From volume purchasing through quality control of the materials to precision construction and timely delivery, panelized housing results in a good reputation for the builder and a fine structure for the homeowner.

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Manufacturing & Transportation Considerations of the Panelized Building Systems Alternative

Abstract

Two important considerations when choosing a method of panelized building systems are manufacturing and delivery. Each phase represents the efforts of many individuals over the years who have committed themselves to create methods and means to make and transport components to building sites. The following paper has the following objectives: 1) to present an historical perspective of prefabricated housing, 2) Review the manufacturing process, 3) review the delivery process and 4) explore the cost effectiveness of panelization. This paper by no means is meant to be an exhaustive report but merely and overview of the general processes involved in manufacturing both open and closed wall panels and their delivery.

Introduction

Prefabricated housing, or we could call it "prefabs" have been with us since man moved from cave dwelling to a nomadic existence, a life in tents. Since that time tent cities have sprung up all over the world, most notably, in American Indian villages but also during many wars and more recently to house refugees in various parts of the world. Over time these semi-permanent dwellings gave way to more permanent structures. During the great age of exploration the need was for shelter once the explorers left the relative safety and comfort of their ships. During the last years of the reign of Queen Elizabeth of England there was an expedition led by Sir Martin Frobisher. Sir Martin took with him "knocked down" wooden housing for shelter. Unfortunately damage in transit caused the buildings to be unable to be constructed on site. Prefabricated housing hit the shores of America in 1573 and has not stopped being improved on since that time. It seems that not every colony employed Sir Martin's novel approach to dwellings. However, many f the colonies could have benefitted greatly from the quick erection and the reduced labor force required for construction. During the 18th century buildings were cut and put together in one location and then shipped to be erected in another location.

This was an accepted practice, especially when it came to colonization of frontiers. During the California Gold Rush of 1849 the need for housing was enormous in California. The entire world saw a market opportunity and met it, however short-lived. Five thousand units were shipped from New York, with other units arriving from England, France, Germany, Belgium, China, New Zealand and even as far away as Tasmania. Many of these structures were of cast or corrugated iron, the precursor of the World War II Quonset huts. At the beginning of the 20th century two types of housing were introduced into the commercial arena via catalogue and through the mail-order system: they were the panelized house and the pre-cut house. "Panelized buildings invariably were of very lightweight construction, with studs of two-inch-square or two-by-three-inch dimension, preassembled into sections of walls, roofs, partitions, and floors. Wall sections were three to six feet wide and one story high. They were assembled on site into buildings and fastened together usually by patented bolting systems; neither saws nor hammer and nails supposedly were needed, nor did the projects require much skill and time." 1 "Pre-cut houses, on the other hand, were completely full dimensioned balloon type, with most or all of the boards precut at the factory for assembly on site with hammer and nails. Savings resulted from minimal on-site labor to saw boards, compared with conventional balloon-frame construction in materials, where the lumber dealer/distributor was cut out and mass-production cutting efficiencies could be achieved; and in mass-merchandised plans, where no architectural fees applied to individual homes." 2 There were six large suppliers of pre-cut housing during this time and they were: Gordon-Van Tine, Alladin, Sears, Ward [Montgomery Ward & Co.], J Lewis/Liberty and Sterling Homes. Obviously there is a great more detail that can be explored concerning these six major operations. Sufficient for our discussion is the fact that manufactured housing is certainly not a new concept. Its inception goes as far back as the need for quick, efficient, quality dwellings. Since the colonization of America to the present, men of vision have continually sought for a better way to house the ever growing population. Pre-cut or prefabricated structures have sought to answer that need in the most systematic and efficient means possible.

Materials

Prefabricating two dimensional wall sections [open or closed] and other materials for home construction requires a facility wherein raw materials can be turned into "finished" product. "Finished product" may not be an absolutely accurate term, however, the implication is that the product is ready for easy installation on site once it has finished its fabrication stage. Due to the nature of large scale fabrication it follows that a large quantity of materials are required to achieve maximum production capabilities. The need for large volume purchasing of lumber, sheet goods, nails and other goods required for building translates into cost effective purchasing. This low cost purchasing then translates into a more cost efficient product for the builder and ultimately the consumer. Material back-up is no longer a problem in factory settings as it may well be on the jobsite when building is done conventionally. In a production environment materials must be strictly quality controlled. For production to occur smoothly and in the most time-efficient manner materials must go through a quality control check prior to on-line installation. The "culling" process [quality control check] ensures that only the top grade materials are used when fabricating structural components. The "cull" pile then becomes a resource to be recycled for other smaller items which need to be fabricated, i.e., a warped, twisted or otherwise useless stud not suitable for wall framing may be cut for cripple studs, bridging, fire blocking and many other uses. Coordination of materials on a conventional jobsite may be very difficult at times. However, in a production shop environment the materials are easily staged for proper use at the proper time. Controlling inventory can be very difficult on the conventional jobsite. Theft, waste and/or damage may account for as much as a 10% overage, which translates into dollars wasted on non-productive activity. Not only does the material have to be replaced but there is time expended to re-order and coordinate replacement material deliveries and return crews for installation. These extras in a job can eradicate cost effectiveness. In the manufacturing process material usage is maximized. Waste, theft and damage no longer pose a threat to jobsite efficiency. Single sourcing of a product can be the most effective means a builder has of reducing his cost overruns from the start to the finish of his job.

