is small but looking to grow.

Company Description 

Company A is a wholly owned subsidiary of the Larger 

Company. The Larger Company originated as stick-built 

apartment builders; the company got into modular home 

construction with Company A.

Production

This plant produces about three to four modules per day 

(three to four floors per day), with a home on average being 

about three modules. They build standard models typically, 

but are willing to customize standard models, or even take a 

non-modular floor plan and consider converting it to modular. Plant A can build up to a 69-ft-(21-m-) long module. 

Plant A made some Cape Cod model homes with separate 

roof/room modules. Most simply had the flip/prop-up roof 

sections with knee walls (a short or partial support wall) in 

the attic. Plant A could allow for the roof sections to flip up 

from any side of the module (Fig. A1). The flip-up wall has 

a drop-down knee wall (Fig. A2). 

Based on estimated Company A sales and 150 employees, 

we estimate Plant A’s productivity to be $94,666 per person 

year.

Process Description

The factory has three subcomponent lines: floors, walls, 

and roofs. The main line brings all three subcomponents 

together. Company A purchases roof trusses from an outside 

company. In terms of wood products, they use southern yellow pine (SYP) for floor joists and bands and roof rafters, 

spruce-pine-fir (SPF) for studs and engineered joists (Open 

Joist 2000, Trois-Rivières, Quebec, Canada (Fig. A3)). Laminated veneer lumber beams are used for long spans including sliding glass door openings and open living space. They 

do use 2 by 3s in marriage walls (walls between modules). 

Relam, a fingerjointed stud from Lamco Forest Products 

(Lamco Forest Products Inc., St-Félicien, Québec, Canada), 

was used in the bathroom and kitchen because according to 

the plant manager, “they are straighter.”

We did not observe much impressive technology in this 

plant. Floors are built on a pneumatically adjustable jig that 

was not working at the time of our visit (Fig. A4). Overhead 

cranes lift and move subsystems (floor, walls, roof) so they 

can be connected. Floors are placed on heavy duty rollers on 

metal tracks and are pushed down the production line. They 

had a total of 26 modules on the floor (almost nine days of 

product, assuming they produce three modules per day). 

They employ pneumatic technology for nail guns and screw 

drivers. Material is cut according to print drawings from 

the engineering department. A floor plan and quality control 

(QC) check-sheet are attached to each module, which is 

numbered and lettered according to the job (e.g., 1854C) on 

the end band. 

Layout of joists and studs appeared to be done by hand, and 

nailing accuracy was judged by eye. Some nailing appeared 

excessive, which we also saw in other manufacturing facilities. Wiring and hole-drilling was also totally done by 

hand in the factory. The walls were constructed on a table 

(Fig. A5); the drywall extended to the edge of the wall, so 

when the walls were assembled on the floor, the drywall 

extended to the outside corner of the wall (Fig. A6). All wall 

seams (drywall, outlets, drywall to stud) were sprayed with 

foam for insulation (air movement) and to prevent cracking 

of the drywall seam (Fig. A7).

Company A notches wall studs to insert a T-strip diagonally 

along walls to strengthen the house during transport. This 

T-strip was stated to be exclusive to Plant A, although we 

have seen it in other facilities. Galvanized nail protectors 

were only used on the outer side of studs, which seems to be 

the accepted industry standard. This would prevent factory 

workers from puncturing wires while sheathing the module; 

however, it would not stop the homeowner from puncturing 

a wire with a nail from inside the home.

Once the modules had been completely assembled, they 

were lifted onto delivery trailers with “the crab,” a converted boat lifter. The sales manager said that Company A 

brings large items (such as bathtubs) into the modules before enclosing them; he stated this can be a costly mistake if 

any re-work is necessary.

Other Impressions

Overall quality was generally good. The sales manager 

noted the difficulty in precisely joining the top floor to the 

lower floor, especially in terms of common walls lining up, 

as along staircases. Plant A allowed for up to 1 in. (2.5 cm) 

between the modules once they were set on the foundation. 

After visiting other manufacturing plants, this seems to be 

an accepted standard. The model home (3,300 ft2) we toured 

was nice; however, it had some soft spots in the floor. The 

house also had visible and noticeable bulges in the wall, 

especially around where the upper and lower modules met. 

The model house had a specialized central vacuum system 

add-on. The sales manager estimated that the typically subcontracted foundation is a problem about 10% of the time 

when setting a modular home.

When asked, the sales manager said factory-direct sales to 

homeowners would be “a nightmare” because the numerous 

Technology Assessment of Automation Trends in the Modular Home Industry
8

details that must be obtained prior to manufacture. When 

discussing transportation costs, the sales manager said that 

transportation to Atlanta, Georgia, (roughly 400 miles) 

would be about $2,400 per module ($6/mile/module). 

Figure A8 shows the floor plan of this plant.

Figure A1. Module end showing flip roof.

Figure A2. Example of fall-down knee wall in attic. 

Note that the metal connector plate is hinged.

Figure A3. Floor made with Open Joist 2000.

Figure A4. Floor being assembled on non-functioning adjustable jig. These men are constructing 

a floor section on a floor jig, the metal framework 

that the wood floor is resting on. Wheels on the jig 

base allow the overall frame to move.

Figure A5. Inventory and construction table for 

wall assembly.

General Technical Report FPL–GTR–188
9

Plant B 

Contact: Sales Manager

June 3, 2004

Key Points

•	 Modules are mass produced. 

•	 Exterior walls are built with 2- by 6-in. lumber for energy 

conservation.

•	 Plant B builds many subcomponents (roof trusses, stairs, 

window frames) onsite.

•	 The customer can choose from selection of brand name 

floors, cabinets, and carpets.

Company Description

Plant B is the largest system builder of single family homes 

in the United States, with multiple facilities. The sales manager suggested that because modular built homes can be 

confused with other terms, he likes to call it “systems-built 

housing.” 

Production

This 10-year-old factory produces 600 homes per year, with 

a target of 29 floors per week. Their average home has about 

2.8 modules. It takes 4-1/2 days for a floor to move through 

the 35 stations or steps in this factory. This plant employs a 

total of 225 people, with 165 of them working on the floor. 

The estimated productivity is 600 homes × $50,000 ⁄ 225 = 

$133,333 per person. Plant B seemed to target the middle 

range of modular housing. This estimate of $30 million in 

sales for this plant fits within the sales range published by 

the 2004 Harris Infosource Selectory of North Carolina 

Business (Harris Infosource, a division of Dun and Bradstreet, Twinsburg, Ohio).

Process Description

The layout of the plant was good, with separate areas for 

(1) floor systems; (2) exterior walls built with 2 by 6s, which 

differentiates Plant B homes from other modular homes; 

(3) marriage walls using 2 by 3 studs; (4) interior walls using 2 by 4s. Housekeeping was fair to good, with an airpad system used to move the modules as they are built. 

Plant B also manufactures many components of the home, 

such as roof trusses, window frames, and stair systems 

(Fig. B1). These components were manufactured in cells 

along the assembly line. These cells were adjacent to where 

the components should enter the house, which allowed for 

good material flow. The sales manager stated that whenever 

a module was being problematic (especially because it was 

a custom job), the assembly line schedule would be delayed, 

causing the component cells production schedule to no longer align with the modules in the assembly line. There were 

35 stations along the assembly line, although not that many 

modules were on the floor.

Technology Assessment of Automation Trends in the Modular Home Industry

Figure A6. Corner of module showing drywall 

coming to end of wall section (see arrow).

Figure A7. Foam spray 

sealing drywall gaps from 

rear and adhering to studs.

Figure A8. Floor plan of plant.
10

Plant B used two floor jigs, one to build the floor frame and 

the other to glue the oriented strandboard (OSB) decking to 

the floor frame (Fig. B2). The framing station was an adjustable jig, though the sales manager indicated that they use 

it for only two widths (13 feet, 9 in. and 12 feet). The jig 

adjusts in width and has lay-up fingers to position the joists 

(Fig B3). However, this joist jig was designed for 16-in. 

on-center 2 by 10s and could not be adjusted (neither spacing between joists nor the width of the joists) to accommodate the Open Joist 2000 type of floor joists, which allow 

19-1/2 in. on center spacing, or their approximately 3-in. 

widths. Because the Open Joist 2000 joists did not fit in the 

jig fingers, the Open Joists were set on top of the jig (not in 

the jig fingers) and then affixed to the 2 by 10 frame. 

As a side-note: An average 60-ft module needs 45 joists at 

16-in. on-center spacing. That same module with 19.5-in. 

on-center spacing needs only 37 joists. By not using the 

Open Joist 2000s at their correct 19.5-in. on-center spacing, 

on a 60-ft module, Plant B would use 8 excess joists.

We saw the following standard products being used:

•	 Fingerjointed spruce-pine-fir (SPF) 2 by 4 studs for interior walls

•	 Fingerjointed SPF 2 by 6 studs for exterior walls 

•	 Southern yellow pine 2-in. by 10-in. floor joists and 

bands (Fig. B2)

•	 Open Joist 2000 made of SPF 2-in. by 3-in. lumber

Spruce-pine-fir roof trusses were made on site, surprisingly.

The sales manager commented that he preferred using 

relam for either interior or exterior wall studs because of the 

straightness of these fingerjointed studs. In addition, Plant B 

uses Trus Joist TimberStrand (a thick oriented strandboard 

(OSB)) structural member, (Weyerheuser Company, Federal 

Way, Washington) as a 6-in. stud behind kitchen and bathroom walls behind vanities. This was due to the straightness 

of the strand lumber, which reduced manufacturing time.

The sales manager also mentioned the Chief Architect 

design and drafting software (Chief Architect, Inc., Coeur 

d’Alene, Idaho) that has 3-D capability, but indicated that 

Plant B’s engineered drawings were done with AutoCad 

(Autodesk, Inc., San Rafael, California). On the floor, workers only have access to the floor-plan drawing, not a side 

elevation view. For machining components of the house 

(window frames, headers, door frames, etc.), employees 

looked at the floor plan of the home. In addition to the 

above-mentioned components was a code that correlated to 

a second sheet of paper at each station. On the second sheet, 

the code was deciphered for the component (width, height, 

thickness). The components used seemed very standardized. 

The sales manager explained four ways to identify a modular home:

1.The modular home must have an ID code somewhere 

within, indicating that it has been manufactured to code. 

Plant B stamps inside the electrical panel.

2.The roof trusses often have some type of a flip installed. A 

cap may be on top of the two roof sides.

3. A marriage wall will likely be inside the house. Older 

modular homes had thick marriage walls (two 2 by 4s 

mated together), but with the use of 2 by 3s, the marriage 

wall is not as thick. 

4. Mating of modules (including plumbing and electrical) is 

generally visible in the crawlspace. 

The plant can be divided into six major build process areas:

1.Roof build

2. Sub-component build

3.Wall storage

4. Floor build

5. Home assembly

6. Home finishing

These can be subdivided into 35 separate stations that encompass the major process steps:

•	 Floor build (Stations 0–5)

•	 Floor decking and wall build (1–6)

•	 Wall set and roof jig (3–8)

•	 Roof set (5–10)

•	 Electrical bottom (5–10)

•	 Plumbing and electrical top (7–12)

•	 Electrical test (8–13)

•	 Underlayment (9–14)

•	 Hang and tape (10–15)

•	 Insulation (11–16)

•	 First and second coat/wall sheathing (1–16)

•	 Third coat (12–17)

•	 Ceilings/windows and doors (13–18)

•	 Deck and load (13–18)

•	 Roof sheathing (15–20)

•	 Sanding (16–21)

•	 Shingles (18–23)

•	 Siding (18–23)

General Technical Report FPL–GTR–188
11

•	 Painting (18–23)

•	 Rough cleaning (20–25)

•	 Cabinets (21–26)

•	 Shelves and specials/doors and window trim (21–26)

•	 Basetrim/rework (21–26)

•	 Plumbing and electrical (22–27)

•	 Pitched roof (23–28)

•	 Wrap (25–30)

•	 Shiploose (small items not attached until home is sited 

and closed in) (26–31)

•	 Clear/final clean/under plumbing (27–32)

•	 Quality assurance sales inspections (28–33)

•	 Cleared/load and lab (34)

Other Impressions

Our impression was that although the sales manager said 

Plant B would customize, overall this plant would prefer 

not to because their goal is volume production. When asked 

about future challenges, the sales manager suggested that 

the challenge that might prevent plant automation would be 

the need to customize. He seemed unaware of existing technology in the modular housing industry.

Technology Assessment of Automation Trends in the Modular Home Industry

Figure B1. Plant B built its staircases and roof trusses 

in-house.

Figure B2. Floor frame constructed on jig table.

Figure B3. Open Joist 2000 

floor joists were used but 

could not fit into the positioning fingers shown.

Figure B4. Walls and floors are moved with overhead 

cranes (top left and top right); modules in process 

are moved using pneumatic air pads (bottom left); 

completed modules are loaded onto trailer for delivery using boat transporter (bottom right).

Figure B5. Modular home techniques include use of 

foam adhesive to fasten ceiling (left), attic modules 

with folding trusses (center), and engineered floor 

joists such as Open Joist 2000 product (right).
12

Plant C

Contact: Vice President, Manufacturing

June 16, 2004

Key Points

•	 This plant uses a team-based management approach.

•	 They are interested in technology and are looking to modernize.

