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MITEK ® ROOF AND FLOOR TRUSS MANUAL FOR ARCHITECTS AND ENGINEERS MiTek Industries, Inc. 14515 N. Outer Forty Suite 300 Chesterfield MO 63017 800.325.8075 • (Fax) 314.434.5343 www.mii.com 4/05 2.5M

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Page 1: Truss Manual

MITEK®

ROOF ANDFLOOR TRUSS

MANUAL

FORARCHITECTS

AND ENGINEERS

MiTek Industries, Inc.14515 N. Outer Forty Suite 300

Chesterfield MO 63017800.325.8075 • (Fax) 314.434.5343

www.mii.com4/05 2.5M

Page 2: Truss Manual

Joint The intersection of two or more members.(Also referred to as a Panel Point.)Joint Splice A splice of the 4x2 chordmember at a chord-and-web joint.Kneewall A short partition stud wall toincrease a wall height, typically from theconcrete wall plate to the floor decking.Lateral Brace A member placed andconnected at right angles to a chord or webmember of a truss.Level Return A lumber filler placedhorizontally from the end of an overhang tothe outside wall to form a soffit.L/D Ratio The ratio of the truss span (L) toits depth (D), both dimensions in inches.Live Load Any temporary applied load to afloor truss chord; typically roof live load issnow, while floor live loads are furniture,human occupancy, storage.Load-Bearing Wall A wall specificallydesigned to transfer a roof load and/orupper floor load into the foundation.Machine Stress Rated Lumber (MSR)Lumber which has been individually testedby a machine at the lumber mill todetermine its structural design properties.MSR Lumber is designated by a flexural(bending) stress and Modulus of Elasticity,e.g., 1650F-1.5E.Moisture Content of Wood The weight of themoisture in wood expressed as a percentageof its oven-dry weight.Moments A structural measure of the effectsof bending on a member due to appliedloading.Overall Rise Vertical distance frombottommost part of the bottom chord touppermost point on peak.Overhang The extension of the top chord ofa truss beyond the heel measuredhorizontally.PCT Abbreviation for Parallel Chord Truss,the Truss Plate Institute (TPI) specificationdesignation for trusses with parallel chordsand 4x2 chord orientation, titled “DesignSpecification for Metal Plate ConnectedParallel Chord 4x2 Wood Trusses”.PLF Pounds per lineal foot, acting along astructural member, usually equal to theuniform load (PSF) times the truss spacing.PSF Pounds per square foot of uniform load.Panel Length The distance between thecenterlines of two consecutive joints alongthe top or bottom chord.Panel The chord segment defined by twoadjacent joints.Panel Point The point where a web or websintersect a chord.

Peak Point on truss where the sloped topchords meet.Pitch Inches of vertical rise for each 12inches of horizontal run.Plate A horizontal wood framing member,typically the top and bottom 2x4 members ofa stud wall and the 2x6 sill plate bolted to aconcrete wall for floor structural attachment.Plenum Typically, the use of the entire floortruss cavity formed by the floor above andthe ceiling below as a supply or return air“duct”.Plumb Cut Top chord end cut to provide forvertical (plumb) installation to fascia (facetrim board).Plumb Rise Vertical overall measurementsat the end of a truss where the top andbottom chords meet.Pre-Splice Plates Connector Plates pressedinto the top and bottom 3-1/2" faces of two4x2 chord members prior to final floor trussassembly to achieve a structural chord splice.Purlins Secondary structural components,spanning between primary structuralmembers and supporting the decking.1/4 Point point on triangular, Fink or Howetruss where the webs connect to the top chord.1/3 Point Point on triangular, Fink trusswhere the webs connect to the bottomchord.Reaction The total load transferred from theuniform load (PSF) applied to the floor trussdeck, then into the floor truss, and ultimately,to the floor truss bearing or support.Ridge Line formed by truss apexes.Rim Joist An exterior transition membersupporting the decking edge and wallsheathing, usually tying the ends of floortrusses together. (Also referred to as aRibbon or Band Board.)Rise Vertical distance from bottom most partof the bottom chord to inside of the peak.Scab Additional timber connected to a trussto effect a splice, extension or generalreinforcement.Shop Drawing Detailed drawings of a rooftruss or roof framing showing criticaldimensions such as span, overhang,cantilever, slope, etc.

Slope See Pitch.Spacing The centerline-to-centerlinedistance between trusses.Span The overall distance between adjacentinterior supports or to the outside of supportswhen at the end of a truss. (See detail above.)Splice Point (Top & Bottom chord splice). Thepoint at which two chord members are joinedtogether to form a single member. It mayoccur at a panel point or between panel points.Square Cut End of top chord cutperpendicular to slope of the member.Strongback A 2x6 lateral brace, used withits long dimension in a vertical orientation,running perpendicular to the trusses, andattached to the truss vertical web members.Support The structural element resisting thetruss, usually a wall or beam. (Also referredto as a Bearing.)Symmetrical Truss Truss with the sameconfiguration of members and design loadingoccurring on each side of truss centerline.Top Chord The continuous 4x2 memberforming the top of the floor truss.Top Chord Bearing A floor truss supportcondition in which the truss load istransferred to the bearing or support throughthe top chord and 4x4 block end detail.When the 4x4 block length is extended, thisis referred to as Mid-Chord Bearing.Truss A pre-built component that functions asa structural support member. A truss employsone or more triangles in its construction.Truss-clip Metal component designed toprovide structural connection of trusses towall plates to resist wind uplift forces.Visual Grade Lumber Lumber which has beenvisually rated at the lumber mill for structuralproperties through rules established bynational lumber species associations.Warren Truss A general truss configurationwith repetitive web “W” orientation. For floortruss applications, the top and bottom chordpanels are typically 30" length, usually witha 24" wide rectangular chase or ductopening at the centerline.Web A vertical or inclined member connectingthe top and bottom chords of a truss.

