RESOURCE EFFICIENT WOOD FRAMING TECHNOLOGY FROM JAPAN

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1 RESOURCE EFFICIENT WOOD FRAMING TECHNOLOGY FROM JAPAN James Scott BREW 1 1 LHB, Inc., 21 West Superior St., Suite 500, Duluth, MN, 55802, USA, james.brew@lhbcorp.com AIA, FCSI, CCS, CCCA, LEED Accredited Professional Keywords: efficient, digital, house, wood, frame, connector, sustainable, structure Summary While worldwide wood fiber is abundant, large diameter, older growth timber is not. Resource efficient use of wood fiber continues to be one of the primary timber management issues today. Innovations in wood framing systems have been developed to help address the efficient use of timber. As the world population becomes older, the loss of skilled labor has been realized by many labor organizations and builders. Systems building techniques continue to grow in popularity due to the aging workforce and shifts in career choices. This paper will explore both past and present methods of wood frame systems-building techniques and introduce a resource efficient, digital house, structural wood framing technology which demonstrates reduced wood fiber usage, zero-waste on-site, decreased labor needs, improved durability and design flexibility. The merging of technology with efficient resource material use is logical and necessary for advancement of the design and construction processes. Continued development that optimizes manufacturing, labor and energy efficiencies will improve these types of structural technologies. 1. Wood Framing Background Worldwide, wood is used for a significant percentage of all housing as well as numerous support buildings and light-commercial structures. Wood has also proven to be a renewable and sustainable resource when properly grown, managed, and harvested. While new framing techniques have been introduced, few have grasped the larger issue of simple, affordable and adaptable techniques that can fundamentally change the approach to construction labor and affordability. Some of the housing technology advancements have had limited impact on affordability and ease of use. Nearly all systems-built techniques have contributed to the reduced numbers of labor intensive, hand-framed, site-cut framing and have reduced on-site waste. Japan has demonstrated leadership in the world with some of the most advanced, automated and industrialized approaches to housing. Digital House systems which can be manufactured in one day and constructed in one to three days, by low skilled labor, are available and manufactured with a high degree of automation. These systems promise to be the next generation home building as they offer advantages for the consumer, builder and the environment. 2. Wood Framed Housing 2.1 Methods The methods of constructing a wood framed home vary from site built (custom) homes to 100% factory built manufactured and modular homes. Housing that includes almost any amount of factory-built elements such as engineered floor/roof trusses or walls, is considered to employ or utilize system-built housing techniques. This paper does not include review of HUD code manufactured housing (mobile homes). Between 1908 and 1940, Sears Company sold over 75,000 precut, numbered kit houses through their popular catalog. Other companies came and went with similar offerings, many were designed by famous architects such as Frank Lloyd Wright, LeCorbusier among others. The depression, World War II and federal legislation changes eventually ended an industry set up to increase homeownership rates

2 Today, worldwide factory-built housing dominates total new housing supply in countries such as Japan and Sweden. Switzerland Australia and the UK are also gaining in the number of units which are factory-built in whole or in part. Factory-built housing in the US is nearly 20% of all starts (excluding HUD). 2.2 Stick-Framed Stick framing refers to hand framing or site-built applications of framing. stick-built housing accounted for 69% of US conventional housing starts in 2001, down from 80% in The shortage of skilled labor and trades people (carpenters, framers, bricklayers, electricians) are forcing builders to look for alternative solutions. 2.3 Structural Insulated Panels (SIP) Structural Insulated Panels (SIP s) are typically rigid polystyrene foam insulation sandwiched between two single layers of oriented strand board (OSB) or plywood, to form large (2.4 x 7.3 meters) wall, roof or floor panels. These panels are precut with window, door and roof openings and shipped to the site for assembly. Assembly on-site typically requires a crane and some skilled labor to properly set and seal panels properly. The popularity of SIP s has grown rapidly. SIP s promise and often deliver more energy efficient homes and straight walls. Some manufacturers are beginning to employ panel cutting with Computer Aided Design (CAD) and Computer Aided Manufacturing (CAM) techniques to improve efficiencies and accuracy in manufacturing. 2.4 Panelization Panelized housing is most commonly represented by off site framing of wall and floor assemblies which are then hauled to the site and set using a crane. This technique is the fastest growing technique in the US today. While typically costing 5-10% more than stick frame, labor and speed of enclosure are most commonly cited reasons for employing this method by builders. This method has great potential for further automation beyond panel nailing. 2.5 Modular Homes While modular home starts dropped in 2001, they are expected to increase gradually as more people seek affordable homes and manufacturers diversify their offering styles and types. Manufacturer s who are providing designer units, featuring steeply pitched roofs and neo-traditional neighborhood design elements, such as porches and detached garages, are gaining the attention of the mid-range buyers. 3. The Digital House 3.1 Digital Housing of Today It is possible in Japan today to , fax or otherwise send a plan to a housing system provider, receive an estimate the same day, place an order for your custom house, and have it delivered the same week. This same technology is now available in the US although turnaround from order to delivery is about 4 weeks at present. The materials you would receive includes the entire framing and enclosure package including roof framing and decking and exterior insulted panels, similar to SIP s. Perhaps more amazing than the manufacturing itself, is the assembly process. Using numbered pieces of lumber and unique metal connectors, frames can be assembled quickly and accurately with low-skilled labor. Precut, numbered wall panels are also placed and secured easily. Some houses have been enclosed in as little as one day, though most require two or three days time. Figure 1 Computer (CAD) image showing entire frame and wall panels in 3-D.

