Why “In-Play Structure” Sprinklers Are Often the Wrong Answer for Indoor Playgrounds

Indoor playgrounds are dynamic, high-activity environments where children move quickly through tight spaces, tunnels, and multi-level play structures. That reality often conflicts with prescriptive sprinkler requirements that were never written with these occupancies in mind. In a recent 12,000-sf indoor children’s playground project in Boston, Engineering Fire Protection (EFP) evaluated whether fire sprinklers should be installed inside multi-level play structures—beneath platform decks and within enclosed play volumes. The conclusion was clear: installing sprinklers inside play structures is often not recommended, and there are practical, code-supported alternatives that can provide equal or improved fire and life safety.

The code-driven rationale for installing sprinklers inside play structures typically stems from obstruction rules in NFPA 13. Many play structures include horizontal platforms that are wide enough to obstruct sprinkler discharge from the ceiling above. When fixed obstructions exceed 4 ft in width, NFPA 13 often requires supplemental sprinkler protection beneath the obstruction to ensure water reaches the hazard below. From a prescriptive standpoint, the logic appears straightforward: if the platform blocks the spray pattern, add sprinklers underneath.

However, applying that logic directly to indoor play structures often produces poor real-world outcomes. These structures are narrow, low-clearance, and designed for constant movement. Introducing sprinkler heads, piping, and hangers into those spaces creates impact and snag hazards directly within children’s paths. Even when installers attempt to coordinate components carefully, the geometry and use of the structure frequently defeat those efforts. In addition, play structures experience continuous vibration. Sprinkler piping attached to vibrating elements is more susceptible to leakage, displacement, or long-term reliability issues. For facilities that operate seven days a week, an avoidable sprinkler leak can lead to operational shutdowns, lost revenue, and reputational damage.

When prescriptive compliance creates impractical or unsafe conditions, both the IBC and NFPA 13 allow for modifications and alternatives, provided the proposed solution meets the intent of the code and does not reduce fire and life safety. This forms the basis of an effective AMMR approach: rather than arguing against the prescriptive requirement, the design demonstrates that the same objectives—life safety and property protection—are achieved through a solution better suited to the occupancy. For the Boston project, the AMMR was formally reviewed by the Boston Inspectional Services Department (ISD) and the Boston Fire Department, and the proposed approach was accepted by the Authorities Having Jurisdiction as meeting the intent of the applicable codes.

A key step in developing a defensible alternative is recognizing that sprinklers inside play structures are often expected to serve two distinct objectives. One is property protection: delivering water to hazards shielded by platforms or decks. The other is life safety: providing detection and alarm to support occupant evacuation. Treating these objectives separately allows each to be addressed more effectively.

From a property protection standpoint, the alternative approach focuses on strengthening the ceiling sprinkler system above the play structure rather than placing sprinklers within it. The system can be designed to account for extensive shielding conditions, with Extra Hazard Group II classification used to reflect the potential for obstructed discharge. NFPA 13 explicitly contemplates such shielding scenarios, and this approach keeps sprinkler components out of the play environment while still addressing the protected hazard.

From a life safety standpoint, smoke detection above the play structure provides earlier notification than sprinklers located within enclosed play volumes. For the Boston project, EFP modeled a representative shielding fire scenario using Fire Dynamics Simulator (FDS). The analysis showed that sprinklers beneath the playhouse ceiling activated at approximately 72 seconds. When waterflow switch delay was included, alarm notification could occur as late as 162 seconds. By comparison, the first ceiling-mounted smoke detector activated at approximately 38 seconds—nearly two minutes earlier. Earlier detection translates directly to earlier evacuation, which is a critical life-safety outcome in a children’s play environment. This result is also consistent with fundamental fire detection principles, as smoke is typically present well before sprinkler-level heat develops.

Taken together, this intent-driven approach avoids introducing physical hazards into play structures, improves system reliability, and provides earlier occupant notification, all while remaining aligned with code intent and acceptable to AHJs. It demonstrates that in many indoor playground applications, sprinklers inside play structures are not only unnecessary but may be counterproductive.

Engineering Fire Protection (EFP) provides code consulting and performance-based fire and life safety engineering for indoor recreation and children’s play facilities. We support project teams in developing buildable, defensible solutions through AMMR narratives, sprinkler and detection alternatives, performance-based modeling (including FDS), and AHJ documentation. For projects involving multi-level play structures or obstruction-driven sprinkler challenges, we help teams reach “yes” without compromising safety. Please don’t hesitate to contact us via email at contact@engineeringfireprotection.com.