Do I Need an Engineer to Build a Metal Building in Illinois?

Illinois jurisdictions — Chicago, Aurora, Naperville, Joliet — require an engineer-sealed plan set for commercial and industrial metal buildings, and the PE seal is the standard requirement for the foundation and site-specific structural sheets. The seal must show the engineer's name, Illinois PE number, and date, with the engineer in responsible charge. The manufacturer supplies PE-sealed drawings for the building itself — the rigid frames, purlins, and girts — but the foundations, site-specific load verification, and the permit set are designed and sealed by the Illinois engineer of record. Owner-builders don't escape the requirement: the building department asks for the seal regardless of who drew the plans, and the engineer must verify the building for heavy snow, deep frost, and New Madrid seismic risk downstate.

The engineer designs the foundations for deep frost footings for snow-belt reactions — the engineer sizes piers below frost for the frame loads, with seismic checks in the southern counties, and verifies the rigid frames for rigid frames with snow-rated purlins and lake-effect wind checks — the engineer verifies drift at parapets and unbalanced snow across the roof. Purlins, girts, eave struts, and rod bracing go on the sealed plan set — member sizing for gravity and lateral loads, bracing layouts, and the anchor-bolt detailing that ties the building to foundations designed for heavy snow, deep frost, and New Madrid seismic risk downstate. Bring the manufacturer's anchor-bolt plan and column reactions, a geotechnical report for the lot, and the building dimensions and eave height. The engineer verifies drift at parapets and unbalanced snow across the roof — snow-rated purlins with lake-effect wind checks.

Use this checklist before engaging an engineer for your metal building: • Engineer of record holds an active Illinois PE license, verifiable on the state roster • Foundations designed for the manufacturer's anchor-bolt reactions against heavy snow, deep frost, and New Madrid seismic risk downstate • Rigid frames, purlins, and girts verified for heavy snow, deep frost, and New Madrid seismic risk downstate per ASCE 7 • Rod bracing or portal-frame lateral system detailed on the sealed set • Anchor bolts, base plates, and hairpin ties detailed for uplift and overturning • Eave height, clear span, and bay spacing called out and checked • Geotechnical report reviewed before foundation design • Engineer confirms they'll respond to plan-check corrections on sealed sheets