Designing Sustainable, Prefabricated Wood Buildings
CONTINUING EDUCATIONDESIGNING SUSTAINABLE,PREFABRICATED WOOD BUILDINGSPresented by:LEARNING OBJECTIVES1. Demonstrate why prefabrication is an efficientand sustainable building practice2. Evaluate the use of wood components in sustainableprefabricated buildings as well as design andengineering challenges that wood can solve3. Discuss the advantages of building withprefabricated wood components in terms of speedand efficiency of construction, design flexibility,waste reduction, environmental performance andimproved life safety4. Analyze, through case studies, the differentstages of wood building prefabrication fromdesign to installationCONTINUING EDUCATIONAIA CREDIT: 1 LU/HSWGBCI CREDIT: 1 CE HOURAIA COURSE NUMBER: AR072018-3GBCI COURSE NUMBER: 0920016493Use the learning objectives above to focus yourstudy as you read this article. To earn credit andobtain a certificate of completion, visithttp://go.hw.net/AR072018-3 and complete thequiz for free as you read this article. If you arenew to Hanley Wood University, create a freelearner account; returning users log in as usual.Image courtesy of Lawrence AndersonPREFABRICATION THEN AND NOWPrefabricated wood buildings should beconsidered when designing and building bothmulti-family and commercial buildings, suchas multi-family housing, education, retail,healthcare and institutional buildings, asprefabrication is an efficient and sustainablebuilding practice. Prefabricated woodcomponents used in both light wood frameand mass timber construction can help tosolve many design and engineering challengessuch as material and process efficiency,environmental performance and life safety.The practice of prefabricating building elementsin a factory was adopted in the United Statesonly in the past century. Prior to that, mostbuildings were constructed on-site. There wasa boom in kit-of-parts building post-WorldWar II. Consumers were enthralled withindustrial production and replication, aka massproduction, and prefabricated buildings helpedfulfill the need for affordable, quality housingpost-war. Although mass production hasremained vital to our economy and almost allindustries, interest in prefabricated buildings felloff in the 1970s. The design and constructionindustry did not fully embrace the conceptbecause it wasn’t well integrated into theirtraditional business model.The building industry is now embracingdigital tools such as 3D modeling, buildinginformation modeling (BIM) and computernumeric control (CNC) machines, makingprefabrication and communication amongstbuilding professionals easier. As JamesTERMSOff-Site Manufacture (OSM)Off-site manufacture is the manufacture ofconstruction components or systems in a factoryenvironment to be transported and assembledon-site.Prefabricated (Pre-Fab Construction)Prefabrication can cover off-site prefabricationof materials and parts, prefabrication ofcomponents and subassemblies as well asvolumetric units or modules.Modular ConstructionModularization of construction is a way to reducecomplexity but still offer customized solutions.The Modular Building Institute defines modularconstruction as an off-site process performed in afactory setting, yielding three-dimensional modulesthat are transported and assembled at the building’sfinal location.