192 GLOSSARY OF TERMS

Headquartered in St. Louis, Missouri,MiTek Industries, Inc. is the leadingsupplier of connector plates, trussmanufacturing equipment, designsoftware, and engineering services for the worldwide component industry.

For over 35 years MiTek companies have developed and refined theirconnector plates into the state-of-the-artproducts they are today...consistent anddependable!

With MiTek you’re assured of the bestquality. MiTek connector plates aremanufactured under strict quality controland undergo extensive testing in our R & D facility.

MiTek’s connector plates meet or exceedall building code and industry associationrequirements. Acceptances includeBOCA, ICBO, HUD/FHA, SBCCI,Dade County, Wisconsin/ DILHR, andLA City.

MiTek also offers the very best inframing layout and engineering softwarefor roof and floor trusses, as well as wallpanel design. These programs provideour fabricators with fast and accuratelayout and design capabilities.Our engineering department is availableto review and seal our customers’ designs.With offices in NC, Missouri andCalifornia, MiTek’s professional engi-neers can furnish seals for all 50 states!Look to a MiTek fabricator for the bestthe industry has to offer! This brochurereviews the benefits of roof and floortrusses, but MiTek fabricators also offer a full line of builders hardware and acomplement of other building compo-nents including wall panels and steelframing.At MiTek, we are committed toproviding the best products and services in the industry and will continue ourtradition of customer support.

Introduction ...........................................................................................................2Wood Truss Advantages ........................................................................................3Truss Advantages .................................................................................................. 3Handling, Installation and Bracing .......................................................................4Basic Roof Truss Configurations ......................................................................5-6Construction Details

Support Details .................................................................................................7Joint Details ..................................................................................................... 8Lateral Bracing Information ............................................................................ 9Cantilever Framing ........................................................................................ 10Stairway Framing ...........................................................................................11

Technical InformationArchitectural Specifications ...........................................................................12Recommended Depth, Deflection and Camber Limitations ..........................12Construction Guidelines .................................................................................12Mechanical Service Guidelines ..................................................................... 13Cantilever Concentrated Loads ..................................................................... 13Floor Decking Information ............................................................................ 14Connector Plate Code Approvals .................................................................. 14Fire Rating Information ................................................................................. 15Sound Transmission Ratings ......................................................................... 16Construction Material Weights ...................................................................... 16Representative Floor and Roof Loads ........................................................... 16

Floor Loading Max-Span Information ............................................................... 16Floor Loading Max-Span Tables ........................................................................ 17Glossary of Terms ..........................................................................................18-19

TABLE OF CONTENTS PAGE NO.

MITEK INDUSTRIES, INC.800.325.8075 • www.mii.com

Typical Floor Truss

Span No.1

Overall Truss Length

Span No. 2

30” Panel 60” Panel Modu;e

TrussDepth

CantivelerLength

Page 3: Truss Manual

318

ARCHITECTS ANDDEVELOPERS◆ Savings in design costs-one basic

structural design for shell with minor floor plan variations.

◆ Better project cost control, with component costs known in advance.

◆ Better cash flow with earlieroccupancy due to reduced on-sitelabor.

◆ Faster shell completion time.◆ Using trusses of smaller

dimension lumber, in place of beams and columns.

◆ Greater flexibility in locatingplumbing, duct work, and electrical wiring.

◆ Floor plan freedom in locatinginterior partitions often withoutadditional support required.

CONTRACTORS/BUILDERS◆ Pre-determined, pre-engineered

truss system.◆ Fewer pieces to handle and

reduced installation time.◆ Wide 3-1/2” nailing surface for

easy floor deck application.◆ Eliminate notching and boring

joists for electrical wiring and plumbing.

◆ Floor trusses offer better availability and less in-place cost than 2x8 or 2x10 joists.

◆ Factory-manufactured components to exact span requirements.

◆ Reduced HVAC, plumbing, and electrical subcontractor time on job.

◆ No column pads to pour, no steel beams and posts to place.

◆ Job site material pilferage and cutting waste reduced.

HOMEOWNER◆ Lower construction costs.◆ Clearspan flexibility.◆ More flexibility in architectural

appearance and floor plans.◆ Easier remodeling possibilities in

moving interior walls.

ADVANTAGESOF TRUSSESOVERCONVENTIONALFRAMING…

ROOF AND FLOOR TRUSS ADVANTAGESGLOSSARY OF TERMS

WHY USEWOODTRUSSES?CONTRACTORSAND BUILDERSKNOW!

Contractors and Builders know thata MiTek engineered roof or floortruss system ensures quality andefficiency.

