High-Piled Storage: Steps to Determine Protection Scheme
NFPA 13, 2013 Edition referenced throughout unless noted otherwise: Philip M. Gunning, P.E. (P) 401-225-9761
1. Determine commodity classification
a. Look and/or ask following questions:
i. What is being stored? (not just what is being sold)
ii. What packaging materials are used? (the packaging materials contribute to the fuel load /
commodity classification)
iii. Do quantities fluctuate throughout the year due to demand?
iv. If plastics are part of the load:
1. Investigate the type of plastic - Group A, B, or C (examples are in NFPA 13, Section
5.6.4)
2. Determine quantity, % by weight and % by volume of the unit load. Refer to Class III
and IV commodity definitions in NFPA 13, Chapter 5 for allowable amounts.
3. Is it free flowing (free flowing materials can pour or fall out of the container/carton
similar to a liquid). Refer to Class IV commodity definition in NFPA 13, Chapter 5.
4. Is it unexpanded, or expanded (unexpanded plastic is rigid/stiff, and expanded plastic
is squishy and contains air pockets )
5. Is it cartoned or uncartoned?
v. Don’t forget to look or ask if idle pallets are stored inside
vi. If mixed commodities, err on the side of caution and protected to the most demanding
commodity type, otherwise, be sure to understand the facility operations to ensure higher
hazard commodities meet the quantity and arrangement requirements (NFPA 13, Section
5.6.1.2)
b. Be sure to include as many of the following people when determining/finalizing the commodity
classification:
i. Owner
ii. Authority Having Jurisdiction (AHJ)
iii. Insurance Underwriter
iv. Consultant
v. Contractor
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2. Are the unit loads encapsulated?
a. More than 50% of the top of the unit load must be covered with plastic wrap to be encapsulated
Unencapsulated
Encapsulated
b. Depending on the type of sprinkler used, more water is required to protect encapsulated
commodities, which is indicated in the tables with the storage chapters of NFPA 13.(When using
Control Mode Specific Application (CMSA) or Early Suppression Fast Response Sprinklers (ESFR),
encapsulation does not require more water from the sprinkler system. More water (greater design
discharge density) is required from the sprinkler system for encapsulated unit loads when using
standard spray sprinklers.
3. Identify pallet type
a. All testing done in 60’s and 70’s used conventional wood pallets or solid, flat bottomed combustible
wood pallets (slave pallets). Note: For rack and palletized storage, all area/density curves and
protection tables in the storage chapters of NFPA 13 assume conventional wood pallets are used.
When Spray Sprinklers (standard or extended coverage) are installed, the ceiling design density must
be increased if solid, flat bottom wood pallets (slave pallets) are used (NFPA 13: 16.2.1.3.4.7 Where
solid, flat-bottom, combustible pallets (slave pallets) are used with storage height up to and including
25 ft (7.6 m), the densities that are indicated in the design curves shown in Figure 16.2.1.3.2(a)
through Figure 16.2.1.3.2(g), based on conventional pallets, shall be increased 20 percent for the
given area.)
Conventional Wood
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Solid, Flat Bottom (Slave)
Plastic
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b. If plastic pallets are used, determine:
i. Are they stamped / classified as a certain commodity type? If no, determine if they are:
1. Unreinforced (causes commodity to jump up 1 classification)
2. Reinforced (causes commodity to jump up 2 classifications except for Class IV
commodities, which are increased to Cartoned, unexpanded Group A plastic. NFPA
13, 5.6.2.3))
3. Notes
a. If there is no commodity stamp or indication of the type (reinforced vs.
unreinforced), you must classify the pallets as reinforced (worst case
scenario)
b. When comparing the two pallet types during fire conditions, reinforced
pallets present a greater fire hazard because the unit load (fuel) stays in
place and exposes its surface area for longer, which allows the fire to grow
faster and release more heat. Unreinforced plastic pallets lose the ability to
support the weight of the unit load as long and, which causes the unit load to
fall toward the fire and slow down the combustion process, resulting in a
smaller fire
ii. This rule does not apply if listed storage sprinklers with a k-factor of 16.8 or larger are
installed (NFPA 13, 2007 and later, Section 5.6.2.6)
4. Determine storage arrangement
a. Idle pallets (NFPA 13, Chapter 12, Section 12)
i. Present a high fire challenge
ii. Many insurance policies do not allow indoor storage
iii. NFPA 13: 12.12.3.2 Idle pallets shall be permitted to be stored on the lowest level of storage
only where no storage or shelves are located above the stored pallets and the applicable
protection criteria referenced for on-floor storage in Section 12.12 are applied.
iv. NFPA 13: 12.12.3.3 Where idle pallet storage is above a door, the idle pallet storage height
and ceiling height shall be calculated from the base of storage above the door using the
applicable protection criteria referenced in Section 12.12.
b. Miscellaneous storage- storage up to 12-feet in height that is incidental to the use of the building
(NFPA 13, Chapter 13)
c. Solid Pile, Palletized, Bin Box, Shelf Storage or Back-to-Back Shelf Storage (NFPA 13, Chapters 14 &
15)
i. Solid Pile – commodity on the floor without pallets
ii. Palletized – Unit loads on pallets on the floor (no shelf or rack)
iii. Bin box - Storage in five-sided wood, metal, or cardboard boxes with open face on the aisles
in which boxes are self-supporting or supported by a structure so designed that little or no
horizontal or vertical space exists around boxes.
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i.
ii.