3 3.2 Framing and Enclosure Process Once a design is furnished, it is entered into a computer using a unique CAD program designed to speak to the manufacturing (precut) machines. A design file or plan is ed to one of 6 or 7 precut plants, depending on which plant is nearest the proposed construction site. Figure 2 CAD generated Shop Drawing for quality control and field assembly use. The manufacturing begins with standard engineered lumber, glued laminated members (glulams) or laminated strand lumber (LSL). Some types of engineered lumber can be made from fast growing species or low value species, such as aspen and poplar. These members are selected for lengths required by the CAD program and layed up in the sequence needed for precut. Plants are usually operated by two or three plant workers. Once lumber is sequenced, the machines are started and a single family home can be cut in a matter of 4-6 hours, depending on complexity. Precut plant waste is very limited, often amounting to less than 0.5% of the volume of lumber cut each day. During the precut operations, each piece is automatically marked with a unique number to correspond to assembly (site) drawings. After a quality control review, the entire house frame is packaged for shipping. Wall panels are created in a separate plant, in a less automated environment, set up to correspond with delivery of the framing. Figure 3 Glued laminated lumber (glulams). Figure 4 Computer Aided Manufacturing (CAM) precut plant. After a concrete slab, foundation or floor cap is ready to receive the home, the framing materials and panels arrive on the site numbered and ready to assemble. Typically a project leader is in charge of directing workers to tasks such as retrieving framing members for assembly, placing connectors in precut slots and holes (prior to lifting) and placing wall studs.

4 A typical project might have 4-8 workers, most of whom need no prior experience, except a project leader or director. Sill sections are set first, leveled and secured using conventional techniques (anchor bolts, hold down straps, etc.). Next, post to sill connectors are placed in sills and principal posts are placed in designated locations. Principal posts are those which connect at the top with a connector to a beam. Once principal posts are set, beams which span between or over these posts are lifted, sometimes with the assistance of a crane for large spans, and drift pins are placed to secure the beams in place. Figure 5 Placing the sill to post connector. Once principal post and beams are set, infill studs which are precut and can be slid into place in notched sill and beam locations. These are then toe-nailed for attachment. This process is best accomplished with one person placing studs and another nailing. All framing for window and door openings is also precut and placed using notched guidance for locating placement. Figure 6 Placing in-fill stud framing. Figure 7 Connection of post & beam.

5 While upper level framing is continuing, wall panels may be placed until all framing is complete. After verifying that the structure is plumb, wall panels may be fastened. Figure 8 Precut insulated wall panels. 3.3 Mechanicals, Design and Waste Upon completion of wall panel installation, a house is ready for installation of windows, additional insulation, if any, wiring, mechanicals, roofing and siding. Many of these items can be performed simultaneously. The general framing and enclosure process is often less than three days but has been as little as one day on many smaller projects. Mechanical and electrical systems are installed in the same fashion as conventional framing allows. Due to manufacturing tolerances and tight connections, frames are typically very square and plumb, requiring less or no additional furring, compound mitering of trim or scribing of cabinets to walls. Figure 9 A two story traditional neighborhood home. Completed homes may be done in almost any design style. Some homes and restaurants have been completed using an exposed frame to appear more like a timber frame style. Figure 10 A country home in Minnesota.

6 Figure 11 Stick-framed project waste (left) compared to precut project (right). Onsite project waste can be reduced to zero since all cutting of every component is performed off-site. This saves not only wood, but also labor, hauling and waste services costs. Figure 12 Post to beam connection. 3.4 Digital Housing of Tomorrow It is very likely that more integration, both in modular units and in precut systems, will drive the future of systems-built housing. Pre-plumbed and wired units are being tested and prototyped every month now, in several countries. Emphasis on reduced site labor and costs will continue while demand for higher quality, durable and healthy housing will grow. As more manufactured home suppliers consult with traditional builders and designers, a new version of the mobile home could evolve into a modular sectional system that is set up for plug and play operations. References Woodbridge Associates, Inc, 2003, How significant are factory built technologies?, Marketing Opportunities in Factory Built Housing, pp. 99. MasterFit System, MF Technologies, Inc., 2005, MetalFit Company, Ltd., 2005,