roof truss facts mitek

8/12/2019 Roof Truss Facts Mitek

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M

ROO

FLOOR

MA

ARC

AND EN

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

Chesterfield MO 63017800.325.8075 (Fax) 314.434.5343

www.mii.com4/05 2.5M


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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 to

the 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 12

inches 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 airduct.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-cedistance between trusses.

Span The overall distance beinterior supports or to the outwhen at the end of a truss. (SSplice Point (Top &Bottom cpoint at which two chord memtogether to form a single meoccur at a panel point or betwSquare Cut End of top chordperpendicular to slope of theStrongback A 2x6 lateral braits long dimension in a vertirunning perpendicular to theattached to the truss vertical Support The structural elemetruss, usually a wall or beamto as a Bearing.)Symmetrical Truss Truss witconfiguration of members anoccurring on each side of truTop Chord The continuous 4forming the top of the floor tTop Chord Bearing A floor trcondition in which the truss transferred to the bearing or sthe top chord and 4x4 block When the 4x4 block length isis referred to as Mid-Chord Truss A pre-built component a structural support member. one or more triangles in its cTruss-clip Metal componentprovide structural connectiowall plates to resist wind upVisual Grade Lumber Lumbervisually rated at the lumber mproperties through rules estanational lumber species assoWarren Truss A general trusswith repetitive web W orien

truss applications, the top anpanels are typically 30" lenga 24" wide rectangular chaseopening at the centerline.WebA vertical or inclined methe top and bottom chords o

2 GLOSSARY OFTERM

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

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

With MiTek youre assured of the bestquality. MiTek connector plates aremanufactured under strict quality controland undergo extensive testing in ourR & D facility.

MiTeks 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 customersdesigns.With offices in NC, Missouri andCalifornia, MiTeks 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 offera 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 servicesin 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 ............................................................................14

Connector 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 OFCONTENTS PAGE NO.

MITEKINDUSTRIES, INC.800.325.8075 www.mii.com

Typical Floor Truss

Span No.1

Overall Truss Length

Span No. 2

30 Panel 60 Panel M


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18

ARCHITECTS ANDDEVELOPERS Savings in design costs-one basic

structural design for shell withminor floor plan variations.

Better project cost control, with

component costs known inadvance.

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

Faster shell completion time. Using trusses of smaller

dimension lumber, in place ofbeams and columns.

Greater flexibility in locatingplumbing, duct work, andelectrical wiring.

Floor plan freedom in locatinginterior partitions often withoutadditional support required.

CONTRACTORS/BUILDERS Pre-determined, pre

truss system. Fewer pieces to han

reduced installation

Wide 3-1/2 nailingeasy floor deck app Eliminate notching

joists for electrical wplumbing.

Floor trusses offer bavailability and lessthan 2x8 or 2x10 jo

Factory-manufacturcomponents to exacrequirements.

Reduced HVAC, pluelectrical subcontracjob.

No column pads to beams and posts to

Job site material pilcutting waste reduce

HOMEOWNER Lower construction Clearspan flexibility More flexibility in a

appearance and floo Easier remodeling p

moving interior wal

ADVANTAGESOF TRUSSESOVERCONVENTIONALFRAMING

ROOF ANDFLOORTRUSSADVANTAGGLOSSARY OFTERMS

WHYUSEWOODTRUSSES?CONTRACTORSANDBUILDERS

KNOW!

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

MITEK TRUSSESSAVEMONEY

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

MITEK TRUSSESARERELIABLE

Every MiTek truss has individually designed adesign is checked and acertified engineers for sadequacy.

MITEKTRUSSESAre Versatile

MiTek trusses provide flexibility, inside and oconventional framing. Onumerous custom desigour trusses present an eand structurally superiorapid 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 structuralefficiency of the member. The CSI shallnot exceed 1.00.Concentrated Load Loading applied at aspecific point, such as a load-bearing wall

running 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 certifiedengineers 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 tosit 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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4 FLOORTRUSSMAX-SPANHANDLING, INSTALLATION ANDBRACING

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 storedfor more than one week, the solid-blocking, generally provided bythe 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 ends

should be left open for ventilation.If trusses are made with interiorrated fire retardant lumber, extremecare should be taken to limit outsideexposure.

FIELDASSEMBLY

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 DOnofrioDrive, Suite 200, Madison, WI53719.

