Home/ Customer Resources/ Building Glossary


Arco understands that this may be your first time purchasing a metal building and some of the industry terms can be confusing. So, we have provided this glossary to help eliminate confusion. We hope that you will find it useful. If you have any questions feel free to contact us.


An extra building component added to a basic ARCO Building such as a door, window, vent, etc.
Aluminum coated steel.
Anchor Bolts
Bolts set in concrete, used to anchor structural members to concrete foundation.
Approval Drawing
A product drawing sent to the customer to verify design and dimensions and to verify the sales contract description of materials and services the manufacturer has agreed to furnish.
A closure between the two leaves of a double swing or a double slide door used to close the joint.
Auxiliary Loads
All specified dynamic live loads other than the basic design loads which the building must safely withstand – such as cranes, material handling systems and impact loads.


Base Angle
A continuous angle secured to foundation to support wall panels.
Base Plate
A shop-welded, pre-punched plate on that portion of a beam or column which rests on the supporting surface.
The space between frame center lines or primary supporting members in the longitudinal direction of the building. Also called stanchion spacing.
The distance between the centerline of the first interior frame to the inside of the endwall panel.
The distance from centerline to centerline of two interior columns.
Bead Mastic
Sealant furnished in a continuous roll, normally used for sealing roof panel laps.
A structural member which is ordinarily subject to bending and is usually a horizontal member carrying vertical loads.
Bearing Frame Endwall
Frame composed of corner columns, end columns, flush girts, and channel rafter beams, which is designed to carry one-half bay weight. Also referred to as “light endwall”.
Bird Screen
Wire mesh used to prevent birds from entering the building through ventilators and louvers.
Blind Rivet
A small headed pin with expandable shank for joining light gauge metal. Typically used to attach flashing, gutter, etc. also referred to as Pop Rivet.
Brace Rods
Rods used primarily on roof and sidewalls of RF (Rigid Frame) or BC (Beam & Column) buildings for plumbing the structures and to transfer wind force to foundation.
A structural support projecting from a wall or column on which another structural member is fastened. Example: Crane runway brackets.
Bridge Crane
A material handling system within a building which moves longitudinally on a runway constructed of rails and beams.
Structural member used to give weak axis stability to joist or purlins.
Building Codes
Regulations established by a recognized agency describing design loads, procedures and construction details for structures. Usually apply to designated geographical areas.
Built-Up Member or Section
A structural member, usually an “I” section, made from individual web, flange and base plates by welding them together.
Built-Up Roof
A roof composed of layered felt or jute, saturated with tar, with each layer set by mopping of hot tar or asphalt.
Butt Plate (or Splice Plate)
The prepunched end plate of a structural member which usually rests against a matching plate of another member in forming a bolted connection.
By-Framed Girts (or By-Pass)
Girts which overlap outside column flange to form a continuous member.


“C” Section
A member cold-formed from steel coil in the shape of a “C”, used primarily in bearing frame endwalls and framed openings.
A predetermined curvature designed into structural member to offset the anticipated deflection when load is applied.
Any overhanging or projecting structure with extreme end usually unsupported.
A projecting beam that is supported and restrained at one end only.
Cap Plate
A plate located at the top of a column or end of a beam for capping the exposed end of the member. Used for pinned conditions.
To seal and make weather tight joints, seams or voids by filling with waterproofing compound or material.
An open-ended “C” shape with no return lips, which may be either cold-formed or hot-rolled.
Clear Span
Building without internal columns.
A plate used for fastening several members together.
An angle used for fastening various members together.
Closure Strip
Sealant material formed to match either inside or outside wall or roof panel configuration, used at base, eave, rake or accessory locations to provide closure against the elements.
Various shapes such as angles, channels, girts and purlins formed from steel at room temperature.
A vertical structural member.
Continuous Girt or Purlin
Girt or purlin that overlaps at columns or frames to form a continuous member.
Continuous Ridge Vent
10′ long roof ventilator located along roof peak line.
Corner Column
Corner column (usually a “C” shape) located at the corner of a bearing frame endwall.
Corner Trim
Preformed color sheet metal trim used to close the junction of side and endwall sheets.
Crane Rail
Track upon which a top running crane moves (usually hot-rolled A.S.C.E. rails).
Crane Runway Beam
Support for bridge crane.
Raised flashing around a roof accessory to provide water rightness at the roof opening.
Curtain Wall
Perimeter wall panels which carry only their own weight.


A baffle used to open or close the throat of ventilators.
Dead Load
The weight of the structure itself plus any permanent stationary loads.
The transverse displacement of a structural member in the direction of load and measured from its no-load position.
Diaphragm Action
The action of wall panels on flush-framed walls to act as one unit to resist longitudinal wind force.
A hollow rectangular, square or round tubular section used to carry water from a gutter to the ground.
A tapered pin used to align holes in steel members to be connected. Also called “Spud Wrench”.