Company Description

Plant C began in 1972 as a manufactured (mobile) home 

plant, but today makes mostly modular housing. The homes 

constructed in this plant today are all already sold. Twenty 

percent of their homes are on-frame (HUD code 1% or onframe modular 19%) and 80% are off-frame modular. The 

plant layout overall was good (Fig. C1), but plant housekeeping suffered. 

Production

The plant employs 250 production employees working four 

10-hour days per week. Employees construct nine floors per 

day four days per week, or 36 total per week. The Vice President says these 36 modules build 14 to 18 homes per week.

Every 56 minutes, the line will shift down to the next station, and there are 30 stations in the plant. They can build 

a house in three days once the order is entered into the system, and the homes spend two days in the yard for repair. 

We observed many homes in the yard awaiting delivery.

Process Description

Drafting is done with DataCAD (DATACAD, LLC, Avon, 

Connecticut). The engineering process is as follows:

Initial inquiry

↓

Rough sketch

↓ 

Preliminary plan

↓

Customer input

↓

Agreed plan

↓

Order

Plant C has its own metalworking shop to build frames upon 

which all floors are built, and upon which the “on-frame” 

homes remain. They are capable of building up to 60 frames 

per week.

The floor area was in a different building from the wall and 

roof area. In the floor “department,” the flow of process was 

as follows:

1. Construct wooden frame on flipper jig 

2. Insulate between stringers

3. Install black plastic insulation retainer 

4. Attach metal frame with wheels (Fig. C2)

5. Screw the assembly to the flipper jig

6. Flip the assembly

7. Roll to next station on low-profile wheels (Fig. C3) 

8. Run ductwork, plumbing (PEX tubing), electrical

9. Glue (and nail) tongue and groove OSB to 2 by 10 

frame

10. Cut holes for plumbing, electrical, air ducts, flush trim 

OSB edge, sand floor

11. Mark floor with chalk lines for placement of interior 

walls

12. Lay plastic sheeting for floor protection

Floors were 13 ft, 8 in. standard width, with a maximum 

length of 72 feet (average length is 56 feet, according to the 

vice president). If exterior wall construction is with 2 by 6, 

width is 13 feet, 10 in.

Finished kitchen and bathroom cabinets manufactured inhouse (Fig. C4) were placed on top of the floor section for 

later installation. Interior cabinet door panels are purchased 

from outside. Plant C also purchases trusses and floor joists 

outside.

The houses had three wall lines: short walls that could be 

for angled ceilings or flat ceilings (run perpendicular to 

length of module); long walls that run the length of the floor 

(Fig. C5); and the marriage wall line (Fig. C6). The first 

wall line mentioned above employed a movable saw (moved 

by hand) with an adjustable carriage to select the angle 

needed (Fig. C7). Studs were loaded onto the saw uncut; the 

saw would cut all studs to the correct length, at the correct 

angle.

Once framed and drywalled, wall sections were moved to 

the floors by crane with wall sections being clamped by 

visegrips. Wall sections were connected to floors with 3-in. 

screws. 

Roofs and ceilings were constructed in the upstairs loft 

(Fig. C8). While we were there, Plant C workers were constructing an interior ceiling with a 12-in. wide band to have 

room for the interior heating/cooling duct. As we have commonly seen, no screws or nails held ceiling drywall to the 

trusses. Instead, adhesive foam was used. These sections 

were moved by crane to the floor and wall assembly 

(Fig. C9). 

Other Impressions

The vice president seemed excited that we were researching 

technology, stating that he hopes to modernize the manufacturing process at Plant C. The vice president also said that 

he had sent off for information on an automated panel production machine; however, no one had contacted him with 

information.

General Technical Report FPL–GTR–188
13

The vice president’s managerial style was very “independent.” He has encouraged workers to come up with solutions 

to their own issues on the shop floor. Numerous times he 

stated that he had “the best guys” working for him. The vice 

president explained that he let the employees decide on the 

four-day week. He also explained that Plant C always has 

a few extra employees on the shop floor to substitute in for 

anyone who does not come in to work. Plant C has relaxed 

their attendance policy over the last years to keep quality 

workers. Plant C’s vice president says that with the team 

approach of the factory, team members do not tolerate other 

team members being excessively absent, because it causes 

the team to be behind schedule. A few times during the tour, 

he said, “Do everything that you can do well.”

Technology Assessment of Automation Trends in the Modular Home Industry

Figure C1. Floor plan of Plant C.

Figure C2. Metal frame with wheels being attached 

to constructed floor frame.

Figure C3. Metal frame is placed on top of lowprofile wheels.

Figure C4. Plant C constructs kitchen and bathroom cabinets.

Figure C5. Long wall tables with completed walls 

standing to the side.
14

Figure C6. Marriage wall characterized by lack of insulation and a gasket seal. Note the small drywall panels 

providing additional support.

Figure C7. An adjustable carriage was used to select the 

angle required to saw the wall for angled ceilings.

Figure C8. Roofs constructed in the upstairs loft were 

moved by overhead cranes.

Figure C9. This ceiling (middle floor) section shows adhesive foam used to attach drywall to ceiling joists. Note 

the metal bracket and chain used by a crane to hoist the 

ceiling section.

General Technical Report FPL–GTR–188
15

Plant D 

Contacts: President, Engineer

June 16, 2004

Key Points 

•	 This plant handled material well.

•	 Plant D focuses on customization.

•	 Their assembly line is clean.

•	 Plant D maintains a low inventory throughout, as they 

practice “lean” techniques.

Company Description

Plant D is an independent manufacturer of modular homes 

that sells directly to builders. The company started in 1970 

as a manufacturer of mobile homes, which they made for a 

year or so. They had a $2–$3 million investment and expansion three years ago, and the president said that they were 

trying to make the investment pay for itself. Three years ago 

they employed 100 people; now they have 180 employees. 

Plant D now focuses on mass customization, contrasted 

with their former production-process focus (i.e., standard 

modules). With the rising prices of steel and wood, they are 

facing challenges to remain profitable.

Production

Basically, the manufacturing floor has 23 stations and produces five floors per day with 180 employees. We were told 

that the average module produced by Plant D is 12 feet wide 

and 36 to 44 feet long. The president said that the average 

Plant D home is two to three modules. It takes one week for 

the house to get through the manufacturing process. 

One floor plan had four modules and their factory cost was 

$69,000 base price. Assume that with options, it works out 

to $20,000 per module, or $100,000 per day production 

sales (five floors or modules per day). If they work 225 days 

per year, then their total sales is $22,500,000. Per person 

(total of 180), their productivity is $125,000 per person.

Process Description

Basic process areas (Fig. D1) were about the same as found 

in the three previous plants we had toured: 

1. Dormers (shipped separately) are built.

2.Rafters are constructed in the millroom. (Other manufacturers have used truss systems, instead of the rafter system 

used at Plant D.) 

3.Walls are built on tables, including the exterior wall table 

and interior wall table. The maximum wall length was 

66 feet. A simple cart was pushed along-side the wall 

table for the workers to unload the studs onto the table.

4. Floors are framed on a table including a joist dealer or 

carriage that had been end-trimmed with a precision endtrim (PET) saw, and then flipped on the floor (Fig. D2). 

Floor frame construction used a band consisting of laminated veneer lumber (LVL) on the inside and spruce rails 

on the outside, with I-beam floor joists made with 2 by 3 

cords and OSB web. In the Plant D plant, small wheels 

were attached to the flooring as it traveled down the line. 

To move through the stations, two employees used motorized pullers (or tugs) to pull on the sides of the modules.

5. Floors were decked with plywood.

6.Electrical and plumbing are installed, and drywall is 

erected and mudded.

7.The roof is constructed.

In the millroom, we saw a chop saw that was capable of 

swiveling to different angles set to preset stops, used to cut 

parts for rafters (Fig. D3).

One thing we noticed was that OSB sheathing was nailed to 

the wall after the wall was erected on the floor. We believe 

that this is standard operating procedure for all the previously visited factories and that we just had not noticed this earlier. This allows wiring to be done once the wall frame (with 

drywall attached) was connected to the floor. With Plant D, 

the exterior OSB sheathing was one solid piece vertically. 

Our Plant D contacts told us they are experimenting with a 

new software system that will allow their builders to directly 

price, option, and order homes, much as an online carbuilder would work. The system is known as the Home Base 

Program, made by Base 3 Technologies (Base 3 Technologies, Greenwood, Delaware). Base 3 Technology, “specifically designed for the Modular Home Industry, this software 

supports a 3 tier information pipeline where information 

coming from the manufacturer is immediately available to 

the Builder/Dealer as well as the Sales Professional (Base 

3 Technologies 2008).” Plant D is the second or third user 

of this software we observed. Again, the program would 

control (1) sales entry, eliminating a sales representative, 

as the builder will price the house; (2) pricing with options 

for special items; and (3) orders. This will enable the user 

to follow the order from beginning to end; ensure that the 

order matches prints; include drafting and production; and 

provides a “stop changes” function that prevents further 

changes and hence finalizes the order. 

Plant D had many modules in their yard waiting to be delivered; however, they said they have spoken with their 

builders about staggering their orders so Plant D could avoid 

holding a finished module. This problem would be remedied 

with the new ordering program.

Plant D placed a large emphasis on lean manufacturing. 

When walking through the plant, little excess material was 

lying around waiting to be used. We were told that Plant D 

focused on the production process in the past, but that they 

now focus on mass customization. We were told that 95% of 

their homes are a customized product.

We saw good organization of raw material. For example, 

each window or door had an order number that correlated 

Technology Assessment of Automation Trends in the Modular Home Industry
16

with the order number of the module. This was the first time 

we had seen such material handling/lean warehousing.

Other Impressions

Their product seemed to be high quality. The engineer noted 

that they tried to build a product that they would not have to 

service in the field. Some of the quality points we noticed 

included their use of plywood for floors and over-building 

of studs around doors and windows. Plant D was also using 

seat-belt straps to strap their exterior walls to the floors, in 

addition to screws to provide extra wall stability.

This was a good plant in terms of flow and housekeeping 

and low inventory of raw materials. We noted that the operation was done well, but potential improvements could 

be in the areas of production planning, delivery scheduling, 

and in-house data flow. They currently employ six to seven 

draftsmen who use Cadsoft software (Cadsoft Corporation, 

Guelph, Ontario, Canada).

As has been a common theme with all modular manufacturers, we were told that builders want to do less and less, 

meaning they want more complete modules shipped to the 

site. This may be a major reason for the increasing popularity of modular housing.

Reference

Base 3 Technologies. 2008. HOMEBase+ modular home 

builder software. Greenwood, DE: Base 3 Technologies. 

http://www.base3tech.com/HOMEBase+/00.htm. Accessed 

Jul 1, 2009.

Figure D1. Plant D floor plan.

Figure D2. Precision end trim (PET) saw used to trim 

lengths (left) and joist dealer carriage (right).

Figure D3. In the mill room, chop saw used to cut 

different angles on rafters.

General Technical Report FPL–GTR–188
17

Plant E

(no photos allowed) 

Contacts: President, Engineer

June 30, 2004

Key Points 

•	 Plant E builds mostly custom homes.

•	 They keep a very large materials inventory by buying in 

bulk.

•	 Their housekeeping is poor.

Company Description

Plant E is a 4- to 5-year-old subsidiary of Company E producing both modular and Housing and Urban Development 

(HUD) code homes (Note: Plant E is not producing HUDular units (a cross between a manufactured home and a custom modular home)). 

Plant E can produce up to 72-feet-long floors, with the average being 54 to 62 feet. The engineer estimated that the average Plant E home is three or four modules. Standard floor 

widths were 13 feet, 9 in. and 11 feet (the latter for the center of a triple wide); however, different floor widths could be 

accommodated.

Production

Plant E produces 22 floors per week; 15 or 16 modules were 

on the shop floor during our visit. The engineer said 15 stations are on the line, and four to five line moves per day 

(four to five line moves per day = 16 to 20 floors per week). 

Plant E employs 160 total people. We did not see good 

housekeeping: screws, nails, and bolts were on the floor 

along the assembly line.

Process Description

Five drafters worked in engineering. Plant E uses AutoCAD 

2000 Architect for their drafting. We were shown the drawings that are sent to the shop floor. In AutoCAD, the drafters 

had standardized blocks, essentially pre-drawn components 

that could be lifted into another drawing. 

At the floor station, the joists were set on a table and nailed 

to the lumber bands; the floor was then craned over to the 

assembly line and set on rollers on steel tracks. Unique 

numbers are spray painted onto the ends of the floors. Plant 

E uses 3/4-in. tongue and groove OSB for flooring, 1/2-in. 

OSB for siding, and 5/8-in. OSB for roofing. 

All exterior walls were 2 by 6 Southern Pine and were held 

onto the floor with 4-in. screws; the exterior walls had a 

gasket between the wall and OSB sub-flooring. On exterior 

sheathing, Plant E set a moisture barrier at OSB joints (behind top OSB sheet, in front of bottom OSB sheet). Plant 

E used 2 by 3s sheathed in OSB for the marriage wall. The 

engineer did not know if this internal void would be sealed 

by the builder. As with other manufacturers, we saw signs 

of overbuilding by Plant E; for example, triple 2 by 4s were 

used as headers over doors. Once the module was at the end 

of the assembly line, it was transferred onto different rollers and rolled out of the factory to where it was transferred 

(again) onto a trailer. 

