Why Not All Fire Sprinkler Systems Are Alike

Automatic fire sprinkler systems have an enviable record of protecting life and property in those buildings where they are installed and maintained. According to the National Fire Protection Association (NFPA) data, in structure fires large enough to activate sprinklers, the systems operated and were effective 87 percent of the time. Reasons for the number of system failures are the subject of a different article, but for now it is important to know that not all sprinkler systems are designed and installed for a single purpose. image

This four-story multi-family condominium is typical of the type of residential buildings that may be protected by a NFPA 13R-design sprinkler system that omit sprinklers from many combustible spaces, including the attic that covers the entire structure. Photos by Rob Neale

The design goals often align with the building and fire code requirements for the installation of sprinklers for the huge variety of hazards that exist in the built environment. Firefighters and code officials need to understand these important differences that may affect fire ground tactics, code enforcement and even post-incident investigation.

Building construction safety codes are an important element in the economy and security of our communities. The codes that are adopted by state and local jurisdiction establish the minimum acceptable risk the elected officials are willing to accept. While property owners are welcome and encouraged to provided fire protection and life safety features above what is required by the legally adopted codes, it is often a question of benefit versus cost of the added items.

What the Codes Require

Fire protection personnel may wish that every building were fire resistive or non-combustible construction and protected by fire detection and sprinkler systems. The reality is something different. Even in structures protected to the highest known levels of fire resistance and automatic suppression, it usually is the operations or contents that cause fires.

When sprinklers are provided in pitched combustible attics, they must be a special design like this one to assure all combustibles are sprayed with water in case of a fire.

In the Carolinas, state and local governments use some version of the International Code Council® (ICC) building and fire codes to regulate the safety of new construction and existing buildings. ICC codes are “model” codes that are developed by professional, interested parties who care about building and life safety. Depending upon state law, these “model” codes may be amended by state or local authorities to meet specific needs. It’s akin to ordering a base model car and adding extra features to customize it.

Both the International Building Code (IBC) and International Fire Code (IBC) have requirements for automatic sprinkler systems. While similar, they are not identical. For example, the IBC includes language that permits sprinkler systems to serve as alternatives to some types of building construction features or design limits. Where a building might be required to be entirely of one-hour fire resistive construction, the installation of an automatic sprinkler can be used as a substitute for the fire resistive features such as the installation of gypsum wallboard, fire dampers and fire-rated door assemblies. Sprinkler requirements in the IFC typically pertain to the protection of hazardous operations or storage.

When sprinkler systems are required, they must meet one of the three NFPA design and installation standards that are common throughout the United States:

  • NFPA 13, Standard for the Installation of Automatic Sprinkler Systems,
  • NFPA 13R, Standard for the Installation of Sprinkler Systems in Low-Rise Residential Occupancies, or,
  • NFPA 13D, Standard for the Installation of Sprinkler Systems in One- and Two-Family Dwellings and Manufactured Homes.

The IBC and IFC provide guidance regarding which sprinkler standard may be used for specific applications. Table 1 summarizes some of the fire sprinkler requirements and design standards found in the International Building Code or International Fire Code. (Note: Table 1 is intended to be illustrative only; it is not the complete list or description of all areas where fire sprinkler systems are required. For that information, always refer to the jurisdiction’s legally adopted version of the codes).

The key takeaway from Table 1 is there are very few conditions where a sprinkler systems designed in accordance with NFPA 13R is allowed.

Sprinkler Design Differences

The selection and application of a sprinkler design standard has important consequences for the building, its occupants and the fire service that responds to a fire in a protected property.

NFPA 13 was developed in the late 1800s and today remains a design guide primarily for property protection. Consequently, systems designed to this standard are intended to detect and control or suppress a fire in combustible spaces or where combustible materials are used or stored. Generally, the entire building is protected, but sprinklers may be omitted from some non-combustible concealed spaces — between a ceiling and non-combustible roof, for example — and areas where the application of water may create a dangerous condition such as calcium carbide storage. Calcium carbide and water combine to release acetylene gas that has a wide flammability range and increases the fire hazard in a building.

Plastic sprinkler pipe is common in the light-hazard occupancies because of its ease of installation, cost savings and superior flow characteristics. Note how the insulation is “tented” over the pipe to help collect heated air from the living space to prevent pipe freezing.

After observing many years of data that showed the effectiveness of automatic sprinkler systems in life safety as well as property protection, two additional sprinkler standards were created: NFPA 13D (created in 1975) for one-and two-family dwellings and NFPA 13R (1991) for low-rise multi-family dwellings. “Low-rise” multi-family dwellings, according to NFPA 13R, are residential properties not exceeding four stories or 60 feet above grade. NFPA 13R leaves it to the locally adopted building code to define “stories.”