The line along the top of the sidewall, formed by the intersection of roof and wall panels.
Eave Canopy
A roof extension beyond the sidewall of building. May also be cantilevered below the eave.
Eave Height
The vertical dimension from finished floor to top of eave strut.
Eave Strut
A cold-formed structural member at the eave to support roof and wall panels; also transmits forces due to wind on endwall from roof brace rods to wall brace rods.
Eave Strut Gusset
A small gusset shop-welded to main frame on RF and BC buildings to support eave struts and afford alignment with by-framed girts.
Eave Trim
Trim used to close off top of sidewall panels in lieu of eave gutter.
The on-site assembly of pre-engineered components to form complete structure.
Expansion Joint
A break of space in construction to allow for thermal expansion and contraction.


Fascia, Facia
Decorative trim or panel projecting from the face of a wall.
Fixed base
A vertical structural member, bolted to and positioned at 90 degree to a sidewall column to provide additional base fastening and to prevent column rotation.
The projecting edge of a structural member.
Flange Brace
A brace from flange of column or rafter to girt or purlin to provide lateral support and stability.
A sheet metal closure to insure weather-tightness.
A pad or mat, usually concrete, located under a column, wall, or other structural member, used to distribute loads from the member into supporting soil.
The substructure on which a building rests.
Primary structural members, made up of columns and rafters, which support the secondary framing.
Framed Opening
Opening in a wall that is framed with light gauge members.


A triangular portion of the endwall of a building, directly under the sloping roof and above the eave height line.
Thickness of steel or distance between holes punched in flanges, base or splice plates.
Tradename of Bethleham Steel Company for their aluminized 20 year guarantee steel.
Zinc coated steel.
A main horizontal or near horizontal structural member that supports vertical loads.
A secondary horizontal structural member attached to sidewall or endwall columns to which wall covering is attached and supported horizontally; usually a cold-formed “Z” shape.
Glaze or Glazing
The process of installing glass in window or door openings.
A mixture of cement, sand and water used to fill cracks and cavities. Often used under base plates to obtain uniform bearing surfaces.
Gusset Plate
A steel plate used to connect two or more structural members in the same plane.
The member used for carrying rain water off the roof.


Reinforcing bar used to help transfer anchor bolt shear (due to column thrust) to concrete floor mass. The “U” shaped hair-pin wraps around the anchor bolts inside the slab.
Also Knee. The deepened portion of a column or rafter, designed to accommodate the high stress where column and rafter intersect and connect.
A horizontal member over a wall opening.
Header Trim
Trim used above a wall opening.
High Strength Bolts
Any bolt made from steel having a tensile strength in excess of 100,000 pounds per square inch (p.s.i.). Some examples are ASTM A-325, A-354, A-449.
High Tensile Steel
Structural steel having a yield stress in excess of 36,000 pounds per square inch.
Hip Roof
A roof which rises by incline planes from all four sides.
Hot-rolled Shapes
Steel sections (angles, channels, I-beams, etc.) which are formed by rolling mills while the steel is in a semi-molten state.


Shock loads caused by dynamic application.
Inner Liner
Liner paneling on the inside of walls.
Inside Corner Trim
Trim which flashes inside corners.
Any material used in building construction to reduce heat transfer.
Intermediate Bay
A distance between two main frames within a building, other than end frames.


Jack Beam
A beam used to support another beam or rafter to eliminate a column support.
Jack Truss
Truss used to support another beam, truss or rafter to eliminate a column support.
A side column of a doorway or opening.
Jib Crane
A cantilevered boom or horizontal beam with hoist and trolley. This lifting machine may pick up loads in all or part of a circle around the column to which it is attached.
Beam for supporting the floor or roof.
ARCO long-bay structural system, composed of built-up frames and long-span joists.


Kilo-pound (1000#)
Knee (or Haunch)
The connecting area of a column and rafter of a structural frame.


A structure having only one slope or pitch and depending on another structure for partial support.
Liner Panel
Sheeting on inside of building; may be either full or partial height.
A flange stiffener.
Live Load
Any moving or variable load which the structure must support; roof live load is usually snow load.
An opening provided with fixed or adjustable blades to allow air flow.


A tilted fascia system mounted to the roof, outside the steel line, and above the roof line to form a decorative fascia appearance and hide the roof line.
Main or Primary Framing
Steel frames which support secondary framing members such as girts, purlins or eave struts.
Caulking or sealant furnished in rolls, normally used in sealing roof panel laps.
Force times distance (torque).
Moment Connection
A joint capable of transmitting moment to another member of the system.
Vertical member connecting two windows located side by side. Trim piece between the roll up doors on a mini warehouse
More than one building tied together; multiple gable buildings.


An electric hand tool used to cut steel roof or wall sheet openings.



