Big Box Retail: Wood Saves Nearly 1 Million - Wood WORKS

Transcription

Big Box Retail:Wood Saves Nearly 1 MillionCost and environmental studies compare wood to steelWhile many U.S. apartments are wood-frame, wood structureis far less common in stores and restaurants—even thoughit’s permitted by code in numerous applications—and its use inthe sub-category known as ‘big box’ retail is infrequent at best.To evaluate the opportunity, WoodWorks commissioned twostudies, one cost comparison and one life cycle assessment(LCA), on the same big box project designed in steel vs. wood.This report summarizes the results of those studies andhighlights opportunities for greater wood use in this segmentof the construction market. FRA-533 BigBox CaseStudy Brochure.indd 310/30/15 2:31 PM

Among developers, architects and engineers, costtends to be cited as the number one reason to specifywood as a structural material. For multi-unit residentialbuildings, for example, design teams often say thatwood-frame construction allows them to achievegreater density at less cost, while meeting performancegoals and allowing more budget for amenities. Morerecently, environmental considerations such as wood’srelatively light carbon footprint have been getting agreater share of the attention, with some governmentsgoing so far as to call for the use of wood as a lowcarbon alternative to other materials.iIn addition to the study highlights, this paper includesoptions for achieving the design requirements of big boxstores (see page 8). These requirements include: Large, open floor plan with tall ceilingsMinimal structureInterior space flexibilityAdaptability—i.e., the ability to adapt to futureneeds through redesignAlthough these requirements are often met withsystems that include structural steel columns, openweb joists and joist girders, and steel roof decking, theycan also be achieved with wood framing—likely at lesscost and with less impact on the environment.Wood DesignOutperforms SteelCOSTNearly 1 million savings (22%), primarily: Structure cost savings – 425k Roof insulation savings – 400keNVIRONMeNTbetter than steel in 5 out of 6impact categories: Global warming potential Acidification Potential Eutrophication potential Smog potentialProject ScopeHaving received the drawings for a one-story, 54,800-sfsteel-frame big box retail store in California (referencebuilding), WoodWorks commissioned Parker StructuralEngineering to design a comparable building usingwood materials (proposed building). Both buildingsare designed according to the 2010 California BuildingCode which is based on the International Building Codemodel code.The two designs share the same geometry, structurallayout, and column grid, including: Rectilinear building footprint Sloping roof deck on joists supported by a systemof beams and perimeter load bearing walls 23'-8"in height System of columns which support the beams,spaced at 30' – 45' by 30' – 64' Spread footings supporting the columns and stripfootings supporting the perimeter walls A 400-sf equipment platform, slab-on-gradeconstruction and no basement levelThe buildings have the same gross floor area, floorplan and layout, functions, location, orientation andoperating energy performance. For the LCA study,equivalent energy performance was established byproxy in lieu of performing an energy simulation foreach building design. This was done by maintainingthe same window-to-wall ratio and designing theproposed building envelope to be thermally equivalentto the reference building envelope. Table 1 provides asummary of the two designs.WoodWorks then provided both sets of drawingsto two firms. SSA Quantity Surveyors was asked toundertake a detailed cost comparison of the referenceand proposed structures. Coldstream Consulting, a firmspecializing in LCA of buildings, was asked to undertakea cradle-to-grave analysis of the material effects ofstructure, envelope and interior partition assemblies.Sixty years was selected for the service life because itis commonly used in North American LCA studies andis the minimum requirement for the LEED v.4 wholebuilding LCA credit. Non-renewable energy use2 FRA-533 BigBox CaseStudy Brochure.indd 210/30/15 2:31 PM