CONTINUING EDUCATIONThe building industry is now embracing digital tools such as 3D modeling, building information modelingand computer numeric control machines, making prefabrication and communication amongst buildingprofessionals easier.Timberlake, FAIA, says in the foreword of RyanSmith’s book, Prefab Architecture: A Guideto Modular Design and Construction, “Weare now capable of sending a fully visualized,and virtually formed, model to a productionline, bypassing the document interpretationphase, with all of its back and forth checking,redrawing and margin for additional errorsand omissions, ultimately improving thequality of the final product.” Also, improvedsafety measures and greater productivity arenow high priorities, which prefabricationcan help achieve. The off-site constructionenvironment is a way to provide workerswith safer working conditions to reduce therisks of accidents and related liabilities.An increase in productivity is especially importantbecause of the high demand for, but short supplyof, skilled labor in the construction industry.Some believe that standardizing and automatingconstruction in a factory setting deskills thetraditional trades. In reality, it upskills the industryand prepares the trades to efficiently deliverbuildings through technologically advanceddesign, fabrication, logistics and assembly.“We think the recession actually benefited ourindustry,” says Thomas Hardiman, ExecutiveDirector of the Modular Building Institute.“During the last recession, many skilled laborersleft the construction industry and did not return.That, coupled with developers needing to findgreater efficiency, made prefabricated buildingsmore appealing. The construction industry is veryreluctant to change. When things were goingwell, developers and general contractors may nothave felt the pain or need to change. Now theydo, and there’s no turning back.”In addition, environmental views are changingregarding construction waste, the productWood prefabrication has a multitude of benefits, including process efficiency, a controlled environment, agreater return on investment, material efficiency, reduced waste both on- and off-site and sustainability.supply chain, re-use of building materials andcarbon footprint. Wood buildings, particularlyprefabricated components, can help designersto balance cost objectives, function andenvironmental impact. James Timberlakesays, “Integration modeling, the backbone ofoff-site fabrication and manufacturing, leansthe product supply chain, helps architects andcontractors manage the number of materialsneeded and allows for a positive repurposing ofthe leftover materials. Further, off-site assemblyoffers the promise of disassembly and re-use.”BENEFITS OF WOOD PREFABRICATIONWood prefabrication has a multitude of benefits,including process efficiency, a controlledenvironment, a greater return on investment,material efficiency, reduced waste both on- andoff-site and sustainability. All of these benefitshelp to meet demands from owners, designersand tenants for better buildings. Processefficiency is possible at every stage, from designto fabrication to construction. Detailed planningallows construction processes to be standardizedand streamlined, including constructionefficiency that meets aggressive schedules anddecreases on-site assembly time. Sequencingis improved, as prefabricated components aresorted and loaded onto trucks, minimizingon-site handling. The process is also moreintegrated with better communication amongstparties, which reduces costly change orders.Because prefabricated components are producedin a controlled environment, quality andprecision of components improve, fabricationproductivity increases, safety for tradespeopleimproves and weather is not a factor in slowingdown the construction process. Budgets shouldbe easier to meet because redundancies andwaste in both materials and time are streamlined.Although building components are often moreexpensive up front, the complete installed costis usually less because on-site construction isminimized. Material efficiency results becauseprefabricated components are made off-siteand typically via modeling technologies thatprovide extreme precision. Reduced waste bothon- and off-site minimizes the environmentalimpact of a project, as specific sizes anddimensions of components are determinedin advance and components are made or cutto tight specifications. This also relates to thesustainable nature of prefabrication.According to Ryan Smith, author of PrefabArchitecture: A Guide to Modular Design andConstruction, “The environmental impact ofbuilding requires a quantifiable measurementof impact in total lifecycle from design throughfacilities management. By controlling the meansand methods by which buildings are producedthrough prefab, architects and constructionprofessionals are able to ensure more sustainablematerials and practices for construction as wellas have a greater opportunity to predict futureenergy performance. Prefabrication may beused as a method to revamp the sustainabilityof construction from the perspective of thetotal lifecycle of a facility, especially regardingdemolition or reuse, as the case may be. Thecapacity of prefab to deliver buildings thatrespond to time, change and reuse/recycle maybe its greatest benefit toward total lifecyclesustainability in the future.”We will review several case studies thatdemonstrate these benefits, including anextensive case study to conclude the course thatdetails the process of erecting a prefabricatedbuilding from design to construction.
