PEB Fundamentals
PEB Glossary: Metal Building Terms Explained
A PEB glossary is a reference list of the terms used to describe pre-engineered metal buildings, their parts, dimensions and loads. It helps owners, architects and contractors read proposals and drawings with confidence and discuss the building clearly with the supplier and engineer.
Key facts
- Terms are grouped alphabetically for quick scanning.
- Definitions are plain-English explanations, not code wording.
- Exact meanings can vary slightly between regions and codes.
- Use the drawings and design criteria of your project as the final reference.
A to B: anchor bolts to bypass girts
Anchor bolts: Threaded rods cast into the foundation that hold the column base plates in place and transfer forces to the concrete.
Aspect ratio: The relationship between building length and width, which affects bracing layout and wind behavior.
Base angle: A light steel angle fixed to the slab edge that supports and fastens the bottom of the wall panels.
Base plate: The steel plate welded to the foot of a column that sits on the foundation and receives the anchor bolts.
Bay: The space between two adjacent frames or columns, measured along the building length or across an endwall.
Bay spacing: The center-to-center distance between frames, which sets the span of purlins and girts.
Bracing: Rods, cables, angles or portal frames that keep the building stable in the direction the main frames cannot resist.
Bridging: Members fixed between purlins or girts to keep them straight and restrain them against twisting.
Built-up member: A beam or column made by welding steel plates into an I-shape, often with a tapered web.
Bypass girt: A girt mounted on the outside face of the columns so the wall panels run past them.
C to E: clear span to expansion joint
Cladding: The roof and wall sheeting that forms the outer skin of the building.
Clear span: A frame that spans the full building width with no interior columns.
Cold-formed section: A steel profile shaped from coil at room temperature, such as a Z or C purlin.
Collateral load: The weight of permanent items hung from the structure, such as ceilings, lighting, sprinklers and ducts.
Dead load: The self-weight of the structure and the permanently fixed building materials.
Deflection: How far a member moves under load, checked so finishes, doors and drainage still work.
Downspout: A vertical pipe that carries water from the gutter to the ground or drainage system.
Eave: The line where the roof meets the sidewall.
Eave height: The height from the finished floor to the top of the eave strut at the sidewall.
Eave strut: A member along the top of the sidewall that supports the roof and wall panel edges and ties the frames together.
Endwall: The wall at either end of the building, usually parallel to the frames.
Expansion joint: A planned break in the structure or envelope that lets long buildings move with temperature changes.
F to J: flange brace to jack beam
Fascia: A vertical or angled panel along the eave or gable that hides the roof edge or gutter for appearance.
Finished floor level: The reference elevation of the slab from which building heights are measured.
Flange brace: A small angle that connects a purlin or girt to the inner flange of a frame to stop that flange from buckling sideways.
Flashing: A formed metal strip that seals joints at corners, edges, openings and changes of plane.
Framed opening: Steel members around a door or window opening that support the panels and carry the loads around it.
Gable: The triangular upper part of an endwall below a pitched roof.
Girt: A horizontal secondary member that supports the wall cladding and spans between columns.
Gutter: A channel at the eave or valley that collects rainwater from the roof.
Haunch: The deepened part of a rafter or column near the knee where bending is highest.
Jack beam: A beam that supports a frame rafter where an interior column has been removed to create a wider bay.
K to P: knee to purlin
Knee: The connection between the column and the rafter of a rigid frame, normally the deepest point of the frame.
Lap: The overlap of two purlins, girts or panels, used to create continuity or a weather seal.
Lean-to: A smaller structure with a single-slope roof that leans against and is supported by a main building.
Liner panel: A light metal panel on the inside face of walls or roof that protects insulation and gives a clean finish.
Live load: Temporary load on the roof or floor from people, equipment or maintenance work.
Mezzanine: An intermediate floor inside the building, supported by its own columns or by the main frames.
Multi-span: A frame with one or more interior columns, used to make wide buildings more economical.
Parapet: An extension of the wall above the roof line.
Pitch: The roof slope, often expressed as rise per 10 or per 12 units of run.
Portal bracing: A small rigid frame placed between columns where diagonal bracing would block an opening.
Purlin: A horizontal secondary member that supports the roof panels and spans between rafters.
R to S: rafter to standing seam
Rafter: The sloping beam of a rigid frame that supports the purlins.
Rake: The sloping edge of the roof at the endwall.
Ridge: The highest line of a pitched roof where the two slopes meet.
Rigid frame: A primary frame with moment-resisting connections between columns and rafters.
Roof extension: A part of the roof that projects beyond the endwall or sidewall to shelter the face of the wall.
Sag rod: A rod that ties purlins or girts together across their span to stop them sagging or twisting.
Sandwich panel: A factory-made panel with metal skins bonded to an insulating core.
Self-drilling screw: A fastener that drills its own hole and fixes panels to secondary framing in one step.
Sidewall: The longer wall of the building, parallel to the ridge.
Skylight: A translucent panel in the roof that brings in daylight.
Span: The distance between supports of a frame or member.
Standing seam: A roof panel joined by raised seams and fixed with concealed clips that let the panels expand and contract.
T to W: tapered member to wind column
Tapered member: A built-up beam or column whose web depth changes along its length to follow the bending demand.
Thermal block: A strip of insulating material placed between the purlin and the roof panel to reduce heat loss through the fixing line.
Trim: A formed metal piece that finishes edges, corners and openings for weathertightness and appearance.
Valley gutter: A gutter set between two roof slopes of a multi-gable building.
Vapor retarder: A facing or membrane on the warm side of insulation that limits moisture moving into it.
Wall panel: A profiled or insulated sheet that forms the wall cladding.
Width: The building dimension measured across the frames, from outside of girt to outside of girt on each sidewall.
Wind column: An endwall column designed mainly to resist wind pressure on the endwall.
X-bracing: Pairs of crossed rods or cables that form the diagonal bracing in roof and wall bays.
Frequently Asked Questions
Why do metal building terms differ between suppliers?
Terminology developed regionally, and codes in North America, Europe and Australia use slightly different names. Always check the definitions on your project drawings and design criteria.
How is building width usually measured?
It is commonly measured from the outside face of the sidewall girts on one side to the outside face on the other. Confirm the convention used in your proposal.
What is the difference between a frame and a bay?
A frame is the physical structure of columns and rafters. A bay is the space between two neighboring frames.
Engineering content is general guidance. Every World Steel building is designed by qualified engineers to the code and loads of the project.