As the floor assembly made its way down the assembly line 

(see flow diagram in Fig. E1), the roof was craned onto the 

module. Plant E purchases trusses for their homes. Cranes 

in the Plant E factory were split between the left and right 

side of the factory. By aligning a crane track from each side, 

loads could be transferred (unlike at Plant D where loads 

could only transfer at certain stations). Plant E made some 

three unit roof sections (for covering a triple-wide). 

One interesting specialized tool we saw was a large dormer 

jig. This was basically two large steel tables that were angled (one side lifted into the air) to simulate a roofline. This 

allowed Plant E to build its dormers by simulating the angle 

of the roof of the in-place home. Pegs on the jig tables allow 

easier placement of the lumber. 

The machining department was divided into stations for the 

dormer, stairs, and wall/floor. Carts were used to move material and finished goods around in the factory. 

In addition to the typical vinyl siding, Plant E offered Hardiplank siding and window trim (James Hardie Industries, 

Amsterdam, The Netherlands). Plant E installed brand-name 

cabinets. We were told that Plant E buys in bulk to save 

money. We saw a large amount of inventory sitting around 

the factory. Plant E is presently building extra storage buildings on their property. Material handling did not seem to be 

as efficient as possible. 

Other Impressions

•	 The engineer emphasized that Plant E only produces 

HUD code homes for one builder.

•	 The engineer was against the production of HUD homes. 

•	 The engineer said that on average, a site-built home costs 

$100 per square foot, compared with $75 per square foot 

for a modular home.

Technology Assessment of Automation Trends in the Modular Home Industry

Figure E1. Plant E floor plan.
18

Plant F

Contact: Vice President

July 1, 2004

Key Points 

•	 Plant F has a shotgun layout.

•	 They practice very good housekeeping.

•	 Parts cut and subassemblies are built away from the main 

production line, allowing the assembly line to focus on 

module assembly.

Company Description

The original plant was constructed in the 1950s. Today at 

least four manufacturing buildings are on site, with a total of 

400 employees. Plant F is owned by Company F, which has 

other manufacturing facilities in the region. The Plant F site 

produces an average of three modules per day and emphasized recycling scrap cutoffs.

Production

As noted, this factory produces three modules per day. Assuming $20,000 per module (based on an estimate from 

another producer), 245 days per year, the first approximation 

of its annual productivity is (only) $36,750.

Process Description

Although the facility was stated to be space-constrained, we 

found that Plant F was well organized in terms of process, 

labor, and layout. As with previous plants, we did not see 

much in the way of computer technology being used on 

the floor. The module assembly line at Plant F is a “shotgun” layout, meaning that all modules move down the line 

lengthwise, as opposed to all other plants we have seen in 

which the modules move down the line sideways (Fig. F1).

The first section of floor assembly at Plant F starts on a 

flooring table with three floor stations beside the table 

where interior walls are set on the floor (Fig. F2)). The 

floors are constructed with spruce-pine-fir (SPF) joists or 

engineered laminated trusses (depending on the price class 

of the module) and Southern Pine lumber bands. They use 

a lumber buggy over the floor to distribute the joists. At the 

floor stations (normal floor widths of 12, 14, and 16 feet, 

none narrower than 10 feet), either 3⁄4-in. OSB or 1⁄2-in. plywood flooring is nailed, heating registers cut out, a layer of 

plastic is placed on the floor for protection, and the walls 

are placed. They have two wall tables (Fig. F3); long walls 

(maximum of 64 feet) are drywalled on the table and then 

lifted in place with a crane (at the flooring station). A short 

wall table was used for interior and end walls. Spruce-pinefir wall studs were used and were predrilled by supplier 

for electrical (Fig. F4). They also build folding roof (and 

drywall ceiling) rafter systems on the factory floor (Figs. F5 

and F6) (as opposed to trusses) and use the crane to lift these 

onto the modules. Necessary attic work must be done in the 

rough end of the module building because this newer part 

of the plant has adequate height. They use a floor pit for 

sub-floor plumbing and electrical work. 

After plumbing, the module is moved to the cross-over area 

and essentially the two-line process becomes a three-line 

process. It is important to note that modules move through 

the production process end to end, rather than crosswise. 

After inspection and exterior wall insulation, the module 

is sheathed with 3/8-in. pine plywood. The vice president 

pointed out to us that only QC folks use red markers to note 

deficiencies that must be corrected (Fig. F7, which is also 

a good example that missed staples occur even in factory 

production). Mud and spackling of dry wall is not begun 

until the module is totally sheathed in plywood (Fig. F8). 

They also use plywood sheathing on marriage walls because 

the marriage wall is load bearing. For interior finishing, two 

coats of paint are rolled. The vice president said the builder 

could leave this second coat as the finish coat. In bathrooms, 

Plant F offers three paint colors.

Other Impressions

Plant F takes pride in producing a customized product and 

classifies each job according to the level of customization: 1 

is standard, 2 is changes required, and 3 is complete custom 

special. The vice president pointed out that the details of 

customization limit the amount of computer technology that 

can be incorporated into the process. Stated otherwise, standard, repeated products are easier to automate with computerized systems. Plant F also takes pride in being the upper 

end of the price point (quality) scale for modular homes.

Housekeeping was excellent throughout this plant. Notable 

was its philosophy of having the production line focus on 

assembly, and having its on-site component plant cut and 

prepare parts (Figs. F9 and F10). As the vice president told 

us, their goal is for the assembly plant to be an assembly 

plant (using line workers) and not to modify any material 

(for example, not cutting 2 by 4 or sheathing plywood). He 

stressed that, “The assembly line workers should pick up 

and install components and parts.” The component plant 

produced rafters, doors, doorframes, cut countertops, and 

ripped wall panels. The plant used a second story area to inventory kitchen cabinets, commodes, sinks, insulation, and 

flooring (all goods going into houses). The vice president 

says the doors are made in-house to better control inventory. 

The vice president said Plant F has just enough inventory 

to meet orders immediately, although we observed what appeared to be large quantities of inventoried materials. For 

example, lights come into the factory on a per-house basis. 

To bring material to the manufacturing (assembly) line, a 

per-house buggy of inventory is assembled and delivered to 

the line.

The vice president discussed the daily complication of a 

builder not being ready to accept that day’s delivery of a 

module. He stated that the delivery process generally requires two weeks to plan/execute (a few days to process the 

Department of Transportation wide-load permit delivery 

application, and then one week already scheduled).

General Technical Report FPL–GTR–188
19

For drafting purposes, the vice president said Plant F uses AutoCad (year not known). The vice president also said Plant F 

had purchased and experimented with a drafting system to create the parts list and materials purchasing list; however, he said 

that the software did not meet expectations, so Plant F now 

again does this manually.

The vice president told us that a pilot car (as is sometimes 

necessary for overlength modules on highway) costs $2.10 per 

mile. One unique feature was that Plant F sets all of its homes 

rather than relying on either builders (the purchasers) or outside contractors. The set crews target setting two homes per 

week (each a 2-day set). The builder only assists the set crew.

Technology Assessment of Automation Trends in the Modular Home Industry

Figure F1. Looking down the “shotgun” 

manufacturing line toward the cross-over area. 

Figure F2. Manufacturing flow at Plant F Homes.

Figure F3. Joists installed at floor framing table.

Figure F4. Wall construction (left), and use of predrilled 

spruce-pine-fir (SPF) wall studs (right).

Figure F5. Installing rafters on ceiling drywall.
20

Figure F6. Installed rafters and knee brace in 

attic module.

Figure F7. Quality control uses 

red markers to visibly flag 

problems.

Figure F8. Plant F typically uses 3/8 in. pine plywood wall sheathing.

Figure F9. Component plant produced 

rafters, doors, doorframes, cut countertops, 

and inventoried purchased items such as 

cabinets, commodes, sinks, insulation, and 

flooring.

Figure F10. Rafters being built in 

component plant (top). Constructed 

dormers (center) and component 

parts assembled in kits by module 

(bottom).

General Technical Report FPL–GTR–188
21

Plant G

Contact: Truss design manager

August 11, 2004

Key Points

•	 Plant G is a truss and wall panel manufacturer.

•	 This plant had four truss assembly areas (two lines, each 

with two stations).

•	 The wall panel used two lines.

Company Description

Plant G is part of a larger company that makes doors and 

supplies lumber. The truss plant is five years old, whereas 

the wall panel plant is three months old. This new building 

is 80 ft by 120 ft and has two wall-panel lines. Five years 

ago, three truss designers were employed; today, 10 truss 

designers are employed. Plant G has $6 million in sales 

(with about $1 million of that being walls). They have been 

making wall panels for three years. Plant G is in the process 

of opening a new truss operation elsewhere in the state. 

Plant G ship trusses as far as 120 miles.

Production

We spent a lot of time with the truss design manager looking at the Mitek software (MiTek Australia Ltd., Melbourne, 

Victoria) that is used to design trusses. This was obviously 

where the truss design manager is more comfortable (as 

opposed to being out on the floor), and it was the first time 

we had toured and visited a truss operation. The truss design manager explained that the MiTek software has two 

major functions: layout, where the truss is designed, and 

engineering, where the design is evaluated based on load. 

The software then lets the designer know whether the truss 

design meets design loads. Designs typically assume a 

40-pound per square-foot load. Different lumber grades are 

purchased and their specifics are entered into the software. 

Southern Pine is often used in girder trusses because of its 

high strength. They sometimes use piggy-back trusses as the 

crown of large trusses, but sometimes use hinged joints to 

accomplish this.

Process Description

This company requires a two-week lead time to produce 

normal trusses. Complex trusses may take three weeks just 

to draft. The MiTek software is complex; the truss design 

manager said that it might take a new designer two to three 

months to learn how to do a simple design, even though the 

designer is proficient with AutoCad. It might take a new 

designer a year to be able to perform a moderate design. 

The truss design manager said that a large house (10,000 ft2) 

that might have a 7,000 ft2 roof and require $32,000 in roof 

trusses.

Other Impressions

The wall panel plant has two lines, which were not running 

because it was the end of the shift. One line was the interior 

wall line while the other was the exterior wall line and used 

Panels Plus equipment (Panels Plus, Albert Lea, Minnesota). 

These simple lines needed three people each approximately. 

The exterior walls were sheathed on one side with OSB. 

No drywall was used, and thus these were not closed-wall 

panels. We noted that the jigs at the framing station were not 

being used. These simple lines consisted of a framing station 

with manual nail guns, a panel station with panels loaded 

manually, and a stationary bank of nail guns.

Plant H

Contact: Operations Manager

August 11, 2004

Key Points 

•	 Plant H produces seven to eight modules per day.

•	 The plant has a two-line shotgun layout.

•	 Housekeeping is poor.

Company Description

Plant H produces both modular and a “united frame” HUD/

modular on-frame model for “land-lease” situations. Plant H 

produces on average seven modules per day, again applying 

the mass-production mentality. Our contact told us that Plant 

H would also produce completely custom modular homes. 

Plant H employs 300 people, with about 280 in production 

and five in engineering/drafting. Housekeeping seemed to 

be a low priority in the factory. The factory was built several 

years ago; an addition was made to the original factory in 

1997. 

Production

Floors were assembled in a building separate from the main 

assembly line. The floors were assembled directly on the 

castors on which they rode down the line (attaching castors 

is an extra step). The employees manually pulled the floors 

down their line. Before the floors were transported to the 

main assembly line, plumbing, insulation, and wiring were 

run. Felt-back vinyl flooring was also installed to prevent 

tearing due to racking caused by transportation and setting. 

Our contact explained to us that for two-story homes, the 

floors were assembled one on top of the other to ensure that 

the floors were the same size (a problem we have seen with 

marriage walls in other manufactured homes). Alongside 

the final assembly line were the four tables used to assemble walls. One large table with a plastic top was used to 

assemble the long walls (both exterior and interior) with a 

maximum length of 70 ft (average 60 ft). Three shorter 

tables were used to assemble smaller interior and gable 

Technology Assessment of Automation Trends in the Modular Home Industry
22

walls. Exterior walls were standard 2 by 6, and interior 

walls were 2 by 4. We were told that a module takes four 

days to move down the assembly line from start to finish. 

Our contact estimated that there are 30 stations along the 

assembly line. Our contact stated that Plant H presently has 

a 14- to 15-week backlog for home orders. 

Process Description

Plant H uses 14-foot sheets of 0.5-in. drywall for interior 

walls and 14-foot sheets of 5/8-in. drywall on the ceilings. 

Plant H mixes its own interior paint. Plant H buys the trusses for its homes. 

Other Impressions

This visit raised a question: is ordering a modular home really faster for the consumer? Plant H has a 14- to 15-week 

backlog now. Then, assuming the builder is ready, delivering the home takes a week. Our contact said that to make the 

modular home “turn-key,” builders often need another 60 

days (8 weeks) after the modules have been set.

Plant I

Contact: Operations Manager 

August 12, 2004

Key Points

•	 Plant I produces between 3,000 and 3,500 ft of wall panel 

per day on the two wall-panel lines.

•	 They use Mitek truss software and truss equipment (MiTek Industries Inc., Columbia, MO).

•	 They use Intelligent Building Systems (IBS) (Intelligent 

Building Systems, Arlington, TX) wall panel software and 

equipment.

