Fire sprinkler systems for tire storage in Washington State

Tire storage is a special commodity under NFPA 13 Chapter 17 — standard occupancy hazard tables do not apply above five feet. A technical guide for auto parts warehouses, tire dealers, fleet maintenance yards, and any facility where tire inventory exceeds a single row of display stock.

Why tires are not ordinary merchandise storage

Walk into any commercial tire storage area and the fire protection designer's first question is not "what's the occupancy hazard classification?" — it's "how high are the tires stacked and how are they oriented?"

That question matters because NFPA 13 Chapter 17 governs tire storage as a special commodity. Special commodities are materials whose fire behavior is too severe, too unusual, or too configuration-dependent for the standard density/area tables in NFPA 13 Chapter 12 to produce a reliable protection solution. Rubber tires fall into this category for three reasons:

High heat release rate. Tires have a heat release rate comparable to Group A plastics — materials like expanded polystyrene and polyurethane foam that produce dense, fast-moving fires. The steel cord, textile cord, and rubber in a radial tire all contribute to a fire that can release three to five times the energy of an equivalent mass of ordinary Class II commodity.

Difficult water penetration. A closed tire (standing on tread) creates an air pocket at the center. Water from ceiling heads flows over and around the outer sidewall surface rather than penetrating to the interior. The most dangerous ignition scenario — a fire that starts in a tire pile and radiates inward — is not well controlled by ceiling-only suppression once it's past the incipient stage.

Configuration-dependent fire spread. Tires stacked on their sides (bore horizontal, stacked flat) create a vertical chimney through each bore that accelerates upward fire spread dramatically. Tires standing on tread create densely packed rows with limited air circulation but can tip and roll once supports burn away. Each configuration has a different fire growth rate, and the NFPA 13 design approach accounts for both.

NFPA 13 Chapter 17 classification and design

NFPA 13 classifies tire storage as a specialized commodity covered in Chapter 17. The design approach differs from Chapter 12 occupancy-hazard tables in a fundamental way: the protection approach is determined by storage height and configuration, not by the standard hazard classification.

For practical purposes in Washington commercial facilities, the key design thresholds are:

Up to 5 feet above the floor. Tire storage up to 5 feet in display-height single rows — typical in a retail tire sales showroom — can be protected using standard NFPA 13 Ordinary Hazard Group 1 or Group 2 ceiling design criteria depending on the total building hazard. This is the configuration most commonly seen in small tire shops where showroom stock is floor-level display, not warehouse storage.

5 to 14 feet. Storage above 5 feet in solid pile or racked configurations requires design calculations based on Chapter 17 tire storage criteria, which produce significantly higher water demand than standard OH1 or OH2 tables. The specific density/area curve and maximum ceiling head spacing depend on whether tires are stored on-side (bore horizontal) or on-tread (upright). On-side stacking above 5 feet generates higher water demand because of the bore chimney effect.

Above 14 feet. Tire storage above 14 feet in solid pile configurations, or above 20 feet in racked configurations, typically triggers an in-rack sprinkler requirement in addition to ceiling-level protection. The in-rack heads are placed at intermediate levels within the storage array to address the fire that grows inside the stack before ceiling heads can respond effectively.

ESFR as an alternative. Early Suppression Fast Response (ESFR) sprinkler heads provide an alternative to in-rack sprinkler systems in some tire storage configurations. ESFR heads deliver a high-momentum water discharge designed to penetrate the fire plume and reach the base of the fire. The trade-off is that ESFR systems have strict ceiling height limits, minimum clearance requirements above the top of storage, and very specific head spacing rules — an ESFR design for tire storage requires a full hydraulic analysis specific to the building geometry and cannot be substituted for a standard ceiling system without a complete redesign.

Occupancy classification and building context

Tire storage facilities are typically classified as IBC Group S-1 (Moderate-Hazard Storage). The S-1 sprinkler trigger is 12,000 square feet of fire area — a threshold that small tire shops and service centers routinely fall under. But staying below the IBC code-minimum sprinkler trigger does not address the NFPA 13 Chapter 17 requirement for the fire protection design if a sprinkler system is present or required by a lender, insurer, or franchisor.

The scenarios where this matters most:

Auto parts warehouses. A warehouse mixing general merchandise (oil, filters, belts, tools) with a dedicated tire storage zone is a common configuration in South Pierce County retail warehouse developments. The general merchandise area might be adequately protected with an OH1 or OH2 ceiling design. The tire storage zone requires a separate hydraulic design under Chapter 17, and the two zones need to be reconciled into a single water supply calculation that accounts for the simultaneous demand of both.

Fleet maintenance yards. Municipality and private fleet operators often store several hundred tires — enough to rotate a fleet of buses, utility trucks, or commercial vehicles — in a dedicated storage room attached to the maintenance shop. The storage is dense and may extend to 10–14 feet on standard pallet racking. At that height, the Chapter 17 threshold is active, and a standard OH1 system designed for the maintenance shop is insufficient for the tire room.

