Industry Terminology

**Industry Terminology provided courtesy of**
WTCA - Wood Truss Council of America

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A

American Softwood Lumber Standard

Voluntary product standard of the U.S. Department of Commerce that serves as a basis for the preparation and revision of industry-sponsored grading rules for lumber.

American Standard Lumber

Lumber conforming to the basic provisions of the American Softwood Lumber Standard.

Anchorage

Connection between the roof or floor framing members (e.g., trusses, bracing, etc.) and the building structure, which is required to transfer the forces from these members into the building.

ANSI/TPI 1, American National Standard, National Design Standard For Metal Plate Connected Wood Truss Construction

Publication of the Truss Plate Institute (TPI) developed under the American National Standards Institute (ANSI) consensus process. Provides the analysis, design and manufacturing criteria for the metal plate connected wood truss industry.

ANSI/TPI 2, American National Standard, Standard For Testing Performance For Metal Plate Connected Wood Trusses

Publication of the Truss Plate Institute (TPI) developed under the American National Standards Institute (ANSI) consensus process. Provides a state-of-the-art consensus standard for testing and evaluating wood trusses designed and manufactured in accordance with ANSI/TPI 1.

Architect

Any registered architect who designs all or a part of the Building Structural System and/or who produces all or part of the Building Structural System Design Documents.

Attic Scuttle

Framed opening with removable cover providing access to the attic.

Axial Force

Push (compression) or pull (tension) force acting along the length of a member. Usually measured in pounds, kips (1000 lb), tons (2000 lb) or the metric equivalents.

Axial Stress

Axial force acting at a point along the length of a member, divided by the cross sectional area of the member. Usually measured in pounds per square inch.

B

Beam Pocket

Void or cut-out built into truss to allow beam support

Bearing

Structural support, usually a beam or wall, that is designed by the building designer to carry the truss reaction loads to the foundation.

Bending Moment

Measure of the bending effect due to the live load and dead load on a given truss chord member. The bending moment at a given point along a member equals the sum of all perpendicular forces, either to the left or right of the point, times their corresponding distances from the point.

Bending Stress

Force per square inch of area acting at a point along the length of a member resulting from the bending moment applied at that point. Usually measured in pounds per square inch (psi) or metric equivalent.

Bird's Mouth Cut Notch

Formed by a plumb and seat cut at the eave end of a rafter that allows the rafter to sit on the top plate.

Board

Lumber less than 2" in nominal thickness

Board Foot

Unit of measurement represented by a board 1' long, 1' wide, and 1" thick. Abbreviation ft. b.m., bd. ft., or fmb. In finished or surfaced lumber, the board-foot measure is based on the nominal size. In practice, the working unit is 1000 board feet. Abbreviation M bd. ft., M B.M., or M B.F.

Bottom Chord

Inclined (e.g., scissors truss) or horizontal member that establishes the bottom of a truss, usually carrying combined tension and bending stresses.

Bottom Chord Bearing

Bearing condition of a parallel chord truss that bears on its bottom chord.

Bottom Chord Upset

See Butt Cut.

Bottom Plate

Bottom horizontal framing member of a stud wall.

Bow

Distortion of a piece of lumber in which there is a deviation in a direction perpendicular to the flat face from a straight line from end to end of the piece.

Bracing

See Permanent Bracing and Temporary Bracing.

Break Point Joint

Top chord joint of a hip truss where the sloping chord member and horizontal member meet.

Building

A structure intended for supporting or sheltering a specific use or occupancy.

Building Designer

The Owner of the Building or the individual or organization who contracts with the Owner for the design of the Building Structural System and/or who produces the Building Structural System Design Documents. The Building Designer may be an Architect or Engineer.

Building Officials and Code Administrators International (BOCA)

Group that oversees the National Building Code (NBC), one of the model building codes and part of the International Code Council (ICC).

Building Structural System

The completed combination of Structural Elements, Trusses, connections and systems, which serve to support the Building's self weight, the applicable live load, and environmental loads.

Building Structural System Design Documents

The architectural drawings, structural drawings, and any other drawings, specifications and addenda, which set forth the overall structural design of the Building Structural System.

Built-Up Beam

Single member composed of two wood members having the same thickness but not necessarily the same depth, which provides greater load carrying capability as well as lower deflection (e.g., garage door, stairwell and fireplace headers).

Built-Up Roof

Roofing composed of three to five layers of asphalt.

Butt Cut

Vertical cut at outside edge of a truss bottom chord to ensure uniform nominal span and tight joints, typically 1/4".

