NFPA 13 2025 Edition: What Changed for Sprinkler Drawing Review

What is a supplemental sprinkler under NFPA 13 2025?

Supplemental sprinkler is now a defined term in NFPA 13, describing a sprinkler installed below an obstruction, a duct, soffit, or beam, to make sure water reaches the floor area the obstruction would otherwise shadow. Under the 2022 edition, drawings handled these below-obstruction heads as a subset of the general obstruction rules, without a name or a distinct design path. The 2025 edition gives them their own definition and sets out thermal sensitivity, K-factor, and water-shielding requirements specific to that role.

The detail that matters most for review: supplemental sprinklers are not required to be balanced with the ceiling sprinklers above them. A reviewer working from 2022-edition habits may flag a design that is actually compliant under the new framework, or miss one that isn't, if the drawing doesn't clearly label which heads are supplemental versus standard ceiling sprinklers. Our NFPA 13 sprinkler requirements guide covers the baseline obstruction rules this new framework builds on.

What changed for sprinklers on ceilings over 30 feet?

For ceilings over 30 feet, the 2025 edition restricts which sprinkler types can be used and raises the minimum K-factor for higher hazard classifications. Sidewall sprinklers are now prohibited for Ordinary Hazard Group 1 and higher classifications at that ceiling height. OH-2 and higher hazard classifications require a minimum K-factor of 11.2, and certain extended-coverage and standard-response sprinklers are prohibited depending on the hazard classification and ceiling height combination. The prior edition gave designers more latitude to choose sprinkler type and K-factor for tall spaces; the 2025 edition narrows that choice by hazard tier under its high-ceiling provisions.

For drawing review, this shows up as a specific pair of callouts: the ceiling height notation on the reflected ceiling or sprinkler plan, and the sprinkler schedule's K-factor and type column. A high-bay warehouse or manufacturing space drawn to a 2022-edition sprinkler schedule with sidewall heads, or a sub-11.2 K-factor at OH-2, would not satisfy the 2025 edition on that sheet.

Can storage sprinklers be installed under sloped ceilings now?

Yes. The 2025 edition allows storage sprinklers under sloped ceilings up to a 4-in-12 pitch, a design the prior edition did not permit. The change followed research from the Fire Protection Research Foundation into how control mode specific application and early suppression fast response sprinklers perform on sloped storage ceilings. Previously, those sprinkler types were not permitted on sloped ceilings in storage occupancies at all, which forced designers into workarounds: stepped ceiling framing, false flat sections, or reduced storage heights, to keep the layout compliant.

On a drawing set, this is worth a second look on any storage or high-piled storage building with a sloped or gable roof. A layout that avoided sloped-ceiling storage sprinklers under the old rules may now use a simpler, more direct design, and a reviewer checking against 2022-edition assumptions could flag a compliant sloped-ceiling layout as an error when it is not.

What changed for obstructions from concrete tees?

The 2025 edition caps the depth of concrete tee construction at 30 inches, while retaining the existing rule that sprinkler deflectors sit at least 1 inch below the bottom plane of the tee. Under the 2022 edition, there was no depth limit on concrete tee construction for obstruction purposes, only the 1-inch deflector clearance below the tee's bottom plane. In practice that let very deep tee sections go unaddressed by the standard obstruction language.

For structural systems using precast or cast-in-place concrete tees deeper than 30 inches, this is a coordination point between structural and fire protection drawings that a 2022-edition review would not have caught. Cross-check the structural tee section against the fire protection reflected ceiling plan on any project using deep tee construction.

What changed for dry pipe systems?

Gridded pipe configurations are now prohibited in dry pipe systems because of the water-delivery delay they cause, while dry pipe protected from corrosion by vapor corrosion inhibitors or vacuum systems can now use the bonus C-factor ratings. Section 8.2, covering dry systems, was substantially reorganized in the 2025 edition, and the gridded pipe prohibition is the functional change inside that reorganization: gridded systems fill from multiple directions, which works for wet systems but adds delay when a dry system has to fill with air first. The standard now requires tree or looped configurations instead.

Drawing review should check the pipe configuration on any dry system riser diagram against the tree/looped requirement, and confirm the corrosion-protection method noted on the drawings matches the C-factor used in the hydraulic calculations submitted with the set.

Did the area limitation for wet-pipe systems change?

Yes. The protected area for an electrically supervised, light-hazard wet-pipe system increased 50 percent, from 52,000 square feet to 78,000 square feet. The increase applies specifically to light-hazard wet-pipe systems with flow and supervisory alarms transmitted to a supervising station. A 2022-edition design capped at 52,000 square feet per system may now cover the same floor area, or more, under a single zone, which changes riser and zone valve counts on a floor plan.

For drawing review, a sprinkler zoning plan showing multiple wet-pipe zones sized to the old 52,000 square foot cap on a light-hazard occupancy can still be a valid design choice. Confirm with the design engineer whether the zoning reflects a deliberate choice or an unrevised 2022-edition assumption.

NFPA 13 2022 vs. 2025: what changed, side by side

The table below lines up the six changes covered in this guide against the 2022 baseline described in our NFPA 13 sprinkler requirements reference.

Which NFPA 13 edition is actually adopted?

Publishing the 2025 edition doesn't make it enforceable everywhere at once. Each state and local jurisdiction adopts a sprinkler code edition on its own schedule, often with amendments, and adoption lag varies widely: some jurisdictions are still enforcing the 2019 or 2022 edition. Confirm the governing edition with the authority having jurisdiction before flagging anything on a sprinkler set as non-compliant. This is the same edition-first discipline we cover for the NEC 2026 update and the 2024 IBC changes.

What this means for drawing review

Translating the code text into checks a reviewer can run against a sprinkler set, using the workflow described in how to read fire sprinkler drawings:

• Ceiling height notation: cross-check any noted ceiling height above 30 feet against the sprinkler schedule's type and K-factor columns for sidewall heads or sub-11.2 K-factors at OH-2 and higher.
• Sloped-ceiling storage layouts: before flagging a sloped-ceiling storage sprinkler layout as non-compliant, confirm the pitch is within 4-in-12 and check whether it's a legitimate use of the new provisions rather than an error.
• Dry system riser diagrams: verify the pipe configuration is tree or looped, not gridded, and that the corrosion-protection method matches the C-factor used in the hydraulic calculations.
• Wet-pipe zoning plans: check whether zone sizing reflects the updated 78,000 square foot light-hazard limit or an unrevised 52,000 square foot assumption, and confirm supervised alarm connectivity to NFPA 72.
• Concrete tee sections: on structural drawings showing tees deeper than 30 inches, confirm the fire protection set addresses the obstruction under the new depth cap, not just the 1-inch deflector rule.
• Supplemental sprinkler labeling: confirm below-obstruction heads are labeled as supplemental where relevant, since they carry different balance requirements than the ceiling sprinklers above them.

Our fire protection symbols guide and fire protection drawing review field notes cover the surrounding coordination checks, above-ceiling clashes, standpipe routing, alarm device placement, that a sprinkler-focused review should still include.

How Helonic helps

Helonic screens sprinkler drawings against the configured NFPA 13 edition, catching the drawing-visible items above, ceiling height mismatches with sprinkler schedule callouts, sloped-ceiling storage layouts, dry system pipe configuration, and zoning against the current area limitation, and cites the page location for each finding. See how it fits alongside a licensed fire protection engineer's review on our code compliance checking page.

NFPA 13 2025 Edition FAQ