MITEK TRUSSESSAVE MONEY

Because costs are known in advance,there’s no guesswork. Your siteerection time is greatly reduced anddollar losses from job site materialshortages and pilferage areeliminated.

MITEK TRUSSESARE RELIABLE

Every MiTek truss has beenindividually designed and thatdesign is checked and approved bycertified engineers for structuraladequacy.

MITEK TRUSSESAre VersatileMiTek trusses provide more designflexibility, inside and out, thanconventional framing. Offeringnumerous custom design options,our trusses present an economicaland structurally superior method forrapid erection.

4x2 Member A 2x4 lumber section used asa structural component oriented such thatits 3-1/2" (4" nominal) face is horizontal.Allowable Stress Income A percentageincrease in the stress permitted in amember, based on the length of time thatthe load causing the stress acts on themember. The shorter the duration of theload, the higher the percent increase inallowable stress.Apez/Peak The uppermost point of a truss.Axial Force A push (compression) or pull(tension) acting along the length of amember. Usually measured in pounds, kips(1,000 lbs.) or tons (2,000 lbs.), or metricequivalent.Axial Stress The axial force acting at a pointalong the length of a member divided by thecross-sectional area of the member. Usuallymeasured in pounds per square inch.Balcony Cantilever A floor truss cantileverserving only as a balcony with no additionalwall loading acting on the cantilever portion.Battens/Purlins Timber sections spanningtrusses to support roof covering.Beam Pocket A rectangular opening within atruss to accept a header beam for positiveload transfer.Bearing A structural support, usually a wall,that occurs at the top or bottom chord orbetween the end points of a roof or floortruss.Bending Moment A measure of the bendingeffect on a member due to forces actingperpendicular to the length of the member.The bending moment at a given point alonga member equals the sum of allperpendicular forces, either to the left orright of the point, times their correspondingdistances from the point.Bending Stress The force per square inch ofarea acting at a point along the length of amember, resulting from the bendingmoment applied at that point. Usuallymeasured in pounds per square inch ormetric equivalent.Bottom Chord The continuous 4x2 memberforming the bottom of the truss.Bottom Chord Bearing A floor truss supportcondition in which the truss load istransferred to the bearing or support throughthe bottom chord “sitting” on the support.Butt Cut Slight vertical cut at the outside edgeof truss bottom chord made to ensure uniformspan and tight joints - usually 1/4 inch.Camber An upward curvature built into atruss during fabrication to counteractdownward deflection of the loaded truss.

Cantilever The portion of a truss extendingbeyond the exterior face of a support.Chase The opening in some floor trusses orstructural components in which themechanical equipment (ducts, plumbing,etc.) runs, typically a rectangular opening atthe centerline. (Also referred to as a DuctOpening.)Check A lengthwise separation of woodfibers, usually extending across the rings ofannual growth, caused chiefly by strainsproduced in seasoning.Chord Splice A splice of the 4x2 chordmember between joints, joined by pre-spliceconnector plates into the 3-1/2" faces andoccasionally side plates into the 1-1/2" edges.Clear Span Horizontal distance betweeninterior edges of supports.Combined Stress The combination of axialand bending stresses acting on a membersimultaneously, such as occurs in the topchord (compression + bending) or bottomchord (tension + bending) of a truss.Combined Stress Index (CSI) Thesummation of axial and bending stressesdivided by their respective allowablestresses for a specific truss member. Thisratio, or index, represents the structural“efficiency” of the member. The CSI shallnot exceed 1.00.Concentrated Load Loading applied at aspecific point, such as a load-bearing wallrunning perpendicular to a truss, or a roof-mounted A/C unit hanging from a truss.Connector Plate Pre-punched metal toothedconnectors located at the joints and splicesof a truss and designed to hold the forceswhich occur at those locations.Cripple Rafter Infill rafter installed tocontinue the roof line - fixed to valley boardin valley construction.Dead Load Any permanent load such as theweight of roofing, flooring, sheathing,insulation or ceiling material, as well as theweight of the truss itself.Design Loads The dead and live loadswhich a truss is engineered to support.Deflection The maximum verticaldisplacement of a structural member due toapplied loading. (Live load deflection is thedisplacement due to live load deflection.)Depth The overall distance from the top ofthe top chord to the bottom of the bottomchord.Dimensional Adjustment The adjustmentnecessary to alter standard repetitive floortruss panel modules to achieve the desiredoverall truss span. Dimensional adjustment