Butt Joint

Interface at which the ends of members meet in a square cut joint.

C

CAD

Computer aided design and drafting software.

Camber

Upward curvature built into a truss bottom chord to compensate for deflection due to loading conditions

Cambium

Layer of cells that lie between the inner bark and the wood of a tree, that repeatedly subdivides to form new wood and bark cells.

Cantilever

Part of a truss that extends beyond its support, exclusive of overhang.

Center Bearing Truss

Truss with structural support at center of truss span as well as at heel joints

Center Line Span

Theoretical span sometimes used to design trusses

Chase Opening

Rectangular opening in a floor or sloping flat truss for the purpose of running utilities through it, such as heating and air conditioning ducts

Check

Separation of the wood along the fiber direction that usually extends across the rings of annual growth, commonly resulting from stresses set up in wood during seasoning

Chord

See Top Chord and Bottom Chord

Clear Span (Clear Opening)

Indicates the inside or interior frame-to-frame dimensions. Not to be confused with span

Clinched Nail

Nail selected to be longer than the member it is driven through and which is bent back the dimension of its excess length

Clipped End

See Stub Truss

Collar Beam

Wooden member connecting opposite roof rafters

Collar Tie

Horizontal member placed between two rafters a specific vertical distance above the very top plate line for the purpose of limiting outward thrust of the rafters

Combined Stress

Combination of axial and bending stresses acting on a member simultaneously, such as occurs in the top chord (compression + bending) or bottom chord (tension + bending) of a truss

Combined Stress Index (CSI)

Summation of axial and bending stresses divided by their respective allowable stresses for a specific truss member. This ratio, or index, represents the structural "efficiency" of the member. The CSI shall not exceed 1.00

Composite Lumber (Structural, Wood Composites)

Family of materials that contain wood in whole or fiber form bound together with an adhesive of natural or synthetic form

Compound Cut

Double cut made across the member width

Compression Chord

Chord members in a truss that resist compression (push) forces

Compression Parallel-To-Grain

Compression, endwise (parallel to the grain). The imposition of a compressive stress that acts in a direction parallel to the grain of the wood, as in a column

Compression Perpendicular-To-Grain

Compression, sidewise (perpendicular to the grain). The imposition of a compressive stress that acts in a direction approximately perpendicular to the grain of the wood

Compression Wood

Abnormal wood formed typically on the lower side of branches and inclined trunks of softwood tress. Compression wood is identified by its relatively wide annual rings, usually eccentric, relatively large amount of late wood, sometimes more than 50% of the width of the annual rings in which it occurs, and its lack of demarcation between early wood and late wood in the same annual rings. Compression wood shrinks excessively lengthwise, as compared with normal wood

Concentrated Load

Loading applied at a specific point, such as a load-bearing wall running perpendicular to a truss, or a roof-mounted A/C unit hanging from a truss

Conifer

Tree belonging to the order Conifer, usually evergreen, with cones and needle-shaped or scale-like leaves, and producing wood known commercially as "Softwood."

Construction Design Documents

Architectural drawings, structural drawings, mechanical drawings, electrical drawings, and any other drawings, specifications, and addenda that set forth the overall design of the structure and issued by the Building Designer

Continuous Lateral Bracing

See Lateral Bracing

Contract

A legally recognized document between two or more parties and includes the agreement between the Truss Manufacturer and its customer which sets forth the terms and conditions (and scope of work) applicable to the Truss Manufacturer

Contractor

The Owner of the Building or the individual or organization who contracts with the Owner for the construction of the Building Structural System

Conventional Framing

Framing with conventional joists, rafters and wall studs

Creep

Time-dependent deformation of a structural member under constant load

Cricket

Drainage-diverting roof framing. Generally found on the high sloped end of a chimney

Crook

Distortion of a piece of lumber in which there is a deviation in a direction perpendicular to the edge from a straight line from end to end in a piece

Cross Bracing

Bracing installed in the web member plane of trusses to transfer lateral loads out of the truss system and up into the roof and down into the ceiling diaphragms.

Cross Bridging

Wood or metal members that are placed between trusses or joists in an angled position intended to spread the load.

Cup

Distortion of a board on which there is a deviation flat-wise from a straight line across the width of the board.

Cutting Sheets

(Cut Sheets) Diagram of lumber lengths and angles of cut for truss web members and chords.

D

Dead Load

Any permanent load such as the weight of the truss itself, purlins, sheathing, roofing and ceiling, acting vertically on the truss or truss members.

Decay

Decomposition of wood substance caused by action of wood-destroying fungi, resulting in softening, loss of strength and weight, and often in change of texture and color.

