Terminology
The following glossary of words includes defined terms that are words used within the component manufacturing and truss industry that have specific and potentially unique meanings. In SBCA documents, the defined terms are shown italicized.
Unless otherwise expressly stated, the following words and terms shall have the meanings shown. Words used in the present tense include the future; words stated in the masculine gender include the feminine and neutral; the singular number includes the plural and the plural, the singular.
ANCHORAGE: Connection between the roof or floor framing members (trusses, bracing, etc.) and the building structure, which is required to transfer the forces from these members into the building.
Blocking: A solid member placed between structural members, usually at the bearings, to provide lateral support and transfer lateral loads perpendicular to the span direction of the structural member from the structural member to a diaphragm or the lateral force resisting system.
Bottom chord: The horizontal or pitched member(s) that defines the lower edge of a truss, usually carrying combined tension and bending stresses.
Bottom chord plane: The two-dimensional area formed by the top or bottom edge of adjacent similar bottom chords allowing for the connection of a rigid plane, diaphragm, or bracing members in a linear fashion.
Bottom chord temporary lateral restraint (BCTLR): Structural members installed at right angles to the bottom chord of a truss during construction to reduce the laterally unsupported length of the bottom chord.
Brace, Bracing: Member(s) that provide stability and prevent unintended movement or motion.
Building: Any structure used or intended for supporting or sheltering any use or occupancy.
Building Designer: Owner of the building or the person that contracts with the owner for the design of the building structural system and/or who is responsible for the preparation of the construction documents. When mandated by the legal requirements, the building designer shall be a registered design professional.
Building Official: Officer or other designated authority charged with the administration and enforcement of the building code, or a duly authorized representative.
Construction Documents: Written, graphic and pictorial documents prepared or assembled for describing the design, location and physical characteristics of the elements of a project necessary for obtaining a building permit.
Competent person: One who is capable of identifying existing and predictable hazards in the surroundings or working conditions which are unsanitary, hazardous, or dangerous to employees, and who has authorization to take prompt corrective measures to eliminate them. From OSHA 29 CFR 1926.32(f)
Contractor: Owner of a building, or the person who contracts with the owner, who constructs the building in accordance with the construction documents and the truss submittal package. The term “contractor” shall include those subcontractors who have a direct contract with the contractor to perform all or a portion of the construction.
Cross Bracing: A type of diagonal bracing in which the bracing members are crossed to form and “X.” Cross bracing is installed in the web member plane of trusses to transfer lateral loads out of the truss system into the roof and ceiling rigid sheathing. Also referred to as “sway bracing” or “X-bracing”.
Diagonal Brace: Structural member(s) installed along a portion of a top chord, bottom chord, or web plane, at approximately 45 degrees to a lateral restraint member to provide a load path for the lateral restraint.
Diaphragm: Horizontal or sloped system defined by the ceiling, floor or roof plane acting to transmit lateral forces to the vertical lateral force resisting system (e.g., braced wall lines, braced frames, shear walls, etc.).
Gable End Frame: A component manufactured to complete the end wall of a building. The bottom chord of the gable end frame has continuous vertical support provided by the end wall or beam. The vertical members function as Load carrying members and as attachment members for sheathing or other end wall coverings.
Girder Truss: Truss designed to carry loads from other structural members framing into it.
Ground Bracing: Used to provide stability for the first truss or group of trusses installed. It is composed of vertical and diagonal members providing support for the installed trusses from the earth, floor, foundation or slab.
Heel Height: Vertical depth of the truss at the outside face of bearing.
Hip Set: Series of step down trusses of the same span and overhang, that decrease in height to form the end slope of a hip roof system.
Hip Truss: Trusses used in a hip set roof system. Each hip truss has the same span and overhang as the adjacent standard trusses but decreases in height with the top and bottom chords of its center portion parallel to each other and horizontal. Also referred to as a step-down truss.
I-Reinforcement: Two pieces of stress-graded lumber attached to a web as reinforcement against buckling instability. The wide face of each reinforcing member is attached to the narrow faces of the web, forming an I-shape.
Jurisdiction: Governmental unit that is responsible for adopting and enforcing the building code.
