The National Association of Home Builders (NAHB) provided a list of 26 code changes affecting multifamily construction which were approved for incorporation into the 2018 International Codes. The changes affect the International Building Code (IBC), International Energy Conservation Code (IECC), International Fire Code (IFC), and International Mechanical Code (IMC). A companion report, Estimated Costs of the 2018 IRC Code Changes, covers changes approved for the 2018 International Residential Code (IRC) and their impact on one- and two-family dwellings. Home Innovation Research Labs estimated the expected cost impact of these code changes on construction practices and materials. Cost estimates are aggregated in ranges of high to low based on various methods or components that might be used to comply with the code.
Baseline metrics for five representative multifamily buildings built to the 2015 IBC, IECC, IFC and IMC1 were defined in order to determine the cost impact resulting from the revisions approved for the 2018 codes. Elevations and floor plans for these reference buildings are provided in Appendices C through G.
The reference buildings define a starting point for the analysis of the cost impact to a builder resulting from adoption of the 2018 codes (relative to the 2015 IBC/IECC/IFC/IMC baseline).