Chambers Truss Terms

Anchorage is the connection of the roof or floor truss to the building structure.

ANSI is the American National Standards Institute.

ANSI/TPI 1 1-1995 is a publication of the Truss Plate Institute (TPI) and ANSI defining a standard for design and manufacture for Metal Plate Connected Wood Trusses (MPCWT).

ANSI/TPI 2 1-1995 is a publication of the Truss Plate Institute (TPI) and ANSI defining a standard for testing  and evaluation of  Metal Plate Connected Wood Trusses (MPCWT) designed & manufactured per ANSI/TPI 1 1-1995.

Architect is the registered architect responsible for the design of the structure.  Webster's defines  Architect as  "one who designs buildings and supervises their construction". 

Bearing or Load Bearing is the structural support, a wall or beam, that carries the truss.

Bending Moment is the measurement of the stress across the cross section of a truss member.

Board Foot is the standard measurement of lumber, one board is equal to a nominal board 12" long, 1" wide & 1" thick.

BOCA is a Model Code sponsored by  the Building Officials and Code Administrators International.

Bottom Chord a member that forms the bottom of the truss.

Bottom Chord Upset is a small vertical cut, usually 1/4", at ends of the bottom chord. It insures uniform span.

Bow or crown, is deviation flatwise from a straight line drawn from end to end of the piece of lumber.

Bracing is applied by the truss installer to provide support to the trusses and is a part of the truss system. See Permanent, Temporary and Web Bracing.

Building Designer designs the building and  prepares building plans.

Builder is the person or organization responsible for the construction of the building and the safe installation and bracing of trusses.

Butt Cut or Upset is a small vertical cut, usually 1/4", at ends of the bottom chord. It insures uniform span.

Cantilever is the part of the truss that extends beyond the trusses support or bearing. is the part of the truss that extends beyond the trusses support or bearing. is the part of the truss that extends beyond the trusses support or bearing.

Chase is the opening in a floor or flat truss in which utilities such as ducts are run. Strongbacks often run next to Chases.

Chords   are the wood truss members that establish the top or bottom of the truss.

Combined Stress Index (CSI) is the total of axial and bending stresses as a ratio of allowable stress in truss members. The CSI ratio can be up to .99. Maximum CSI are shown on truss design drawings.  

Compression Member is a truss member that is resisting compression, or pushing. Truss top chords are in compression.

Compression Parallel To Grain is compression acting on the end of a piece of lumber. Lumber is better in resisting Compression Parallel To Grain as compared to Compression Perpendicular To Grain.

Compression Perpendicular To Grain is compression acting on the side of a piece of lumber. Lumber is worse in resisting Compression Perpendicular To Grain as compared to Compression Parallel To Grain.

Concentrated Load is a load applied at one specific point on a truss such as an air conditioner hung from a truss. 

Contractor is the person or organization responsible for the construction of the building and the safe installation and bracing of trusses.

Construction Design Documents are the any drawings specifications, and addenda set forth the overall design of the structure issued by the Building Designer.

Creep is the deflection or sagging of wood over time. Wood gets tired with time causing creep. Engineered products such as trusses and beams allow for creep.

Cricket is a small ridge framed between two parallel roof planes to drain water off the roof.

Crook is a distortion of lumber along the length of a board that the characterized by twist.

Crown or Bow is deviation flatwise from a straight line drawn from end to end of the piece of lumber.

CSI (Combined Stress Index) is the total of axial and bending stresses as a ratio of allowable stress in truss members. The CSI ratio can be up to .99. Maximum CSI are shown on truss design drawings.  

Cup is the distortion of lumber across the width of the board.

Dead Loads are permanent, long duration loads such as weight of the truss itself , sheeting, roofing and ceiling material.

Deflection  is the sagging of lumber or trusses under load. Deflection is caused by the elasticity or stretchiness of wood. Engineered components, such as wood trusses, have predicted deflection.

Design Responsibilities per WTCA-1 1995 defines the responsibilities of Owner, Building Designer, Contractor, Truss Manufacturer and Truss Designer as they relate to the design of Metal Plate Connected Wood Trusses. WTCA-1 1995 is referenced by the Standard Building Code. Chambers Truss recognizes WTCA-1 1995 as the authority for defining design responsibilities and references WTCA-1 1995 in its contacts. 

Duration of Load the length of time a load is applied truss. Wood responds to load differently depending on the duration of load allowing stresses to modified in relation to the time a truss is under load. Dead Loads have duration of the life of the structure. Live Loads have short duration measured in minutes or hours.

End Cuts at the ends of the truss are normally Plumb or Square.

Engineer of Record is a registered professional engineer (PE) responsible for the structural design of the building, and  produces the structural drawings included in the Construction Design Documents.