CONTINUING EDUCATIONCASE STUDY: MOTOAt MOTO the panelized light frame wood wall system created adramatic speed of construction that allowed each level to be framedin about a week and the entire project in less than a month, makingthe project viable for the developer. Architecture: Gensler Photos:Ryan GobutyDenver, ColoradoMOTO is an 82,000-square-foot, Type VA mixeduse, 64-unit apartment building with integratedparking and retail that is located in a Denver areaknown for its rich cultural, artistic and musicalofferings. The four-story light frame wood structureis set over a two-level concrete podium withabove-grade parking. 3,000 square feet of retailare anchored by two tenants that were selectedto work with the theme of the neighborhoodand building. One is an old-time barber shop,and the other is a coffee shop/restaurant thatserves small dishes and drinks in the evening.With Denver becoming a workforce destination,this project addresses the growing desire formore compact housing with shared amenities.Wood was used both as the structural material anda design element that sets the building apart fromits contemporaries. The massing of the wood frameapartment building is what makes it distinctive;each level slides two feet away from the levelbelow, revealing a cedar soffit on the exterior thatcreates a unique experience as one moves aroundthe building. The bathrooms, kitchens and corridorsstack in plan, but the remainder of the apartmentsmove with the two-foot shift, as opposed totraditional apartment stacking with flat verticalfacades. This means the bedrooms on the exteriorwall undulate in and out, with every other unithaving more area than the other.The panelized light frame wood wall system createda dramatic speed of construction that allowedeach level to be framed in about a week and theentire project in less than a month, making thePREFABRICATED WOOD CONSTRUCTIONPrefabricated wood buildings are no longerlimited to single family housing and smallertemporary workspaces but are now beingconstructed for innovative buildings demandedThe massing of the wood frame apartment building is what makesit distinctive; each level slides two feet away from the level below,revealing a cedar soffit on the exterior that creates a uniqueexperience as one moves around the building. Architecture: Gensler Photos: Ryan Gobutyproject viable for the developer. Structural materialsinclude a combination of dimension lumber, I-joistsand laminated veneer lumber (LVL), while woodfinishes include cedar tongue-and-groove soffits, acedar trellis that wraps down the façade and pooldeck railings, pine slab doors in every unit madefrom trees killed by the mountain pine beetle andreclaimed veneer pine at the lobby accent wall. Thepodium is board-form concrete.According to Nick Seglie, architect at Gensler’sDenver office, “One of the major benefits we sawwith wood construction on the apartment levelswas that we utilized a pre-fab wall system. Theybuilt the walls off-site and brought them on-site.That allowed each floor of the residential units tobe framed in about a week. The podium took aboutfour weeks to construct and then an additionalfour weeks until we were framed out, which wasgreat.” Also, “Wood provides a lot of benefits as aconstruction project because it is easy to work with,it’s fast and sometimes less expensive. From a designstandpoint, we like to bring it in projects as a finishmaterial whenever possible to create warmth.”by tenants and owners. Sectors withredundancies, such as multifamily housing (e.g.,condos, student housing and senior housing),education buildings, commercial retail,healthcare and institutional buildings, are morelikely to be built prefabricated.Computer numerical control machining technology is used at theplant to profile wood panels for installation, and sophisticatedconnection systems with a high degree of accuracy and efficiency areincorporated during prefabrication. Image courtesy of StructureCraftWood has many benefits to the buildingindustry, including aesthetics, environmentalperformance, strength and rigidity, lighterweight (compared to concrete) and energyefficiency. In prefabricated buildings, woodis particularly beneficial; it has the structuralsimplicity needed for cost-effective projects anddesign versatility and it can be rapidly installedwith reduced waste.Prefabricated wood wall and floor panels offereasy handling during construction, and a highlevel of prefabrication facilitates rapid projectcompletion. This is a key advantage, especiallyin mid-rise construction from five to 10 stories.Lighter wood panels mean that foundations donot need to be as large and smaller cranes canbe used to lift panels higher. For example, atthe four-story John W. Olver Design Building atthe University of Massachusetts Amherst, four60-foot-tall cross-laminated timber (CLT) panelscomprising one of the building’s shear wallcores were lifted and dropped into place witha crane and anchored to the foundation, all inone weekend.Panelization means framing of dimension lumberor mass timber walls produced with a high degreeof accuracy in a factory. Computer numericalcontrol (CNC) machining technology is used atthe plant to profile wood panels for installation,
