Fire compartmentalization is a design option whereby a building is separated into smaller areas in order to provide passive fire separation between the smaller areas throughout the building. Compartmentalization is a common method the building code recognizes in order to allow designers and builders different options to create safe buildings without the need for automatic fire sprinklers. Incorporating Fire Walls and Fire Barriers into a building design can provide different benefits to the builders and owners depending on the project needs. For a lower budget project, it may be possible to eliminate the need for (and the cost of) fire sprinkler design and installation by providing Fire Walls or Fire Barriers to compartmentalize the building. This decision depends on the building size, occupancy groups, and the allowable fire areas.
When determining the means to compartmentalize the building into separate areas, Fire Walls provide the greatest amount of passive fire protection for building separation in the code. Fire Walls are required to provide a complete separation between areas on each side, including complete structural independence, such that when a Fire Wall is utilized, the code recognizes each side as a separate building. These Fire Walls are typically required to be rated between 2 and 4 hours of fire resistance and the passage between compartments must allow for complete closure during a fire event.
Here is an example of how Fire Walls can be a useful tool in your building cost analysis. Assume a building of Type IIB construction, with a primary Occupancy Group E, with a goal of 20,000 square feet in one ground-level story. The code limits the area of this type of construction to 14,500 square feet, however the code allows area increases above the 14,500 square feet if additional measures are taken, such as converting the building to a more restrictive (and expensive) construction type, or adding automatic fire sprinklers. An alternate solution is to separate the entire building into two compartments with a Fire Wall such that each half is less than the area limit of 14,500 square feet. Remember, the Fire Wall allows each compartment of the building to be recognized as a separate building for area calculation purposes. In this example the construction of a Fire Wall may be more economical than the expense of a sprinkler system or a more restrictive construction type, and will satisfy code requirements for life safety. Not only are the cost savings realized through the reduction of material, design and labor costs, separate water service or tank storage would not be required, as well as the costs saved during the life of the structure by eliminating the need for inspections, testing and maintenance of the fire suppression system.
The designer and builder must understand that Fire Barriers do not provide the same degree of protection as Fire Walls, and thus Fire Barriers are used for different purposes. While Fire Walls result in code-recognized separate buildings, Fire Barriers result in the creation of separate fire areas. The Code, in addition to limiting building areas based on Construction Type and Occupancy Group specifies how large a certain fire area can be based on occupancy before sprinklers are required to provide additional protection. Continuing with the example above, for Occupancy Group E, the code would require the installation of an automatic sprinkler system for any fire area larger than 12,000 square feet. If the anticipated area of the building is 20,000 square feet, and is of Type IIA construction, even though you don’t need the building area increases granted for sprinkler installation, sprinklers will still be required because of the larger fire area. If a Fire Barrier is installed to divide the building into two fire areas each smaller than 12,000 square feet, no sprinklers would be required. Typical Fire Barriers are required to be rated for 2 hours of fire resistance.
Of course, the benefits of Fire Walls and Fire Barriers will be different based on the applicable codes, the project’s Occupancy Groups and proposed Construction Type.
On the Solutions Before side: SBSA offers Plan Review and Code Consulting services to help you determine the most economical building design for your project needs.
On the Solutions After side: SBSA provides Forensic Life/Safety Evaluations to determine if the as-constructed building complies with the minimum code standards for a safe building.
Michael J. Fiebig, RA, AIA, NCARB, LEED GA, CFPS
Forensic Architecture Manager at SBSA
Edward Fronapfel, Owner, SBSA Inc. MSCE, PE, CBIE, CFCC, EDI, CBCP,
Fellow Member of NAFE