When are fire sprinkler systems required for new construction?

Of all building features for new medium sized building projects or for renovation projects, the question on whether or not a building, or a specific portion thereof, requires sprinklers, is always a hot topic of question.  While many building owners and designers gladly incorporate fire sprinklers into their designs, many wish to avoid sprinklers altogether.

This article will discuss when sprinklers are required and what codes require them, and will give an introductory lesson to sprinklers and their components.

What is a sprinkler system?  A visual depiction of a sprinkler system is provided in Figure 1.1 below.  A formal definition of this is provided in NFPA 13, as:

For fire protection purposes, an integrated system of underground and overhead piping de-signed in accordance with fire protection engineering standards. The installation includes one or more automatic water supplies. The portion of the sprinkler system aboveground is a network of specially sized or hydraulically designed piping in-stalled in a building, structure, or area, generally overhead, and to which sprinklers are attached in a systematic pattern. The valve controlling each system riser is located in the system riser or its supply piping. Each sprinkler system riser includes a device for actuating an alarm when the system is in operation. The system is usually activated by heat from a fire and dis-charges water over the fire area.

Figure 1.1:  Visual depiction of a sprinkler system. 

While this definition tends to overcomplicate something already known in simpler terms, some inspection insight can be gained by examining the four major types of sprinkler systems, which are defined and described as follows:

Four Major Types of Sprinkler Systems:

  1. Wet Type System – this type of sprinkler system has pressurized water just upstream of each sprinkler head’s orifice and throughout the sprinkler piping network. The sprinkler system operates when localized heat present at each individual sprinkler head gets hot enough to open each individual sprinkler head.  This system is considered safest as the water is immediately present in the piping to deliver water to the fire.  Like all sprinkler systems, the system can only deliver that water that adequately flows into the sprinkler system from water supply sources, which can be city water, rooftop tank water, or water from dedicated fire pumps.  This is the type of sprinkler system most commonly encountered in AMAA’s special inspections and will comprise about 99% of inspections.
  2. Preaction Type System – this type of sprinkler system is installed where the system is protecting high value contents that cannot tolerate damage from inadvertent sprinkler system actuation. These systems have a supplementary electronic detection system that is wired to a local releasing valve.  In a single interlock system, when these detectors activate, the local releasing valve opens and admits water to the piping network, and from that point on the system functions the same as a wet type system.  In a double interlock system, the detector system has to actuate AND at least one sprinkler head has to fuse in order to admit water into the sprinkler network.  A double interlock system is only permitted in protecting freezer applications.  The single interlock preaction type system will be encountered on AMAA inspections that have expensive electronic network equipment, expensive medical equipment, or compartments that house other expensive equipment where water damage cannot be tolerated.  A preaction system inspection is the same as a wet type inspection except the electronic detection system has to be inspected and verified by test report and the preaction system releasing valve and panel must also be inspected.
  3. Dry Type System – this type of sprinkler system is installed where freezing temperatures obtain and the extra time for a sprinkler network to prime (wet) can be tolerated. The system control valve is a dry type valve that opens to admit water when a sprinkler in the network opens.  The system then functions as a wet type system, with the limitation that the piping network must fill before the system can operate.  These systems are seen on inspections once in a while, normally to protect loading docks and other outside areas.
  4. Deluge Type System – these systems are installed in high hazard areas where system actuation causes all sprinklers to operate simultaneously. The sprinkler heads are open in these systems.  A supplementary detection system operates to open the deluge type valve, which admits water to all sprinklers.  Such systems would be present in flammable liquid storage warehouses and other occupancies that store highly flammable or explosive materials.  These systems are not typically seen in AMAA inspections.

Why are sprinkler systems installed and when are they required?

The answer to this question may seem obvious, but from a building code standpoint, it is indeed more complicated and the answers may lend additional insight into sprinklers.  The International Building Code, and indeed any building code, has two goals when it comes to fire protection:  life safety and property protection.  Compare these goals to that of a life safety code (e.g. NFPA 101), which is designed solely to protect life or, conversely, insurance design guidelines and requirements, which are for property protection and business continuity only. A detailed examination of the International Building code will show that sprinklers are required, for the following reasons:

  • Increase the permitted size of a building – sprinklering a building throughout allows increases in building footprint and height for a given construction type. In other words, the designer may increase the size of the building beyond its code permitted limits without making the building design adhere to a more conservative (i.e., fire safe) construction type.  These design options are within Chapter 5 of the IBC.
  • A specific occupancy requires it – a certain occupancy use group, or occupancy use group above a certain size or occupant load, could require sprinklering. For example, all residential occupancies require sprinklers.  For other occupancies, the sprinkler size threshold is either defined by fire area or occupant load.  For example, sprinklers are required throughout a Group S-1 building if the building exceeds 12,000 square feet of fire area.  On the other hand, sprinklers are required in a Group A-3 building if the occupant load exceeds 300, among other things.  These requirements are given in Section 903 of the IBC.
  • Reduce compartmentation requirements – Occupancies or incidental uses (e.g., a mechanical equipment room) that need to be separated by fire resistive construction from other areas of the building may have the hourly separation requirements reduced if one or both spaces are sprinklered. For example, a mechanical equipment room may be required to be separated from an assembly (Group A-3) occupancy by one hour fire resistant rated construction—this separation could go down to zero if both spaces were fully sprinklered.  These reductions can be seen in Tables 508.4 and 509 of the IBC.
  • Because of a special situation or hazard – special cases, as designated in the building code, may necessitate sprinklering of a buiding. For example, the following special cases require sprinklering:  mall buildings, high-rise buildings, atriums, underground structures, Group I-2 occupancies, Stages, Special amusement buildings, Airport traffic control towers, Aircraft hangers, Group H-5 HPM exhaust ducts, Flammable finishes, Drying rooms, Live/work units, Children’s play structures, unlimited area buildings, incidental uses, Smoke-protected assembly seating, and special hazards as required by the International Fire Code.  These special situations are listed in Table 903.2.11.6 of the IBC and in Section 903.2.11.6 of the International Fire Code.
  • To design a compliant egress system – Exit access travel distances, exit separation distances, common path of egress travel distances, corridor fire resistance ratings, and required egress widths are less stringent when sprinklers are installed. While a designer seldom decides to add sprinklers in the middle of a building design project to obtain a code compliant egress system, designing one is certainly less restrictive if sprinklers are installed.  Chapter 10 of the IBC or IFC are filled with different requirements for sprinklered buildings versus unsprinklered ones.

While this article gives an idea of when and why sprinklers are required for new buildings, it does not discuss when sprinklers are required for existing buildings and for existing building renovation projects.  These requirements are more complicated and will be discussed further in another article.  All code references were to the 2015 ICC codes.