L-Reinforcement: A piece of stress-graded lumber attached to a web as reinforcement against buckling instability where the wide face of the reinforcing member is attached to the narrow face of the web, forming an L shape.
Lateral System, Lateral Force Resisting System: A specific structural system within a building designed to withstand and resist lateral loads, such as wind or seismic loads, primarily composed of elements like shear walls, moment frames, or braced frames, which work together to maintain the building's stability.
Lateral Restraint: A structural member installed at right angles to a chord or web member of a truss to reduce the laterally unsupported length of the truss member.
Light-Frame Construction: Construction whose vertical and horizontal structural elements are primarily formed by a system of repetitive wood or cold-formed steel framing members.
Long Span Truss: Trusses with a clear span of 60 feet or greater.
Metal Plate Connected Wood Truss (MPCWT): Engineered, pre-fabricated structural component, assembled from wood members and metal connector plates, and designed to carry superimposed dead and live loads. The truss members form a rigid, planar, structural component and are usually assembled such that the members form triangles.
Mono Truss: Truss that has a single top chord, and a slope greater than 1.5/12.
Multi-Ply Truss: A truss designed to be installed as an assembly of two or more individual trusses fastened together to act as one. Ply-to-ply connections of multi-ply trusses are specified on the truss design drawing.
Nail-On Plate: Light-gauge cold-formed steel metal connector plates with pre-punched holes or, if cut to size, without holes but having identifying marks through which nails are driven by hand or power means into the lumber. They are typically used in repairs.
Owner: Person having a legal or equitable interest in the property upon which a building is to be constructed, and: (1) either prepares or retains the building designer to prepare the construction documents; and (2) either constructs or retains the contractor to construct the building.
Panel Point: Location on a truss where the web members and top or bottom chords intersect and are connected by truss plates.
Parallel Chord Truss (PCT): Truss with top and bottom chords with equal slopes.
Permanent: Part of the final building structure.
Piggyback Truss: Truss made and shipped to the jobsite in two pieces consisting of a supporting truss with a triangular supported cap truss. The supporting truss and cap truss are attached to one another at the jobsite. Piggyback trusses are used when shipping or manufacturing restrictions limit the overall truss height.
Purlins: Structural horizontal members attached perpendicular to the truss top chord used to provide lateral restraint to the top chord and to support and transfer the roof loads to the trusses.
Qualified: One who, by possession of a recognized degree, certificate, or professional standing, or who by extensive knowledge, training and experience, has successfully demonstrated their ability to solve or resolve problems relating to the subject matter, the work, or the project. See OSHA 29 CFR 1926.503(a)(2) for fall arrest qualifications.
Registered Design Professional (RDP): Architect or engineer, who is licensed to practice their respective design profession as defined by the legal requirements of the jurisdiction in which the building is to be constructed.
Ribbon: Framing member installed on the edge of the perimeter, usually tying the ends of floor trusses together.
Rigid Panel: Sheathing material such as a gypsum panel or wood structural panel.
Rim Joist: Full-depth framing member installed on the edge of the perimeter, used to provide lateral support and to tie the ends of floor trusses together. Also referred to as a band board.
Scab Reinforcement: A piece of stress-graded lumber attached to a web as reinforcement against buckling instability. The wide face of the reinforcing member is attached to the wide face of the web.
Scissors Truss: Dual pitch, triangular truss with dual pitched bottom chords.
Short Member Temporary Lateral Restraint: Short pieces of 2x4 or larger members fastened at right angles to the truss chords during installation of the trusses for the purpose of reducing the laterally unsupported length of the truss member. Depending on the method of installation, the length of the 2x4 member is usually slightly less or slightly more than the truss spacing dimension.
Stacked Web Reinforcement: Reinforcement member plated to the narrow face of a web in the truss plant to avoid the need for field-installed reinforcement or lateral restraint and bracing.
Strongback: Nominal 2x6 or greater stress-graded lumber attached perpendicular to floor trusses, often through the chase opening, and placed vertically against a vertical web, or vertical block attached to the side of the truss.