Defect

Any irregularity or imperfection in a tree, log, piece, product, or lumber that reduces the volume of sound wood or lowers its durability, strength, or utility value.

Deflection

Amount a member sags or displaces under the influence of forces.

Dense

(1) Term used in stress grading of certain softwood species to signify a high specific gravity.

(2) A visual estimate of high specific gravity. To be classified as dense, the softwood species shall average on one end or the other of each piece, not less than six annual rings per inch and one-third or more late wood. Pieces not less than four rings per inch shall be accepted as dense if they average one-half or more late wood.

Depth Effect Factor

See Size Factor.

Design Loads

Dead and live loads for which a truss is designed to support.

Diagonal Bracing

Used in conjunction with lateral bracing to transfer brace forces into the supporting structure. Diagonal braces are installed in the same plane as lateral bracing but at 45° angle to the lateral brace.

Dimension Lumber

Type of lumber from nominal 2" through 4" thick and 2" or wider.

Dressed Lumber

Type of lumber that is surfaced by a planing machine on one side (S1S), two sides (S2S), one edge (S1E), two edges (S2E), or any combination of sides and edges (S1S1E, S2S1E, S1S2E, or S4S). Dressed lumber may also be referred to as planed or surfaced.

Dressed Size

Dimensions of lumber after surfacing with a planing machine. Usually 1/4" or 3/4" less than nominal size. The American Softwood Lumber Standard lists standard dress sizes.

Drywall

See Gypsum Board.

DSB-89, Recommended Design Specification for Temporary Bracing of Metal Plate Connected Wood Trusses

Publication of the Truss Plate Institute (TPI) developed for use by architects and engineers to provide guidance for design specification for temporary bracing.

Dual Pitch Truss

Truss that changes pitch at the top chord peak joint.

Duration of Load

Duration of stress or the time during which a load acts on a member. In wood, a design consideration for modifying allowable stresses, based on the accumulated loadings anticipated in the life of a structure.

E

E

See Modulus of Elasticity.

Early Wood

Less dense, large-celled, part of the growth layer formed first during the annual growth cycle. Also called spring wood.

Earthquake Load

See Seismic Load.

End Jack

Relatively short and usually mono-pitched truss used to frame the hip end of a hip roof system.

Engineer

Any registered engineer who designs all or a part of the Building Structural System and/or who produces all or a part of the Building Structural System Design Documents.

Engineer of Record

Registered professional engineer responsible for the structural design of the structure and who produces the structural drawings included in the construction design documents.

Equilibrium Moisture Content

Moisture content at which wood neither gains nor loses moisture to the surrounding air.

F

Fascia

Trim board applied to ends of overhangs.

Feather Cut

Heel cut that has been made with a zero butt cut.

Fiber Saturation Point

Moisture content at which the cell walls are saturated with water (bound water) and no water is held in the cell cavities by capillary forces.

It usually is taken as 25 to 30% moisture content, based on weight when ovendry.

Fire Retardant

Having or providing comparatively low flammability or flame spread properties.

Force Diagram

Graphical solution of axial forces as they interact within the members of a truss.

G

Gable

Portion of the end wall above the eave line of a double sloped roof.

Gable End Frame

A component manufactured to complete the end wall of a building. The bottom chord of the gable end frame is continuously supported by the end bearing wall. Verticals between the top and bottom chords are typically spaced at 24" on center.

The verticals function as load carrying members and as attachment members for sheathing or other end wall coverings. The gable end frame must be incorporated into the end shear wall by the building designer.

Gambrel

Roof having two slopes on each side of the peak, the lower slope usually steeper than the upper one.

Gang Nail

See Metal Connector Plate.

Girder Truss

Truss designed to carry heavy loads from other structural members framing into it. Usually a multiple-ply truss

Grade

Designation of the quality of a manufactured piece of wood.

Green

(1) Freshly sawed wood, or wood that has received no drying; unseasoned. Lumber that may have become wet to above the fiber saturation point may be referred to as being in the "green condition."

(2) Wood above a stipulated moisture content, as lumber above 19% moisture content in accordance with the American Softwood Lumber Standard.

Gypsum Board

Interior finish sheet material manufactured with gypsum.

H

Header

Structural member located between stud, joist, rafter, or truss openings.

Heart Shake

Shake that starts out at or near the pith and extends radially. Also know as Heart crack and rift crack.

Heartwood

Inner layer of a woody stem wholly composed of nonliving cells and usually differentiated from the outer enveloping layer (sapwood) by its darker color. It is usually more resistant to decay than sapwood.

