Work on an existing building follows the International Existing Building Code, which scales requirements to the scope of work rather than treating every project as new construction. The IEBC's work-area method sorts alterations into Levels 1, 2, and 3 — from simple finishes and equipment replacement, up through reconfiguration and additions — with each level triggering progressively more compliance. It also governs change of occupancy (which can require significant upgrades), additions, and relaxed pathways for historic buildings.
The common mistake is applying full new-construction requirements to a modest alteration (over-designing), or the reverse — missing that a change of occupancy or a Level 3 alteration triggers accessibility, egress, or structural upgrades. Reviewers confirm the alteration level and whether a change of occupancy applies, then check that the triggered upgrades are addressed. Getting the IEBC pathway right early is often the difference between a feasible renovation budget and one that balloons.
This guide describes the model code for general understanding and is not a substitute for the adopted code and amendments enforced by your local authority having jurisdiction. Verify all figures against your jurisdiction's codes of record.