The 2025 edition of NFPA 13 includes many technical additions and revisions from the 2022 edition. This document will only highlight some of the significant technical changes and additions to the 2025 edition of NFPA 13. This summary will not be a list of every change to the standard but rather highlight some of the major changes to the 2025 edition of NFPA 13 from the 2022 edition.
Several revisions for sprinkler placement and allowable omissions are included in the 2025 edition. The allowable omission of sprinklers in elevator pits and in elevator hoist ways and machine rooms in most situations, has been added to Chapter 9 (9.2.14 Elevator Hoist ways and Machine Rooms).
System Area Limitations (4.4.1): The longstanding system area limitations (floor area protected with a single sprinkler system) was modified. The area limitations for light hazard wet pipe systems that are electrically supervised has been increase by 50 percent, from 52,000 square feet to 78,000 square feet.
In Chapter 4, Miscellaneous Storage and low-piled storage protection requirements have been divided into two different sections to make it easier and apply the applicable criteria (4.3.1.7)
Supplemental Sprinklers
NFPA 13 has long required sprinklers to be installed under fixed obstructions over 4 feet in width. This concept remains, but the 2025 edition of NFPA 13 includes numerous additions and clarifications to requirements for sprinklers below obstructions. New Definitions related to Supplemental Sprinklers:
- Supplemental Sprinkler (Section 3.3.223.3.6) now defines a supplemental sprinkler as “A sprinkler that is installed below an obstruction (ex. Duct > 4ft.).”
- Non-Flat Obstruction (3.3.143): now defines a non-flat obstruction as “An obstruction where the underside of the obstruction is not in the same plane and not capable of collecting heat.”
- Non-Solid Obstruction (3.3.144): now defines a non-solid obstruction as “An obstruction that consists of openings that constitute at least 30 percent of the footprint of the obstruction.”
New Requirements for Supplemental Sprinklers (9.5.5.3.3):
- Must be quick response or have a fast response element.
- Permitted to have different K-factor, orientation, and coverage than the ceiling sprinklers under certain conditions.
- Required to have water shield (or otherwise shielded) where installed:
- Under non-flat obstructions
- Under non-solid obstructions
- Beyond outer edge of obstruction
- Under open grating
High Ceilings for Non-Storage Occupancies
New requirements for sprinklers installed in non-storage occupancies with ceilings over 30 ft high (high ceilings) have been provided in Chapter 9 – Sprinklers for Ceiling Heights over 30 ft (19.2.3.2.5): The 2025 edition of NFPA 13 will restrict sprinkler types for ceilings over 30 ft as follows:
- OH-1 and higher – sidewall sprinklers not permitted
- OH-2 and higher – minimum K-factor 11.2
- OH-2 and higher – no extended coverage sprinkler with a K-factor of 22.4 or less
- OH2 with ceiling height over 40 ft – no standard response sprinkler
Sprinkler Density/Areas for Ceiling Heights over 30 ft (19.2.3.5.2): New design areas and density requirements for ceilings over 30 ft are summarized in the below table:
Sloped Ceilings (20.9.1) – Storage
Based on large-scale fire testing (Fire Protection Research Foundation Report), new guidance is provided for sprinklers installed under sloped (steeper or over 2 in 12 or about 9.5 degrees) ceilings. Testing has demonstrated that that fire control can be achieved with sprinklers protecting storage under ceilings up to and including a slope of 4 in 12, or about 18.5 degrees. This resulted in a change to NFPA 13 whereby early suppression fast response (ESFR) sprinklers, as well as control mode specific application (CMSA) sprinklers, can now be installed in spaces with a ceiling slope of up to 4 in 12. Testing has also clarified when sprinkler deflectors in buildings with slopped ceilings should be aligned to be parallel with the ceiling or stairs and when it is permissible for them to be aligned parallel to the floor (See 9.5.4.3).
Section 20.9.1.1 gives six (6) options for protecting storage occupancies where the ceiling slope exceeds 2 in 12:
- In-rack sprinklers (no storage above in-racks)
- Install false celling that can withstand 3 lb./ft² uplift force
- Install per Chapter 20 through 26 (which permits ceiling in excess of 2 in 12)
- CMDA (up to 4 in 12) – sprinklers in every channel
- Unobstructed (up to 4 in 12) – increase design area by 50%
- Obstructed (up to 4 in 12):
- a. Purlins run across roof slope
- b. Purlins do not exceed 18 in deep and 5 ft O.C.
- c. Purlins supported by girders 40 ft O.C or less
- d. Purlin channels are provided with blocking above each girder
ESFR Design Area with Sloped Ceilings above 2/12: Along with the changes above, sloped ceilings above 2/12 for ESFR sprinklers, the requirement for how many ESFR sprinklers need to be calculated in certain sloped ceiling arrangements. The existing criteria of 12 sprinklers with four sprinklers on three branchlines remains; however, when the design area for an ESFR system is increased from 12 to 18 sprinklers, the design area will be 18 ESFR sprinklers with five sprinklers on most demanding three branchlines and three sprinklers on next most demanding branchlines. The 18 sprinkler design area is mandated by Option 5 of Section 20.9 which states that for unobstructed construction where the ceiling slope does not exceed 4 in 12, increase the design area of the ceiling sprinklers by 50 percent (12 x 1.5 = 18).