can be made at one end, both ends, or inthe center. (Also referred to as DimensionalTake-Up.)Doubled Chords The use of two 4x2members along specified top or bottomchord panels to achieve added strength.Dropped Cantilever The use of overlapping4x2 floor truss top chord members to framea balcony cantilever with a “step-down” of1-1/2" or 3" to provide positive drainage orapplication of concrete deck.End Detail Typically the location fordimensional adjustment. The end detailprovides the support condition andnecessary web orientation and panel lengthto create the desired truss span.Engineer Certified Drawing A truss designwhere loading requirements, lumberspecies, sizes, grades and connector platerequirements are detailed and a certifiedengineer’s seal is affixed.Extended Top Chord Bearing A floor trusssupport condition in which the truss load istransferred to the support through the singleor doubled top chord member extending to“sit” on the support. Popular for floortrusses used as roof purlins.Fan Truss A floor truss with 30" top chordpanels and 16" bottom chord panels and afan web configuration.Forces Axial compression or tension instructural components due to applied loads.Girder A structural member carrying largeloads due to attachment of headers ortrusses framing into the girder (commonlycalled tie-in trusses).Girder Truss Usually a multiple-ply trussdesigned to carry other trusses over anopening.Header Beam A short beam typicallysupporting framing adjacent to a stairopening, running perpendicular to the floortrusses.Header Truss A truss with 4x2 chordstypically supporting roof, wall and/or upperfloor loads, spanning over door or windowopenings. (For example, a garage dooropening header truss.)Heel Point on a truss at which the top andbottom chords intersect.Heel Cut See Butt Cut.Interior Bearing Any intermediate supportcondition in addition to the two exteriorsupports. A truss joint must be locatedabove an interior bearing.Jack Rafter Infill rafter installed to continuethe roof line - fixed from wall plate to hipboard in hip end construction.

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Page 4: Truss Manual

174 FLOOR TRUSS MAX-SPANSHANDLING, INSTALLATION AND BRACING

STORAGE

Trusses should be stored in a stableposition to prevent toppling and/orshifting.

If trusses are stored horizontally, theblocking should be eight to ten footcenters to prevent lateral bending. If the truss bundle is to be stored for more than one week, the solid-blocking, generally provided by the receiving party, should be at asufficient height to lessen moisturegain from the ground.

During long-term storage, trussesshould be protected from theelements in a manner that providesfor adequate ventilation of thetrusses. If tarpaulins or other waterresistant materials are used, the endsshould be left open for ventilation.If trusses are made with interiorrated fire retardant lumber, extremecare should be taken to limit outsideexposure.

FIELD ASSEMBLY

In some cases, the size or shape ofwood trusses is such that some fieldassembly is required. The installer isresponsible for proper fieldassembly.

Complete details on handling,installing and bracing can be foundin the Truss Plate Institute (TPI)publications HIB-91 and DSB 89,available from TPI, 583 D’OnofrioDrive, Suite 200, Madison, WI53719.

*Reprinted from the “Commentary &Recommendation for Handling, Installing &

Bracing, Metal Plate Connected WoodTrusses, HIB-91”, by permission of Truss

Plate Institute, Inc.

Depth(inches) 24" o.c. 19.2" o.c. 16" o.c. 12" o.c.

12131415161718202224

17-1118-0919-1720-0421-0121-0922-0623-1025-0126-03

20-0321-0222-0122-1123-0924-0725-0426-1028-0329-07

20-0622-0223-1125-0326-0227-0127-1129-0731-0232-07

20-0622-0223-1125-0727-0429-0030-0934-0236-0337-11

Depth(inches) 24" o.c. 19.2" o.c. 16" o.c. 12" o.c.

12131415161718202224

16-0417-0217-1118-0719-0319-1120-0621-0922-1124-00

18-0819-0620-0421-0221-1122-0823-0524-0926-0127-04

20-0621-0822-0723-0624-0425-0225-1127-0628-1130-04

20-0622-0223-1125-0727-0329-0030-0532-0333-1135-06

Depth(inches) 24" o.c. 19.2" o.c. 16" o.c. 12" o.c.

12131415161718202224

15-0215-1016-0617-0217-1018-0519-0020-0221-0222-02

17-0318-0118-1019-0720-0421-0021-0822-1124-0225-04

19-0220-0020-1121-0922-0623-0324-0025-0526-0928-01

20-0622-0223-1125-0626-0527-0428-0229-1031-0532-11

Depth(inches) 24" o.c. 19.2" o.c. 16" o.c. 12" o.c.

12131415161718202224

14-0815-0416-0016-0717-0217-0918-0419-0520-0621-05

16-0817-0618-0218-1119-0720-0320-1122-0223-0424-05

18-0619-0420-0221-0021-0922-0623-0324-0725-1127-01

20-0622-0223-0824-0725-0626-0427-0328-1030-0431-09

Depth(inches) 24" o.c. 19.2" o.c. 16" o.c. 12" o.c.

12131415161718202224

13-0914-0515-0015-0716-0216-0817-0318-0319-0320-02

15-0816-0517-0117-0918-0519-0019-0820-1021-1122-11

17-0518-0219-0019-0920-0521-0221-1023-0124-0425-06

20-0521-0422-0323-0223-1124-0925-0727-0128-0629-10

Depth(inches) 24" o.c. 19.2" o.c. 16" o.c. 12" o.c.

12131415161718202224

13-0013-0714-0214-0915-0315-1016-0417-0318-0219-00

14-1015-0616-0216-1017-0518-0018-0719-0820-0921-09

16-0517-0217-1118-0819-0420-0020-0721-1023-0024-01

19-0320-0221-0021-1122-0823-0524-0225-0726-1128-03

40/10/0/5 = 55 PSF @ 0% 40/10/0/10 = 60 PSF @ 0%

50/10/0/10 = 70 PSF @ 0% 40/25/0/10 = 75 PSF @ 0%

50/20/0/10 = 85 PSF 0% 50/35/0/10 = 95 @ 0%

Note:Above max-spans are valid for lumber design only. Platingor other considerations may further limit the truss design.