Manufacturing

Henry Ford believed, and rightly so, that the end-user could purchase a quality product and that the product could be made on an assembly line. An assembly line allowed for the same process to be done repeatedly and in so doing create a”perfecting" of that process because of repetition. The end result is a superior product manufactured the same way every time. This principle has been translated into the housing field quite successfully. Manufactured housing has made great strides since World War II and has been in part responsible for the United States of America being the envy of the entire world in the area of housing. Manufacturing allows for a large quantity of units to be produced in a small period of time. One of the main reasons for such great productivity is due in part to a "controlled environment". A "controlled environment" is simply a workplace that is not subject to the elements. Without having to contend with the variations in weather, production can continue uninterrupted. Unlike conventional building where weather can be a retardant, the elements do not come into play in a manufacturing environment. This allows for a concentration in the field of erecting a finished product rather than component layout and building followed by erecting.

Controlled environment is only part of the equation. Controlled computerized engineering along with controlled set-up and construction form the other two parts of the formula. Because most facilities are computerized in their engineering, waste factors and layout have been reduced to a science. The computer produces cut sheets and parts lists which enable the set-up of the lines for maximum production. Once the paperwork has been done then the assemblers put together sub-assemblies ready to drop in place at the appropriate time in the assembly process. With special machinery or "jigs" the material is placed on the assembly line ready for precision construction. All of the material is firmly held in place by hydraulics until all pieces are firmly attached one to another plumb and square. Each time the nail guns or staplers fire the pattern is always constant and code approved. This type of uniformity of construction also saves later on in the inspection process and the possible rejecting of conventional field assembly for divergences from the standard codes. Within the panelized grouping of manufacturers there are two sub-groups, they are: open wall and closed wall construction. The open wall system comes with the exterior sheathing applied in the factory to the stud wall and totally open interior wall partitions. Insulation, wiring, plumbing and drywall all take place in the field by qualified subcontractors. In the closed wall system the entire wall is made complete, interior finishes in place, such that the only field work to be done is attaching each section with the next and making the appropriate, electrical and plumbing connections. Each system has its own merits and requires different levels of competence in the field.

Delivery

Different manufacturer's have different means of transporting their finished goods to the jobsite. Many panelizers use a flat bed trailer method for delivery, however, even in this means of delivery there exist differences. Some trailers have their own cranes which lift the panels to the site and/or assist in the erecting phase. Others simply off-load the panels on the jobsite. Another method of delivery is an open top box trailer where the panels are shipped in an upright position. These methods can allow for a pre-installation of windows into the panels. Delivery of materials to the jobsite is a well coordinated procedure. Many panelizers offer an erecting service as part of their service to the customer. If this is the case then the erector times his deliveries such that the crew is always working and as soon as they need more material it is delivered. If a builder wishes to use his own crew to erect then the coordination takes place between a dispatcher and the builder designated representative. Depending on the manufacturer the deliveries may require immediate offloading, off-loading with-in the day or off-loading at the pace required by the builder with the trailer staying on site till all materials have been erected and/or off-loaded. Most panels are built such that two men can move them from place to place; however in structures of two or three story height it may be advantageous depending on the terrain to utilize a crane for erecting.

Summary

"Prefab" housing has been a method of construction that began when man first needed quality portable shelter and has since grown to be a means of providing quality housing worldwide. Manufacturing and delivery are two critical phases in the building process. It is clearly seen that manufactured components offer a more cost effective, time effective and labor effective method of construction. From the design through manufacturing all the way to delivery, the panelized home reduces the risk that the builder faces when building a home. The cost effective nature of manufacturing helps the builder to be more competitive and at the same time more profitable. Never sacrificed during the entire process is quality. From volume purchasing through quality control of the materials to precision construction and timely delivery, panelized housing results in a good reputation for the builder and a fine structure for the homeowner.


1 Robert Schweitzer and Michael W.R Davis, America'sFavorite Homes (Detroit, Michigan: Wayne State University Press, 1990) p.63
2
Ibid. p.63

References

Robert Schweitzer and Michael W.R. Davis. America's Favorite Homes, 1990, Wayne State University Press, Detroit, Michigan 48202 Hallahan Associates, "Factory Built Housing in the 1990's". 1990, Building Systems Council NAHB, 15th & M Streets, N.W., Washington, D.C. 20005 Eskow, Dennis "Special Section - Factory-Built Housing" Popular Mechanics, ,July, J 991, pp. 57-77

 

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