NFPA Journal

BY JONATHAN HART 

Many businesses are rethinking how their office spaces will be utilized post-pandemic, and a significant number will undergo renovations or redesigns. Add this to regular tenant fit outs, including shell space in newly constructed buildings, and there will likely be thousands of existing sprinkler systems requiring modification to adequately protect these redesigned spaces.

These changes often raise questions as to the extent a sprinkler system must be brought up to date with the latest standard, whether the system needs to be recalculated, and how extensive testing of the modified system must be. Fortunately, the 2019 edition of NFPA 13, Standard for the Installation of Sprinkler Systems, included a new chapter that compiled the requirements for these instances, information that carries over to the recently issued 2022 edition.

For the purpose of this discussion, we will focus on situations where the use or occupancy classification of the space remains the same—in cases where that changes, a more complex analysis is likely required to determine the impact of changes to design densities, areas of operation, and several other possible changes. In those instances, NFPA 25, Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems, places responsibility on the owner for ensuring an evaluation is conducted. Many of those evaluations go beyond the reconfiguration of office space, where the space protected is likely to remain a light-hazard occupancy.

When a building undergoes a renovation or remodeling, the removal or addition of walls, partitions, and ceilings can negatively impact the effectiveness of the originally designed sprinkler system. In these instances, numerous sprinklers must often be relocated or added in order to appropriately protect the reconfigured space. This does not necessarily mean that the entire system must be reevaluated to ensure complete compliance with the latest edition of the standards. In fact, portions of the existing system that are not subject to the modifications can be considered previously approved under the retroactivity clause of NFPA 13 and do not need to be evaluated. Whenever additions or modifications are made to an existing system, enough of that system must be indicated on the plans to make all conditions clear for the authority having jurisdiction (AHJ) to evaluate.

NFPA 13 requires calculations be provided to verify that the system design flow rate will be achieved where hydraulically calculated systems are modified. This does not necessarily require a full set of hydraulic calculations, particularly if the modifications are made in a part of the system that is not the hydraulically most demanding. In this case, the modified portion of the system can be hydraulically calculated back to the branch line or riser to the point where original calculations are used to show that the design flow rate can be met. It should be confirmed with the AHJ to determine that they will accept this for these instances.

Newly installed sprinkler systems must be hydrostatically tested to check for leaks at a pressure of at least 200 psi (14 bar) for a period of at least two hours. When existing systems are modified such that the work affects fewer than 20 sprinklers, the system only requires testing at the system working pressure. Where the modification affects more than 20 sprinklers, that portion of the system must be isolated and tested at 200 psi (14 bar) for two hours. If the new work cannot be isolated, the testing can be done at system working pressure even if the modifications involved more than 20 sprinklers. In general, existing portions of the system do not need to be subjected to a new hydrostatic test.

The provisions for existing sprinkler system modifications in NFPA 13 are intended to ensure that a modified space has adequate coverage, that the system demand can still be met, and that the workmanship of the modification has been completed well enough. This is meant to strike an appropriate balance between ensuring that the changes are not simply ignored, and calling for everything to be brought up to the requirements of the latest edition of the standard. 

JONATHAN HART is technical lead, Fire Protection Engineering, at NFPA. NFPA members and AHJs can use the Technical Questions tab to post queries on NFPA 13 at nfpa.org/13. To follow the progress on the upcoming edition of the code, visit nfpa.org/13next.