Table 1Building Design SummaryElementReference Steel DesignProposed Wood DesignFoundations Spread footings: 3'x3'x2', 5'x5’x2', 6'x6'x3', 7'x7'x3'reinforced concrete Spread footings: 2'x2'x2', 3'x3'x2', 4'x4'x2', 5'x5'x2',6'x6'x3' reinforced concrete Typical strip footing: 2'x2' reinforced concrete Typical strip footing: 1'-9"x2' reinforced concrete Other strip footings: 2'-deep reinforced concrete (width varies)Slab-on-grade Sub-base: 7" crushed rock Typical slab-on-grade: 5" reinforced concrete, 15 mil vapor retarder Slab-on-grade at freezer/cooler: 4" reinforced concrete, 15 mil vapor retarder, 6" extruded polystyrene insulation,5½" reinforced concrete Slab-on-grade at exterior truck ramp: 7" reinforced concrete, 15 mil vapor retarderFloor construction 12"-deep light-gauge steel joists 2x12 sawn lumber joists Structural steel beam Glulam beam ¾" plywood sheathingRoof construction 1½" 18-gauge metal deck 15 /32 " OSB sheathing 18"–40"-deep open web steel joists @ 8'-6" o.c. 24"–54"-deep prefabricated wood trusses @24" o.c. 6"–8"-deep @16" o.c. light-gauge steel joists 2x6, 2x8 @16" o.c. sawn lumber joists 36"–54"-deep girder trusses 13½"–36"-deep glulam beams Misc. structural steel beams (W, C, MC, HSS shapes) Misc. wood beams (solid sawn lumber, glulam) 4"–9"-deep HSS columns 6x–14x-deep solid sawn lumber columns Aluminum mesh, structural steel-framed canopies 1½" 18-gauge metal deck, HSS-framed entry towersExterior walls Walls supporting cladding: 6"-deep @16" o.c. lightgauge steel stud wall Walls supporting cladding: 2x6 @16" o.c. sawn lumberstud wall Structural walls: 8" reinforced concrete masonry unitwall, 6"-deep @16" o.c. light-gauge steel wall at northelevation Structural walls: 2x10 @16" o.c. sawn lumber stud wall(2-2x10 at wall sheathing edges) with 15 /32 " plywoodsheathing, 8" reinforced concrete masonry unit wall atloading dock below slab-on-grade Insulation: R-11 fiberglass batt (3½" thick) wherenoted on plans Interior: 6"-deep @16" o.c. light-gauge steel,5/ 8 " gypsum board where noted on plans Insulation: R-13 fiberglass batt (3½" thick) wherenoted on plans Interior: 5/8 " Type X gypsum board Solid sawn lumber lintels Holdowns Cladding: 7/8 " exterior cement plaster, thin brick veneer, slate tie veneer, ipe wood panelingLateral forceresisting systems Horizontal system: 1½" 18-gauge metal deckdiaphragm Vertical system: 8" reinforced concrete masonry unitshear wallsExterior windows 1" insulated glazing with aluminum framesExterior doors Insulated sectional overhead Horizontal system: 15 /32 " OSB sheathing diaphragm Vertical system: 2x10 sawn lumber shear walls with15 / 32 " plywood sheathing Hollow steel Automatic sliding entryRoof coverings 60 mil thermoplastic polyolefin (TPO) membrane, tapered extruded polystyrene insulation, ½" cover board,vapor retarder, ½" protection board R-22 extruded polystyrene insulation (4½" thick) R-22 fiberglass batt insulation (5½" thick, withinroof trusses) Resilient channels, 5 /8 " Type X gypsum boardPartitions 3 5 /8 ", 6"-deep @16" o.c. light-gauge steel stud walls 2x4, 2x6 @16" o.c. sawn lumber stud walls 5 /8 " gypsum board each side R-11 fiberglass batt acoustic insulation where noted on plansInterior doors Solid core birch veneer Polyethylene clad Wood with glass3 FRA-533 BigBox CaseStudy Brochure.indd 310/30/15 2:31 PM

Cost Comparison: Wood vs. SteelFigure 1Total Building Cost Comparison 5.0 4,489,000 4.5MILLIONS OF DOLLARS 4.0 3,500,000 3.5 3.0 2.5SteelWood 2.0Hard costs associated with each building were limitedprimarily to structure and envelope. Stairs and elevators,interior finishes, fittings and equipment, electrical andmechanical were noted but not assigned values. 