Company Description

Plant I produces roof trusses, floor trusses, and wall panels. 

The roots of Plant I are around 150 years old; however, 

Plant I was officially started in 1975 (according to the Web 

site). Overall, we were impressed with the equipment and 

operation. The wall panel line at Plant I is semi-automated. 

Plant I is producing a minimum of 3,000 feet of wall panel 

per day; our contact told us that up to 3,500 feet per day is 

normal. The wall-panel line area showed good housekeeping. The wall panel assembly lines were two and three years 

old. 

Production

Eight-foot tall wall panels are normally 12 feet wide, 

whereas Plant I panels greater than eight feet high are eight 

feet wide. Our contact said this size weighs less and is advantageous for transportation and panel-placement reasons. 

The panels over eight feet high were manually assembled/

sheathed on a special table in the truss building (probably 

manually framed). Plant I also made some special “enclosed 

wall panels” for surrounding fireplaces. These were also 

manually sheathed (and probably manually framed) on the 

special table.

Process Description

Wall panels were designed using Intelligent Building Systems’ software. As we have seen with the Mitek truss software, this software automatically inserted studs where they 

belong, seemingly shortening drafting time. This file was 

then sent to the wall panel supervisor, who then decided on 

which line the panels would be made. Once the supervisor 

had decided which line to use, the operators would see the 

panel visually displayed on their monitor. 

A schematic of Plant I wall panel lines is shown in Figure 

I1. The employees involved with the wall panels were sawyer, part assembly (parts included decks, ladders, jacks, Ts, 

corners), component assembly, and assembly line. An employee pre-cut the sheathing to go on the framed wall panel. 

After parts were made in part assembly, they were carried 

to the component assembly table, which fed directly into 

the assembly line. The two operators on the framing section 

of the assembly line viewed a line drawing of the wall they 

were making on a monitor. Jig fingers could be used for 

standard dimension walls; however, whenever components 

were set into the wall, the jig fingers were often useless and 

the tape measure printed on the table was used. 

The workers then squared the wall panels on the table, and 

the semi-automated nail gun was pulled along the framed 

wall panel. The wall panel then went to sheathing where two 

employees set the pre-cut wall skin on the frame. The semiautomatic nail station only was used where there was uninterrupted wall section; i.e., not around windows and door 

openings. Around these openings, the operators manually 

nailed the sheathing. At the time we visited, only a type of 

fiberboard was being run as sheathing. Staples were used for 

the sheathing, and the staples did not seem to consistently 

penetrate the panel skin. The wall panel also exhibited visual deflection whenever the nail gun row was lowered onto 

the panel. There was a router station after the skin section; 

however, we did not see this station being used. The router 

station was again semi-automated. Once finished, panels 

were lifted off of the assembly line and stacked according 

to a stack sheet. Here an operator used a crane to lift and set 

the panels.

Other Impressions

We saw nine employees per assembly line; however, a total 

of 27 employees worked in the wall panel section of the 

plant during the day. Fourteen employees worked the wall 

panel section during the night. These extra positions include 

forklift driver, lumber puller, supervisor, the panel pre-cut 

employee (as mentioned above), and the extra person outside the building to stack the interior panels from the right 

side assembly line. 

General Technical Report FPL–GTR–188
23

Each assembly line cost approximately $150,000. Our contact said the average employee in the panel department is 

paid $10.50 per hour, plus medical and dental insurance and 

a 401K-plan option. 

Our contact explained to us that most component plants 

(truss and wall panels) will do about $3–$5 million in business every year; meaning that manufacturers tend to be 

“mom and pop” shops that have developed over the years. 

As for homeowners’ move-in time, we were told that the 

panelized homes from Plant I typically have a 120-day 

move-in time. Our contact stated that Plant I used to have 

one of the first CAD/CAM wall panel assembly lines installed in 1994 ; however, eventually their operational requirements outgrew this system. 

Appendix B—Technology 

Assessment of U.S. Modular Home 

Plants

In the following table, four questions are answered for each 

major process. These answers are a guide to the level of 

technology employed at each of these processes.

We asked four questions:

How is the raw material transported?

How is the raw material sized?

How are the components fastened?

How is the finished product moved?

Technology Assessment of Automation Trends in the Modular Home Industry

Figure I1. Plant I floor plan.
24Table 1—Technology assessment 

Process/Technology Plant A Plant B Plant C Plant D Plant E Plant F Plant H 

Customer input Standard or custom Standard with options Standard or custom Standard or custom Standard or custom Standard or custom Standard or custom Plant design — AutoCad DataCAD CADSofta AutoCAD 2000 

Architecture 

AutoCADb — 

Plant plans Printed Printed Printed Printed Printed Printed Printed 

Floor framing Manual/cut-off saw/ 

manual nail gun/crane 

Manual/cut-off saw/ 

manual nail gun/crane 

Manual/cut-off saw/ 

manual nail gun/ 

frame-flippedc

Manual with joist 

dealer/PET saw/manual 

nail gun/crane-flipped 

Manual/cut-off saw/ 

manual nail gun/ 

crane to trackd

Manual with joist 

dealer/cut-off saw/ 

manual nail gun/ 

crane to track 

Manual/cut-off saw/ 

manual nail gun/rollers 

Floor decking Manual/circular saw/ 

manual nail gun/ 

crane to track 

Manual/circular saw/

manual nail gun/ 

air pads 

Manual/circular saw/

manual nail gun/ 

frame on rollers 

Manual/circular saw/ 

manual nail gun/ 

crane to rollers 

Manual/circular saw/|

manual nail gun/ 

NA 

Manual/circular saw/ 

manual nail gun/ 

NA 

Manual/circular saw/ 

manual nail gun/ 

NA 

Floor infille Manual Manual Manualf Manual Manual Manualg Manual 

Wall framingh Manual/cut-off saw/ 

manual nail gun/crane 

Manual/cut-off saw/ 

manual nail gun/crane 

Manual/cut-off 

saw/manual nail 

gun/cranei

Manual/cut-off saw/ 

manual nail gun/crane 

Manual/cut-off saw/ 

manual nail gun/crane 

Manual/cut-off saw/ 

manual nail gun/crane 

Manual/cut-off saw/ 

manual nail gun/crane 

Wall sheathing (OSB or plywood) 

Manual/circular saw/ 

manual nail gun/ 

NA 

Manual/circular saw/

manual nail gun/ 

NA 

Manual/circular saw/

manual nail gun/ 

NA 

Manual/circular saw/ 

manual nail gun/ 

NA 

Manual/circular saw/ 

manual nail gun/ 

NA 

Manual/circular saw/ 

manual nail gun/ 

NA 

Manual/circular saw/ 

manual nail gun/ 

NA 

Wall set Crane/NA/manual 

pneumatic screw/NA 

Crane/NA/manual 

pneumatic screw/NA 

Crane/NA/manual 

pneumatic screw/NA 

Crane/NA/manual 

pneumatic screw/NA 

Crane/NA/manual 

pneumatic screw/NA 

Crane/NA/manual 

pneumatic screw/NA 

Crane/NA/manual 

pneumatic screw/NA 

Wall infill Manual Manual Manual Manual Manual Manualj Manual 

Roof framing OSP of trusses Manual/cut-off saw/ 

plate press/ 

manual to cart 

OSP of trusses Manual/cut-off saw/ 

manual connected/ 

manual to cart 

OSP of trusses Manual/cut-off saw/ 

manual connected/ 

manual to cart 

OSP of trusses 

Roof assembly Manual/NA/ 

manual nail gun/ 

cranek

Manual/NA/ 

manual nail gun/ 

cranel

Manual/NA/ 

manual nail gun/ 

crane 

Manual/NA/ 

manual nail gun/ 

crane 

Manual/NA/ 

manual nail gun/ 

crane 

Manual/NA/ 

manual nail gun/ 

cranem

Manual/NA/ 

manual nail gun/ 

crane 

Roof decking Manual/circular saw/ 

manual nail gun/NA 

Manual/circular saw/

manual nail gun/NA 

Manual/circular saw/

manual nail gun/NA 

Manual/circular saw/ 

manual nail gun/NA 

Manual/circular saw/ 

manual nail gun/NA 

Manual/circular saw/ 

manual nail gun/NA 

Manual/circular saw/ 

manual nail gun/NA 

Roof set Crane/NA/manual 

pneumatic screw/NA 

Crane/NA/manual 

pneumatic screw/NA 

Crane/NA/manual 

pneumatic screw/NA 

Crane/NA/manual 

pneumatic screw/NA 

Crane/NA/manual 

pneumatic screw/NA 

Crane/NA/manual 

pneumatic screw/NA 

Crane/NA/manual 

pneumatic screw/NA 

Roof infill Manual Manual Manual Manual Manual Manual Manual 

a Plant is in the process of implementing Base 3 Technology’s Home Base Program (Base 3 Technologies, Greenwood, DE). b Plant bought software for a parts list and materials purchasing list, but found the software problematic. c Floor is attached to transport frame and then flipped. d At the end of the assembly line, modules are lifted onto a different set of rollers that are perpendicular to main assembly line. The modules are rolled out of the plant and transferred onto 

 a trailer. 

e Floor, wall, or roof infill—plumbing, wiring, duct work, and insulation. f Floor infill begins on framing table, before being flipped. g Floor pit used for sub-floor plumbing and electrical work. h Sheetrock was attached to wall framing on the framing table at all manufacturers. i Special cut-off saw table for short wall sections. j Plant F used studs with a predrilled hole about 30 in. from one end. k Ceiling sheetrock not attached at roof assembly. l Ceiling sheetrock was attached at roof assembly. m Unlike other manufacturers, Plant F installed infill while roof was on the floor. 

General Technical Report FPL–GTR–188
25

Appendix C—Trip Reports Summarizing German Modular Home Plants

Plant GA

Contact: Technical Manager

June 15, 2005

We were told that Plant GA (Fig. GA1) was one of the top 

10 factory home builders in Germany, reputable for building 

a high-quality though expensive home. They manufacture 

95% custom homes and 5% Teuton (no options). They sell 

through free agents that use one of their 20 demo houses 

built throughout Germany. They do engage the customer 

directly and use their on-site home and option display for 

the customer to use and finalize plans (and flooring, doors, 

and windows and such) after the architecture plan has been 

finalized. 

Plant GA does not use laminated beams in its homes. Instead, they use solid timber beams. In situations where large 

open rooms are designed without support walls or columns, 

steel I-beams are used to support the wood timbers.

After plans are finalized, the house can be completed in 8 to 

12 weeks. Once transported to the building site, the house is 

finished in one day. They use three different software programs in the process of selling, designing, and producing a 

house: 

1. Sales drawing (light-duty CAD (computer-aided design))

2. Architectural drawings, which are again made by a 2-D 

program. This program can use some of the information 

from the sales drawing which is a dxf file, a data format 

developed by Autodesk used for CAD vector image files, 

such as AutoCAD documents.

3.The 3-D construction program CADWORK (Cadwork 

Informatik CI AG, Basel, Switzerland) is supposed to extrude the 2-D file written; however, the technical manager 

states that the extrusion is seldom correct, and therefore 

this option is not often used.

Plant GA employs 200 people, 100 in production and 100 in 

the office. They manufacture 200 complete homes, known 

in German as schlüsselfertig (turn-key) per year, and about 

100–150 Aus-Bau Homes (customers complete the inside or 

a part of the inside).

In Germany, 15% of the housing is timber frame (wooden) 

homes, and 85% is traditional cement and stone. The German housing market share for timber frame houses is down, 

and many factories closed in 1995. These were factories 

built in East Germany that failed because of the lack of demand (lack of money) in East Germany after the fall of the 

wall. Typically, a German customer builds only one house in 

his lifetime.

Process Description

Timber frame processing—According to the technical manager, “the heart” of the Plant GA factory is two machines, 

the Hundegger CNC timber frame processor (Hundegger 

GmbH, Hawangen, Germany) (Figs. GA2 and GA3) and a 

Giben automated (CNC) panel processor (Giben International S.p.A., Pianoro (Bo), Italy) (Fig. GA4). At the time 

of our visit, the timbers being worked on were fingerjointed 

spruce 5 cm by 10 cm (this was the minimum size timber 

used by Plant GA). The Hundegger station notched timbers 

and drilled holes for the connectors (lag or normal bolts) and 

cut the timbers to length with angles other than 90 degrees 

as needed (Fig. GA5). The infeed had at least six groups of 

differently sized timbers, which were automatically preloaded into the machine (Fig. GA6). Selection and machining 

of timbers was done by the computer program. The timber 

processing machine was located between the wall table and 

the roof table to easily feed both processes. The automated 

timber loader was a Weinmann timber loader (Weinmann 

Holzbausystemtechnik GmbH, St. Johann-Lonsingen, Germany). For short timbers, a manual cut-off saw was used at 

a separate station (Fig. GA7).

Panel processing—A very large Giben automated (CNC) 

panel processor was used to cut OSB, particleboard, or plywood panels to size (Figs. GA8 and GA9). In combination 

with the Hundegger timber frame processor, these form “the 

heart” of the factory. Only those panels that need trimming 

are cut here, such as those that will not fit into a standard 

4 by 8 space (Note: panels were not measured to ensure that 

standard European size is indeed 4 by 8). 