Heel Cut

See Butt Cut.

Heel Joint

Point on the truss where the top and bottom chords intersect.

HIB-91, Commentary and Recommendations for Handling, Installing and Bracing Metal Plate Connected Wood Trusses

Publication of the Truss Plate Institute (TPI) providing recommendations and guidelines to contractors for handling, installing and bracing metal plate connected wood trusses for applications up to 2' on center.

Hip Corner

Either truss or conventional framing, that along with the end jacks, forms the hip ridge and roof areas between the end wall and hip girder.

Hip Girder

Truss designed to carry end jacks and hip corners or common framing.

Hip Roof

Roof system in which the slope of the roof at the end walls of the building is perpendicular to the slope of the roof along the sides of the building.

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.

Horizontal Shear

Shear that occurs in planes parallel to the longitudinal axis of the member; sometimes referred to as longitudinal shear.

Hydraulic Press

Press consisting of a "C" clamp hydraulic cylinder; or an I-beam platen, or flat upper pressing platen, powered by hydraulic cylinders that are used to embed metal connector plates into a truss.

I

I-Joist

Structural member manufactured using sawn or structural composite lumber flanges and structural panel webs, banded together with exterior exposure adhesives, forming the cross-section shape of the capital letter "I".

These members are primarily used as joists in floor and roof construction.

Impact Load

Load resulting from moving machinery, elevators, craneways, vehicles or other similar forces and kinetic loads.

Incise

To make slit-like lacerations generally parallel to the grain in the lateral surface of timbers that are resistant to treatment so that deeper and more uniform penetration of preservative may be obtained.

Interior Bearing

Supports that are interior to two exterior supports.

International Code Council (ICC)

Group that oversees the International Building Code (IBC) and the International Residential Code (IRC).

International Congress of Building Code Officials (ICBO)

Group that oversees the Uniform Building Code (UBC), one of the model building codes and part of the International Code Council (ICC).

J

Jig

Fixture that holds the truss in position until rigidly fastened with connectors.

Joint

See Panel Point.

Joist

Horizontal roof or floor framing member.

Juvenile Wood

Wood formed adjacent to the pith, characterized by progressive change in cell dimension, different microstructure than mature wood, and greater shrinkage parallel to grain.

K

Kicker

Web at panel point above a cantilever bearing.

Knee Brace

Brace positioned between a column and truss panel points when trusses are supported by columns lacking transverse bracing.

Knot

Portion of a branch or limb that has been surrounded by subsequent growth of the wood of the tree. As a knot appears on the cut surface it is merely a section of the entire knot, its shape depending upon the direction of the cut.

L

Ladder Panel

(Ladder Framing) Prefabricated panel fastened to the roof eave to create a sloped overhang.

Laminated Veneer Lumber (LVL)

Composite of wood veneer sheet elements joined with an adhesive with wood fibers primarily oriented along the length of the member. Veneer thickness does not exceed 0.25".

Late Wood

Denser, smaller-celled, later-formed part of a growth layer. Also called Summer Wood.

Lateral Bracing

Members installed at right angles to a chord or web member of a truss to provide stability to the truss.

Legal Requirements

Applicable provisions of all statutes, laws, rules, regulations, ordinances, codes, or orders of any governmental authority of the United States of America, any state, and any political subdivision or quasi-governmental authority of any of the same, including, but not limited to, departments, commissions, boards, bureaus, agencies, counties, municipalities, provinces, and other instrumentalities.

Let Tails Run

When a piece of lumber making up the top chord is not cut off to a specified overhang length, but retains the length of the lumber used for the purpose of meeting specific overhang requirements in the field.

Level Return

Lumber filler placed horizontally from the end of an overhang to the outside wall to form a soffit.

Live Load

Loads produced by the occupancy of the building or structure, not including construction loads or environmental loads such as wind loads, snow loads, rain loads, earthquake loads, flood loads or dead

Live loads on a roof are those produced during maintenance by workers, equipment and materials, and during the life of a structure by people and moveable objects.

Load

Forces or other actions that arise on structural systems from the weight of all permanent construction, occupants and their possessions, environmental effects, differential settlement and restrained dimensional changes.

Load-Bearing Wall

Wall specifically designed to transfer loads from above to the framing or foundation below.

Local Building Official

The individual or organization who in accordance with the Legal Requirements may impose requirements on Truss Manufacturers and Truss Designers relating to the Trusses and the Truss Submittals.

Longitudinal

Direction parallel to the grain of wood.