HANDLINGINSTALLATIONAND BRACING*It is the responsibility of theinstaller to select the mostsuitable method and sequenceof installation available tohim which is consistent withthe owner’s (architectural)plans and specifications andsuch other information whichmay be furnished to him priorto installation. Trusses maybe installed either by hand orby mechanical means. Themethod generally dependsupon the span of the trusses,their installed height abovegrade, and/or the accessibilityor availability of mechanicalinstallation equipment (suchas a crane or forklift).

The installer should beknowledgeable about thetruss design drawings, trussplacement plans, and all notesand cautions thereon.

TEMPORARYBRACING

Temporary or installationbracing is the responsibilityof the installer. Temporarybracing should remain inplace as long as necessary for the safe and acceptablecompletion of the roof orfloor and may remain in placeafter permanent bracing isinstalled.

800.325.8075 • www.mii.com

Page 5: Truss Manual

516 BASIC ROOF TRUSS CONFIGURATIONSTECHNICAL INFORMATION

KINGPOST DOUBLE FINK

QUEENPOST DOUBLE HOWE

FINK HIP

HOWE SCISSORS

FAN MONOPITCH

MODIFIED QUEENPOST CAMBERED

REPRESENTATIVEFLOOR AND ROOFAPPLIED LOADS

Residential Flooring40 psf Tc live Load10 psf TC Dead Load (3/4"

plywood decking)0 psf BC Live Load5 psf BC Dead Load (1/2" to 5/8"

drywall)55 psf Total Load(If heavy insulation or 2-ply drywallceiling, BC Dead Load = 10 psf and40/10/0/10 = 60 psf Total Load)

Commercial(Also Multi-Family Dwellings)40 psf TC Live Load25 psf TC Dead Load (1-1/2" to 2"

thick lightweight concrete cap)0 psf BC Live Load

10 psf BC Dead Load75 psf Total Load

Commercial Floors(Concrete deck)50 psf TC Live Load (commercial use)35 psf TC Deal Load (3" concrete

floor)0 psf BC Live Load

10 psf BC Dead Load95 psf Total Load

Residential andCommercial Roofing20, 25, 30, 40, 50 psf TC Live Load

(dependent on local building code requirements)

10 psf TC Dead Load (includes future re-roofing)

0 psf BC Live Load10 psf BC Dead Load40 to 70 psf Total Load (dependent

on TC Live Load)

Notes:◆ Above representative loads are typical loading requirements for many regions in the country.

However, the required applied loading for design purposes is the responsibility of the building designer, within the limitations of the prevailing local, state, or regional building code specifications.

◆ Roof trusses to be checked for local wind loadings.◆ Commercial floors may require additional load cases.

MITEK FLOOR TRUSSMAX-SPANS

The chord max-spans shown on the nextpage are intended for use in bidding,estimating, and preliminary designapplications. They are presented for sixrepresentative floor loadings. For properinterpretation of these max-spans, notethe following:◆ The max-spans are valid for the

following (or better) species grades:No. 1 KD Southern Yellow PineNo. 1 and better Douglas Fir2100Fb-1.8E Machine Stress Rated(MSR) lumber.Shorter spans will be achieved using lesser grade 4x2 lumber, while longer spans are generally possible with higher grade lumber.

◆ The max-spans represent truss overall lengths, assuming 3-1/2" bearing at each end. The spans are

equally valid for top chord-bearing and bottom chord-bearing support conditions.

◆ The minimum truss span-to-live load deflection is 360 for floor application. For example, the maximum permissible live load deflection for a 20' span floor truss is (20 x 12)/360=0.67".

◆ In addition to the consideration of lumber strength and deflection limitations, the maximum truss span-to-depth ratio is limited to 20 for floor loadings. For example the maximum span of a floor application truss 15" deep is 15" x 20' = 300" span = 25' - 0" span.

◆ Floor loadings have included 1.00 Load Duration Increase and 1.15 Repetitive Stress Increase.

TRUSS TYPES

800.325.8075 • www.mii.com

Page 6: Truss Manual

Description

Basic Wood Floor - consisting of wood joist (I-joist,solid-sawn, or truss), 3/4” decking and 5/8” gypsumwallboard directly attached to ceilingCushioned Vinyl or LinoleumNon-cushioned Vinyl of Linoleum1/2” Parquet Flooring3/4” Gypcrete® or Elastizel®

1-1/2” Lightweight Concrete1/2” Sound Deadening Board (USG)*Quiet-Cor® Underlayment by Tarkett, Inc*Enkasonic® by American Enka Company*Sempafloor® by Laminating Services, Inc.*R-19 Batt InsulationR-11 Batt Insulation3” Mineral Wood InsulationResilient ChannelResilient with InsulationExtra Layer of 5/8” Gypsum WallboardCarpet and Padding

36000

7-87-8114121110130-20

33201115813110008152-4

20-25

STC HighFrequency

IIC LowFrequency

156 TECHNICAL INFORMATIONBASIC ROOF TRUSS CONFIGURATIONS

DUAL PITCH INVERTED

GAMBREL PIGGYBACK

POLYNESIAN STUDIO

ATTIC CATHEDRAL

BOWSTRING SLOPING FLAT

STUB FLAT

SOUND TRANSMISSIONRATINGS

Various floor-ceiling systems exhibitdifferent abilities to reduce sound transferfrom one room to another. This soundtransmission resistance is measured bytwo indices - the Sound TransmissionClass (STC) which rates airborne soundsto evaluate the comfortability of aparticular living space and the ImpactInsulation Class (IIC) which rates theimpact sound transmission performance of

an assembly. These ratings are used byregional building codes to regulatepermissible sound transfer.For more detailed information referencethe Metal Plate Connected Wood TrussHandbook, ©1993 Wood Truss Council ofAmerica, Section 18.0 - Transitory FloorVibration and Sound Transmission.

