Building code revisions adopted between 2009 and 2021 increased the cost of constructing a typical multifamily apartment building by 9.9%, according to a study funded by the U.S. Department of Housing and Urban Development by researchers at Purdue University.

Renters in the nation’s largest cities would need to devote 3.4% of their annual income, on average, to cover the impact of these code changes, the report says.

The report examines 130 total revisions to the International Building Code across four triannual updates and classifies them into categories: structural safety, fire protection, evacuation and egress, safety in use, hazard protection, well-being, and aesthetics.

Of the 130 revisions identified as affecting multifamily housing, 36 were found to at least marginally increase development costs across various multifamily structures in the U.S. Of those, 16 directly impacted the three-story, 32,790 sf apartment building prototype used in the research.

Fire protection requirements accounted for roughly 67% of the estimated increases and structural safety provisions accounted for 20%. 

Natural hazard mitigation represented the most common category of code revisions during the study period. Resilience and structural safety requirements were among those most likely to increase construction costs.