Lumber

Product of the sawmill and planing mill usually not further manufactured other than by sawing, resawing, passing lengthwise through a standard planing machine, crosscutting to length, and matching.

M

Machine Evaluated Lumber (MEL)

Type of machine-graded lumber designated by the letter "M" followed by a number (e.g., M-10, M-19, etc.) which increases with increasing values for design properties.

MEL grade design properties are listed in the NDS.

Machine-Graded Lumber

Type of lumber that has been evaluated by mechanical grading equipment approved American Lumber Standards Committee (ALSC) Board of Review.

Machine-graded lumber is distinguished from visually graded lumber in that each piece is nondestructively evaluated and marked to indicate a grade classification. Machine-graded lumber is also required to meet certain visual requirements as set forth by the grading agency.

Examples of machine-graded lumber include: Machine-Stress Rated Lumber (MSR) and Machine Evaluated Lumber (MEL).

Machine-Stress Rated Lumber (MSR)

Type of machine-graded lumber designated by the design bending stress, Fb, and modulus of elasticity, MOE or E, values.

For example, an MSR grade of 1650f-1.5E designates the bending stress of 1650 psi and an MOE of 1.5 million psi. Other design properties are listed in the NDS.

Mechanical Property

Property of wood that relates to its ability to support load or resist deflection.

Metal Connector Plate

Connector plate manufactured from ASTM A653/A653M, A591, A792, or A167 structural quality steel protected with zinc or zinc-aluminum alloy coatings or their stainless steel equivalent.

The metal connector plate has integral teeth and shall be manufactured to various sizes (i.e., length and width) and thickness or gauges and shall be designed to laterally transmit loads in wood. Also known as truss plate, plate, metal plate, etc.

Miter Cut

Single cut made at an angle to the member length.

Model Building Code

Building codes developed by national organizations for adoption by state and local building officials.

Also called model code.

Modulus of Elasticity (MOE or E)

Measure of the inherent rigidity or stiffness of a material. For a given geometric configuration, a material with a larger MOE deforms less under the same stress.

Moisture Content

Amount of water contained in the wood, usually expressed as a percentage of the mass of the ovendry wood.

Moment

Force that produces rotation of a member and resulting bending stresses.

Monopitch Truss

Truss that has a single top chord, and a slope greater than 1.5/12.

N

Nail-On Plate

Light-gauge cold-formed steel metal connector plates with pre-punched holes or, if cut to size, without holes having identifying marks through which nails are driven by hand or pneumatic means into the lumber.

They are typically used in repairs.

Nailer

See Scab.

National Design Specification® (NDS ®) For Wood Construction

Publication of the American Forest & Paper Association (AF&PA) providing an appendix of lumber sizes, grades, species and allowable stresses.

National Evaluation Report (NER)

Product acceptance research report prepared for construction products in compliance with requirements of the three model codes and the International Code Series of the International Code Council.

National Evaluation Service, Inc. (NES) prepares this evaluation report.

Net Free Ventilated Area

Area required by building codes to allow for proper ventilation in enclosed building spaces.

Nominal Size

As applied to products such as lumber, traditionally the approximate rough-sawn commercial size by which it is known and sold in the market. Actual rough-sawn sizes may vary from the nominal.

Reference to standards or grade rules is required to determine nominal/actual finished size relationships.

Notch

Vertical and horizontal cut at the end of a chord, joist or rafter.

O

Old Growth Timber

Timber in or from a mature, naturally established forest. If the trees have grown during the most of their lives in active competition for sunlight, the bole is usually straight and relatively free of limbs.

On Edge

Vertical placement of a member's wide edge.

On The Flat

Horizontal placement of a member's wide edge.

Out-To-Out Span

See Overall Span.

Outrigger

Wood member nailed to a truss to form a rake overhang beyond the wall line.

Overall Span

Outside-of-frame dimensions, not outside-of-sheathing dimensions.

Overall Truss Depth

Vertical distance between bearing and the uppermost point of the peak.

Overhang

Extension of the top chord of a truss beyond the outside of the bearing support.

Owner

The individual or organization who owns the Building, and:

(a) either designs and prepares, or retains the Building Designer to design and prepare, the Building's Structural System and the Building Structural System Design Documents; and

(b) either constructs, or retains the Contractor to construct, the Building's Structural System.

P

Panel

Chord segment defined by two adjacent panel points.

Panel Length

Horizontal distance between the centerlines of two consecutive panel points along the top or bottom chord.

Panel Point

Location on a truss where the web members and top or bottom chords intersect and are connected by metal connector plates.