Wall table processing—This operation constructed the timber frame as a wall, placed sheathing (plywood or OSB), 

and laid down batts of insulation (Figs. GA10, GA11, and 

GA12). Wall studs were fastened with a nail gun, as were 

panels to the wall frame. After sheathing one side, the wall 

panel is flipped with a crane. Electrical conduits and insulation are then installed (Fig. GA13), and final sheathing is 

done. This outer sheathing may be OSB or it may be foam 

insulation if the house will be bricked on site. Windows 

were also installed on this line. All void spaces (including 

those around insulation) were filled with expanding foam 

(Fig. GA14). Wiring conduits were routed up the wall to a 

channel at the top of the panel (Fig. GA15) and connects to 

the adjoining panel via this channel. Wires were then run 

through the conduit, with coiled wire left hanging off of the 

panels (Fig. GA16).

Floor/ceiling table (middle floor)—This station used an 

automatic board dealer and automatic nail gun to fasten furring strips to larger beams (Fig. GA17). Drywall ceiling or 

flooring panel can then be attached to these strips; the strips 

function as support for the ceiling or flooring. A flipper finishes the other side of this component (Fig. GA18).

Technology Assessment of Automation Trends in the Modular Home Industry
26

Roof table/line—Furring strips were manually attached to 

larger beams using a nail gun. Plastic water proofing sheet 

was attached to the construction. Tile shingles were installed 

at the construction site, after the entire wall/floor/roof panels 

have been set and the space under the walls filled with concrete (Figs. GA19, GA20, and GA21). 

Finished panels were oriented vertically by crane and loaded 

onto a metal platform, which in turn was hydraulically lifted 

and placed on a truck bed for transport (Fig. GA22). The 

technical manager stated that window breakage because of 

transport is so seldom a problem (one broken window per 

year) that it is not even considered.

Plant GA also has a stair-production line manufacturing 30 

staircases per week, mainly of beech with some oak. These 

stairs are customized products for more than just Plant GA’s 

houses. Target moisture content for this raw material was 

6%–9%. With these staircases, glued hardwood panels are 

bought in different thicknesses, widths, and lengths and 

CNC-machined to the needed size/shape (Fig. GA23).

Figure GA1. Plant G-A manufactured home facility 

in Germany.

Figure GA2. Infeed side of Hundegger timber 

processor.

Figure GA3. Shielded sawing and notching area 

of the Hundegger K2. The red clamps are feeding 

a timber to the cutting heads.

Figure GA4. Giben computer numerical controlled 

(CNC) panel processor.

Figure GA5. Example of timber cuts made by 

Hundegger K2.

General Technical Report FPL–GTR–188
27

Technology Assessment of Automation Trends in the Modular Home Industry

Figure GA6. Weinmann automated timber loader 

selected and picked up timbers from the infeed 

bays using screws.

Figure GA7. Manual cut-off saw used for short 

timbers (infeed bays for the Hundegger shown in 

background).

Figure GA8. Large Giben computer numerical 

controlled (CNC) panel processor cut oriented 

strandboard (OSB), particleboard, and plywood.

Figure GA9. Giben infeed with many panels available for vacuum lift.

Figure GA10. Nailing sheathing to the timber 

frame at the wall table station.

Figure GA11. Timber frame showing red electrical 

conduits, mineral wool insulation, and exterior 

window shade.
Figure GA12. Stud member fitting into notched 

gable roof. Note mineral wool insulation.

Figure GA13. Framed and drywalled wall showing 

bats of mineral wool and plastic electrical conduit.

Figure GA14. Expanding foam used to fill voids 

and completely insulate wall panels.

Figure GA15. Top of wall panel shows channel 

developed for electrical conduit placement.

Figure GA16. Wiring conduits exiting wall panel 

with wiring.

Figure GA17. Automatic board dealer and 

automatic nail gun fastens furring strips to joists 

at the middle floor station (floor and ceiling).

28

General Technical Report FPL–GTR–188
Figure GA18. Butterfly table flips the middle floor 

construction so other side can be worked on.

Figure GA19. Roof table showing furring strips for 

tile shingles (installed on site), blue plastic water 

proofing, and painted exposed joist.

Figure GA20. Roof table showing furring strips 

and sheet of plastic water proofing.

Figure GA21. Edge view of roof showing exposed 

beam (right), insulation bat (left).

Figure GA22. Finished wall sections are oriented 

vertically and loaded onto a metal platform, which 

is placed on truck bed for transport.

Figure GA23. Beech stair 

stringer machined with computer numerically controlled 

(CNC) router.

Technology Assessment of Automation Trends in the Modular Home Industry

29
Plant GB

Contact: Engineer 

No photos were allowed in factory, but photos were allowed 

in showcase homes on site.

June 17, 2005

Plant GB is one of the premier home builders in Germany. 

The company has been in existence since 1912. In 1972, 

they began building post and beam homes designed by 

architect Manfred Adams. These homes are very open in 

design and have large glass windows. They use laminated 

beams throughout made of Scandinavian spruce (Fig. GB1).

The architect works with customers to design the completely custom floor plan. All Plant GB homes have open 

floor, open wall, and open roof sections; this is the Plant GB 

architectural style (Fig. GB2).

Plant GB builds about 125–135 houses per year, and employs 300 employees total: 100 in production; 100 in “building science” (CAD design, planning and scheduling); and 

100 in administration and in other cities (example houses). 

They work five days per week with four weeks holiday per 

year. They have show houses throughout Germany and Europe (Fig. GB3). The average Plant GB home in Germany 

is 200 m2. In Great Britain, the average Plant GB home is 

300 m2.

Processes

Plant GB has two main buildings, Carpentry Hall and Assembly Hall. In the Carpentry Hall, their main piece of 

equipment was the Fezer CNC machine.

This machine was approximately 40 m (120 feet) long, but 

the plant is limited by what length they can haul on their 

trailers (limit is 11.66 m overall length). Their new Fezer 

can saw, drill holes, make grooves for the beams to interlock, and produce sloped horizontal surfaces by sawing. 

Timbers are grouped by the job. They also use their older, 

more manual Fezer machine to process shorter beams. 

All hand tools in the Plant GB factory were Festool (Festool Germany, TTS Tooltechnic Systems AG & Co. KG, 

Wendlingen, Germany).

The beams then enter a QC area where visible, loose knots 

or other defects (such as sap pockets) are removed and plugs 

inserted. The beams are then sanded using a three-head buffering sander, stained (five coats for exposed sections and 

three coats for interior beams), and then air dried. Not all 

exterior stains are applied at this time, however.

Also in the Carpentry Hall is an IMA HullHorst CNC (IMA 

Klessmann GmbH, Lubbecke, Germany) which cuts, drills, 

grooves, and sands stairway parts—stringers and rails. This 

two-table CNC uses a pod system.

The Assembly Hall had eight work areas:

•	 Roof table

•	 Angled roof table for roof sections with large windows 

(no automatic angle setting)

•	 Wall table—triple-glaze windows are built into exterior 

wall sections. Cranes load these wall sections onto trucks 

vertically.

•	 Wet wall area—a separate wall for bathroom plumbing 

that goes in front of the regular wall

•	 Interior floor area

•	 External first floor wall section

•	 Interior first floor wall area—cranes are used to move interior walls, which are 16 cm thick

•	 Interior second floor wall

At the roof table, they first work on the ceiling. The layers, 

starting with the layer visible by the customer (looking up at 

the ceiling) are the following:

•	 Tongue and groove paneling (installed manually) or 

drywall

•	 OSB

•	 Lathe

•	 Plastic membrane

•	 Insulation between beams

•	 Beams

After the tongue and groove is installed, the roof section is 

flipped by crane, and layered with two thick layers of mineral wool, a breathable membrane, and a lathe for the roof 

tile, which is installed at the building site. The roof sections 

are then placed on transport trailer.

Note: The actual sequence of roof construction layers may 

not be totally correct, but do correctly show the detail involved.

Our contact stated that Plant GB tried to maximize the level 

of panel completion in the factory to minimize required 

work at the construction site. Many Plant GB homes are 

shipped each year to Britain. Our contact referred to Plant 

GB as “the Mercedes of homes,” saying that she knew of no 

other home manufacturer in Germany with higher quality 

homes.

30

General Technical Report FPL–GTR–188
Plant GC

Contact: Construction Engineer 

June 17, 2005

Plant GC is a custom-build homebuilder, with 150 employees (30% are in the office and the remainder are in production and assembly). This plant sells its houses directly to 

the customer through a dealer network, using example 

houses throughout Germany to help customers determine 

options (Fig. GC1). Their office staff makes building plans 

and manages construction paperwork to meet government 

paperwork. Their construction plans are drafted using 

Nemetschek software (Nemetschek AG, Munich, Germany), 

which is similar to AutoCad. Our contact noted that one 

advantage of Fertigbau (prefabricated construction) homes 

is the guaranteed pricing of a new home. Plant GC sells 150 

homes per year.

Plant GC is currently operating on one shift. Last year they 

ran two shifts, as the housing market was boosted by a 

2-year government program to provide loans at a 4%, 10-

year adjustable rate mortgage for certain income brackets. 

Plant GC buyers are typically young families that purchase 

unfinished (do-it-yourself) homes. A 20% down payment for 

the home is typical. 

Our contact mentioned that home manufacturers discussed 

timber size requirements with sawmills so they could have 

the desired dimensions and quality provided (these were 

fingerjointed timbers from Germany, but they were not 

laminated (Fig. GC2)). Standard height of interior walls was 

2 m, 50 cm. The studs used for interior walls were standardized (cut to length) to accommodate this height requirement. 

Our contact said that Plant GC produced custom homes, so 

any interior wall height could be accommodated; however, 

Plant GC would have to wait on their manufacturer to custom cut the longer timbers/studs for taller walls. Walls are 

limited by truck length to 15 m long. The maximum allowable height for wall panels is 4 m. 

Processes

In the Plant GC home manufacturing process, walls and 

floor sections (called wall and floor elements by most in Europe) were built using specialized tables (Figs. GC3–GC8). 

Roof trusses and gable ends were also cut and constructed 

(Fig. GC9 and GC10); however, roof elements were not 

assembled in the factory. Plant GC ran the conduit for the 

wires of the home to be placed in; however, the home was 

wired on site. The home was also plumbed on site, but 

major plumbing apparatuses (the connections to the toilet 

and showers) were installed in the factory. In the wall sections where plumbing would be run, the drywall was simply 

screwed to the wall framing so it (the drywall) could be easily removed and re-installed on the construction site.

Typical dimensions for their solid wood members were 

6 by 8 cm for interior studs and either 8 by 14 cm for 

Figure GB1. Painted laminated beams are used 

throughout Plant GB homes. 

Figure GB2. Plant GB homes 

are characterized by an open 

architectural style.

Figure GB3. Plant GB model home located on site.

Technology Assessment of Automation Trends in the Modular Home Industry

31
exterior walls or 10 by 14 or 14 by 14 cm for joists or other 

main structural members. This plant’s typical exterior wall 

layered construction (Fig. GC11) from the outside, would be 

stucco board, particleboard, 14-cm thick stud with insulation, particleboard, moisture barrier, and interior drywall.

At the factory, elements (components) of the home are 

built, such as interior and exterior walls, wooden part of the 

middle floor (5 cm of concrete is poured on site over each 

completed floor). These wall and floor components were 

transported by truck to the site (Fig. GC12), electrical wiring and plumbing was installed on site, and roofs were assembled on site, the rafters being cut and painted at the factory (Fig. GC13). Plant GC also manufactured the concrete 

panels to be used in the construction of the basement of its 

homes. These concrete panels were placed/set at the home 

site and a cement slab would be poured at the home site. For 

all interior wall elements that would have any angle on their 

upper corner (walls on the second floor), the wall elements 

would be constructed on a jig made by building one of the 

gable end walls on the factory floor. This would ensure that 

all walls, rafters, and gable ends lined up when being assembled at the construction site.

Our contact stated that Plant GC was in the top one-third 

of wooden home quality in Germany, and that the price of 

a Plant GC home was about average (the 50th percentile). 

Our contact said that all Plant GC homes have a 4-year, all 

inclusive warranty, and a 20-year structural–construction 

warranty. 

Our contact stated that most customers of Plant GC homes 

said that they needed approximately 1,700 liters of oil to 

heat the home and the hot water for an average home size 

of 150 m2. This works out to be 447.4 gallons of oil to 

heat (house and hot water) 1,614 ft2 of home (equates to 

0.2772 gallons of heating oil per square foot) for an entire 

year. 

Figure GC1. An example of a typical Plant GC 

showcase home.

Figure GC2. Fingerjointed exterior walls are 14 cm 

thick.

Figure GC3. Frame table with air-activated cylinders 

to clamp and hold frame.

Figure GC4. Wall-build table 

showing stops used to position 

wall-frame elements.

32

General Technical Report FPL–GTR–188
Figure GC5. Specialized wall table clamp that can 

retract into table to remove trip hazard.

Figure GC6. Stop bracket on wall table used to 

position wall frame elements.

Figure GC7. Light 

curtain reflector at wall 

table used to protect 

workers during clamping by halting clamping 

operations if workers 

break the light perimeter.

Figure GC8. Elevated cart for worker access to 

vertical wall.

Figure GC9. Gable walls are built one on top of 

the other to ensure symmetry.