1.5 1.0 0.5 0The largest cost savings were associated with thestructure and roof insulation. The structure categoryincluded items such as roof framing (beams, trussesand decking) and vertical framing (columns and wallframing). A large number of items such as the slab-ongrade, roofing, wall finishes, and exterior windows anddoors were identical for both buildings and are includedin the Other category. See Figure 2 for a savings bycategory summary associated with the proposedwood building.TOTAL ESTIMATED CONSTRUCTION COSTFigure 2Total Cost Savings of Wood Buildingover Steel BuildingStructure 400,350Structure cost savings associated with the wood designtotaled approximately 425,000. In order from highest tolowest savings, they were concentrated in roof framingbeams, roof decking, roof framing columns, primaryroof framing such as trusses and joists and wall framing.Table 1 shows a comparison of the sub-componentsin each of these elements and Figure 3 depicts theallocation of savings in each structure category elementassociated with the proposed building.RoofInsulation 424,759Contractor’sFees 162,706Other 811It is interesting to note that the wood roof optionrequired a direct-applied ceiling due to the use of battinsulation (as opposed to rigid insulation on top of thedecking for the steel option), which consisted of onelayer of 5/8 " gypsum and resilient channels. While thisadded about 80,000 to the overall cost, the structurecost savings was still approximately 425,000.Figure 3Structure Cost Savings of Wood Building over Steel BuildingWood BuildingTotal Structure Savings 424,759Roof FramingSavingsRoofBeams 163,621According to the comparison, the reference steelbuilding design was estimated to cost 4,488,597,while the proposed wood building design wasestimated to cost 3,499,971, resulting in a total costsavings of 988,626 for the wood design. The totalbuilding cost difference, equal to a 22% savings or 18 per square foot savings for the wood building,is illustrated in Figure 1.RoofDecking 113,697Vertical FramingSavingsTrusses 66,405Columns 107,403WallFraming 53,571CeilingCostAdditionCeilingand RC*- 79,938*Resilient channelsSavings associated with roof insulation representedthe largest single element savings (over 400,000),due to the cost difference between rigid insulation(steel design) and batt insulation (wood design). Therigid insulation was 4½" XPS (extruded polystyrene) andthe batt insulation was 5½" fiberglass. Each insulationoption provided a roof insulation R-value of 22.Due to the lower hard costs associated with the wooddesign, a total additional savings of 162,706 wasachieved in contractor’s general requirements andcontingencies. Two factors contributed to savingsassociated with contractor fees: the contractor’s generalrequirements and fees (14% of hard cost totals) and theconstruction contingency (5% of total hard costs plus4 FRA-533 BigBox CaseStudy Brochure.indd 410/30/15 2:31 PM

contractor’s fees). This savings is included in the totalbuilding savings cited at the beginning of this sectionand illustrated in Figure 2.Environmental Performance:Wood vs. SteelLife cycle assessment is an internationally-recognizedmethod for measuring the environmental impactsof materials, assemblies or buildings over their entirelives—from extraction or harvest of raw materialsthrough manufacturing, transportation, installation,use, maintenance and disposal or recycling. It allowsdesign professionals to compare different buildingdesigns based on their environmental impacts andmake informed choices about the materials they use.LCA is increasingly being used instead of a prescriptiveapproach to material selection, which assumes thatcertain prescribed practices (such as specifyingproducts with recycled content) are better for theenvironment regardless of the product’s manufacturingprocess or disposal. This shift is reflected in all ofthe major green building rating systems, codes andstandards, including LEED v.4, Green Globes, theInternational Green Construction Code, CaliforniaGreen Building Standards Code and ASHRAE 189.1.LCA studies consistently show that wood outperformsother materials in terms of embodied energy, air andwater pollution, and carbon footprint.iiScope of Life Cycle AssessmentThe LCA described in this paper was conductedin conformance with the Committee for EuropeanStandardization (CEN) standard EN 15978, whichstipulates an LCA-based calculation and reportingmethod for whole buildings or building parts. WhileEuropean in scope, many EN 15978 provisions arebecoming the standard manner by which whole-buildingLCA work is conducted worldwide.EN 15978 uses 22 environmental indicators to measurea structure’s life cycle impacts. Five of these indicatorswere not in the scope of this project. For sake of