*Reprinted from the Commentary &

Recommendation for Handling, Installing &

Bracing,Metal Plate Connected Wood

Trusses,HIB-91, by permission of Truss

Plate Institute, Inc.

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

12

13

14

15

16

17

18

2022

24

17-11

18-09

19-17

20-04

21-01

21-09

22-06

23-1025-01

26-03

20-03

21-02

22-01

22-11

23-09

24-07

25-04

26-1028-03

29-07

20-06

22-02

23-11

25-03

26-02

27-01

27-11

29-0731-02

32-07

20-06

22-02

23-11

25-07

27-04

29-00

30-09

34-0236-03

37-11

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

12

13

14

15

16

17

18

2022

24

16-04

17-02

17-11

18-07

19-03

19-11

20-06

21-0922-11

24-00

18-08

19-06

20-04

21-02

21-11

22-08

23-05

24-0926-01

27-04

20-0

21-0

22-0

23-0

24-0

25-0

25-1

27-028-1

30-0


12

13

14

15

16

17

18

20

22

24

15-02

15-10

16-06

17-02

17-10

18-05

19-00

20-02

21-02

22-02

17-03

18-01

18-10

19-07

20-04

21-00

21-08

22-11

24-02

25-04

19-02

20-00

20-11

21-09

22-06

23-03

24-00

25-05

26-09

28-01

20-06

22-02

23-11

25-06

26-05

27-04

28-02

29-10

31-05

32-11


12

13

14

15

16

17

18

20

22

24

14-08

15-04

16-00

16-07

17-02

17-09

18-04

19-05

20-06

21-05

16-08

17-06

18-02

18-11

19-07

20-03

20-11

22-02

23-04

24-05

18-0

19-0

20-0

21-0

21-0

22-0

23-0

24-0

25-1

27-0


12

13

14

15

16

17

18

20

2224

13-09

14-05

15-00

15-07

16-02

16-08

17-03

18-03

19-0320-02

15-08

16-05

17-01

17-09

18-05

19-00

19-08

20-10

21-1122-11

17-05

18-02

19-00

19-09

20-05

21-02

21-10

23-01

24-0425-06

20-05

21-04

22-03

23-02

23-11

24-09

25-07

27-01

28-0629-10


12

13

14

15

16

17

18

20

2224

13-00

13-07

14-02

14-09

15-03

15-10

16-04

17-03

18-0219-00

14-10

15-06

16-02

16-10

17-05

18-00

18-07

19-08

20-0921-09

16-0

17-0

17-1

18-0

19-0

20-0

20-0

21-1

23-024-0

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 tr uss design.

HANDLINGINSTALLATIONANDBRACING*

It is the responsibility of theinstaller to select the mostsuitable method and sequenceof installation available tohim which is consistent withthe owners (architectural)plans and specifications and

such 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 necessaryfor the safe and acceptablecompletion of the roof orfloor and may remain in placeafter permanent bracing isinstalled.

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16 BASICROOFTRUSSCONFIGURATIOTECHNICALINFORMATION

KINGPOST DOUBLEF

QUEENPOST DOUBLEH

FINK HIP

HOWE SCISSOR

FAN MONOPIT

MODIFIEDQUEENPOST CAMBER

REPRESENTATIVEFLOOR ANDROOFAPPLIEDLOADS

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 TCDead 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 TCDeal 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 localbuilding code requirements)

10 psf TC Dead Load (includesfuture 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 buildingdesigner,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.

MITEKFLOOR 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 usinglesser grade 4x2 lumber, whilelonger spans are generally possiblewith higher grade lumber.

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

equally valid for top chord-bearingand bottom chord-bearing supportconditions.

The minimum truss span-to-liveload deflection is 360 for floorapplication. For example, themaximum permissible live loaddeflection for a 20' span floor trussis (20 x 12)/360=0.67".

In addition to the consideration oflumber strength and deflectionlimitations, the maximum trussspan-to-depth ratio is limited to 20

for floor loadings. For example themaximum span of a floorapplication truss 15" deep is 15" x20' = 300" span = 25' - 0" span.

