Structure

Building Framing

Rigid frames, purlins, girts, and openings — the skeleton of the building.

Frame Types Purlins & Girts Openings
Primary
Rigid frames · columns & rafters
Secondary
Purlins · wall girts · eave struts
Bracing
Roof & wall X / rod systems
Openings
OH doors · walk · windows · vents

PEB Anatomy

Components of a steel building frame

A PEB is a kit of engineered steel: primary frames carry gravity and wind; purlins and girts support panels; bracing keeps it stable; framed openings land doors, windows, and vents.

Bay spacing (frame-to-frame), eave height, width, and roof slope set the geometry. Endwalls may use lighter posts and beams; sidewalls pick up girts between main frames. Everything is designed as a system for your wind, snow, and use case.

  • · Rigid frame — main columns + rafters (often tapered / haunched)
  • · Endwall columns — posts & beams on the short walls
  • · Purlins — roof secondary, frame bay to frame bay
  • · Wall girts — wall secondary for panel attachment
  • · Eave strut / eave purlin — at the eave line
  • · Roof & wall bracing — X-bracing, rods, or portal frames as required
Color-coded diagram of PEB framing components: rigid frames, purlins, girts, openings

Original Stamps Steel diagram — educational labels (not a manufacturer copy)

Primary Frames

Common frame types

Clear-span and modular options cover shops, hangars, warehouses, retail, and lean-tos. Your loads, clear height, and interior use pick the type.

Seven common PEB frame types: straight column, tapered, modular spans, single slope, lean-to

Straight column

Constant-depth columns with rafters forming a gable clear span. Simple geometry for many mid-size shops and barns.

Tapered column

Haunched / tapered members put steel where stresses peak at the knee — efficient clear-span for wider buildings and higher loads.

1-, 2-, 3-row modular

Interior column lines split the width into modules. Ideal when full clear span is not required and width grows large (warehouses, multi-bay).

Single slope

One-way roof pitch — strong for drainage toward one eave, strip centers, and modern commercial elevations.

Lean-to

Attached side bay sharing a main-building eave or sidewall. Covered storage, wash bays, equipment lean-tos, porch-style additions.

Engineered for site

Frame size, plate thickness, and bracing respond to wind, snow, seismic, crane loads, and local code — not a one-size catalog only.

Red iron modular PEB frame with roof deck and wall girts on slab

Modular clear bays · primary red iron with secondary roof & wall members

Secondary Members

Purlins & wall girts

Secondary framing turns primary frames into a surface the panels can attach to — and carries wind and live load into the main steel.

Diagram of roof purlins on rafters and wall girts on columns

Roof purlins

Span from frame to frame (bay spacing). Support roof panels and insulation. Commonly Z-purlins or Cee sections, nested or continuous over frames, clipped to rafter flanges.

  • · Spacing set by panel type, snow/live load, and wind uplift
  • · Work with ridge, eave, and roof bracing
  • · Accept panel screws / standing-seam clips as specified

Wall girts

Horizontal members between columns that carry wall panels and wind. Can be bypass (outside the column face) or inset / flush systems depending on finish and insulation.

  • · Girt lines coordinate with window & door heads
  • · Base condition may use base angle or channel
  • · Eave strut ties the wall system into the roof line
Interior view of metal building roof purlins and primary frames

Key dimensions you’ll hear

Eave height
Finished floor to eave strut / eave line
Bay spacing
Distance between primary frames (often 20′–25′+)
Clear span
Open width without interior columns
Roof slope
Rise:run (e.g. 1:12, 2:12) — drainage & look

Openings & Accessories in the Frame

Framed openings, doors, windows & vents

Openings are engineered into the secondary system — headers, jambs, and trims — so panels finish cleanly and loads path around the hole.

Wall elevation showing framed overhead door, walk door, window, louver, and roof vent

Overhead / roll-up openings

Large framed openings with structural headers and jambs sized for the door. Locations set bay-by-bay for vehicle and equipment access. Coordinated with mini storage roll-up packages when needed.

Walk doors

Personnel doors in framed openings — typically 3070 / 4070 and similar — with jambs tied into girts. Hardware, sidelights, and canopies available via accessories.

Windows

Framed window units (fixed, sliding, or thermal) set between girt lines. Headers and sills maintain panel module and weather line.

Wall louvers & fans

Ventilation openings framed like doors/windows — intake louvers, exhaust fans, and wall vents for shops and ag buildings.

Roof vents & ridge

Ridge vents, low-profile vents, cupolas, and roof curbs for HVAC. Openings and curbs must align with purlin layout and panel ribs.

Canopies & lean-tos

Framed projections at walk doors or full lean-to frames. Connect to main eave or sidewall steel as engineered.

Quick term guide

Term What it means
Rigid frame Primary moment-resisting frame: columns + rafters forming the building “ribs”
Haunch Deepened knee region of a tapered frame where column meets rafter
Girt clip Connection plate/clip that attaches girts (or purlins) to primary steel
Endwall column spacing Spacing of posts across the endwall between corner columns
Portal frame / rod bracing Lateral-force systems when X-bracing would block a door or opening
Framed opening Header + jambs built into the secondary system for a door, window, or vent

Related: projects · panels · insulation · accessories · 3D designer

Tell us how you’ll use the space

Clear span vs. modular, door layout, lean-tos, and vents — we’ll match the frame and openings.

(615) 629-8217 info@stampssteel.com
Get a Quote

Framing Quote

Size, clear span, doors, and site — we’ll take it from there.

info@stampssteel.com  •  (615) 629-8217