Fascia is the trim flat lumber surface at the end of the overhang or end of the truss over the sub-fascia.

4X2 truss has its members have the nominal 2" face up for plate embedment, the 4x2 truss is a nominal 4" deep rather than a nominal 2" deep. 4x2 design is used for shallow floor trusses.  

Hangers connect carried trusses to the carrier or girder. Hangers also connect conventional framing, such as joists to beams. Chambers Truss supplies all truss to truss hangers.

Heel is the point on either end of the truss where the top and bottom chords come together.

Heel Height is the vertical measure of the truss at the heel.

HIB-91  is “Commentary and Recommendations For Handling Installing & Bracing Metal Plate Connected Wood Trusses”. HIB-91 is published by the Truss Plate Institute (TPI). HIB-91 should be studied and understood by anyone installing wood trusses.

Jack Truss  is a small, mono-pitched, usually open ended truss that with a hip girder forms a hip end.

Jack Scab is small or partial truss attached, or scabbed to a truss to change or repair the truss.

Loads are forces or other actions on the structure from the weight of the structure, occupants & their possessions, & environmental factors such as wind. Truss loads are expressed as live and dead loads.

Load Bearing or Bearing is the structural support, a wall or beam, that carries the truss.

Level Return is a lumber filler attached to the end of the overhang running horizontal to the wall to form a soffit.

Live Loads are those short duration loads produced by the construction, maintenance, wind, and occupancy of the structure.

Members are the wood pieces, chords and webs that make up the truss.

Metal Connector Plates have integral teeth, are manufactured in various grades and sizes, are pressed into the truss members to connect the members forming the truss.

Mono-Pitched Truss has a single pitched top chord.  

Overhang is the extension of the top chord of the truss beyond the heel.

Owner is the person or organization who the building is being built for.

Pitch is the angle of the roof described as Inches of Rise over Inches of Run. 5/12 is 5" of rise over 12" run.

Plumb Cut is a truss end cut the is perpendicular to the wall. Also see Square Cut.

Scab is addition lumber or truss attached by nailing to a truss to add strength to or repair the truss.

Set Back is the distance from the end of a hip truss that the flat top chord begins.

Slope is the angle of the roof  described as Inches of Rise over Inches of  Run (same as pitch).

Square Cut is a truss end cut that is perpendicular to slope of the truss. Also see Plump Cut.

Strap ties a truss to bearing to resist seismic of wind force. Strap or clip tie down in used Florida. Chambers Truss does not provide tie down straps.

Strongback is a 2" by lumber attached perpendicular to a truss. Normally applied to a floor truss the Strongback can help a roof truss.  Usually placed against a vertical web the Strongback adds rigidity and uniformity to a truss system.

Sub-Fascia is the rough flat lumber surface at the end of the overhang or end of the truss on which the fascia is applied.

Tension Member is a truss member that is resisting tension, or pulling. Truss flat bottom chords are in tension.

Triangle is a 3 sided plane geometric shape. The triangle is the only rigid geometric shapes. Trusses are based on the rigid  triangle.

Truss (Metal Connected Wood Truss) is an engineered structural component made of lumber and metal connector plates. Click on Truss Diagram to see the parts of a truss.

Truss Design Programs design & engineer trusses. The programs are written and maintained by manufactures of Metal Connector Plates , such as MiTek Inc, and independent firms. Chambers Truss uses the MiTek 2000 program.

Truss Designer is a registered engineer (PE) how is responsible to individual truss design.

Truss Design Technicians prepare Truss Setting Layouts and Truss Drawing for a Truss Manufacturer. They are not Profession Engineer and are also called Cutlist and Layout persons. 

Truss Drawing is a drawing of  an individual truss & engineering design specs.

Truss Layout  is a drawing showing the location of trusses. Chambers Truss  uses the Layout as a contract document defining materials. 

Truss Placement Plan or Truss Layout is a drawing showing the location of trusses. Chambers Truss  uses the Layout as a contract document defining materials. 

Uniform Load is a load applied to the entire truss, such as the weight of the roof shingles. 

Valley Set is a set of non-structural trusses that sit on trusses to frame the valley formed by two roof planes.

Upset or Butt Cut is a small vertical cut, usually 1/4", at ends of the bottom chord. It insures uniform span.

WTCA 1-1995 Standard Responsibilities Document defines the responsibilities of Owner, Building Designer, Contractor, Truss Manufacturer and Truss Designer as they relate to the design of Metal Plate Connected Wood Trusses. WTCA-1 1995 is referenced by the Standard Building Code. Chambers Truss recognizes WTCA-1 1995 as the authority for defining design responsibilities and references WTCA-1 1995 in its contacts.