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

TRUSS TYPES

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Description

Basic Wood Floor - consisting of wood joist (I-joist,

solid-sawn, or truss), 3/4decking and 5/8 gypsum

wallboard directly attached to ceiling

Cushioned Vinyl or Linoleum

Non-cushioned Vinyl of Linoleum

1/2 Parquet Flooring

3/4 Gypcrete or Elastizel

1-1/2 Lightweight Concrete

1/2 Sound Deadening Board (USG)*

Quiet-Cor Underlayment by Tarkett, Inc*

Enkasonic by American Enka Company*

Sempafloor by Laminating Services, Inc.*

R-19 Batt Insulation

R-11 Batt Insulation

3 Mineral Wood Insulation

Resilient Channel

Resilient with Insulation

Extra Layer of 5/8 Gypsum Wallboard

Carpet and Padding

36

0

0

0

7-8

7-8

1

1

4

1

2

1

1

10

13

0-2

0

STC HighFrequency

6 TECHNICALINFORMATIOBASICROOFTRUSSCONFIGURATIONS

DUALPITCH INVERTED

GAMBREL PIGGYBACK

POLYNESIAN STUDIO

ATTIC CATHEDRAL

BOWSTRING SLOPINGFLAT

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 regional building codes to rpermissible sound transfer.For more detailed informatithe Metal Plate Connected WHandbook, 1993 Wood TAmerica, Section 18.0 - TraVibration and Sound Transm

Description

Carpet and Padding

3/4 Gypcrete

Wood Truss Floor

Resilient Channel

0

7

36

10

20

1

33

8

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 Southern Pine Council, 1993.

TYPICALCONSTRUCTIONMATERIALWEIGHTS

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 psf

1/2 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 .............1-1/8 in. plywood ..........1 in. sheating (nominal).2 in. decking ..................Tectum (1 in. thick) ......Poured gypsum (1 in. thVermiculite concrete (1 i

.....................................Partition Wall Weights(8' Nominal Height)Interior partition - (studs

................................ 50Exterior partition - (studand composition exterior

................................ 85Exterior partition - (studand brick exterior) .. 180

Calculation Example

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14 FLOORTRUSSCONSTRUCTIONDETAITECHNICALINFORMATION

SUPPORTDETAILS

Bottom Chord Bearing onExterior Frame or Masonry Wall

Bottom Chord Exterior Fram

Masonry F

Intermediate Bearing - Simple Span TrussesIntermediate Bearing - Continuous F

(Special Engineering Requir

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

Intermediate Bearing - Floor Truss Sby Steel or Wood Beam

(Special Engineering Requir

Top Chord Bearing on Frame Wall Top Chord Bearing on Masonry

FLOOR TRUSSONE-HOURFIRERATINGThe 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 Research

1151 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 nailedwith alt. lightweight concrete

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

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

Furring Channels

1 layer 5/8 thick Type C, USG gypsumwallboard secured with screws, jointsfinished

3/4T&G plywood, glued and nailed

with 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 4x2ParallelChord

Trusses @max.24o.c.

1 layer 5/8 thick Type C, USGgypsum wallboard secured withscrews, joints finished

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

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

4x2 Wood Block Z-clip

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

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8 TECHNICALINFORMATIOFLOORTRUSSCONSTRUCTIONDETAILS

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

JOINTDETAILS

FLOORDECKINGINFORMATIONVirtually 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

Conventional Double-Layer

Plywood Underlayment over

Plywood Sub-Flooring

48/2440/20

32/16

24/16

23/32, 3/4, 7/819/32, 5/8, 3/4, 23/32

15/32, 1/2, 5/8, 19/32

7/16, 15/32, 1/2

219

1

16

215/32, 1/2, 5/8, 19/3219/32, 5/8, 3/4, 23/32

32/1640/20

Wood Strip Flooring over

Plywood Sub Flooring

(installed at right angles)

1-1/2 to 2 Lightweight

Concrete Cap over Plywood

Subflooring

40/20 19/32, 5/8, 3/4, 23/322

(Spac

Panel

Panels

be TonGroov

Betwe

23/32, 3/4, 7/819/32, 5/8

19/32, 5/8

7/8, 1

1-1/8

2420

16

32

48

APASturd 1-Floor (must be

nailed or glued and nailed

according to APA)

APAGlued Floor System

(must be glued according

to APA Spec. AFG-01 andnailed)

24 Spacing

19.2 Spacing

16 Spacing

(Available thicknessfor either conventional

subflooring plywood or

for Sturd-I-Floor

Panels.)

CONNECTORPLATECODEAPPROVALS

BOCA NationalBuilding CodeBuilding Officials and CodeAdministrators, International(BOCA) Research ReportNo. 96-31, 96-67

Uniform BuildingCode (UBC)International Conference ofBuilding Officials (ICBO)Report No. 3907 and 4922.

