Overview

Previous revisions of the NEC exempted the garage area from the floor area calculation of a dwelling unit. The 2023 NEC has updated this language to include the garage area. This update has been implemented as a new subsection in section 220.5. Installers will need to be aware that this change will affect the calculated load for dwelling units, building, and other spaces that depend on floor area to calculate unit loads. This change was made because occupants generally use the garage area as additional space for events, parties, and gatherings. Open porches are still excluded from the floor area calculations.

Applying the 2023 Code

Many of the calculations in Article 220 are dependent on the square footage of the building. In previous editions of the code, this was addressed in Section 220.11, which specified that the floor area was to be calculated based on the habitable space only, and excluded garages, unused spaces, and open porches. This section has been removed from the 2023 NEC, and has been relocated to section 220.5(C). The relocated section has been updated to require garages and unused spaces to be included in the floor area calculation by removing them as an exemption. Open porches are still excluded from the square footage calculation, and therefore do not need to be included. The installer will need to keep these changes in mind when doing load calculations, as this change will lead to larger calculated loads for dwelling units and other related spaces that require square-foot calculations.

What’s New for the 2023 NEC?

2020 NEC

In the 2020 NEC Section 220.5(C) did not exist, but instead had the information located in 220.11, which reads as follows:

220.11 Floor Area.

The floor area for each floor shall be calculated from the outside dimensions of the building, dwelling unit, or other area involved. For dwelling units, the calculated floor area shall not include open porches, garages, or unused or unfinished spaces not adaptable for future use.

2023 NEC

In the 2023 NEC Section 220.5(C) read as follows:

(C) Floor Area.

The floor area for each floor shall be calculated from the outside dimensions of the building, dwelling unit, or other area involved. For dwelling units, the calculated floor area shall not include open porches or unfinished areas not adaptable for future use as a habitable room or occupiable space.