Description

Carpet and Padding3/4” GypcreteWood Truss FloorResilient Channel

073610

201338

6253Total

STC IIC

*Estimates base on proprietary literature. Verify with individual companies.The above chart information was excerpted from the Construction Guide for Southern Pine Joist & Rafters.Southern Pine Council, 1993.

TYPICAL CONSTRUCTIONMATERIAL WEIGHTS

FloorsHardwood (1 in. thick)............. 3.8 psfConcrete

Regular (1 in. thick) ............ 12.0 psfLightweight (1 in. thick) ....... 8.0 psf

Linoleum ................................. 1.5 psf3/4" ceramic or quarry tile .... 10.0 psfCeilingsAcoustical fiber tile ................. 1.0 psf1/2 in. gypsum board .............. 2.0 psf5/8 in. gypsum board 2.5 ........ 2.5 psfPlaster (1 in. thick) .................. 8.0 psfMetal suspension system ......... 0.5 psfWood suspension system ........ 2.0 psfMiscellaneousSprinkling system ......... 1.0 to 1.5 psf

Ductwork (24g) ............. 3.0 to 5.0 psfRigid fiberglass (1 in. thick) .... 1.5psfRoll or batt insulation (1 in.) .. 0.3 psfGlass or rock wool (1 in. thick) .. 0.3 psfFloors Truss WeightsSingle chord ............. 5.5 plf (approx.)@ 24" o.c. spacing .. 2.75 psf (approx.)Double chord ............ 8.5 plf (approx.)@ 24" o.c. spacing .. 4.25 psf (approx.)Composition Roofing235 lb. shingles and paper ...... 2.5 psf2-15 lb. and 1-90 lb. ................ 1.7 psf3-15 lb. and 1-90 lb. ................. 2.2 psf3-ply and gravel ........................ 5.6 psf4-ply and gravel ........................ 6.0 psfRoof and Floor SheathingAnd Decking1/2 in. plywood ....................... 1.5 psf5/8 in. plywood ........................ 1.8 psf

3/4 in. plywood ....................... 2.3 psf1-1/8 in. plywood .................... 3.4 psf1 in. sheating (nominal) ........... 2.3 psf2 in. decking ............................ 4.3 psfTectum (1 in. thick) ................. 2.0 psfPoured gypsum (1 in. thick) ... 6.5 psfVermiculite concrete (1 in. thick) .......

............................................... 2.7 psfPartition Wall Weights(8' Nominal Height)Interior partition - (studs @ 16" o.c.)..

................................ 50 plf (approx.)Exterior partition - (studs @ 16" o.c.).and composition exterior)....................

................................ 85 plf (approx.)Exterior partition - (studs @ 16" o.c.and brick exterior) .. 180 plf (approx.)

Calculation Example

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Page 7: Truss Manual

714 FLOOR TRUSS CONSTRUCTION DETAILSTECHNICAL INFORMATION

SUPPORT DETAILS

Bottom Chord Bearing on Exterior Frame or Masonry Wall

Bottom Chord Bearing on Exterior Frame Wall with

Masonry Fascia Wall

Intermediate Bearing - Simple Span TrussesIntermediate Bearing - Continuous Floor Truss

(Special Engineering Required)

Header Beam Pocket - Floor Truss SupportingHeader Beam (Special Engineering Required)

Intermediate Bearing - Floor Truss Supportedby Steel or Wood Beam

(Special Engineering Required)

Top Chord Bearing on Frame Wall Top Chord Bearing on Masonry Wall

FLOOR TRUSSONE-HOURFIRE RATINGThe Truss Plate Institute has authorizedfire tests be conducted to achieve aone-hour fire rating for a typical floorand ceiling assembly. Copies of thosereports are available from the issuingagencies.

Additional information regarding one-hour fire ratings using wood trusseswith gypsum board ceiling may beobtained from ICBO Research ReportsNo. 1632 and 1352.

Fire rating test results are summarized inthe adjacent illustrations.

* International Conference of Building Officials 1313 East 60th Street • Chicago, IL 60637

** Underwriters Laboratory, Inc.333 Pfingsten Road • Northbrook, IL 60062

*** Factory Mutual Research1151 Boston-Providence Road • Norwood, MA 02062

ICBO* Design No. 4431

UL** Design No. L528

UL** Design No. L529

Factory Mutual*** Design FC214

3/4” T&G plywood, glued and nailed with alt. lightweight concrete

1 layer 5/8” thick USG Firecode C, Type C gypsumwallboard fastened with 1-7/8” Type S screws @ 8” o.c.