Parallel Chord Truss (PCT)

Truss with top and bottom chord slope less than 1.5/12.

Parallel Strand Lumber (PSL)

Composite of wood strand elements joined using an adhesive with wood fibers primarily that are oriented along the length of the member.

The least dimension of the strands shall not exceed 0.25", and the average length shall be a minimum of 150 times the least dimension.

Particleboard Underlayment

Underlayment grade particleboard made or machined to close thickness tolerances for use as a leveling course and to provide a smooth surface under floor covering materials.

Peak

Point on the truss where the sloped chords meet.

Penny

Common nail length. Originally, nails were sold by "penny weight", or price per hundred.

Permanent Bracing

Bracing installed to provide support at right angles to the plane of the truss to hold it in its assumed design position. Permanent bracing stays in place for the life of the structure.

The Building Designer may design the permanent bracing to resist lateral forces imposed on the completed building by wind load or seismic load.

Piggy Back Truss

Truss made in two pieces usually consisting of a hip type truss with a triangular cap fastened to it. Designed when shipping or manufacturing limitations are affected by overall truss height.

Pitch

(1) Incline of the roof described as inches of rise over inches of run. For example, 5/12 is 5" of rise over 12" of run. (2) Resin occurring in the wood of certain conifers.

Pith

Small, soft tissue occurring in the structural center of a tree trunk, branch, twig, or log.

Plate

See Metal Connector Plate.

Plenum

The cavity formed by the floor above and the ceiling below a floor truss as a supply or return air duct.

Plumb Cut

Top chord end cut to provide for vertical (plumb) installation of fascia.

Ply

One truss of a multiple-truss girder.

Plywood

Usually, a cross-banded assembly made of layers of veneer or veneer in combination with a lumber core or other wood-based panel material joined with an adhesive.

Plywood generally is constructed of an odd number of layers with grain of adjacent layers perpendicular to one another. Outer layers and all odd-numbered layers generally have the grain direction oriented parallel to the long dimension of the panel.

Press

See Hydraulic Press.

Press-On Plate

See Metal Connector Plate.

Pressure-Treated Wood

Wood treated by applying pressure to force the preservative into it.

Professional Engineer (PE)

Registered Professional Engineer holding a current license in each state in which s/he conducts business.

Profile Drawing

Sketches of truss profiles used by a mechanical engineer to determine where mechanical ducts, piping, etc., are located.

Purdue Plane Structures Analyzer (PPSA)

Wood structures computer program developed at Purdue University. This program is currently used primarily as a research tool.

Purlin

Horizontal member attached perpendicular to the truss top chord for support of the roofing (e.g., corrugated roofing or plywood and shingles).

Q

R

Radial

Coincident with the radius from the pith to the circumference of the tree or log. A radial section is a longitudinal section in a plane that passes through the pith of the tree.

Rafter

Sloping roof framing member.

Rake

Edge of a roof with the intersection of the gable.

Reaction

Total load transmitted by a framing member to its bearing.

Ridge

Line made by the intersection of two roof planes.

Ridge Vent

Prefabricated and formed metal strip placed along the peak of the roof to aid in ventilation.

Rim Joist

Framing member installed on edge of the exterior parameter, usually tying the ends of floor trusses together. Also called ribbon or band board.

Rise

Vertical distance from low end to the high end of a sloping member.

Roller Press

Press that embeds metal connector plates by forcing them through two opposing rollers.

Roof Jack

See End Jack.

Roof Scuttle

Framed opening in commercial roofs surrounded by a hinged door used for access to a commercial roof.

Run

Horizontal distance from the low end to the high end of a sloping member.

S

Saddle

Covering on the ridge of the roof so that water will drain. Also called cricket.

Scab

Member fastened by nails to another member for reinforcement.

Scissors Truss

Dual pitch, triangular truss with dual pitched bottom chords.

Scupper

Opening in a roof or parapet usually faced with metal flashing to drain water from the roof at a given point.

Sealed Drawings

Drawings prepared, checked and/or approved by and having the seal of a registered professional engineer or architect.

Seasoning

Drying; often applied to the process of removing moisture from wood to achieve a moisture content appropriate for the performance expected of the final product.

Second Growth

Timber that has grown after the removal, whether by cutting, fire, wind, or other agency, of all or a large part of the previous stand.

Often limited to that growth following removal of old growth timber.

Seismic Load

Assumed lateral load acting in any horizontal direction on the structural frame due to the dynamic action of earthquakes.

Set Back

Distance from the outside edge of the wall exclusive of veneer to the face of a girder truss.

