Massachusetts is adopting its 10th edition of 780 CMR, Massachusetts State Building Code, with the conclusion of the current concurrency period slated to end on July 1, 2025. This marks Massachusetts’ completed transition to the 2021 International Building Code (IBC), where it joins the majority of jurisdictions across the country that are now enforcing the 2018, 2021, or 2024 IBC.
One of the new code allowances that is of particular interest relates to changes to the Business Use occupant load factor, especially regarding its impact on the required number of exits from a floor. Historically, office spaces were calculated using a factor of 100 gross square feet per occupant and first changed to 150 gross square feet per occupant in the 2018 edition of NFPA 101, Life Safety Code and then subsequently followed by the International Building Code.
This factor, along with those used to establish occupant loads for conference rooms and breakout areas, could often push larger office floors above the 500-person threshold. As a result, the number of exits required from the floor would need to be addressed through an additional exit enclosure or, perhaps more creatively, a horizontal exit. We often see office floor plates in the 30,000 SF to 50,000 SF range, historically yielding an aggregate occupant load close to or above the 500-person threshold. For example, a 40,000 SF office floor plate with 3,000 SF of assembly space and 37,000 SF of office space would yield an aggregate occupant load of 570 occupants, requiring three exits. Under the new provisions, this same arrangement would result in an aggregate occupant load for the floor of 447 occupants and a minimum of two exits based on the occupant load.
Both new and existing buildings benefit from this change, as applying the new occupant load factors may enable floor plans to have more rentable square footage (more efficient floor plans) while reducing long-term operational costs for the building. If these provisions are applied to existing buildings, it should be noted that approval of the building department via permit documents should be sought.
In addition, the building code also introduced a new occupant load factor for concentrated business use areas (50 SF/person or lower). This factor is intended for unique office areas with higher densities, including call centers, trading floors, or data processing centers. The appropriate application of these new concentrated occupant load factors can be nuanced. It should be reviewed by a competent registered design professional who is experienced in applying building, fire, and life safety codes and standards.
For more details on this code change, please see our previous blog post here or contact us for more information.