📘 About This Cheat Sheet
This comprehensive reference guide covers essential terminology for Pre-Engineered Metal Buildings (PEMB) and Light Gauge Steel Frame (LGSF) construction. Each component includes detailed definitions, functions, and visual diagrams to enhance understanding for estimators, engineers, and construction professionals.
Main Frame
The primary structural system consisting of columns and rafters
Columns: Vertical I-beam or built-up sections that transfer all roof loads to the foundation. Typically spaced 20-30 feet apart.
Rafters: Sloped or horizontal beams spanning between columns. Form the roof profile and support all secondary framing.
Function: Bears all primary loads (dead, live, wind, snow, seismic) and defines building shape
Purlins
Horizontal secondary framing attached to rafters
Z-shaped or C-shaped cold-formed steel members running parallel to building length. Attached perpendicular to rafters, typically spaced 4-6 feet on center.
Function: Support roof panels, distribute roof loads to rafters, provide lateral bracing
Girts
Horizontal secondary framing attached to columns
Similar to purlins but for walls. C-shaped or Z-shaped members running parallel to building length, spaced 4-6 feet on center vertically.
Function: Support wall panels, provide lateral stability to columns, resist wind loads
Eave Strut
Structural member at roof-wall intersection
Heavy-duty C-shaped or custom-formed member at the eave line. Connects both roof and wall systems at this critical junction point.
Function: Supports both roof and wall panels, provides connection point for purlins/girts, crucial for structural integrity
Rod/Cable Bracing
Diagonal tension elements for lateral stability
Steel rods (typically 5/8" to 1" diameter) or cables installed diagonally in roof and wall planes. Creates X-bracing or single diagonal patterns.
Function: Resists lateral forces (wind/seismic), prevents building racking, transfers loads through triangulation
Flashing & Trim
Metal closure and weatherproofing components
Includes ridge cap, eave trim, corner trim, base trim, door/window trim. Typically 26-gauge pre-finished steel matching panel color.
Function: Weatherproofing at joints and edges, finished appearance, protects against water infiltration
C-Studs
Vertical C-shaped structural wall members
Cold-formed steel studs with C-shaped cross-section. Common sizes: 2½", 3⅝", 6" depths with 16, 18, or 20 gauge thickness. Typically spaced 16" or 24" on center.
Function: Resist vertical loads, provide substrate for finishes (drywall, sheathing), transfer loads to foundation
Tracks (U-Track)
Horizontal U-shaped top and bottom plates
U-shaped channels matching stud width. Form top and bottom of wall assembly. Studs slide into track during installation and are fastened with screws.
Function: Hold studs in position, distribute loads, provide connection to floors/ceilings
Joists (C-Joists)
Horizontal C-shaped floor/ceiling supports
Similar to C-studs but used horizontally. Common depths: 6", 8", 10", 12" for longer spans. Sized based on span, spacing, and load requirements.
Function: Support floor/ceiling decks, carry live and dead loads, maintain deflection limits
Headers/Lintels
Load-bearing members above openings
Constructed by boxing two or more C-studs back-to-back or using built-up track assemblies. Size determined by opening width and loads above.
Function: Transfer loads from above around door/window openings to king studs
Trusses
Prefabricated triangular roof frameworks
Engineered assemblies of top chord, bottom chord, and web members. Light gauge steel alternatives to wood trusses. Common spans: 20-50 feet residential.
Function: Support roof loads over long spans without interior columns, efficient load distribution
Strap Bracing
Diagonal steel straps for lateral stability
Flat steel straps (typically 1¼" to 2" wide) installed diagonally in wall cavities. Alternative: structural sheathing (OSB, gypsum) provides shear resistance.
Function: Create shear walls, prevent racking, resist wind/seismic lateral forces
🎯 Key Terms Summary
O.C. (On Center): Measurement from the center of one member to the center of the next
Gauge: Thickness measurement for steel (smaller number = thicker)
Clear Span: Distance between supports with no interior columns
Lateral Bracing: Components resisting horizontal (wind/seismic) forces
Secondary Framing: Members supported by primary frame (purlins, girts)
Cold-Formed: Steel shaped at room temperature (LGSF)
Hot-Rolled: Steel shaped at high temperature (PEMB)
Eave: Lower edge of roof where it meets the wall
Ridge: Highest point of the roof
King Stud: Full-height stud adjacent to door/window opening
Cripple Stud: Partial-height stud above/below opening
Shear Wall: Wall designed to resist lateral forces