CONTINUING EDUCATIONand sophisticated connection systems with a highdegree of accuracy and efficiency are incorporatedduring prefabrication. Panelizing lowers cost andspeeds up the delivery of walls to a site whereframing crews install quickly, when comparedwith on-site framing. The faster and safercontractors and developers can finish a building,even if off-site construction methods are moreexpensive, the greater the return on investment.For light wood frame construction, on-siteframing is still the norm because it continues tomake sense from a quality versus cost perspective,but that is slowly changing. In the future, largerprojects that demand panels be erected quicklyand en masse are more likely to be prefabricatedfor light wood frame construction.QUIZ1. Which of the following is a benefit of wood prefabrication?a. Process efficiencyb. Controlled environmentc. Material efficiencyd. Sustainabilitye. All of the above2. True or False: Sectors with redundancies such as multifamily, education, commercial retail, healthcare and institutionalare more likely to be built prefabricated.3. Which of the following is the most common type of wood construction in North America?a. Cross-laminated timberb. Light wood frame constructionc. Nail-laminated timberd. Dowel-laminated timber4. True or False: Glulam is stronger than steel at comparable weights and stronger and stiffer than dimensionallumber, making the material a cost-effective choice for long, structural spans and tall columns with minimalneed for additional support.5. Which prefabrication approach is typical for mid-rise wood buildings?a. Kit-of-partsb. Finished modules6. True or False: Open structural panels are complete pre-assembled wall panels that may include windows, doors, plumbing,ducting, electrical, finishes, etc. They are larger and heavier, so a crane is typically needed for on-site assembly.7. True or False: Because wood panels are manufactured using CNC equipment to precise tolerances, panel joints fit moretightly, resulting in a high degree of accuracy and better energy efficiency for the structure.8. At Brock Commons, which technology provided a comprehensive 3D model composed of all building elements, fromthe structure to interior finishes to the mechanical and electrical systems?a. Computer numeric control machinesBuilding kits include prefabricated elements or sections that arethen delivered and assembled on-site. The kit-of-parts approach, viapanelization, is typical for mid-rise wood buildings. Image courtesy ofLEVER ArchitectureTYPES OF WOOD PREFABRICATIONThere are two types of industrialized approachesto prefabricated buildings: building kits (kitof-parts) and finished modules. Building kitsinclude prefabricated elements or sections thatare then delivered and assembled on-site. Thesemay include the roofing package (roof panels,fascia, gutter, etc.), roof structure (ceiling deckand beams), glazing package (windows andentrances) and building structure (wall panels,beam pockets, columns and shear paneling). Thekit-of-parts approach, via panelization, is typicalfor mid-rise wood buildings.Within panelization it is helpful to understandthe difference between open structural panelsversus closed structural panels. Open structuralpanels are a pre-assembled wall frameworkthat is later fitted with other elements suchas insulation, exterior cladding and weatherbarriers on-site. While this aids in time savingsand flexibility, there is still a lot of site workinvolved. By contrast, closed structural panelsare complete pre-assembled wall panels thatmay include windows, doors, plumbing,b. Virtual design and construction modelc. Building information modeling9. True or False: At Brock Commons the tolerances for the mass timber components were 2 millimeters, a requirementthat would have been challenging to meet without the use of the VDC model.10. Which of the following was a benefit of prefabrication at Brock Commons?a. Decreased on-site assembly timeb. Improved quality and precision of componentsc. Better safety for tradesd. Reduced wastee. All of the aboveducting, electrical, finishes, etc. Closedstructural panels are larger and heavier, so acrane is typically needed for on-site assembly.Finished modules, on the other hand, arean entire building delivered and assembledon-site. Individual modules are joined togetherto make a single building. They are built ina factory, transported to the site, and whenon-site the modules can be placed side byside, end to end or stacked, allowing a widevariety of configurations and styles in thebuilding layout. Finish levels on modularunits leaving the factory generally includeplumbing, electrical, paint, flooring, fixtures,cabinets and appliances. After the modules arecraned into place, licensed sub-trades makeelectrical, plumbing, mechanical and structuralconnections before finish work is completedand the building is prepped for occupancy.ÄThis article continues onhttp://go.hw.net/AR072018-3. Go onlineto read the rest of the article and completethe corresponding quiz for credit.SPONSOR INFORMATIONThink Wood represents North America’s softwoodlumber industry. We share a passion for woodand the forests it comes from. Our goal is togenerate awareness and understanding of wood’sadvantages in the built environment. Join theThink Wood community to make a differencefor the future. Get the latest research, newsand updates on innovative wood use. VisitThinkWood.com/ceus to learn more and join.