Set-Up

Manufacturing term for a run of trusses of the same design currently being manufactured

Shake

(1) Longitudinal separation of the wood. Generally two forms of shake are recognized, although variations and combinations may be used in industrial definitions.

(2) Rectangular, board-like element for roof cover construction, similar to shingles.

Shear

Relative displacement of adjacent planes in a member.

Shear Stress

State of stress where internal adjacent planes in a member tend to slip on one another.

Shoulder Joint

See Break Point Joint.

Shrinkage

Reduction in dimensions due to lowering the moisture content below the fiber saturation point.

Sill

Horizontal wood member forming the lowest part of the framework of a construction.

Size Factor

Factor included in deriving the allowable bending stress for rectangular members that takes into account the somewhat lower unit strength developed in larger members as compared to smaller members.

Slider

Two inch dimension lumber inserted between the top and bottom chords at the heel joint in the plane of the truss to reinforce the top or bottom chord.

Slope

See Pitch.

Sloped Soffit

Sloped overhang with no level return.

Soffit

Level return or underside of an overhang or truss cantilever end.

Soffit Vents

Prefabricated soffit material with perforated openings created for the purpose of providing intake ventilation.

Softwoods

One of the botanical groups of trees that in most cases have needle-like or scale-like leaves; the conifers; also the wood produced by such trees.

The term has no reference to the actual hardness of the wood.

Sound-Deadening Board

Specially manufactured cellulosic fiberboard product for use in building construction in wall and floor assemblies to reduce sound transmission.

Southern Building Code Congress International (SBCCI)

Group that oversees the Standard Building Code (SBC), one of the model building codes and part of the International Code Council (ICC).

Span

Horizontal distance between outside edges of exterior bearings.

Specific Gravity

The ratio of the ovendry weight of a sample of wood to the weight of a volume of water equal to the volume of the wood sample at some specific moisture content, as green, air-dry, or ovendry.

Splice

Location at which two chord members are joined together to form a single member. It may occur at a panel point or between panel points.

Spring Wood

See Early Wood.

Square Cut

End of top chord perpendicular to the slope of the member. Cut made at 90º to the length of the member.

Stacked Chords

In agricultural trusses when two members are positioned on top of each other to create a bottom chord.

Step Down Truss

Truss used in a hip set roof system. Each step down truss has the same span and overhang as the adjacent standard trusses, but decreases in height with the top and bottom chords of its centered portion parallel to each other and horizontal.

See also Hip Set.

Stick Framing

See conventional framing.

Stress

Force per unit of area.

Stress-Graded Lumber

Lumber of any thickness and width that is graded for its mechanical properties.

Strongback Bridging

Two-inch dimensional framing member attached perpendicular to floor trusses - often through the chase opening - and placed vertically against the vertical web.

Stub Truss

Truss that is shortened in length but maintains the original profile.

Structural Board

Board graded for structural applications requiring stress grading for assignment of allowable properties.

Also referred to as a Stress Rated Board.

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 wood or steel roof trusses, floor trusses, floor panels, wall panels, I-joists, or engineered beams and headers.

Structural Composite Lumber (SCL)

Composite of wood veneer sheets, elements, or wood strand elements, joined with an adhesive with wood fibers primarily oriented along the length of the member. These materials are intended for structural use.

Examples included LVL and PSL.

Structural Element

A single joist, rafter, beam, or other structural member (not including the Trusses) designed by others and supplied for the Building Structural System by either the Truss Manufacturer or others.

Structural Element Submittals

Documentation relating to the Structural Elements that are supplied by the Truss Manufacturer, if required by the Contract, submitted by the Truss Manufacturer to the Local Building Official, Owner, Building Designer and/or Contractor for their review and/or approval.

Stud

One of a series of slender wood structural members used as supporting elements in walls and partitions. In softwood grading, a stress grade to describe lumber suitable for stud use.

Studded Gable

Gable end frame built as a wall and resembling a stud wall built in the shape of a triangle.

Chords are usually on the flat.

Substrate

Surface upon which the roofing membrane is placed.

Summer Wood

See Late Wood.

T

T-Brace

A piece of lumber attached to a web as reinforcement against buckling instability. The T-brace is installed so that in cross-section it forms a letter "T" with the web.

See also Web Reinforcement.

Tangential

Strictly, coincident with a tangent at the circumference of a tree or log, or parallel to such a tangent.

In practice, however, it often means roughly coincident with a growth ring.

A tangential section is a longitudinal section through a tree or limb perpendicular to a radius.

