Designing for very high ceilings (in non-storage occupancies) just got more complicated. Historically, NFPA 13 did not distinguish between a 20 ft high and a 40 ft high room for sprinkler design in, say, an office or an assembly hall – there were no special rules, which sometimes raised eyebrows. The 2025 edition addresses this by adding criteria for ceilings over 30 ft high in Chapter 19. In a nutshell, certain sprinklers are no longer permitted at great heights, and higher demand may be required. For example, if your ceiling is above 30 ft in an Ordinary Hazard (OH) occupancy, you cannot use sidewall sprinklers (they don’t throw water far enough). In OH2 (or higher) occupancies above 30 ft, you now need a minimum K-factor of 11.2 on sprinklers – smaller 5.6K or 8.0K heads won’t cut it. Also, any extended coverage sprinklers used in OH2+ above 30 ft must be large orifice (K > 22.4). And if the ceiling exceeds 40 ft in OH2, standard response sprinklers are forbidden – you’d need quick-response types. On top of sprinkler type limits, NFPA 13 (2025) introduces new density/area requirements for these high ceilings. For instance, an OH2 occupancy with ceiling > 40 ft might now require a 0.45 gpm/ft² density over a larger area (with a 30% design area increase) – beefier than the usual OH2 requirements.

These height-related restrictions are brand new, so it’s easy to overlook them if you flip open your old design tables from 2022. A designer might unconsciously specify the same sprinklers for a 35 ft tall warehouse mezzanine as they would for a 20 ft space – which now could violate code (e.g. using an 8.0K head where 11.2K is minimum). It’s also tricky because the rules vary by hazard class and height range, so there’s a bit of a matrix to remember. If you miss the fine print, you might end up with under-performing sprinklers (not enough water) for a tall ceiling fire scenario. Conversely, you might over-design out of caution, potentially adding unnecessary cost, if you’re not aware of the specific thresholds. In short, high ceilings now demand high attention.

Height is now a design factor – don’t ignore it. When working on any non-storage project with ceilings ~30 ft or higher, check the new Section 19.2.3.2.5 and associated tables. Ensure your sprinkler selection meets the new criteria (e.g. upright/pendent only, adequate K-factor, quick response if needed). For ceilings above 40 ft, be extra cautious: confirm if a density increase or larger design area applies per the new tables. A good practice is to mark on your plans “Ceiling height = X ft” and flag any special design rules that trigger above 30 ft, so nothing slips through. If you’re unsure, use the exact guidance from NFPA 13 (2025) – for example, OH2 over 40 ft? Then plan for at least 0.45 gpm/ft² and quick-response, 11.2K+ sprinklers. By proactively adjusting your design to these limits, you’ll avoid the nasty surprise of an AHJ citing you for non‑compliance on a tall building project. 😉