Stand-alone tire storage buildings. Developers building dedicated tire storage and retreading facilities in the Sumner, Auburn, and south King/Pierce industrial corridors are constructing buildings specifically around Chapter 17 tire storage. The sprinkler design drives the building geometry choices — ceiling height, rack layout, and column spacing — more directly than in most other storage occupancies.

When a storage expansion triggers a redesign

The most common scenario in which a tire storage fire protection problem surfaces is an expansion: an existing auto parts warehouse or service center adds a dedicated tire storage room, extends an existing tire storage area to a higher rack height, or increases the stored tire count beyond what the original system was designed to protect.

NFPA 13 is clear that a system must protect the hazard as-installed and as-stored, not as-originally-designed. When the stored height, configuration, or commodity classification changes beyond what the original hydraulic calculations addressed, a re-design is required — not just a system extension.

The triggers most commonly missed in Washington:

• Adding racking that takes storage from 8 feet to 12 feet in an existing building with a ceiling system designed for the original 8-foot height
• Adding a tire storage zone to an existing warehouse that was designed for general merchandise only, without reconciling the Chapter 17 demand into the existing hydraulic calculations
• Converting a storage bay from boxed tire storage (similar to Class III commodities in boxes) to loose on-side tire stacking (on-side stacking produces higher fire growth rates and higher water demand than boxed storage of equivalent height)

Pierce County AHJ context for tire storage permits

Tire storage at commercial scale — racked above 8 feet or in a building specifically designed for warehouse tire storage — typically requires a fire suppression plan review that explicitly addresses Chapter 17 compliance. Pierce County Fire Prevention, East Pierce Fire & Rescue, and the City of Tacoma Fire Department have reviewed Chapter 17 tire storage submittals and are familiar with the requirement.

In practice, the plan review process for Chapter 17 tire storage is similar to other high-piled storage permits: the sprinkler contractor submits hydraulic calculations that demonstrate adequate water supply and density/area coverage for the specific tire storage configuration. If the existing water service at the site can't meet the calculated demand, a fire pump or water service upgrade is part of the permit package.

Flow tests at the site's public hydrant are required before final hydraulic calculations can be completed. Schedule flow tests 2–4 weeks in advance with the relevant water utility — Pierce County Utilities, the City of Tacoma Water Division, or the municipal utility in Puyallup or Bonney Lake depending on the parcel.

Common mistakes in tire storage fire protection

1. Applying standard OH1 or OH2 tables to racked tire storage above 5 feet. The most common error is treating tire storage as ordinary merchandise and designing or extending a ceiling system under Chapter 12 hazard tables without reviewing Chapter 17. This produces a system that may pass plan review if the plan reviewer doesn't flag the commodity classification — but that is under-designed for the actual hazard.

2. Failing to distinguish on-side from on-tread stacking in the hydraulic calculations. The design basis for tire storage differs by stacking orientation. On-side stacking (tires stacked horizontally with bore vertical) has higher fire growth potential than on-tread storage (tires upright on their tread surface) because of the bore chimney effect. A design prepared for one orientation is not automatically valid for the other if the storage configuration changes.

3. Adding tire storage racking to an existing building without re-running hydraulic calculations. Many TI projects in auto parts warehouses add new tire storage racking without treating it as a significant modification to the suppression system. If the new racking extends storage height above the original design basis, the existing hydraulic calculations are no longer adequate. A permit for the racking typically triggers a fire suppression system modification permit.

4. Designing for current inventory without accounting for maximum storage height. Designers sometimes base the Chapter 17 design on the current inventory level rather than the maximum intended storage height. If the owner intends to use the full rack height eventually, the system should be designed for that height from the start — a system designed for 10-foot storage that is later extended to 14-foot storage will need to be redesigned.

5. Assuming boxed tire storage (new stock) matches the hazard of loose tire stacking. New tires arriving in manufacturer packaging (cardboard boxes) are stored at a lower fire hazard classification than the same tires removed from their cartons and stacked loose. Some facilities start with boxed storage and transition to unboxed stacking as they move product — if the suppression system was designed for boxed storage only, the change to loose stacking changes the design basis.

6. Omitting in-rack heads on high-bay tire storage above 14 feet. In a high-bay configuration where tires are stored above 14 feet in solid piled stacks, ceiling-only sprinkler coverage is typically insufficient. In-rack heads at intermediate storage levels are the standard approach, but they're sometimes omitted from initial designs to reduce cost. The in-rack heads are the most fire-suppression-critical component of the system in high-bay configurations — their omission is not a minor scope gap.

Last reviewed by Michael Berger, Owner · 1st Choice Fire · WA L&I #1STCHCF770OF