Structural Building Components: Specialized structural building products designed, engineered and manufactured under controlled conditions for a specific application. They are incorporated into the overall building structural system by the building designer. Examples are roof trusses, floor trusses, floor panels, wall panels, I-joists, beams, headers, lintels, structural sheathing, columns, etc.
Structural Sheathing: The structural covering used directly over the roof, floor or wall framing members that transfers perpendicular Loads to the framing members. structural sheathing commonly used with Trusses includes plywood, oriented strand board (OSB), and certain types of metal decking. Properly sized and installed, structural sheathing provides both lateral restraint and stability to the truss members.
Submittal Documents: Construction documents, special inspection and structural observation programs, data, guides, reports, and manufacturer’s installation instructions submitted for approval with each permit application or available at the jobsite at the time of inspection.
T-Reinforcement: A piece of stress-graded lumber attached to a web as reinforcement against buckling instability. The wide face of the reinforcing member is attached to the narrow face of the web, forming a T-shape.
Temporary: Used during construction and installation of the trusses and not necessarily required to remain in place after the structure is complete.
Top Chord: Inclined or horizontal member(s) that establishes the top edge of a truss, usually carrying combined compression and bending stresses.
Top Chord Plane: The two-dimensional area formed by the top or bottom edge of adjacent similar top chords, allowing for the connection of a diaphragm or bracing members in a linear fashion.
Top Chord Temporary Lateral Restraint (TCTLR): Structural members installed at right angles to the top chord of a truss during construction to reduce the laterally unsupported length of the top chord.
Truss: Individual metal plate connected wood component manufactured for the construction of the building.
Truss Design Drawing (TDD): Written, graphic and pictorial depiction of an individual truss that includes information required in ANSI/TPI 1.
Truss Designer: Individual responsible for the design of the individual truss members and preparation of the truss design drawings. The truss designer shall be a registered design professional where required by the statutes of the jurisdiction in which the project is to be constructed.
Truss Length: Outside-to-outside distance between exterior bearing locations.
Truss Manufacturer: Person engaged in the fabrication of trusses.
Truss Orientation: Truss position or alignment within a structure relative to bearing walls.
Truss Placement Diagram (TPD): Illustration identifying the assumed location of each truss.
Truss Plate: Individual metal connector plate manufactured from ASTM A446, A591, A792 or A167 structural quality steel protected with zinc or zinc-aluminum alloy coatings or their stainless steel equivalent. The truss plate has integral teeth and is manufactured in various sizes (i.e., lengths and widths) and thicknesses or gages and is designed to laterally transmit loads when embedded in wood members.
Truss Profile: A side view representation or outline of a truss.
Truss Clear Span: Inside-to-inside distance between bearing points, interior and exterior.
Truss Submittal Package: Package consisting of each individual truss design drawing, and, as applicable, the truss placement diagram, the cover/truss index sheet, lateral restraint and diagonal bracing details designed in accordance with generally accepted engineering practice, applicable BCSI defined lateral restraint and diagonal bracing details, and any other structural details germane to the trusses.
U-Reinforcement: Two pieces of stress-graded lumber attached to a web as reinforcement against buckling instability. The wide face of each reinforcing member is attached to the narrow faces of the web, forming a U-shape.
Valley Set: Set of triangular components used to frame the shape of dormers and to complete the roof framing where trusses intersect at perpendicular corners.
Web Member Plane: Two-dimensional area formed by the top or bottom edge of adjacent similar web members allowing for the connection of lateral restraint and bracing members.
Web Reinforcement: Piece of structural material attached to a web as reinforcement against buckling instability. Types of web reinforcement include T-, L-, I-, U-, scab, stacked web and proprietary metal reinforcement.
Web: Member that joins the top and bottom chords to form the triangular patterns typical of trusses. These members typically carry axial forces.
ACRONYMS AND INITIALISMS
BCTLR: Bottom Chord Temporary Lateral Restraint
BCPLR: Bottom Chord Permanent Lateral Restraint
BCSI: Building Component Safety Information
PCT: Parallel Chord Trusses
SBCA: Structural Building Components Association
TCTLR: Top Chord Temporary Lateral Restraint
TDD: Truss Design Drawing
TPD: Truss Placement Diagram
TPI: Truss Plate Institute