Figure GC10. Roof element on transporting 

platform.

Technology Assessment of Automation Trends in the Modular Home Industry

33
Plant GD

Contacts: Draftsman, Technical Leader

June 20, 2005

Plant GD produces high-quality homes and stated that they 

were in third or fourth place in quality in Germany. They 

rank Plant GE higher. Plant GD has been in business for 

75 years, and the factory we toured was 12 years old. Over 

the 75 years of business, Plant GD has produced over 

28,000 homes. They market their homes in Germany, Austria, Switzerland, France, Spain, Great Britain, and Ireland. 

They have six example homes on site. Their maximum wall 

dimensions are 13 m (length) by 3 m (height). 

Processes

Plant GD was unique in its wall-production method. They 

produce standardized elements (one example element was 

1.55 by 2.5 m) and combine these standardized elements to 

produce full-size wall panels. We were told that combining 

standardized size elements allows Plant GD to automate 

production (assembly) of 85% of its needed wall panels. The 

remaining 15% of wall panels are produced on another wall 

table in a manner similar to wall panel construction typically seen in Germany. The 15% of walls produced without 

using standardized elements was stated to mostly be wall 

sections with gable ends; this prevented excess waste. We 

do not know how many standardized wall element sizes exist. These standardized wall elements are further unique in 

that they are entirely glued together; nails are only used to 

affix wall elements to one another. These standardized wall 

elements already have insulation installed, and internal studs 

in the elements have a square notch cut in one side of them 

to allow cables to be run. We did not see the production of 

these standardized wall elements.

The Plant GD wall-panel production process begins with elements being picked from a buffer (Fig. GD1) and delivered 

to a staging table (Fig. GD2). The standardized elements are 

delivered in the order in which they need to be affixed to 

produce the wall panel. After being delivered to the assembly table, workers manually staple and nail the standardized 

elements together (Fig. GD3) using nail guns. After being 

affixed, the wall panel was moved down the assembly line 

(Fig. GD4) and a plastic moisture barrier was installed over 

the OSB (Fig. GD5). 

Plant GD constructs with mostly German spruce timbers 

(both fingerjointed segments and laminated beams) and 

some pine. They use sanded OSB and (pine) plywood: 

15-mm OSB for walls and 18-mm for ceilings. 

Plant GD employs about 300 people; 80–90 in production; 

90 administration; and 90 in construction. They employ 

about 20 draftsmen who use AutoCad with specialized 

Plant GD elements that are standard sizes; custom sizes to 

all components can be entered (constructed), too. Plant GD 

manufactures its own windows, staircases, and front doors. 

Figure GC11. Exterior 

wall construction from 

left: stucco board, particleboard, 14-cm stud, 

particleboard, moisture 

barrier, drywall.

Figure GC12. Wall components are fastened 

in a rack on the transport trailer.

Figure GC13. Roof rafters are cut and painted 

at the factory but assembled on-site.

34

General Technical Report FPL–GTR–188
Customers often have their own architects and supply their 

own plans. Plant GD focuses on building a truly customized 

home with standardized building elements.

They produce an average of two houses per day, about 

350 to 400 per year. Their average home size is 150 m2. 

Our contact told us that the average Plant GD home costs 

about 1,000 euros/m2, excluding the basement. Converted to 

square feet, these homes cost about 93 euros/ft2.

Some of the technology we saw in the factory included a 

3Tec software system used to pick elements and place them 

in the wall assembly line. The HELO TEC machine (HELO 

TEC Automation GmbH & Co.KG, Bueren, Germany) 

bored holes for electrical switches and outlets (Fig. GD6). 

These holes were bored after the wall panels were vertical, 

just before the wall panels were moved into the vertical 

storage racks (Figs. GD7–GD8). The LeWecke machine 

(Lewecke Maschinenbau GmbH, Blomberg, Germany) was 

used to build roof sections and included automatic lathe 

dealers and nail guns for panels (Figs. GD9, GD10). The 

Hundegger CNC drilled, sawed to length and angle, and 

notched, as we have seen in other factories. This Hundegger 

was used to size pieces for roof and floor–ceiling elements.

Plant GD is currently running a backlog of orders, so it takes 

six months to get your house. Normally, three months would 

be the expected turnaround time if the foundations and plans 

were ready. It takes about one week to produce and four to 

six weeks to erect.

The production manager told us that approximately 35% of 

the operating cost for the factory is for electricity. As with 

most other manufacturers, Plant GD built wet walls with 

internal plumbing; these wet walls are set in front of the regular house walls. The technical leader stated numerous times 

that one of the best features of their factory is the linear flow 

through the assembly line (production). Plant GD sells the 

homes with a 5-year all inclusive guarantee and a 30-year 

structural guarantee.

Figure GD1. Wall-panel elements stored in buffer area prior to starting the process.

Figure GD2. Staging area into which wall panel 

elements are correctly sequenced.

Figure GD3. Assembly table workers manually 

connecting standardized elements together.

Figure GD4. View along the length of the assembly table.

Technology Assessment of Automation Trends in the Modular Home Industry

35
Figure GD5. Plastic moisture barrier installed over 

wall panel.

Figure GD6. The HELO 

TEC machine bored 

holes in walls for electrical switches and outlets.

Figure GD7. Wall sections hung on vertical storage racks.

Figure GD8. View of walls vertically hung beyond 

the HELO TEC borer.

Figure GD9. LeWecke machine nailing panels 

onto roof section.

Figure GD10. View of LeWecke machine capable 

of dealing lathe and automatic nailing.

36

General Technical Report FPL–GTR–188
Plant GE

Germany

Contact: Visitor Guide

June 21, 2005

Our contact has been working at Plant GE for 23 years. Its 

two product lines were Plant GE and Twin Home, home 

lines with the same quality but different target customers 

(see Figs. GE1 and GE2 for model home). Plant GE homes 

can be completely customized, whereas the twin homes are 

much more preplanned. Next to the factory was the company founder’s original wood home built in 1963. As we 

walked toward wood storage, we walked past the painting 

booths. Plant GE paints doors and windows and has winter 

gardens and certain special elements. 

Plant GE has a total of 1,000 employees working in two 

factories. In the factory we toured, 160 work in production on two shifts. About 260 employees work in the office, 

and about 240 employees work in erection on site. About 

240 people work at the second factory with approximately 

110–120 in sales.

Plant GE has a total of about 50 apprentices throughout the 

company. Plant GE makes finished roof or ceiling elements, 

though we did not see this. Last year, Plant GE produced 

870 houses. They also have a second factory in Germany. 

Plant GE has erecting crews at both factory locations. 

Processes

Following wood storage, the next section was the metalworking area. Employees were working with copper- and titan–zinc-coated steel for gutters and flashing. Stainless steel 

was also fabricated. The metal came in on coils and was 

straightened and clipped to length. Wood jigs were used for 

shaping metal pieces, welding, and building flashing around 

windows and gable ends. Metal part seams were bent rather 

than welded to allow for expansion and contraction of the 

metal. Timber painting was also done in this area. Exposed 

wood timbers must be painted; the rest is optional. If the 

final paint color is white, the final coat of paint is applied 

in the field after the home has been constructed. Otherwise, 

the final paint coat is applied in the factory. Plant GE also 

makes roof elements that are 2.4 to 2.5 m wide. 

Next, in lumber and panel storage, the wall studs are pre-cut 

to their length for wall height when delivered to the production floor (Fig. GE3). The studs are dried to 12%–15% 

moisture content at a low temperature so the wood will not 

twist. In the winter, studs are staged in the factory to allow 

them to equalize with the assembly line environment. The 

particleboard used contains polyurethane glue, and example 

pieces illustrated how little the particleboard swells when 

soaked in water. The drywall they use is moisture-resistant 

(also called greenboard and typically used in bathrooms). 

Plant GE, however, uses it throughout its whole house, as 

they place an emphasis on using high-quality materials. 

Plant GE does much research and development and quality 

control on its houses. The example our contact gave was, 

“What if it is raining on the day of your construction? Your 

walls need to be of the best material.” Our contacted stated 

that many competitors use cheaper materials, which is why 

their price is lower. Within the first day of construction of 

the house on site, it is rainproof. If any water gets into the 

house, the walls allow moisture out. Plant GE uses three 

suppliers of windows, all local producers.

Machines

All machines seen in the production line were Weinmann. 

Table one was for the outside wall; however, when the 

frame was built on the table, the top of the wall is the interior (Fig. GE4). The wall was framed, the moisture barrier 

installed, and then particleboard and drywall were attached. 

The holes were drilled for electrical outlets and switches 

using a Weinmann multifunction bridge (Fig. GE5), which 

nails or staples the panel to the frame and then cuts rough 

openings and trims panel edges. The wall was then flipped 

using a butterfly table (Fig. GE6). The electrical conduit was 

then run, insulation installed in the wall, and then another 

moisture-diffusible barrier was installed and sheathed with 

cement-bound particleboard. This cement board is 90-minute fire-resistant and appeared to be approximately 3.8 cm 

thick. Barrier strips were manually installed along the outer 

edge of the wall panel, and a machine automatically spread 

plaster 1.5 cm thick. On the exterior of the building, the 

support net for the stucco was installed on the building site 

and wrapped around the entire building so there would be 

no joints (Fig. GE7). After being wrapped, the building is 

spackled, again on site.

Housekeeping was medium to better than medium—but better than any modular factory in the United States we have 

seen. The doors and windows were installed after the walls 

were hung vertically (Figs. GE8–10). The doors were specially noted to be 9.6 cm thick—the guide mentioned how 

the doors and windows used contribute to the homeowner’s 

feeling of security. 

In the factory, only conduit was run for wires and then the 

wires were installed at the construction site. We asked the 

guide why the wires were not run in the factory, and the 

guide responded that this factory was “yesterday’s technology.” Further, Plant GE had worked with its supplier to 

develop electrical, plumbing, and bus connectors that would 

automatically connect when the wall was set into place. 

These houses were called “three-day houses” since that is 

the estimated length of time to assemble components and 

have plumbing and electrical connections completed. Some 

of these houses have been built to prove the connection 

technology. The guide said that at this time the connectors 

are simply too expensive to use on a mass-production scale.

The rolladen rolling exterior shades (rolladen is German 

for shutters) are built into the wall while vertical. Plant GE 

Technology Assessment of Automation Trends in the Modular Home Industry

37
differentiated itself by building these shades totally into 

the wall so that they were flush with the exterior wall. Drywall was then manually cut and fit to cover the hole where 

the rolling shade was installed (on the interior). Window 

choices for the houses were plastic, wood, or wood and aluminum.

In the factory, tile was already put on the wall. Also, special 

protectors were put on passageways that were not doors, 

and then removed once the house was finished on site. This 

prevented damage to passageways during erection and construction. 

Even though greenboard was used, the shower area was 

painted with a layer of liquid rubber. The foam used for insulation was EPS (expanded polystyrene). When processing 

the large timbers, all four sides of the timber can be processed in the same step. They had a four-headed processor.

Plant GE mostly used beech in its stair production. The 

Maka CNC machine used fixtures to hold stair parts. They 

used a hand router to rounding the corner of the stairs. We 

noted that the CNC router was capable of drilling vertically, then rotated and drilled horizontally (Figs. GE11 and 

GE12).

The staircase was built in the factory and then shrinkwrapped. Components for winter gardens were also built in 

Figure GE1. Model home at Plant GE.

Figure GE2. Kitchen typical of quality and 

amenities.

Figure GE3. Infeed timber buffer for Hundegger 

processor.

Figure GE4. Outside wall lay-up with insulation, 

moisture barrier, and particleboard.

38

General Technical Report FPL–GTR–188
Figure GE5. Multifunction bridge station for wall 

panels.

Figure GE6. Butterfly table used to flip wall panels as they move down the line (background).

Figure GE7. Detail showing many layers of the 

exterior wall.

Figure GE8. Troublesome components, such as 

this gable, can be pulled offline. Note eyehooks 

used for vertical hanging.

Figure GE9. Butterfly transfer table raises wall 

panel for vertical hanging onto line (to right).

Figure GE10. Note electrical conduits, interior 

window shade, and installed doors and windows.

Technology Assessment of Automation Trends in the Modular Home Industry

39
the stair-production area.

Plant GF

Contact: Engineer

Wednesday, June 22, 2005

Plant GF, a privately owned company, has been in business 

since 1881. According to the engineer, they are in the middle top range for quality and price. The engineer stated 

that some companies in Germany are more prefabricated 

than Plant GF, but many are less. Plant GF has 220 to 

230 employees, most located at the building site. In 2004, 

they built 206 houses; in 2005, 197–198. Its sales radius is 

300–400 km, which is mostly in Germany around Stuttgart 

but includes Switzerland as well. A model home at the plant 

site is shown in Figure GF1.

Processes

This operation was housed in several buildings. Our overall 

impression was that the operations were space constrained 

(i.e., crowded). Separate buildings housed sequential operations, specifically the Hundeggers that pass components to 

either walls or roof building areas in different buildings, 

which seemed inefficient. Overall housekeeping was not 

good. 

Joinery area—construction of front doors and stairs. Plant 

GF builds 90% the front doors for houses. Ninety-five percent of the stairs are built by Plant GF; the engineer stated 

that stair fabrication required a lot of hand work. An example of an installed finished staircase is shown in Figure GF2. 

