Proper egress analysis is an extremely important aspect of fire safety design that not only involves following applicable codes, but also careful coordination with the project architect. International Building Code (IBC) defines an accessible means of egress as a “continuous and unobstructed way of egress travel from any point in a building or facility that provides an accessible route to an area of refuge, a horizontal exit or a public way.” Adequate means of egress can vary depending on the use of the building and the occupancy load. Facilities with large occupancy loads can present challenging egress design, specifically if the existing building is being retrofitted to accommodate a change of use to contain that larger load. Frequently, the existing exit capacity provided on each floor is not adequate for the new occupancy.
What is a Horizontal Exit? A Definition and How Can It Help
For facilities with large occupancy loads or those that must be retrofitted, designing and constructing a horizontal exit may be the best solution for providing the required egress capacity. Horizontal exits are designed to create a safe refuge area separated from the fire area by a two-hour fire-resistance-rated separation. It is recognized in accordance with the 2015 IBC and/or the 2015 NFPA 101, Life Safety Code.
A Real-World Example
One of our recent projects involved a new tenant space within an existing high-rise office building, which was being retrofitted to include offices and large assembly/conference areas. The tenant space had two existing exit stairs that provided a maximum exit capacity of 440 occupants. The new occupant load of the tenant space would exceed 500, requiring a third exit and additional exit capacity in accordance with the applicable codes.
To achieve this, we needed to maintain a separate level of security for office spaces from the assembly areas. The public would often use assembly areas for events, which meant the office areas had to be kept secure, only allowing entrance for employees by way of a swipe card. The design of the refuge area could not extend into the office spaces and had to be contained within the common areas of the building.
Using a horizontal exit scheme, we designed an exit that included a two-hour separation through the tenant space creating separate compartments with an available exit stair on each side. We based the refuge area on the capacity available by the horizontal exit doors. This horizontal exit solution solved the client’s egress dilemma efficaciously.
Designing an accessible means of egress for large capacity buildings can be complex and innovative solutions can help achieve compliance and keep people safe.
What have been your egress challenges? Shoot us a note at info@big5vn.com or tweet us @jensenhughes .