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

Federal HousinAdministrationU.S. DepartmeHousing and UDevelopment(HUD) Truss CBulletin No. TC

Wisconsin StatWisconsin DepIndustry. LaboRelations (DILApprovalNo. 960022-W

MiTek connector plates have been approved by recognized national and regional model buildinggroups, based on extensive structural testing. Th

approvals may be referenced for more detailed i

Chord Pre-SpliceChord Joint Splice

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12 FLOORTRUSSCONSTRUCTIONDETAITECHNICALINFORMATION

LATERALBRACINGSUGGESTIONS2x6 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 partition

walls 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

Overall

Truss

Depth

(Inches)

Diameter

(D)

(Inches)

Width (W) (Inches)

When Height (H) Equals:

3 4 5 6 7 8

32 25 19 1 2 6 -

34 2 8 2 3 1 7 1 1 5

3 6 3 1 2 6 2 0 1 5 1 0

3 8 3 3 2 8 2 3 1 9 1 4

4 0 3 5 3 1 2 6 2 2 1 7

4 1 3 7 3 2 2 8 2 4 2 0

4 2 3 8 3 4 3 0 2 6 2 2

4 3 3 9 3 6 3 2 2 8 2 5

4 4 4 0 3 7 3 3 3 0 2 6

4 4 4 1 3 8 3 5 3 1 2 8

4 5 4 2 3 9 3 6 3 3 3 0

4 6 4 3 4 0 3 7 3 4 3 1

4 6 4 3 4 1 3 8 3 5 3 2

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 TRUSSCANTILEVERCONCENTRATEDLOADSFloor truss cantilevers often supportload-bearing walls carrying roof liveloads and wall material dead loads. The

adjacent chart provides a convenientmeans of determining an equivalentconcentrated load for representative roofloads which incorporate a 15% loadduration factor for the roof load only.

CONCENTRATEDLOADSAMPLECALCULATIONRoof 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

20

22

24

2628

30

32

865

965

1005

10751145

1215

1285

1040

1125

1215

13001385

1475

1560

1215

1320

1425

15301630

1735

1840

Floor Cantilevered Perpendicularto Floor Truss Span

Section AA - Floor Truss Jacks FScab

Floor Cantilevered Perpendicuand Parallel to Floor Truss Spa

OverallTrussDepth

Roof Load

30-0

Wall Load

(Varies)

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10

Minimum Depth

Maximum DeflectionRecommended Camber

Spa

Span/240 Dead Load

TECHINICALINFORMATIO

Built-up Beamwith Strap

Hanger

Header BeamPocket

Header Beam withStrap 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 beams

must usually be increased beyond

conventional framing opening to permit

necessary headroom.

STAIRWAYFRAMING

FLOORTRUSSCONSTRUCTIONDETAILS

ARCHITECTURALSPECIFICATION

RECOMMENDEDDEPTH,DEFLECTION,AND CAMBERLIMITATIONS

Trusses shall be fabricated by aMiTek truss manufacturer inaccordance with MiTek floor trussengineering 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 Standard

for Metal Plates Converted WoodConstruction, a publication of TrussPlate Institute and generally acceptedengineering practice.

Delivery, handling, anMiTek trusses shall be with the TPI Quality Metal Plate Connected Wpublished by Truss Pl

Truss hangers, anchorabracing, and required shall be the responsibiProject Architect.

MiTek truss connectormanufactured under ricontrol using structura

hot-dipped, galvanizemeeting ASTM SpecifA653.

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 metverified by extensive fulltests. The floor span-to-deis intended to prevent objfloor vibration. All of therecommended limitationsachieved to provide a quasystem and assure complsatisfaction.

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

Span/20

Span/360 (Live Load)Dead Load Deflection

Floor R

CONSTRUCTION GUIDROOFSDONT 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.DONT break banding until

installation begins and the trusses arein a stable,horizontal position.DONT lift bundled trusses by thebands and do not use damaged trusses.DO brace trusses that are storedvertically, to prevent toppling ortipping.DONT 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 trusses

to provide proper installationorientation and to warn against cuttingor modifying trusses.DONT permit stacking of drywall orplywood sheathing during constructionon floor truss balcony cantilevers or attruss mid-span without proper shoring.

DONT use floor trusses exposed to weather, chemcorrosive environment, orhigh humidity.DONT cut truss chords omodify them in any way dconstruction.

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roof truss facts mitek

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