That portion of the wall which extends vertically above the roof line to form a fascia-type appearance to hide roof slope.
An interior dividing wall.
Peak Box
A pre-fabricated trim piece that trims rake trim connection at the apex of gable, and bears a metal plate with the ARCO trademark.
Peak Panel
Rib panel located along building ridge; conforms to roof slope and configuration ( ‘ridge cap’ or ‘ridge roll’).
A concrete structure designed to transfer vertical load from the base of a column to a footing.
A masonry column built into a wall and projecting.
Pop Rivet
A small headed pin with expandable shank for joining light gauge metal. Typically used for flashing trim, etc.
Primer Paint
Initial coat of a paint applied at factory to structural framing for protection against elements during erection and shipping only.
A secondary, cold formed horizontal structural member located in the roof to support sheeting, that is itself supported by the primary structure framing. Purlins in ARCO buildings overlap at frames to form a continuous design.
Purlin Extension Canopy
Cantilevered continuation of roof at rake line.



A fabricated primary structural member with parallel flanges that extends from haunch to apex. Any beam used in a primary frame to support purlins.
The intersection of roof and endwall.
Rake Angle
Angle attached to purlins at rake for attachment of end-wall sheets.
Forces required to resist loads from a structure.
Reinforcing Steel
Steel rods placed in concrete to take tension, compression and shear stresses.
Rib Panel
Standard panel used on roof, liner and soffits.
Peak of a gabled building (apex).
(RF) Rigid Frame
A clearspan structure, characterized by tapered columns, tapered haunches and rafter beams.
Roof Slope or Pitch
Slope of a roof plane expressed as a ratio of vertical rise per unit of horizontal run.


Sag Rod or Sag Angle
Tie rods or angles to support bottom purlin flanges against compression buckling due to special wind force.
Sag Strap
A metal strap used to align purlins during erection.
The process of striking off the excess concrete to bring the top surface to proper finish and elevation.
Any material which is used to close up cracks or joints to protect against leaks.
Secondary Framing
Framing consisting of minor load bearing members of a structure, such as purlins, girts, eave struts, etc.
Seismic Forces
Forces due to earth movement or earthquake.
Self-Drilling Screw
A fastener which combines the functions of drilling and tapping. Used for attaching panels to purlins and girts (as an option).
Self -Tapping Screw
A fastener which taps it’s own threads in a predrilled hole. It is for attaching panels to purlins and girts and for connecting trim and flashing.
Service Door
Swinging hinged door.
A piece of steel used to level or square canopy beams or base plates.
Shop Weld
Weld that is made in plants.
Translucent panel formed like rib panel used on roof or walls in place of certain rib panel sheets to supply natural light to building.
Slide Door
A single or double leaf door which opens horizontally by means of overhead trolleys.
Stitch Screw
A fastener used to connect panels at the side lap.
Structural Steel Members
Load carrying members, may be hot rolled sections, cold formed shapes, or built-up shapes.


The light gauge metal used in the finish of a building, especially around openings and at intersections of surfaces, often referred to as flashing.
Turn of Nut Method
A method of tightening structural bolts in a connection. A rotation of the nut through ½ to ¾ turn from “snug” position will produce at least the desired minimum tension on the bolt. (“Snug” is defined as the point at which the material between the bolt head and nut is rigid. If power tolls are used, “snug” would be the point at which the wrench began to impact.)


UH Crane
A multi-rail, underhung, material handling system, manually or electrically operated.
UHE Crane
An electrically operated UH Crane.
UL Rating
Underwriters Laboratories certification rating.
Uniform Load
Loads that cover all or part of a beam and throughout the portion covered, the amount of load per unit of length is the same.
Wind load on a building which causes a load in the upward direction.


Valley Gutter
A channel used to carry off water from the “V” of roofs of multi-gabled buildings.
Vapor Barrier
Material used to retard the flow of vapor or moisture into walls and thus prevent condensation within them.
The process of supplying outside fresh air to, or removing air from an enclosure.
An accessory usually used on the roof that allows air to pass through.


Wall Covering
The exterior wall skin consisting of panels or sheets and their attachments, trim fascia and weather sealants.
That portion of a structural member between the flanges.
Weep Holes
Openings in flashings, etc., to permit drainage and reduce pressures. (Usually field drilled holes).
Width Extension
A structure dependent upon another structure for partial support and having only one slope or pitch.
Wind Load
A loading representing the pressure exerted on a structure by a given wind velocity. A load caused by the wind blowing from any horizontal direction.
Work Point
An intersection of planes from which dimensions are located.



Yield Stress
The stress at which the strain ceases to be directly proportional to the stress. The stress by which steel is identified such as A-36 indicated 36,000 psi yield.


“Z” Section
A member of cold-formed from steel sheet in the shape of a block “Z”.