CONTINUING EDUCATIONTYPES OF PREFABRICATED WOODCOMPONENTSPrefabricated wood components may includelight frame walls, floors and roof trusses ormass timber elements such as cross-laminatedtimber (CLT) panels, nail-laminated timber(NLT) panels, dowel-laminated timber (DLT)panels and glue-laminated timber (GLT)columns and beams.Light Wood FrameLight wood frame construction has long beenthe go-to framing choice for low- and mid-riseand, increasingly, commercial buildings.Cost-effectiveness, material use efficiency,ease of assembly, minimal environmentalimpact and the ready availability of labor andmaterials make light wood frame constructionthe most common type of wood constructionin North America. Typical light frame roof andfloor systems consist of repetitive framingmembers such as rafters or trusses with woodstructural panel decking. Framing componentsinclude solid sawn dimension lumber, I-joists,structural composite lumber and parallel chordand pitched trusses. Oriented strand board(OSB) and plywood are used interchangeably asdecking and sheathing material for floors, wallsand roof decks. There are several approachesto light wood frame construction, and each issuited for a specific application, most often inType III and Type V categories. As mentioned,on-site framing for light frame constructionis still the industry norm, but increasinglyelements of these buildings are prefabricatedoff-site and assembled on the job.Cross-Laminated TimberMass timber is a category of framing stylestypically characterized by the use of largesolid wood panels for wall, floor and roofconstruction. Cross-laminated timber panelsare formed by stacking and gluing togethersuccessive perpendicular layers of wood. Thelayered stacks are then pressed in large hydraulicor vacuum presses to form an interlocked panel.The panel is then sized and shaped with a CNCmachine into a construction-ready component.The number of layers in a panel can range fromthree to seven or more, and panels can havedoor and window openings, as well as routingsfor electrical and mechanical systems, installedbefore shipment to the building site. In additionto glued CLT, manufacturers have also developeda mechanically fastened CLT using carefullyengineered fastening patterns rather thanadhesives and pressure.The cross-lamination process provides improveddimensional stability to the product, whichallows for prefabrication of long, wide floorslabs, long single-story walls and tall plateheight conditions needed for clerestory wallsor multi-story balloon-framed configurations.By the nature of its design, CLT has inherentload-bearing strength and can serve as materialfor both vertical and horizontal assemblyapplications. Since wall, floor and roof sectionsmade of CLT are formed off-site in a factory,on-site construction time is much shorter. CLTcan be used as a structural system in TypeIII, IV and V buildings today and in tall woodbuildings under alternate means.Often all machining and milling of holes isperformed at the CLT producer’s plant basedon the fabrication drawings and CNC machinefiles and the product is shipped straight tosite. Other times the product is shipped toa fabrication shop for further fitting of steelconnections to speed up site erection.Nail-Laminated TimberNail-laminated timber is a mass timber panelsystem that can be used for floor, wall and roofstructures. NLT floor and wall assemblies havebeen used for more than a century, particularlyin warehouses where solid, sturdy floors wererequired; it is now being recognized againas a valid substitute for concrete slabs andsteel decking in commercial and institutionalbuildings and residential buildings where it isoften exposed to create a unique aesthetic. NLTis created from dimensional lumber stacked onedge—2x4, 2x6, 2x8, 2x10, or 2x12 at 1-1/2inches on center—and fastened together withnails. Plywood sheathing is often added to onetop side to provide a structural diaphragm.Plywood sheathing also allows the product tobe used as a wall panel element.Glulam is stronger than steel at comparable weights, and it isstronger and stiffer than dimensional lumber.1 That makes thematerial a cost-effective choice for long, structural spans and tallcolumns with minimal need for additional support.Glue-Laminated TimberCross-laminated timber panels are formed by stacking andgluing together successive perpendicular layers of wood. Often allmachining and milling of holes is performed