IECC Q&A: Residential or commercial townhouses

In this column, we will address some of the typical questions asked of our technical support team. As always, code opinions issued by International Code Council staff are based on published Code Council codes and do not include local, state or federal codes; policies; or amendments. This opinion does not imply approval of an equivalency, specific product, specific design or specific installation and cannot be published in any form implying such approval by the International Code Council. As this opinion is only advisory, the final decision is the responsibility of the designated authority charged with the administration and enforcement of this code. All code citations reference the 2018 International Energy Conservation Code (IECC) unless otherwise specified.

Is it commercial or residential

Q: Would a four-story townhouse be considered residential or commercial under the International Energy Conservation Code?

A: Section 202 provides a definition of Residential Buildings: For this code, it includes detached one- and two-family dwellings and townhouses as well as Group R-2, R-3 and R-4 buildings three stories or less in height above grade plane. To answer this question we need to first determine if the building in question is a townhouse, or falls into a different category.

Section 202 of the International Residential Code defines a townhouse as: A single-family dwelling unit constructed in a group of three or more attached units in which each unit extends from foundation to roof and with a yard or public way on not less than two sides. Unless we have a group of three or more attached four-story units with yards on two sides (unlikely) this is not a townhouse. If not a townhouse, how is it then classified?

The definition of a residential building is important for not only what it does include, but also for what it does not. One of the primary limitations of this definition is the fact that this term will only include the Group R-2, R-3 and R-4 occupancies where they are three stories or less in height. Therefore, where a Group R-2, R-3 or R-4 occupancy is over three stories in height, it would be defined as a “commercial building”.

Based on the information available, it is reasonable to conclude this four-story building fits the Group R-2 classification of residential buildings, which according to Section 301 of the International Building Code includes apartments and condominiums where three or more units are physically attached. For the purpose of the IECC, the main distinction is the three-story nature of this building, and referring back to the definition of a residential building in the IECC we see that only R-2 buildings three stories or less are residential. Thus, because it is not residential, it is therefore commercial.