Shelf storage – shelving units/structures cannot exceed 30-inches in depth and must be
separated by 30-inches in width, otherwise rack storage criteria applies (Chapters 16 & 17)
Back-to-Back Shelf Storage - Two solid or perforated shelves up to 30 in. (0.76 m) in depth
each, not exceeding a total depth of 60 in. (1.52 m), separated by a longitudinal vertical
barrier such as plywood, particleboard, sheet metal, or equivalent, with a maximum 0.25
in. (6.4 mm) diameter penetrations and no longitudinal flue space and a maximum storage
height of 15 ft (4.57 m).
i.
ii.
Class I-IV commodities (NFPA 13, Chapter 14)
Plastic and rubber commodities (NFPA 13, Chapter 15)
1. Is the pile stable or unstable? Stable piles present a greater hazard than unstable
piles because the unit load (fuel) stays in place and exposes its surface area for
longer, which allows the fire to grow faster and release more heat. Unstable piles
will fall toward the fire and slow down the combustion process, which results in a
smaller fire.
d. Rack storage (NFPA 13, Chapters 16 & 17)
i. Single row- racks up to 6-feet in width AND aisles 3.5 feet or wider in width
ii. Double row- racks up to 12-feet in width AND aisles 3.5 feet or wider in width
iii. Multiple row- racks greater than 12-feet in width OR single or double row racks separated by
aisles less than 3.5 feet in width
Single-row
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Double-row
Multiple-row
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iv. Movable rack shall be classified as Multiple-row racks per NFPA 13: 16.1.3
v. Class I-IV commodities (NFPA 13, Chapter 16)
1. Storage up to and including 25-feet in height (Section 16.2)
2. Storage over 25-feet in height (Section 16.3)
vi. Plastic and Rubber commodities (NFPA 13, Chapter 17)
1. Storage up to and including 25-feet in height (Section 17.2)
2. Storage over 25-feet in height (Section 17.3)
e. Flue Spaces
i. Refer to NFPA 13: 16.1.10
ii. Required for two reasons (1) allow the fire to grow fast vertically to operate ceiling sprinklers
quickly and (2) allow a path for water to reach the fire
iii. Transverse flues are required for all rack storage arrangements between each load and at the
rack uprights (approximately every 5-feet)
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f.
Shelf type (all area/density curves and protection tables assume open shelving)
i. To be open shelving:
1. Shelves must be at least 50% open in area
2. Solid shelves equal to or less than 20 square feet in area WITH required flue spaces
maintained between loads and at rack uprights (approximately every 5-feet)
3. Solid shelving between 20-64 square feet, in-rack sprinklers required at every 6-foot
vertical increment
4. Solid shelving greater than 64 square feet, sprinklers required under every shelf
5. Note: The width of the rack beams, on which the shelves rest on, must be included
when measuring the area of the shelf
g. Storage height
i. Measured from floor, or bottom level to top of storage
h. Clearance
i. Measured from top of storage to sprinkler deflector. The minimum required clearance is
dictated by the type of sprinkler (refer to Chapter 8 or manufacturer’s technical data sheet)
ii. Measured from top of storage to underside of roof
5. Available sprinklers
a. Document construction type(obstructed, unobstructed, ceiling slope)
b. Control Mode (use area/density curves and/or tables before Large Drop tables)
i. Spray sprinklers (minimum k-factor based on required density, refer to Chapter 12, Sections
12.6.1, 12.6.2, and 12.6.3)
1. Standard coverage
2. Extended coverage
ii. In-rack / intermediate level sprinklers
iii. Large Drop (always use Large Drop tables)
iv. Specific Application Control Mode (always use Specific Application Control Mode tables)
v. Always refer to NFPA 13, Chapter 8 or manufacturers cut-sheet to determine if 18-inches or
36-inches of clearance is required from top of storage to sprinkler deflector
c. Suppression Mode
i. ESFR, Early Suppression Fast Response sprinklers (always use ESFR tables)
ii. 36-inches of clearance is required from top of storage to sprinkler deflector
iii. Clearance from top of storage to underside of roof must be known
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6. NFPA 13 Architecture
a. Chapter 12
i. Applies to all storage applications (e.g., roof slope limitations, roof vents and draft curtains,
multiple adjustments, etc.)
b. Chapter 13
i. Miscellaneous storage up to 12-feet in height that is incidental to the use of the building
c. Chapters 14 & 15
i. Solid Pile, Palletized, Bin Box, or Shelf storage
1. Class I-IV commodities (Chapter 14)
2. Plastic and rubber commodities (Chapter 15)
ii. Protection schemes (solid shelving ok as long as shelf width does not exceed 30-inches)
1. Area/density curves (use control mode spray sprinklers, standard or extended
coverage)
2. Large Drop table
3. Specific Application Control Mode table
4. ESFR table
d. Chapters 16 & 17
i. Rack storage
1. Class I-IV commodities (Chapter 16)
a. Section 16.1 applies to all rack storage (e.g., flue spaces, steel column
protection, etc.)
b. Storage up to and including 25-feet in height (Section 16.2)
c. Storage over 25-feet in height (Section 16.3)
2. Plastic and rubber commodities (Chapter 17)
a. Section 17.1 applies to all rack storage (e.g., flue spaces, steel column
protection, etc.)
b. Storage up to and including 25-feet in height (Section 17.2)
c. Storage over 25-feet in height (Section 17.3)
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ii. Protection schemes (assumes open shelving)
1. Area/density curves (use control mode spray sprinklers, standard or extended
coverage)
2. Large Drop table
3. Specific Application Control Mode table
4. ESFR table
e. Chapter 18 – Protection of Rubber Tire Storage
f. Chapter 19 – Protection of Roll Paper
g. Chapter 20 – Special Design of Storage Protection
i. Plastic Motor Vehicle Components
ii. Retail Stores
iii. Protection of Baled Cotton Storage
h. Chapter 21 – Alternative Sprinkler System Designs for Chapters 12 Through 20
i. Chapter 22 - Special Occupancy Requirements
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