Spray Sprinkler Design Area with Sloped Ceilings (19.2.3.2.4): Changes to sloped ceiling situations is not limited to storage occupancies. NFPA 13 has always simply required that for sloped ceilings using the density/area method of calculation be increased by 30%. This concept has been revised and for spray sprinklers, the 30% increase for ceiling slope has been limited as shown in the following table:
Vacuum Systems
A new section on vacuum systems has been added to Chapter 8, but many of the requirements are the same as traditional dry or preaction systems. One major addition is the inclusion of listed vacuum dry pipe systems in Chapter 8. In addition to allowing listed vacuum dry pipe systems, provisions have been added to Chapter 7 allowing vapor phase corrosion inhibitors to be added to the air supply for dry pipe and preaction sprinkler systems as a method to reduce corrosion.
Vacuum systems are sometimes called negative pressure systems and are dry or preaction sprinkler systems that include sprinklers attached to a piping system containing air under negative gauge pressure. Vacuum systems reduce the oxygen in the system, and the vacuum pump removes residual water or condensation to inhibit corrosion. As a result, they are able to use a lower C-value (internal pipe roughness in the Hazen Williams formula) because they have less corrosion in them when compared to dry or preaction systems that contain air.
Seismic Bracing
Another change addresses the seismic bracing section of NFPA 13, which has been overhauled in this edition to correlate with the recent changes to ASCE/SEI 7, Minimum Design Loads and Associated Criteria for Buildings and Other Structures. The section on calculating horizontal force on bracing has been redone to integrate ASCE/SEI 7 and introduce the design spectral response acceleration at short periods, which is used to measure of the maximum force an object experiences in an earthquake. The maximum intervals of sprinkler piping restraints have also been updated to align with ASCE/SEI 7. Revisions to Chapter 18 have been made, including updating load tables to incorporate seismic forces from piping and changing of seismic coefficient (Cp) values to align with ASCE/SEI 7, Minimum Design Loads and Associated Criteria for Buildings and Other Structures. For locations outside of the United States, Annex E has been modified to allow conformance with ASCE/SEI 7.
Documentation Cabinet (16.11.1.3)
New to the 2025 edition of NFPA 13 is the requirement to provide a documentation cabinet. The documentation required by NFPA 13 is essential to properly conducting ITM on a sprinkler system. Additionally, should the system need to be altered or evaluated in any way, this documentation is paramount to the engineer or designer tasked with such work. Too often, vital documents such as the sprinkler plans are not available. This makes ITM and system modifications difficult and often expensive for the owner. To mitigate this problem, this new section requires that a documentation cabinet be installed, and that important documentation be stored in the cabinet. This documentation includes, at a minimum, final documentation of completion documents, final shop drawings and as-builts of the sprinkler system. This documentation may be stored in electronic or hardcopy format.
Signs (16.17)
A related concept is signage. Important signage (such as general information and hydraulic information sign) is often missing or illegible. This new section requires that copies of all required signage be kept in the documentation cabinet in either electronic and/or hardcopy format. See Table A.16.17 Sprinkler System Signage Summary.
Owner’s Certificate (4.2): Numerous changes/updates were made to Section 4.2:
- The title was changed to “Basis of Design for the Owner’s Certificate”. The title was changed as this information is needed for designing the sprinkler system.
- A new requirement was added to provide a Storage Plan (where applicable) which includes the maximum height of storage, the commodities stored, and the storage arrangement. Added because storage layout plans are often required by the fire code.
- A new requirement for the owner or their representative is to provide the water supply data, including any needed adjustments. This requirement confirms that water supply analysis is the responsibility of the owner or owner’s representative. Guidance for this concept is found in the annex to this section.
- A new requirement for the owner or their representative to determine whether seismic protection is required.
Flexible Sprinkler Hose
The 2025 edition of NFPA 13 expanded the requirements and made numerous changes related to this concept. Flexible Sprinkler Hose Fitting Requirements (7.4.5): This new section simply states that flexible sprinkler hose fittings must be installed in accordance with their listing and manufacturer’s instructions. See also Flexible Sprinkler Hose Fitting Lengths (16.8.8-1;2)
C-Factor Changes
In the 2022 edition of NFPA 13, the C-factor for dry systems with nitrogen installed in accordance with the standard was changed from C-100 to C-120. For the 2025 edition, the committee made the same change for both dry systems and preaction systems with Vapor Corrosion Inhibitors (VCI) and for Vacuum systems. See Table 28.2.4.8.1 Hazen–Williams C Values
Written By Lee Rebodos