A Maku CNC router was the “heart” of the joinery 

(Fig. GF3). They cut parts for doors and stairs on this podbased CNC. Stock material for much of this process was 

1-m by 5-m wide beech panels, Verleimt Holzplatten (edgeglued panel) (Fig. GF4). This Maku CNC is also used to cut 

out the holes required in particleboard panels for toilet 

connections.

Component preparation—Plant GF has two Hundegger 

CNC machines. The first is in the preparation area for 

wall components (Fig. GF5). It prepares (bores, notches, 

routs holes, and applies metal plates) wall sill plates and 

top plates. Many of these openings were for electrical and 

plumbing. Electrical wire and final stucco coat are applied 

at the building site, while rough plumbing is run in the 

factory. Particleboard wall panels in plumbing areas are 

removed on the building site to allow plumbing completion. 

The Hundegger used for wall component preparation starts 

with 4.9-m-long lumber that it cuts to required lengths. The 

metal plate capability allows them to use short parts. The 

Hundeggers are run by a German CNC control software program, SEMA Timber Construction Software (SEMA GmbH, 

Wildpoldsried, Germany). 

Exterior wall and partition wall area—(Fig. GF6). 

Hall 1 was in a separate area of the same building as where 

the components are made. They use a standard wall height 

Figure GE11. Maka CNC machine used vacuum 

pods to hold stock used to produce beech stair 

parts.

Figure GE12. Staircase assembly.

40

General Technical Report FPL–GTR–188
for their homes. Interior walls are 6.5 or 9.5 cm thick. 

Exterior walls use timbers 6.5 by 18.4 cm (2.5 in. by 7.2 

in.). Both sides are sheathed with 14-mm particleboard. A 

polyethylene vapor barrier is followed by drywall on the 

inside. Long walls are made in this area using a butterfly 

table to flip the wall. The outside roll shades are installed 

on the inside of the wall. Electrical holes are drilled on the 

side, 4-cm polystyrene applied, and the first layer of stucco 

applied adjacent to the wall table. The two layers of stucco 

applied in factory are 5 mm in thickness. Plant GF tries to 

ship each house on three trucks: wall truck; roof truck; ceiling truck (Fig. GF7). 

Hall 2. The same type of production tables were used for 

gables and eves. Workers were spraying stucco while we 

passed through, using fiberglass mesh as a base (Fig. GF8). 

The engineer commented that they use (true) fir for studs, 

sills, and top plates. They use normal studs for rafters and 

glulams for purlins.

Hall 3. Three programmers worked in an upstairs office in 

this hall downloading the Spirit (software similar to AutoCad from STI International, Inc., Concord, New Hampshire) 

architectural drawings in a dxf format and converting the 

drawings with SEMA software, which writes the code to 

control the two Hundeggers. Hundegger is the big name for 

beams and rafter processing, and they make tenons in addition to the other things. Normal dimensions for the joists are 

8 cm by 22 cm. The floor elements have 12-cm-thick insulation between joists. The particleboard used for flooring is 

22 mm thick. The roof windows are installed at the site; 

however, the moisture barrier and roof insulation are installed at the factory. The rafters are typically 8 by 20 cm; 

however, all these sizes can be customized. The roof insulation is 20 cm thick. Roof insulation is more flexible than 

what is used in the walls, as the latter would slide down 

during transport if it were not stiff. Roofs are shipped laying 

down (Figs. GF9, GF10, and GF11).

Hall 4. Short partition walls not made in Hall 1 were made 

here. They use a shipping truck out of Hall 4 that is shorter 

than that used in Hall 1. The engineer explained that Plant 

GF also set a wet wall in front of regular walls for toilets. 

All tables used in production were butterfly tables. 

Hall 5. Balconies and metal working, exterior handrails, and 

chimney parts were done. The balconies we saw were attached to a header joist for a ceiling, and the balconies were 

built of wood and covered with sheet-metal.

Plant GF employs two architects and three civil engineers, 

and seven draftsmen work in the main office with the purchasing people. Plant GF homes are always customized; 

they do not have standard plans. The software program 

Spirit is used to make floor plans and blueprints, apply for 

building permits, and show the customer the final blueprints.

Plant GF pours cement over floors for noise reduction, and 

the poured cement floor must dry for four weeks before being covered with carpet. Plant GF also builds basements out 

of precast concrete panels. Our contact’s role in the company is to be in charge of the time plan until the project starts. 

Metals used for balconies and gutters were either titan zinc 

or copper. The company makes front doors and buys its internal doors and windows. Basement walls are 20 cm thick, 

and the first floor is 18 cm thick. Our contact estimates that 

80% to 90% of houses built have a basement. The outside 

walls generally have conduit run in the factory while the 

inside walls do not. The 3-D program to make the sales rendering is called ARCON 3D Architect (Eleco Visualisation 

Software, Surrey, UK) Ten percent of the houses have whole 

house ventilation systems (heat exchanger with fresh air), 

and none of the houses have air conditioning.

Figure GF1. Model home at Plant GF.

Figure GF2. High-quality beech staircases were 

the norm in German prefab houses.

Technology Assessment of Automation Trends in the Modular Home Industry

41
Figure GF3. Maku computer-numerical-controlled 

(CNC) router used to machine door and stair components.

Figure GF4. Edge-glued and fingerjointed beech 

panels were common stock for stairs.

Figure GF5. Hundegger computer-numericalcontrolled (CNC) timber processor used for wall 

components.

Figure GF6. Exterior wall and partition wall tables 

in Hall 1.

Figure GF7. Wall components loaded onto truck 

for delivery to building site.

Figure GF8. Stucco being sprayed onto wall 

panels using fiberglass mesh.

42

General Technical Report FPL–GTR–188
Plant GG

Contact: Production Manager

June 23, 2005

Plant GG employs 200 people; 60 in drafting, sales, architecture, managers here and on site, subcontractors; 70 in 

construction on site; 70 in production. Our guide estimated 

that 95% of employees are skilled (have completed an apprenticeship for their occupation). Employees have target 

production goals per day and if they beat target production, 

they are given additional pay; implementation of this pay 

system has boosted production by 10%. Plant GG also has 

a commercial sales division of 15 people that includes four 

architects.

Sales volume is 28 million euros per year. Plant GG sells an 

equivalent of 160 to 180 houses per year. The average home 

is 145 m2 of living area and without the basement, and it 

sells for 160,000 euros (1100E/m2) (Figs. GG1, GG2, GG3). 

Commercial cost is about 800 E ⁄m2. Plant GG offers three 

lines of houses: 1) individual (an example size of 9 m by 

12 m was given (108 m2 or 1160 ft2)), 2) platform housing 

system, where you can choose options like a garage or balcony; 3) no options–customers choose a standard package 

from a plan book.

Plant GG, however, produces only 80 to 100 homes per year 

and the balance is in commercial buildings, office buildings, 

or kindergartens. Factory capacity is 300–350 homes on 

three shifts. About 50% of production is housing and 50% 

is businesses and other. Currently Plant GG is operating one 

and a half shifts. If Plant GG were only producing commercial buildings, we were told they could meet production in 

only one shift; with houses Plant GG would need two shifts.

Processes

Plant GG’s total production time for a house is 20 days. This 

includes the time needed to produce the wooden windows 

for its houses. We were told that because different production processes take different amounts of time, it is extremely 

important to begin the different operations at the correct 

time so all components of the house are ready to be shipped 

at the same time. Plant GG’s bottleneck was production 

throughput at the older Weinmann machine, which (among 

other functions), nailed furring strips to the roof element 

rafters. 

Presently Plant GG uses two computer programs. AutoCad 

is used to do the floor plan, and SEMA draws each wall as a 

component and then writes the machine language for framing and panel stations. Within the next year, they hope to 

eliminate the AutoCad and only use SEMA. An additional 

computer program was used to schedule production for line 

balancing. Our contact stated that this scheduling program 

was not necessary for a company as small as Plant GG.

From 1980–1996, Plant GG produced walls based on standard elements (such as is done by Plant GD today). Today 

Figure GF9. Roof table using pneumatic jigs to 

place and hold rafters.

Figure GF10. Roof table area.

Figure GF11. Stacked roof sections with insulation.

Technology Assessment of Automation Trends in the Modular Home Industry

43
its Weinmann precutting machine (Figs. GG4, GG5) processes all panels—50,000 sheets per year of gypsum and 

particleboard—one sheet every 40 seconds. This machine 

was built for the furniture industry, and on a 2.5-m long 

panel had 0.5-mm tolerance. It sizes the panels, drills holes 

for outlets and sockets, and drills holes for attaching the 

walls. The Weinmann panel processor also cuts a place for 

metal bracket to hold walls to floor. Plant GG produces three 

wall heights: 2.66 m for housing only; 3.1 m for commercial 

only, and 2.8 m for both. Internal walls are 9 cm thick, external walls are 16.5 cm thick.

Plant equipment requires 100–150 houses per year to justify 

the investment. Our contact repeatedly stated that if you are 

paying for the machine, you need to be able to reduce the 

number of employees in that area of production. 

It took Plant GG three years to reach the takt time (the maximum time per unit allowed to produce a product in order to 

meet demand) promised by Weinmann. Plant GG purchased 

its Weinmann equipment in 2000. In 2001, the takt time was 

50 minutes; today the Bumeck (European equipment no 

longer made) has a takt time of 30 minutes per wall. The 

multifunction bridges now have new staplers that staple 

10 staples per second. Eighty percent of all walls go through 

the Bumeck wall machine. Fifteen percent run through the 

short or gable wall table, and 5% run through the special 

wall area (wet walls included). At the Bumeck, as the first 

stud was inserted, lag bolts were manually inserted into the 

stud for future connection to the adjacent wall. The Bumeck 

machine-sizes studs when a non-standard size stud is needed. The Bumeck can also notch into top and bottom plates 

for electrical connections. We were told the Bumeck can be 

used to make walls with angled corners (second-story wall) 

by making the full wall square and then cutting the corner 

off of the wall (Figs. GG6, GG7). 

Coming out of the Bumeck, the interior of the wall is face 

up; a paper moisture barrier is then laid down (Fig. GG8). 

Precut sheathing is laid on the wall and it then goes through 

the automated stapler (Fig. GG9). Some holes were manually cut in the moisture barrier for attaching the walls.

The old fiberglass-batt insulation weighed 17 kg/m3. New 

insulation made of wood fibers and 5% polyethelene 

weighs 55 kg/m3. The insulated value is the same, but the 

thermal mass of the newer insulation slows heat transfer 

(Fig. GG10). Ecological construction techniques are popular 

in Germany, and this type of product change gives customers an opportunity to use a green product (wood-based 

insulation).

Other Observations

Plant GG is producing 24,000 linear m of wall per year. This 

depends on amount of commercial compared with residential homes. 

•	 Plant GG homes featured continuously circulating hot 

water (through the pipes) so home occupants do not have 

to wait for hot water. No toilets were placed on exterior 

walls; a special wet wall would be used if placement in 

front of external wall was needed.

•	 Seven types of wood were offered in 30 colors of waterbased paint for wood siding. The other siding offered was 

stucco, which has a base of 20-mm-thick polyurethane 

sheeting with mesh reinforcement. Stucco is then applied 

in the factory over the polyurethane/mesh. A one-hour application of stucco in the factory would take four hours on 

site. The exterior walls with stucco finish have a 45 degree angle along its corners (edges); when erected on site 

there should be no more than a 2- to 3-mm gap between 

walls. After siding was attached, the wall transporter 

stood the walls vertically and took the walls from production to wall storage.

•	 The automated machines that produce the windows are 

15 years old. We did not see them.

•	 The windows were installed on vertically hung walls. 

2,500 wood windows are made per year. Plant GG machines a V groove into the drywall to allow it to be folded 

90 degrees around the window case.

•	 Plant GG has 1,000 m of wall storage (GG11), or about 

five houses. The average house fits on four trucks. Doors 

are installed in the house on site.

•	 For commercial buildings, trusses were built in house, 

though our contact classified them as a C product, meaning that they were not built too often.

•	 Its 1996 Weinmann bridge was the prototype (Fig. GG12). 

Our contact recommended never buying the first production unit of equipment. He identified this as the bottleneck. The two tables wait on the multifunction bridge, 

which lays down furring strips and staples or nails the 

strips. 

•	 Plant GG also had a Hundegger K-1 beam processor for 

the roof and floor elements. Our contact stated that with a 

Hundegger machine, you plug in air and electric and it is 

ready to go—the machines have no problem. 

•	 Our contact thought it was important to contract with machine vendors concerning future upgrades of the computer 

hardware and software—hardware may only cost 2,000 

euros but software programs may cost 40,000 euros.

44

General Technical Report FPL–GTR–188
Figure GG1. Model home at Plant GG.

Figure GG 2. Kitchen area highlights wood 

paneling in this prefab house.

Figure GG3. Beech stairways were typically 

found in German prefab model homes.

Figure GG4. Weinmann panel processor cuts 

gypsum and particleboard panels.

Figure GG5. Weinmann panel processor cuts 150 

thousand sheets per year.

Figure GG6. The Burmeck wall machine area. 

Note infeed staging area on right.

Technology Assessment of Automation Trends in the Modular Home Industry

45
Figure GG7. Burmeck wall machine requires many 

manual actions.