clarityand conciseness, of the 17 indicators applicable tothis study, the LCA comparison of the steel and woodbuildings focused on the following six required for theLEED v.4 whole-building LCA credit:1. Global warming potential2. Ozone depletion potential3. Acidification potential4. Eutrophication potential5. Smog potential6. Non-renewable energy useFor more information on LCA, including definitionsof common indicators and life cycle phases, visitLife Cycle Assessment:Why Wood Performs WellLife cycle assessment studies consistently showthat wood performs better than other materialsin terms of embodied energy, air and waterpollution, and greenhouse gas emissions.One of the reasons for this is that wood productstend to require less energy to manufacture thanother materials—and very little fossil fuel energy,since most of the energy used comes fromconverting residual bark and sawdust to electricaland thermal energy.iiiA comprehensive review of scientific literatureexamined research undertaken in Europe,North America and Australia pertaining to lifecycle assessment of wood products.iv It appliedLCA criteria in accordance with the InternationalOrganization for Standardization standardISO 14040-42 and concluded (among otherthings) that: Fossil fuel consumption, potential contributionsto the greenhouse effect, and the quantities ofsolid waste tend to be minor for wood productscompared to competing products. Wood products that have been installed andare used in an appropriate way tend to have afavorable environmental profile compared tofunctionally equivalent products made out ofother materials.Increasingly, architects and engineers areutilizing LCA as an objective way to compare theenvironmental impacts of their material choices.This is due in part to the fact that information onLCA, including databases, tools and research, isgrowing. LCA is now also included in most greenbuilding rating systems.the Athena Sustainable Materials Institute ca/technical-details/.Whole-building LCA typically draws on environmentalproduct declarations (EPDs) and/or life cycle inventory(LCI) environmental data sources. Although EPDshave become a standard part of decision makingelsewhere in the world, they are relatively new to NorthAmerica, produced mainly by large manufacturers orindustries committed to being leaders in environmentalperformance and used by leading design firms withthe same objective. The wood industry has been atthe forefront of this trend and EPDs are available for5 FRA-533 BigBox CaseStudy Brochure.indd 510/30/15 2:31 PM

Figure 4 shows the life cycle stages included in theanalysis. Defined in “modules” (e.g., A1, A2, A3, etc.),the results are calculated in two ways, one that includesmodules A, B and C and another that also includesD (steel and concrete recycling, wood combustion,biogenic carbon sequestration of landfilled woodproducts). The four grey modules were not included inthe study for various reasons. For example, operatingenergy and water use were assumed to be the samefor each building type and omitted from the scope.Additionally, these building aspects are not requiredfor attaining the LEED v.4 whole-building LCA credit.many wood products (www.awc.org). However, thisassessment did not use EPDs as a source of data since1) EPDs are not widely available for competitive buildingproducts, and 2) there is, so far, a lack of consistencybetween EPDs in different product categories.The assessment drew on the following three LCIdata sources: The Athena LCI Database tabases/) The US LCI Database (http://www.nrel.gov/lci/) The Ecoinvent LCI Database (http://www.ecoinvent.ch/)LCA ResultsThis study considered the following elements (as shownin Table 1): foundations, slab-on-grade, floor construction,roof construction, exterior walls, exterior windows,exterior doors and roof coverings. This group of elementsbroadly includes structure, envelope and interior partitionmaterials, which corresponds to the current modelingcapacity of the Athena Impact Estimator LCA softwareand is compliant with the requirements of the LEED v.4whole-building LCA credit.Notable assessment omissions include: Non-structural fasteners, clips, etc. Surface treatments (e.g., weatherproofing, fireretarding