A Salisbury warehouse fire compromised its own walls, and the state fire marshal has the building

SALISBURY, Md.

The Maryland State Fire Marshal has opened an investigation into a late-afternoon fire at a commercial warehouse on Farmers Market Lane in Salisbury that left the building's structural walls compromised, according to the Office of the State Fire Marshal.

A warehouse fire that compromises load-bearing walls is a different incident from a warehouse fire that consumes the roof. The roof can be replaced from above. When the wall that carries the roof and the racking is compromised, the building has to be held back from the inside until an engineer says what remains, and the collapse zone becomes the operational boundary for everyone on the site.

The fire marshal's investigative division handles origin and cause determinations in Maryland, and the structure is treated as a scene until that work is complete. No cause classification or damage estimate was included in the information reviewed for this report.

How a warehouse wall gets compromised

Older commercial warehouse stock in the region is built from masonry or tilt-up concrete walls carrying steel joists and a metal deck roof. The walls are designed for gravity and wind loads, not for a fire that has been burning against them for hours.

When fire reaches the contents of a warehouse, the steel members above begin to lose strength well before they melt. Unprotected steel at 1,000 degrees Fahrenheit retains roughly half its room-temperature strength, and a sustained fire inside a racking array can reach that temperature at the joist bearing points. Once the joists deflect, they push outward on the wall they bear on, and a masonry wall with no lateral bracing at the top is exactly the wrong structure to receive that thrust.

The visible sign is a wall that has bowed or cracked, and the correct response is to withdraw and protect the exposures. Firefighters are trained to recognize the change and to leave the interior before it happens, which is why a defensive posture at a warehouse is a decision about construction rather than about the volume of fire.

Contents, racking and the fire load nobody counts

Warehouse fire load is a function of what is on the shelves rather than what the building was designed to hold. A facility permitted for general storage can be holding plastic totes, aerosol products, mattresses, lithium-ion battery packs or pallets of paper at the moment of a fire, and the difference between those contents changes the required sprinkler density under NFPA 13 by a wide margin.

Racking adds a vertical problem. A double-row pallet rack creates a flue between the racks and a horizontal path over the top of the array. Sprinklers installed at the ceiling of a 32-foot building are asked to reach fire that is burning at 20 feet inside a rack, which is why in-rack sprinklers exist and why a change of contents without a corresponding change in protection is one of the most common deficiencies found in warehouse inspections.

Sprinkler protection is a design, not a fitting

A sprinkler system in a warehouse is engineered against a specific commodity, a specific storage height and a specific arrangement. When the storage changes, the design basis is void even though the pipe is still there.

That matters after the fire as much as during it. Buildings that take significant fire and water are frequently left with a portion of the system isolated: a control valve closed for the investigation, a section of pipe damaged by heat, or a dry system that was tripped and not properly restored. NFPA 25 requires an impairment procedure and notification, and where the outage extends past the permitted period the authority having jurisdiction can require a fire watch for the affected areas.

The alternative during that window is an unoccupied commercial building with a compromised roof, no working suppression and a fire load that survived the first fire. That is the exact combination in which a re-kindled or second fire occurs.

The scene is also a security assignment

A fire-damaged warehouse holds three things that attract people: salvageable inventory, copper and metal, and heavy equipment. The building is usually open, the lighting is out, and the fire department's tape is not a barrier.

Fire scene security in a commercial building is a perimeter assignment with a specific purpose: keep unauthorized people out of a structure that may still collapse, and document everyone who goes in. Contractors, adjusters, investigators and the owner all need access, and the record of who entered and when becomes part of the loss file.

Water supply decides whether a warehouse fire stays inside

A commercial warehouse fire is a fire-flow problem before it is anything else. A single-story storage building of thirty thousand square feet with a heavy content load can require several thousand gallons per minute to darken down, and that demand arrives all at once.

Municipal systems in a city the size of Salisbury are generally capable of supplying it, but the delivery depends on the hydrant nearest the building and the mains feeding it. Engine companies lay large-diameter supply line from a hydrant that has been flow-tested, and where the closest hydrant sits on a private loop main serving an industrial park, that main may be sized for domestic demand rather than fire flow. The first arriving company's decision about which hydrant to take defines how the next two hours go.

Long setbacks, private drives and security gates add time to every step of that sequence. So does the hour of day: a late-afternoon fire in an occupied facility has staff on hand who can open gates and describe the contents, and a fire after the shift ends does not.

What a fire marshal's finding will and will not establish

An origin and cause investigation answers two questions. It establishes where the fire started and what ignited it. It is a fire investigation rather than a building code audit, and the finding does not by itself establish whether a suppression system was in service, whether an inspection was overdue, or whether the property complied with its occupancy requirements.

Those questions live in a different record. The local fire authority's inspection history and the building department's permit file establish what was tested and when, and both are public records in Maryland. An insurer's engineering report covers some of the same ground from a different angle.

For a property owner the distinction matters in practice. A cause finding of undetermined is common and is not an accusation. A code deficiency identified during the investigation is a separate process with its own notice and correction schedule. Neither one substitutes for testing the building's systems before the property is returned to use.

Reoccupying a warehouse after a structural fire

A warehouse with compromised walls is not returned to service on a cleaning schedule. The structural evaluation comes first, then the repair design, then the permit, then the work, and for a building of any size that sequence runs in months.

The items that must be closed out before reoccupancy are specific. The structural repair needs an engineer's sign-off. The sprinkler system needs a hydrostatic test and, where piping was replaced, a new acceptance test. The alarm system needs to be recommissioned rather than simply switched back on. Every fire-rated assembly that was opened has to be restored to its rating with documented firestopping. Electrical service needs inspection after water intrusion.

The interim condition is where fire watch and site security sit. A building with no suppression, a damaged roof and a surviving fire load is a building that can burn twice. A building with no occupancy and an open perimeter is a building that gets entered.

The building next door is part of the incident

A warehouse fire in a commercial corridor is fought with the neighbouring structures already in mind. Radiant heat from a fully involved building crosses a lot line quickly, and the distance that protects the neighbour is a function of the fire's height and the wall construction rather than the width of the driveway.

Where the adjacent building has unprotected windows facing the fire, crews pre-wet the fascia and the roof edge and assign a company to that side for the duration. Where the neighbour has its own rated wall and no openings, the work is shorter. Fire walls on commercial parcels are frequently breached over time by doors, conveyors and utility penetrations, and a wall with a door in it is not a fire wall.

For the business next door, the loss is often smoke and water rather than flame. Smoke infiltration into a food, pharmaceutical or electronics tenant can destroy stock that never burned, and the interruption that follows a three-day shutdown is a claim in its own right.

The USPA position

USPA Nationwide Security provides warehouse security for distribution and storage facilities, including perimeter control and documented patrols at buildings that are out of service. Fire watch coverage across Maryland is available for facilities with impaired suppression, and coverage can be opened through the emergency fire watch desk.

Related reporting from the newsroom: Investigators in Hampton are working the cause of an Industry Drive commercial fire, and a Bedford County commercial building was a total loss with 12 to 14 vehicles burned with it.