The design goal of a life safety sprinkler system (NFPA 13D or 13R) is to prevent flashover in the room of fire origin to keep toxic gas and temperature levels low and allow occupants to escape. Systems designed to these standards are not intended for property protection although they have a good record of doing so. Contractors are not required to provide sprinklers in spaces not normally occupied — e.g. attics, garages, or concealed spaces between floors in combustible construction — or small spaces where fires may occur but typically do not result in fatalities — such as small bathrooms, small closets, garages, carports or decks.

The challenge for fire operations personnel, however, is understanding the difference between the system designs and how that may affect fireground operations. Combustible spaces that are not protected by sprinklers are susceptible to rapid fire spread; sometimes overwhelming the system when the fire eventually reaches the sprinklers. There have been a number of significant fires in multiple family dwellings that were protected by NFPA 13R design sprinklers, but resulted in huge property losses. Table 2 identifies a few of these recent events.

The typical fire scenario that leads to a catastrophic loss includes “lightning strikes that ignite the attic, or fires that ignite in the mulch/vegetation immediately surrounding the building and spread up the combustible exterior to involve the walls/attic space. A vehicle striking the building and igniting is another scenario that can overwhelm the sprinkler system. The point: It’s incumbent upon the fire department to not be complacent with these buildings — expect the possibility of a significant fire in them, even though they’re have sprinklers, and use the following considerations to plan accordingly.”

Getting Ahead of the Challenge

Firefighters must be observant to new construction activities in their response districts, especially those projects that are protected by sprinkler systems. Firefighters must learn if a building is “fully protected” or provided with a life-safety system that may not cover all combustible areas. Regular visits during construction can increase awareness and understanding of the level of protection these systems provide, and where protection gaps may occur. If firefighters have questions about the type of protection, they should consult with the local fire marshal or building code official.

These early visits also provide an opportunity for pre-incident planning to identify and document fire protection systems — sprinklers, fire alarms, standpipe systems, fire department connections — and so-called passive fire protection features such as firewalls and fire door assemblies. Fire department access and water supply issues should be identified and documented. Most important, once the pre-incident plan is complete, the fire department should train on it regularly. Pre-incident plans are of little value if they are not reviewed or practiced before a fire.

In the event of a fire, a good size-up by the first arriving company is essential. The currently popular “SLICE – RS” stands for Size-Up, Location of the Fire, Isolate the Flow Path, Cool from a Safe Distance, Extinguish and then Rescue and Salvage are added in as necessary . The SLICE – RS mnemonic can aid in that good size-up.

If the fire appears too threatening or in an attic that sprinklers do not protect, an aggressive exterior attack is warranted using large diameter hose lines or master streams. Knowing the location of reliable, high-flow hydrants and where elevated streams may be placed is important, as well.

To learn more about the strategy and tactics of firefighting in sprinklered buildings, you can obtain the free training guide “Fighting Fire in Sprinklered Buildings” from FM Global at https://www.fmglobalcatalog.com/FMGlobalResourceCatalog/Catalog/tabid/4811/MLCatID/22/PageIndex/2/Default.aspx. The NFPA also publishes NFPA 13E: Recommended Practice for Fire Department Operations in Properties Protected by Sprinkler and Standpipe Systems.


Fire sprinkler systems are an important part of a life-safety and property protection strategy. Fire officials, building code officials and property owners work to assure the appropriate system is designed and installed to satisfy the requirements of the locally adopted building or fire codes. Firefighters must learn the differences among these system designs, and understand how the sprinklers are expected to perform in a fire.


  • Hall, John R., Jr. (2013). U.S. Experience with Sprinklers (NFPA Publication No. USS14). Quincy, Massachusetts: National Fire Protection Association
  • The International Residential Code includes its own standard — P2904 — that is a step-by-step design method to design and install a home sprinkler system.
  • Jakubowski, Greg (2012). Firefighting Tactics for Sprinklered Buildings. Fire Rescue. Retrieved December 28, 2015 from https://www.firefighternation.com/article/strategy-and-tactics/firefighting-tactics-sprinklered-buildings.
  • ModernFireBehavior.com (2014) S.L.I.C.E. – R.S. Retrieved December 28, 2015 from  ModernFireBehavior.com (2014) S.L.I.C.E. – R.S. Retrieved December 28, 2015 from https://modernfirebehavior.com/s-l-i-c-e-r-s/
Rob Neale currently serves as the International Code Council Vice President for Government Relations: National Fire Service Activities. He is responsible for strategic guidance to help local fire organizations adopt and enforce the most recent version of the model codes based on technical merit and build relationships among code enforcement entities. In 2015, Neale retired as Deputy Superintendent for the United States Fire Administration National Fire Academy in Emmitsburg, Maryland. Prior to that, for six years he managed the National Fire Academy’s Technical Fire Prevention curriculum, including fire inspection techniques, prescriptive and performance-based fire and building code interpretation and application, fire protection systems function, design, installation and standards, and plan review for fire inspection personnel.

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