coatings) Adhesives and sealants Soffit, drain covers, vents, roof hatches, etc. Temporary works used during construction anddemolition/deconstruction phases (e.g., shoring,formwork) Freezer and cooler box, including walls and doors Soil treatmentsThe proposed wood building uses less mass ofmaterials than the reference steel building and performsbetter against five of the six environmental indicators.In addition to manufacturing processes, transportationand other factors, the amount of materials usedin a building has an impact on its LCA results. Thetotal mass of materials used by the steel and woodbuilding designs are 6,924 and 5,923 metric tonnes,respectively, a 14% reduction for the proposed building.Relative to the steel building, the wood building uses66% less steel products, 26% less concrete products,1,125% more wood products and 36% more gypsumproducts. Differences between Fossil Fuel Derivedand Other products can be primarily attributed to thechoice of roof insulation—i.e., extruded polystyrene vs.fiberglass batt.Figure 5 shows a comparison of material use over the60-year reference study period, including constructionwaste and materials used for maintenance, repair andreplacement activities.Figure 4Life Cycle Stagesvi (Green boxes included in this analysis)PRODUCTStageCONSTRUCTIONPROCESS StageUSEStageEND OF LIFEStageA1Raw litionA2TransportA5ConstructionInstallation ProcessB2MaintenanceC2TransportB3RepairC3Waste PPLEMENTARYINFORMATIONBEYOND THEBUILDING LIFECYCLEDBenefits and LoadsBeyond theBuilding Life ntB6Operational EnergyUseB7Operational WaterUse6 FRA-533 BigBox CaseStudy Brochure.indd 610/30/15 2:31 PM

Highlights from the LCA Report Raw material supply and manufacturing: woodbuilding has an average of 30% less impact acrossall indicators End of life transport: wood building has 11% lessimpact across all indicatorsImpacts of the proposed wood building are lower thanthe steel building impacts for all indicators except ozonedepletion potential, where the proposed building resultswere 5% higher. (See Figures 6 and 7.)Raw Materials through Demolition/Disposal:Adding the recovery/re-use/recycle stage has minoreffects on the overall comparison between the woodand steel buildings. As with the analysis excluding thisstage, the wood building outperforms the steel buildingoverall and for all indicators except ozone depletionpotential, where the proposed building results wereslightly higher. Global warming potential: wood building saves 642tonnes of carbon dioxide equivalent (CO2e) Non-renewable energy use: wood building saves9,116 gigajoules (GJ)Figure 5Life Cycle Product Use Mass Comparison by Building Product TypeMass (tonnes)Reference BuildingProposed Building5,0003,9634,0002,9173,0002,226 2,2262,0001,0000395 134Steel22Concrete229 310273WoodGypsum602825Fossile FuelDerivedAggregate38OtherFigure 6LCA Results Comparison (Normalized) – Raw Materials through Demolition/DisposalReference BuildingProposed 250.00Global Warming Ozone ergy UseFigure 7LCA Results – Raw Materials through Recovery/Re-use/RecycleReference BuildingProposed 250.00Global WarmingPotentialOzone tionPotentialSmogPotentialNon-renewableEnergy Use7 FRA-533 BigBox CaseStudy Brochure.indd 710/30/15 2:31 PM

Opportunities for ‘Big Box’ Wood Designby public ways or yards 60' wide or greater (IBCSections 507.3 and 507.4). Table 2 provides a summaryof allowable mercantile occupancy building sizes forTypes III, IV and V construction. The proposed buildingis Type VA construction, fully sprinklered.Due to longstanding practices in big box building design,wood framing is seldom used for the structural systems.However, as these cost and LCA comparisons illustrate,there are tangible benefits to using wood-frameconstruction in large commercial structures such asgrocery stores, home improvement stores, wholesalewarehouses, shopping malls, restaurants and departmentstores. Also due to these longstanding practices, manydesigners don’t realize the extent to which building codesallow wood framing in retail structures.Gravity Framing SystemsSpecific occupancy and use requirements for theproposed and reference buildings included 16' ceilings(minimum above finish floor), 23' exterior walls, amonoslope