at the CLT producer’splant based on the fabrication drawings and CNC machine files andthe product is shipped straight to site.Nail-laminated timber is created from dimension lumber stacked onedge and fastened together with nails. Plywood sheathing is oftenadded to one top side to provide a structural diaphragm and allowthe product to be used as a wall panel element.Glue-laminated timber (also called glulam) is astructural engineered wood element commonlyused for beams and columns in residentialand commercial applications. To form aglulam component, dimensional lumber woodlaminations are positioned according to theirstress-rated performance characteristics. In mostcases, the strongest laminations sandwich the
CONTINUING EDUCATIONbeam in order to absorb stress proportionallyand ensure the member’s longevity. Thelaminations are jointed end to end, allowingfor long spans, and are bonded with a durable,moisture-resistant adhesive. The laminations’grains run parallel with the member’s length toimprove its strength.Glulam is stronger than steel at comparableweights, and it is stronger and stiffer thandimensional lumber.2 That makes the materiala cost-effective choice for long, structuralspans and tall columns with minimal need foradditional support. Glulam is a highly visibleform of mass timber in contemporary projects,with long spans framing signature designs thathave been left exposed to take advantage ofwood’s natural aesthetic. In addition to beingused in floors, decks and roofs, GLT and NLTmass timber panels are now used for timberelevator and stair shafts in six-story, light woodframe residential mid-rise apartment buildings.GLT also offers the advantage of beingfabricated in controlled environments basedon certified manufacturing standards. LikeCLT, machining and milling of holes is oftenundertaken at the producer’s plant before theproduct is shipped to the site. Other times thepanels are shipped to the fabricator’s shop forfurther fitting of steel connections.Dowel-laminated timber is a mass timber product that uses wooddowels as the connector and is ideal for floor, wall and roof structures.Dowel-Laminated TimberDowel-laminated timber is a mass timberproduct that is wood and uses wood dowelsas the connector. From larger panel sizes (12feet by 60 feet) for faster erection times to awide variety of wood species, dowel-laminatedtimber is a mass timber product that is idealCASE STUDY: COMMON GROUND HIGH SCHOOLFor the 7.5 million, Type VB, 15,000-square-foot addition, the project team chose a combination of CLT and glulam. The new school buildingwas framed in just four weeks by a crew of five, using prefabricated materials. Architecture: Gray Organschi Photos: David SundbergNew Haven, ConnecticutCommon Ground High School is located on 20acres of city park land at the base of West RockRidge State Park in New Haven, near the SouthernConnecticut State University campus. The CommonGround High School is a program of the New HavenEcology Project, a nonprofit organization that alsooperates a community environmental educationcenter and urban farm on the same site.For the 7.5 million, Type VB, 15,000-square-footaddition, the project team chose a combinationof CLT and glulam. The new school building wasframed in just four weeks by a crew of five, usingprefabricated materials. Black spruce CLT panelsact as the tension surface and final ceiling finishin a revolutionary system of prefabricated stressedskin assemblies that span the upper classrooms andcirculation spaces. Vertical CLT panels form bearingand shear walls throughout the building, whileglulam rafters and heavy timber trusses span thelarge, ground-floor, multi-purpose space. A treatedglulam bridge deck on laminated timber piersprovides access from the upper campus. ArchitectGray Organschi says, “Black spruce was selectedbecause it’s super dense and has an incredibly highbending stress capacity. The grain is tight and verybeautiful. It’s a very exciting material to work with.”for floor, wall and roof structures. DLT does notinclude any glue, chemicals, volatile organiccompounds (VOCs) or nails, equating to ahealthier indoor environment. And becausethere are no nails or metal fasteners, DLT is easyto process through CNC machines. Unique toDLT as a mass timber product, a wide variety ofprofiles can be integrated inexpensively into thebottom surface of the panel. Profiles are fullycustomizable to suit the particular performanceand