Flat-grained lumber is sawed tangentially.

Temporary Bracing

Bracing installed for the purpose of holding trusses true to line, dimension and plumb.

In addition, temporary bracing holds trusses in a stable condition until permanent truss bracing and other permanent components that contribute to the overall rigidity of the roof or floor are in place.

Temporary bracing may consist of ground bracing, continuous lateral sheets or ties, diagonals, cross-bracing or similar items.

See WTCA Job Site Warning Poster and the Always Diagonally Brace for Safety TTB for more information.

Tension Parallel-To-Grain

Imposition of a tensile stress that acts in a direction parallel to the fiber direction of the wood.

Tension Perpendicular-To-Grain

Imposition of a tensile stress that sets in a direction perpendicular to the fiber direction of the wood.

Thrust

Outward horizontal force.

Toenail

Nail driven at an angle to the member.

Top Chord

Inclined or horizontal member that establishes the top member of a truss.

Top Chord Bearing

Bearing condition of a parallel chord truss that bears on its top chord extension. Can also apply to a sloping chord truss bearing on a top chord extension.

Top Plate

Framing consisting of two members on the flat that form the top of exterior stud bearing walls of platform frame construction. A single member on the flat in non-bearing wall construction.

Transverse

Directions in wood at right angles to the wood fibers. Includes radial and tangential directions. A transverse section is a section through a tree or timber at right angles to the pitch.

Trimmer

Conventionally framed wall usually consisting of fastened multiple studs in a framed wall opening, used to carry the header reactions.

Truss

An individual metal plate connected wood element manufactured by the Truss Manufacturer, and supplied for the Building Structural System.

Truss Design Drawing

The graphic depiction of an individual Truss.

Truss Design Standard

The latest approved edition of ANSI/TPI 1 National Design Standard for Metal Plate Connected Wood Truss Construction.

Truss Designer

The individual or organization responsible for the design of Trusses in accordance with this Standard, the Truss Design Standard and all Legal Requirements.

The Truss Designer is also referred to as a Truss Design Engineer when the Truss design calculations and/or Truss Design Drawings resulting from the design of the Trusses shall be sealed by an Engineer.

Truss Manufacturer

An individual or organization regularly engaged in the manufacturing of Trusses and who manufactures Trusses and who may supply Structural Elements for the Building Structural System.

Truss Placement Plan

The drawing supplied by the Truss Manufacturer identifying the location assumed for each Truss.

Truss Plate

See Metal Connector Plate.

Truss Spacing

On-center distance between trusses.

Truss Submittals

The Truss Design Drawings, and the Truss Placement Plan if required by the Contract, submitted to the Local Building Official, Owner, Building Designer and/or Contractor for their review and/or approval.

Twist

Distortion caused by the turning or winding of the edges of a board so that the four corners or any face are no longer in the same plane.

U

Uniform Load

Total load that is equally distributed over a given length, usually expressed in pounds per lineal foot (plf).

V

Valley

Depression in a roof where two roof slopes meet.

Valley Truss

Not a truss, but traditionally called so. Set of triangular components used to frame the shape of dormers and to complete the roof framing where trusses intersect at perpendicular corners.

Valley members usually require support at a maximum distance of 24".

Visual Grade Lumber

Type of lumber that has been visually rated at the lumber mill for structural properties through rules established by the national lumber associations.

W

Wane

Bark or lack of wood from any cause on edge or corner of a piece.

Warp

Any variation from a true or plan surface. Warp includes bow, crook, cup, and twist, or any combination thereof.

Web Member

Members that join the top and bottom chords to form the triangular patterns typical of trusses. These members typically carry axial forces.

Web Reinforcement

A piece of stress-rated lumber attached to a web as reinforcement against buckling instability.

Types of web reinforcement include T-bracing, L-bracing, scab bracing and metal reinforcement. The length of the reinforcement is up to 90% the length of the web.

Wedge

Triangular piece of lumber that has one side equal to the standard 2" dimension lumber widths, and is inserted between the top and bottom chords, usually to allow the truss to cantilever.

Its use is determined through engineering analysis.

Wind Load

Lateral pressure on the building or structure in pounds per square foot (psf), or the metric pascals (Pa), due to wind blowing in any direction.

Wood

Tissues of the stem, branches, and roots of a woody plant lying between the pith and cambium, serving for water conduction, mechanical strength, and food storage, and characterized by the presence of tracheids or vessels.

Wood-Destroying Organisms

Decay-producing fungi, beetle, termites, carpenter ants, marine borers, etc.

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