roof (¼" per foot) capable of supportingHVAC equipment, a loading dock, multiple exterioraesthetic features such as parapets, canopies and anentrance tower, and a small mezzanine for storage,mechanical and other miscellaneous use. Below is adiscussion of the wood structural framing members,systems and details utilized in the proposed buildingthat facilitated the cost and environmental savings.The design flexibilities provided by wood framing—whichinclude everything from conventionally framed wall, floorand roof construction, to mass timber columns, beamsand lateral framing systems, to metal plate-connectedlong-span trusses—offer near endless possibilities interms of building size, shape and configuration.As noted, the vast majority of big box stores haverequirements that include large open floor plans, tallceilings, minimal structure, interior space flexibility andthe ability to adapt to future needs through redesign.In the proposed building, a roof framing grid ofapproximately 45'x45' consisting of glue-laminated(glulam) beams and solid sawn columns was utilizedto achieve an open floor plan with minimal columnsfor space disruption. Glulam beams span 30' to 46'and support an average of 40' to 56' of roof width.They range in size from 8¾"x24" – 8¾"x36" and utilizecantilever connections and hinge hangers to speedconstruction and minimize on-site connection difficulty(see Figure 8). The grids used in the reference buildingand proposed building were identical.Although these requirements are often met withsystems that include structural steel columns, openweb joists and joist girders, and steel roof decking, theycan also be achieved with wood framing—likely at lesscost and with less impact on the environment.The majority of retail buildings fall under theInternational Building Code (IBC) occupancyclassification of mercantile (M). With the installationof an automatic sprinkler system (required for GroupM occupancies with a fire area greater than 12,000sf per IBC Section 903.2.7), significant building sizesare permitted for buildings of Types III, IV and Vconstruction. These construction types may utilizewood framing for all framing components (Types III andIV may utilize fire retardant-treated wood for exteriorwalls). Additionally, one- and two-story buildings ofmercantile occupancy may be unlimited in area for anyconstruction type when an automatic sprinkler systemis installed and the building is surrounded and adjoinedThe proposed building design utilized prefabricated,metal plate-connected parallel chord roof trusses at 24"on center (o.c.) spanning 30' to 64', with depths of 24" to54" in the main area of the building. Trusses were deckedwith 15/32" sheathing and hung from the glulam beamsusing prefabricated hangers supporting the truss bottomchords. The design also provided the flexibility to bear thetruss top chords on top of the glulam beams if that optionproved more cost effective. The glulam elevations wereset to be flush bottom with the deepest adjacent trussbottom chord in order to simplify ceiling installation (seeTable 2Group M NFPA 13-Compliant Sprinklered Buildings – Maximum Floor Areaa,b# of stories1% frontageMaximum floor area per story 7,37066,50042,750100 (60’)cULULULULULUL Unlimited; Source: 2012 Code Conforming Wood Design, American Wood Council8a. Frontage based on open space widths of 30' or moreb. Interpolation permittedc. Sprinklered Group M buildings of one or two stories may be unlimited in area if thefrontage width is at least 60' in accordance with IBC Sections 507.3 and 507.4. FRA-533 BigBox CaseStudy Brochure.indd 810/30/15 2:31 PM