aesthetic requirements of each project.Organschi continues, “Wood is amazing. It isremarkably durable, protective and has enormousbending elasticity, a huge seismic benefit. It’s alsoa beautiful material that looks good even whenscuffed. Wood is also forgiving. If you make amistake in fabrication, you can easily correct it inthe field. That’s not easy to do with steel, and youcertainly can’t do that with concrete.”Black spruce CLT panels act as the tension surface and final ceilingfinish in a revolutionary system of prefabricated stressed skinassemblies that span the upper classrooms and circulation spaces.Architecture: Gray Organschi Photos: David SundbergBENEFITS OF BUILDING WITHPREFABRICATED WOOD COMPONENTSSpeed and Installation EfficiencyBecause wood panels are manufactured forspecific applications, they’re well suited to ahigh degree of prefabrication at the plant,equating to speed and efficiency of installation.Panels are prefabricated, complete with pre-cutopenings for doors, windows, stairs, servicechannels and ducts, and shipped directly from
CONTINUING EDUCATIONCASE STUDY: STELLA APARTMENTSis that changes can be made on-site with simpletools, pending approval by the engineer of record.Thermal Performance and Energy EfficiencyThermal conductivity is a measure of the rateof heat flow through one unit of thickness of amaterial subjected to a temperature gradient.The thermal conductivity of common structuralwood is much less than the conductivity ofme
components used in both light wood frame and mass timber construction can help to solve many design and engineering challenges such as material and process efficiency, environmental performance and life safety. The practice of prefabricating building elements in a factory w
Generally speaking, prefabricated buildings consist of prefabricated walls, staircases, composite floors and other prefabricated components. The whole prefabricated building is made up of many components in the actual construction and construction, which is often similar to the manufacturing enterprises in our country.
Time savings attributed to prefabricated construction revolve around the fact that on-site foundation construction can be done in parallel to offsite component fabrications, while restraining weather delays on the construction schedule [4,5]. From a single prefabricated window system to an intricate prefabricated building module, almost
10-in.) lumber, prefabricated wood I-joists, or parallel chord trusses. Lumber joists typically span from 3.6 to 4.8 m (12 to 16 ft). Span tables are available from the American Forest & Paper Association (AF&PA 1993). Span capabilities of the prefabricated wood I-joists or parallel chord trusses are recommended by the manufacturer.
3 Key Advantages of Wood-based Fuels 1.1 Wood energy is widely used and renewable 1.2 Sustainable wood production safeguards forest functions 1.3 Wood energy is available locally 1.4 Wood energy provides employment and income 1.5 Wood energy supports domestic economies 1.6 Wood energy is modern and leads to innovation 1.7 Wood energy can make a country independent of energy imports
Metal building systems will continue to account for over one-half of total US nonresidential prefabricated building system shipments through 2005, displaying annual growth of 4.3 percent. Among nonresidential prefabricated buildings other than metal building systems, the strongest growth
Keywords: prefabricated buildings; modular construction; structural performance 1. Introduction In Australia, the prefabricated building system (i.e. pre-cut, panelised, modular, and mobile home building system) has been recognized as a one of the alternative solutions to changing the speed of conventional construction methods at a fast rate.
wood (see Section "Role of wood moisture content on corrosion"). 3. Wood preservatives Wood preservatives are chemicals that are injected into the wood to help the wood resist attack by decay fungi, mold, and/or termites. Waterborne wood preservatives are commonly used when the wood may be in contact with humans or will be painted.
Parallel Strand Lumber (PSL) Prefabricated Wood I-Joists . Prefabricated wood I-joists generally weigh from about 3kg per metre (2 lbs. per foot) to 9kg per metre (6 lbs. per foot) for the deepest sections. . Manufacturers are also specific about the use of web reinforcement or blocking at beam supports and points of concentrated loads .
