Sprinkler Design for Pallet Storage Gets Stricter in 2025 Update

Pallet fires burn fast and hot. The stacked design creates air gaps that accelerate flame spread, while upper pallets shield the lower ones, making it harder for water to reach the base of the fire. Even a solid sprinkler layout can fall short when idle pallet storage gets overlooked in the early design.

The NFPA is addressing that risk head-on. Beginning with the 2025 edition of NFPA 13, fire protection requirements for idle pallet storage are becoming more specific. For FLS contractors, that means tighter design rules, clearer separation from standard commodity storage, and less room for interpretation.

The updated code spells it out in Section 20.17, classifying idle pallets as their own hazard type. Whether it’s a warehouse, grocery store, distribution center, or retail backroom, if pallets are part of the operation, a different set of sprinkler rules applies.

First: What Counts as a Pallet?

NFPA 13 defines wood pallets as being fully wood with metal fasteners. Plastic pallets include any pallet that has plastic components, no matter the percentage.

In most cases, plastic pallets carry a higher fire risk than wood. However, NFPA 13 allows them to be treated the same as wood pallets if they’ve been tested and certified (or "listed") as having a similar or lower fire hazard. Without that certification, plastic pallets are considered more hazardous, and some design options are off the table.

Indoor Storage Only

NFPA 13 recognizes idle pallet storage can happen indoors, outside, or in detached structures. But only indoor storage is covered by the new protection requirements.

Arrangements matter. Pallets can be stacked on the floor or on racks. Pile height, ceiling height, and separation between stacks all affect the protection scheme. One key restriction: solid-shelf racks aren’t allowed for idle pallet storage, due to the shielding effect during a fire.

Design Options Under the 2025 Code

The 2025 update to NFPA 13 lays out several design paths for protecting idle pallet storage. The right option depends on pallet type, storage height, ceiling height, and how the pallets are arranged.

Density/Area Method – Ordinary Hazard Group II

For limited quantities of idle pallets:

Wood pallets: Max 6 ft tall
Plastic pallets: Max 4 ft tall
Separation: 8 ft of clear space or 25 ft of other storage
Stack limits: 4 for wood, 2 for plastic

This option suits small factories, department stores, and similar occupancies.

Control Mode Density/Area

This design method applies to larger storage areas and taller pallet stacks, but the requirements differ for wood and plastic pallets:

Wood Pallets

Storage height: 6 to 20 ft
Ceiling height: Up to 30 ft
Density range: 0.2 to 0.6 gpm/ft²
Design area: 2,000 to 4,500 ft²

Plastic Pallets (not in a dedicated room)

Storage height: Up to 10 ft
Ceiling height: Up to 30 ft
Density: 0.6 gpm/ft² (fixed)
Design area: 2,000 ft²
Minimum K-factor: 16.8

Plastic pallets are subject to stricter requirements, including a higher fixed density and a minimum K-factor, due to their increased fire hazard.

Control Mode – Dedicated Room for Plastic

For plastic pallets in isolated rooms:

Room must be separated by a 3-hour fire wall
Max pile height: 12 ft
Sprinkler density: 0.6 gpm/ft² over the whole room
Protection must include steel columns inside the room

CMSA Sprinklers (Wood Only)

For rack or floor storage of wood pallets:

Storage height: Up to 20 ft
Ceiling height: 30–40 ft
K-factor: 11.2–19.6
Not permitted for storage on solid-shelf racks

ESFR Sprinklers

Early suppression fast response (ESFR) sprinklers are a great solution for pallets because they’re geared toward challenging fire hazards.

Wood pallets: Floor or open rack storage, 20–35 ft tall
Plastic pallets: Not height-limited, but ceiling height capped at 40 ft
K-factor: 14–25.2
Pressure range: 15–75 psi for wood, 35–75 psi for plastic

High Expansion Foam (Plastic Only)

Alternate option for plastic pallets stored in dedicated rooms:

Max pile height: 12 ft
Combined system: 0.3 gpm/ft² sprinkler density + high expansion foam
Includes protection for structural steel in the room

In-Rack Sprinkler Protection

Allows pallet storage on racks (wood or plastic), using the expanded plastic commodity rules in Section 25.7:

Design depends on roof-level sprinkler type
Protection based on max horizontal and vertical spacing, not density or number of heads
Solid-shelf racks still not permitted

Test-Based Designs for Plastic Pallets

NFPA gives you some wiggle room on plastic pallets. If you’ve got full-scale fire test data to back it up, you can use a custom protection scheme instead of sticking to the listed ones. However, wood pallets still have to follow the standard setups.

What FLS Contractors Need to Do

The 2025 update makes it clear: if pallets are in the building, you must factor them into your design.

Start by asking:

Are the pallets wood or plastic?
Are the plastic pallets listed as equivalent to wood?
How high are the stacks?
Are they on the floor or on racks?
Is there a dedicated room?
What’s the ceiling height?

Every one of these details impacts your design options and whether you're in compliance.

Ignoring the fire load from idle pallets could leave your system undersized and your client exposed. The 2025 edition of NFPA 13 gives you the playbook. Now it’s on you to build to it.