The proposed wood building design specified loadbearing exterior stud walls. In order to support roofloads while also creating a parapet without kickers, theexterior wall framing detail (Figure 11) specified 2x10at 16" o.c. balloon-framed studs, with 6x12 ledgersFigureS 8 AND 9Glulam Beam and Roof Truss Connection Details15/32"Roof SheathingRoof Trusses @ 2'-0" o.c. (24" to 54" Deep)InteriorGlulam Beams(8 3/4" wide;24"–36" deep)Interior SolidSawn Columns(10"x12" –14"x14")2x10 @ 16" o.c. Exterior BearingWallSolid sawn columns, approximately 18' to 23' tall, werespecified using two options: exposed, larger columns(14"x14") utilizing mass timber’s inherent fire-resistancecharacteristics, and smaller columns (12"x12") sized onlyfor structural loads and protected with two layers ofgypsum board to provide fire protection. This providesthe architect and owner with greater design flexibilityand allows an option of exposing the mass timbercolumns to create a desirable aesthetic uncommonin big box stores. The glulam members utilized in theproposed building design are Douglas-Fir-Larch witha 24F-V8 combination. Figure 10 provides a summaryof the typical gravity framing system.Figure 10Typical Gravity Framing System2x10 @ 16" o.c. Exterior BearingWallFigure 9). The column and beam elevations varied acrossthe building (highest at the front of the building, lowest atthe back) to provide the required roof slope.FigureS 11 AND 12Exterior Wall Roof Support Details9 FRA-533 BigBox CaseStudy Brochure.indd 910/30/15 2:31 PM

attached to the inside face of studs aligned with thesupported truss top and bottom chords. A combinationof truss bottom chord hangers, hurricane clips andholdowns were used to attach the trusses to boththe ledgers and exterior wall for roof load support andout-of-plane load resistance and anchorage. At locationswhere the roof trusses span parallel to the exteriorwalls, a 6x12 ledger in line with the truss top chordsis attached to the inside face of studs to transfer roofdiaphragm forces. A 4x6 ledger in line with the trussbottom chords is attached to the inside face of studsto support the end of the ceiling, while 2x6 kickersbrace the wall studs at the ceiling elevation in orderto maintain consistent wall stud unbraced lengths anddesign spans (see Figure 12).Alternative Roof Framing Options:A variety of wood framing options exist for roofs oflarge, open retail spaces.To achieve the required open floor plan, roof memberspans of 30' to 50' are common. If using closely spacedmembers, prefabricated metal plate-connected woodtrusses spaced at 16" to 32" are effective. With theseframing member spacings, wood structural panelsare commonly used as the decking material, withtypical thicknesses ranging from 15/32" to 7/8". In lieuof the glulam girders specified, multi-ply metal plateconnected truss girders are an option.Alternatives to the solid sawn columns utilized in theproposed building include glulam columns, engineeredwood columns (e.g., parallel strand lumber), or builtup columns composed of multiple plies of solid sawnlumber.Alternative Wall Framing Options:In order to achieve the tall exterior walls requiredto provide tall ceilings, tall wall studs are necessary.However, designers have a choice of two maindesign routes.The exterior walls can be load bearing, supporting theroof loads in addition to out-of-plane wind and seismicloads acting on the wall.Alternatively, a series of beams and columns could beinstalled just inboard of the exterior walls, supportingthe roof loads and making the exterior walls curtainwalls, designed only for out-of-plane wind and seismicloads. Per Tables 601 and 602 of the IBC, this optioncan potentially be used to lower fire-resistance ratingrequirements of exterior walls, depending on fireseparation distance, construction type and occupancy.Although this option requires additional framing forperimeter beams and columns, it may also reducerequired stud sizes.If using load bearing exterior walls in lieu of hangingthe trusses from ledgers on the interior face of studs(as was the case for the proposed building) anotheroption would be to frame the studs to the underside ofthe truss bottom or top chords and bear the trusses onthe exterior walls. This would reduce the required studlengths; however, depending on the required parapetheight, kickers may be required to brace the top of theparapet walls.Lateral Framing SystemsRoof framing: Glulam girders andpurlins, solid sawn lumber sub-purlins,and wood structural panel sheathingAs large ro

Roof construction 1½" 18-gauge metal deck 18"-40"-deep open web steel joists @ 8'-6" o.c. 6"-8"-deep @16" o.c. light-gauge steel joists 36"-54"-deep girder trusses Misc. structural steel beams (W, C, MC, HSS shapes) 4"-9"-deep HSS columns 15/32" OSB sheathing 24"-54"-deep prefabricated wood trusses .