3/4” T&G plywood, glued and nailedwith alt. lightweight concrete

Furring Channels1 layer 5/8” thick Type C, USG gypsumwallboard secured with screws, jointsfinished

3/4” T&G plywood, glued and nailedwith alt. lightweight concrete

Steel Cross Teesand Runners

2 layers 1/2” thick Type FSW-1, NGC gypsumwallboard, secured with screws, joints finished

3/4: T&G plywood, glued and nailed

2x4 or 4x2ParallelChordTrusses @max. 24” o.c.

1 layer 5/8” thick Type C, USG gypsum wallboard secured with screws, joints finished

2x4 or 4x2ParallelChordTrusses @max. 24” o.c.

2x4 or 4x2ParallelChordTrusses @max. 24” o.c.

4x2 Wood Block Z-clip

2x4 or 4x2Roof or FloorTrusses @max. 24” o.co

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Page 8: Truss Manual

138 TECHNICAL INFORMATIONFLOOR TRUSS CONSTRUCTION DETAILS

Extended Top Chord Bearing(Span Limited by Engineering)

Extended Top Chord Bearing(Span Limited by Engineering)

Load-Bearing Wall CantileverBalcony Cantilever

Dropped Chord Balcony Cantilever

JOINT DETAILS

FLOOR DECKINGINFORMATIONVirtually all decking systems may beeasily applied to MiTek floor trusses.The wide 3-1/2” nailing surface assuresthat floor decks are installed accuratelyand quickly. The adjacent table is asummary of plywood deck requirementspresented by various American PlywoodAssociation publications.

Floor Construction Panel Indent Thickness Floor Truss Spacing

Conventional Double-LayerPlywood Underlayment overPlywood Sub-Flooring

48/2440/2032/1624/16

23/32”, 3/4”, 7/8”19/32”, 5/8”, 3/4”, 23/32”15/32”, 1/2”, 5/8”, 19/32”

7/16”, 15/32”, 1/2”

24” Spacing19.2” Spacing16” Spacing

16” o.c. Spacing

24” SpacingPermitted

15/32”, 1/2”, 5/8”, 19/32”19/32”, 5/8”, 3/4”, 23/32”

32/1640/20

Wood Strip Flooring overPlywood Sub Flooring(installed at right angles)

1-1/2” to 2” LightweightConcrete Cap over PlywoodSubflooring

40/20 19/32”, 5/8”, 3/4”, 23/32”24” SpacingPermitted

(Spacing equal toPanel Indent.)Panels must eitherbe Tongue-and-Groove or blockedBetween Trusses.

23/32”, 3/4”, 7/8”19/32”, 5/8”19/32”, 5/8”

7/8”, 1”1-1/8”

2420163248

APA Sturd 1-Floor (must be nailed or glued and nailedaccording to APA)

APA Glued Floor System(must be glued accordingto APA Spec. AFG-01 andnailed)

24” Spacing19.2” Spacing16” Spacing

(Available thicknessfor either conventionalsubflooring plywood orfor Sturd-I-FloorPanels.)

CONNECTOR PLATECODE APPROVALS

◆ BOCA National Building CodeBuilding Officials and CodeAdministrators, International (BOCA) Research Report No. 96-31, 96-67

◆ Uniform Building Code (UBC)International Conference of Building Officials (ICBO) Report No. 3907 and 4922.

◆ Standard Building Code (SBC)Southern Building CodeCongress International (SBCCI) Report No. 9667 and 9432A.

◆ Federal HousingAdministration (FHA/HUD)U.S. Department ofHousing and Urban Development(HUD) Truss Connector Bulletin No. TCB 17.08.

◆ Wisconsin State CodeWisconsin Department of Industry. Labor and Human Relations (DILHR) Approval No. 960022-W, 970036-N.

MiTek connector plates have been approved by allrecognized national and regional model building codegroups, based on extensive structural testing. The followingapprovals may be referenced for more detailed information:

Chord Pre-SpliceChord Joint Splice

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Page 9: Truss Manual

12 9FLOOR TRUSS CONSTRUCTION DETAILSTECHNICAL INFORMATION

LATERAL BRACINGSUGGESTIONS2x6 “Strongback” lateral supportsshould be located on edgeapproximately every 10 feet along thefloor truss. They should be securelyfastened to vertical webs. Blockingbehind the vertical web isrecommended while nailing thestrongback. The strongbacks shouldeither be secured to adjacent partitionwalls or alternate “X”-bridging should beused to terminate the bracing member.

Notes• Special engineering required for girder floor trusses.• Slope for drainage, as required.• Cantilever span controlled by lumber

size and grade deflection limitations.

MAXIMUM MECHANICAL SERVICECLEARANCES - FLOOR TRUSSES

OverallTrussDepth

(Inches)

Diameter(D)

(Inches)

Width (W) (Inches)

When Height (H) Equals:3” 4” 5” 6” 7” 8”

32 25 19 12 6 -

34 28 23 17 11 5

36 31 26 20 15 10

38 33 28 23 19 14

40 35 31 26 22 17

41 37 32 28 24 20

42 38 34 30 26 22

43 39 36 32 28 25

44 40 37 33 30 26

44 41 38 35 31 28

45 42 39 36 33 30

46 43 40 37 34 31

46 43 41 38 35 32

7

8

9

10

11

12

13

14

15

16

17

18

18-1/2

12

13

14

15

16

17

18

19

20

21

22

23

24

FLOOR TRUSSCANTILEVERCONCENTRATED LOADSFloor truss cantilevers often supportload-bearing walls carrying roof liveloads and wall material dead loads. Theadjacent chart provides a convenientmeans of determining an equivalentconcentrated load for representative roofloads which incorporate a 15% loadduration factor for the roof load only.