Figure GG8. Paper moisture barrier placed on wall 

panel section.

Figure GG9. Automated stapler is used to fasten 

moisture barrier.

Figure GG10. New wood-based (5% polyethelene) 

insulation.

Figure GG11. Wall section 

hung vertically: Note cut out 

areas used to connect adjacent walls at building site.

Figure GG12. Older model Weinmann multifunction bridge lays and nails furring strips.

46

General Technical Report FPL–GTR–188
Plant GH

Contact: Manager

June 23, 2005

Plant GH is a large conglomerate with operations in Germany, Romania, Czech Republic, Croatia, England, France, 

and Spain. They own and operate sawmills, dry kilns, laminated beam plants, and window and door plants (many of 

these millwork products with their sister company). The 

entire Corporation had gross sales of 400 million euros. The 

company started 37 years ago with two men and now has a 

total of 3,600 employees.

Processes

This plant manufactures laminated beams up to 215 m 

long (Fig. GH1). This includes grading and trimming the 

lumber, fingerjointing, laminating, and surfacing. The large 

laminated beams are mostly used for commercial buildings. 

They also make stables, barns, homes, and offices. We were 

told that this laminated beam plant manufactures 60,000 m3

of wood per year. The planer used on the large laminated 

beams had an infeed table that was 2.50 m wide. 

Floor area: After seeing many other things, we got to the 

house factory. We started with the middle floor construction. 

In this area, they had two Hundegger beam processors. The 

older one was a prototype and dates to 1973. The newer one 

was used for floors and roofs (Fig. GH2). Data for the home 

are electronically sent to the Hundegger beam processor. 

The operator only selects the program and runs it. Butterfly 

tables were used and the ceiling was worked on first. On 

cheap floors that use particleboard for sheathing, drywall is 

installed on site and not in the factory, most likely for wiring. Special noise protection (low-density fiberboard) was 

sheathed on floors. Some roof elements are cut here. Special 

roofs are assembled at building site.

Roof and ceiling area (Figs. GH3 and GH4). Ceiling 

boards were painted/stained one of four standard colors by 

a machine in this area. Special colors require hand painting 

unless very large. There is a butterfly table in this area to 

allow fastening of external and internal strips, sheathing, or 

paneling. 

It takes two or three hours to erect the roof during the one 

day it takes to waterproof the house. The roof is lag-bolted 

in from the top onto the walls. When the plant releases a 

blueprint for a job, everyone involved in the job (factory 

manufacturers and construction crew) gets the same one. 

This single blueprint covers all aspects of the floor plan/job, 

from manufacturing specifications to special instructions for 

installation. By having one single blueprint, Plant GH prevents confusion when discussing the plans. 

Plant GH still manufactures roof trusses, which started early 

in Plant GH history. Trusses are now a small part of the 

business: offices, stables, supermarkets, and inexpensive 

houses. As a picture shows, the equipment used for building 

the trusses was very simple and outdated (Fig. GH5).

Wall fabrication area. Most toilets are constructed in a 

separate wet wall that will be placed in front of the regular 

wall (Fig. GH6). These toilet walls have a drywall and particleboard panel that will need to be removed to connect the 

installed plumbing. On those sections of particleboard and 

drywall that need to be removed for connection of plumbing, we have often seen the drywall and particleboard held 

in place with a few screws. 

Lag screws are built into the connecting walls for easy connection in the field during construction. These lag screws 

are pre-inserted as the wall is being framed and reached 

via a pre-cut access hole in the drywall and particleboard 

(Fig. GH7). These screws have grease on the tip to assist in 

threading into the adjacent wall section. Our contact said 

that a special wrench is used to turn these screws easily. The 

normal wall construction is with 140-mm-thick studs and 

40 mm of foam. Plant GH has the ability to manufacture using 200-mm-thick studs and 100-mm-thick foam. Maximum 

wall height is 3.13 m. Shipping length restrictions limit 

them to 12.5 m (Fig. GH8). Electrical conduit is run in the 

factory and wire is installed at the building site. The window 

shade pocket is installed from the interior. 

At the framing station, two sets of butterfly tables were 

used. A cut-off saw located in the mezzanine cut studs to 

length and the operator marked top and bottom plates from 

the plan, according to what the carpenters below should 

do (Figs. GH9 and GH10). Note that this operator marked 

studs, headers, and bottom plates, and he worked on an elevated platform, sending the cut wood down to the butterfly 

assembly table (Fig. GH11).

The operator used special markings to illustrate where cut 

studs were to be placed and affixed. By using these universal signs/markings, building workers did not need to look at 

a floor plan to locate the studs in the wall during assembly. 

The walls are numbered according to the order of erection at 

the site. Two men are needed to retrieve the studs and plates 

from the overhead rack. These men also staple the particleboard onto the frame, and cover it with breathable moisture 

barrier (Fig. GH12). Particleboard and drywall stock are 

manually cut to size on a table saw that electronically adjusts cutting width according to information entered by the 

operator. The wall is then flipped with the butterfly table, 

and at least two (maybe three) people attach the moisture 

barrier and staple drywall to this side of the frame.

At the time of our visit, Plant GH was working on 87 houses 

for the 2006 Olympic Games in Turin, Italy. We were told 

that Plant GH manufacturers 900 houses per year at four different factory locations. The factory we visited was said to 

manufacture approximately 350 houses per year.

Technology Assessment of Automation Trends in the Modular Home Industry

47
Figure GH1. Laminated beams in process at Plant 

GH.

Figure GH6. Wet wall used 

for toilet contains installed 

plumbing.

Figure GH2. Newer Hundegger beam processor 

used for floor and roof components.

Figure GH3. Ceiling being constructed.

Figure GH4. Tables used in the ceiling and roof 

building area.

Figure GH5. Older truss-building equipment.

48

General Technical Report FPL–GTR–188
Figure GH7. Lag screw used to connect wall panels accessed by precut hole.

Figure GH8. Vertical wall hanging area.

Figure GH9. Wall components are cut in upstairs 

mezzanine and carpenters reach for them.

Figure GH10. Sawyer marks component placement 

on bottom plate.

Figure GH11. Butterfly table 

flips wall section after one 

side is sheathed.

Figure GH12. Other side of wall panel has moisture barrier and sheathing attached.

Technology Assessment of Automation Trends in the Modular Home Industry

49
Plant GI

Contact: Project Engineer

We were not allowed to take photographs, but were given 

Weinmann (equipment company) videos that have scenes 

filmed in this plant. 

June 24, 2005

Plant GI is part of a very large corporation. Portions of the 

factory were built in 1997, and the equipment is six years 

old. According to our contact, the factory is “the most modern production plant of Europe,” which is approximately 

17,000 m2 (183,000 ft2 or 4.2 acres). The equipment consists 

of computer-controlled production lines whose machines 

were developed particularly for Plant G-I, and that are 

served also with in-house software. The initial investment 

(in 1999) was 24 million Deutschmarks or approximately 

12 million euros. We noted that the large factory floor expanse was lit by skylights and that no electric lights were 

turned on at the time of visit. Our guide said that lights are 

turned on during the winter months whenever there is not 

enough natural light.

The equipment reportedly is capable of producing 

1,000 houses per year on a single shift, and at one time 

the factory was producing 2,000 houses per year with two 

shifts. Currently, however, the factory only produces about 

300 homes per year because of poor market and management conditions. Factory lay out and equipment seemed logical, but we wondered about making such a large investment 

only to have the market drop. Our guide suggested that Plant 

G-I has many problems, mostly managerial, and the company has changed hands at least once, in addition to having 

marketing problems. Our guide stated that factory operation 

has not been a problem. Some of the systems originally designed into the building are no longer being used, however. 

For example, there was an elaborate insulation delivery system that transported insulation all around the factory. This 

insulation delivery system was no longer in use, as it caused 

too much dust in the factory. Insulation is now manually 

delivered to the stations needing it.

Processes

Plant GI had six different process stations: beam cutting, 

panel cutting, framing station, framing completion, moisture 

barrier, drywall table, and multifunction bridge 

1.Beam cutting. Two Hundegger systems process beams. 

One Hundegger is used for roof and ceiling beams and is 

fed manually. Outfeed, however, is by conveyor and automatic lift. The conveyor then transported the sized beams 

through a sander or planer. The other Hundegger is used 

to process wall beams and is fed beams with a screw lift 

from 18 bays. Processed beams are passed downstream by 

conveyor. The one Hundegger that we could view could 

saw angled cuts (end of roof beams, for example), angle 

horizontal notches, vertical notches, small drill, and large 

drill. Although the Hundegger wall beam processor had 

the capability to perform all the above functions, the wall 

beams were processed again (by a separate notcher) as 

they were about to enter the wall framing station. 

2. Panel processing. Two Eima CNC MultiCenter 54s (EiMa 

Maschinenbau GmbH, Frickenhausen, Germany) are fed 

sheet stock (OSB or drywall) from five lines of raw materials via vacuum lift and chains. The outfeed product is 

conveyed to a vacuum lift pick-up point that moves the 

cut panel to an elevated (above the floor about 30 feet) 

conveyor which carries it to one of four storage tray bins 

(buffers). These four storage bins were arranged according to what type of wall they served. The two storage bins 

on the right were for wall sections and the two bins on the 

left were for gable ends. For both bin groups (walls and 

gable ends) one bin was for the first side of the wall, the 

other bin for the second side of the wall. 

3. Framing station. This wall-framing station required one 

man to operate. The top and bottom wall plates were automatically placed, and studs were automatically placed 

and nailed to the top and bottom plates. Plates were also 

notched here, though we do not understand the difference 

between notching here and at the Hundegger initially 

used in beam sizing/cutting. The wall-framing station 

also had the capability to size studs (cut to length). We 

did not understand why this would need to be done at the 

wall-framing station. While we watched, we witnessed a 

problem with a stud being fed. It hung up in the lugs and 

the operator had to climb up to wrestle it free. The operator then manually placed the stud in the wall machine, and 

over-rode the machine so it would nail the stud. The machine then carried out the next stud placement (the empty 

lug) while the operator waited. Studs were stored in an 

elevated mezzanine and were retrieved automatically by a 

robot clamp feeder that placed the pieces onto a lug ladder 

that carried the stud down to placement and nailing area. 

We noted that the operation of the framing station seemed 

slower than what he had witnessed in the video. The elevated mezzanine (as previously mentioned for stud storage) was also the area where window and door modules 

were assembled and placed into a buffering rack. We did 

not see one of the door or window modules being placed/

positioned into the wall. 

4. Framing completion. Shorter pieces (bracing, etc.) are 

added manually using a mallet and nail gun.

5. Moisture barrier. An auto-roller was used to lay down the 

plastic sheeting, but it was manually stapled (though the 

promotional video from Weinmann showed it done automatically).

6. Sheathing and drywall table with multifunction bridge. 

Pre-cut drywall is placed by the multifunction bridge and 

then nailed into place. While we were watching the placement and nailing of sheathing onto the wall frame, we saw 

one of the operators disconnect the trigger on the nail gun 

50

General Technical Report FPL–GTR–188
of the multifunction bridge and use a manual nail gun to 

nail the sheathing to the framing. After one side of a wall 

panel was sheathed, the butterfly table would flip the wall 

panel.

The following schematic shows the flow and function between the different tables in this area of wall construction. 

STORAGE

↓

roller

↓

MFB—DRYWALL

↓

butterfly

↓

INSULATION

↓

roller

↓

INSULATION

↓

roller

↓

MFB

↓

roller

↓

VERTICAL STORAGE

A roof line and a ceiling line were downstream from the 

Hundegger, which was cutting roof and ceiling beams. On 

the roof table there were stops to guide beam placement, 

and the cross beams were manually stapled or nailed. On the 

ceiling line, lathe was nailed by the MFB, which also used 

a saw to trim the drywall and make cut-outs. The roof and 

ceiling lines contained the exact same machinery. 

Plant GI uses two trailers per house, one for the walls and 

one for roof and ceiling.

Plant GJ

Contact: Project Engineer

No photographs were allowed.

June 24, 2005

We visited Plant GJ with our guide after visiting the Plant 

GI factory. Unfortunately, we arrived at Plant GJ after production had ended for the day. Our tour was given, but we 

were only allowed to see the Weinmann manufacturing line. 

Our guide could tell us very little about the manufacturing 

process; essentially we looked at a large line of Weinmann 

machinery that was idle.

The Weinmann line was in a U shape with the panels started 

at one end of the U and was totally finished at the other end. 

A total of seven wall panel tables comprised the manufacturing line; two Weinmann multifunction bridges were on 

the manufacturing line. The two multifunction bridges were 

capable of traveling down the arms of the U. Workers could 

use vacuum-assisted lifts while placing sheathing on the 

wall frame. 

The manufacturing line produced “multi-walls;” these wall 

sections are essentially multiple smaller walls built together 

as one and then separated (cut apart) at the end of the manufacturing process.

On table 1 the wall was framed and windows and doors 

were installed. These windows and doors were already 

framed in, making window and door modules. This method 

had also been seen at Plant GI. Insulation was inserted at 

table 4, the table at the top of the U between the two U 

arms. Table 4 was a part of a butterfly table that flipped the 

wall sections. 

We were told that Plant GJ manufacturers 200 houses per 

year, there are 200 employees at Plant GJ, and seven operators are needed for the Weinmann manufacturing line.

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