CONCENTRATED LOADSAMPLE CALCULATIONRoof Loading = 20/10/0/10 = 40 psf @1.15Roof Load (Roof Truss Reaction) =40 psf x (30'/2) x 2'-0" o.c. - 1200 lbs.8' Stud Wall Weight(@ 85 lbs./lineal ft.) = 85 plf x 2'-0" o.c.= 170 lbs.Equivalent Floor Truss Load =(1200/1.15) + 170 = 1215 lbs.Concentrated Load

Note:Also check floor truss for dead load onlyat end of cantilever.

Concentrated Load at End of Cantilver (lbs.)RoofSpan(Feet)

Roof Load (at 1.15) Plus Wall Load

20/10/0/10 = 40 psf 30/10/0/10 = 50 psf 40/10/0/10 = 60 psf

20222426283032

86596510051075114512151285

1040112512151300138514751560

1215132014251530163017351840

Floor Cantilevered Perpendicular to Floor Truss Span

Section AA - Floor Truss Jacks Floor JoistScab Cantilever

Floor Cantilevered Perpendicular and Parallel to Floor Truss Span

OverallTrussDepth

Roof Load

30’-0”

Wall Load

(Varies)

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Page 10: Truss Manual

1110

Minimum DepthMaximum DeflectionRecommended Camber

Span/24Span/240 (Live Load)Dead Load Deflection*

TECHINICAL INFORMATION

Built-up Beamwith Strap

Hanger

Header BeamPocket

Header Beam with Strap Hanger

Typical BasementStair Framing Cross-

Section

Stairwell Opening withoutStud Walls

Stairwell Opening Carriedby Stud Wall

Stairwell OpeningPerpendicular to Floor Trusses,

Carried by Stud Wall

Note:Framing opening between header beamsmust usually be increased beyondconventional framing opening to permitnecessary headroom.

STAIRWAY FRAMING

FLOOR TRUSS CONSTRUCTION DETAILS

ARCHITECTURALSPECIFICATION

RECOMMENDEDDEPTH,DEFLECTION,AND CAMBERLIMITATIONS

◆ Trusses shall be fabricated by a MiTek truss manufacturer inaccordance with MiTek floor truss engineering specifications.

◆ MiTek engineering design drawingsbearing the seal of the RegisteredEngineer preparing the design shallbe provided to the Project Architectfor his approval.

◆ Truss designs shall be in accord-ance with the latest version ofANSI/TPI1 National Design Standardfor Metal Plates Converted Wood Construction, a publication of Truss Plate Institute and generally acceptedengineering practice.

◆ Delivery, handling, and erection of MiTek trusses shall be in accordancewith the “TPI Quality Standard for Metal Plate Connected Wood Trusses,”published by Truss Plate Institute.

◆ Truss hangers, anchorage, permanent bracing, and required design loads shall be the responsibility of the Project Architect.

◆ MiTek truss connector plates are manufactured under rigid quality control using structural Grade C hot-dipped, galvanized steel meeting ASTM Specifications A653.

In addition to allowable lumber stresslimitations, floor truss designs are alsoregulated by maximum permissibledeflection-to-span and depth-to-spanlimitations, as shown in the chartbelow. The suggested camber to bebuilt into the truss during fabricationis also included. The truss deflection is calculated by

complex engineering methods andverified by extensive full-scale loadtests. The floor span-to-depth limitationis intended to prevent objectionablefloor vibration. All of the followingrecommended limitations should beachieved to provide a quality floorsystem and assure complete customersatisfaction.

* Provide slope of 1/4” per foot of span for proper drainage to prevent water ponding.

Span/20Span/360 (Live Load)Dead Load Deflection

Floor Roof

CONSTRUCTION GUIDELINESROOFSDON’T Unload trusses on roughterrain or uneven surfaces, which couldcause damage to the trusses.DO support trusses that are storedhorizontally on blocking to preventexcessive lateral bending and lessenmoisture gain.DON’T break banding untilinstallation begins and the trusses arein a stable, horizontal position.DON’T lift bundled trusses by thebands and do not use damaged trusses.DO brace trusses that are storedvertically, to prevent toppling ortipping.DON’T walk on trusses that are lyingflat. This is a dangerous practice.

FLOORSDO color-code floor truss ends forcorrect non-symmetrical installations.DO locate trusses to allow forplumbing or duct riser clearances.DO assure that trusses are installedwith a joint located over an interiorbearing.DO use warning tags on floor trussesto provide proper installationorientation and to warn against cuttingor modifying trusses.DON’T permit stacking of drywall orplywood sheathing during constructionon floor truss balcony cantilevers or attruss mid-span without proper shoring.

DON’T use floor trusses whenexposed to weather, chemicallycorrosive environment, or extremelyhigh humidity.DON’T cut truss chords or webs ormodify them in any way duringconstruction.

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