A vacant Lancaster auto parts building burned through its roof, and crews pulled back to defend the lot

LANCASTER, Calif.

A second-alarm fire in a vacant commercial auto parts building in Lancaster burned through the roof and forced Los Angeles County Fire Department crews into a defensive operation, according to the department's command center reports.

Defensive means the building was written off and the fire was fought from outside. Crews protect what is next to a burning structure when the structure itself cannot be entered safely, and the flow of flame through the roof is the clearest signal that the interior is lost. A vacant building reaches that point faster than an occupied one, because nobody has been maintaining the openings, the roof or the protection systems inside it.

No injuries were reported in the command reports reviewed for this report. The cause was not determined in the information available at publication.

Vacant commercial buildings are their own hazard class

Los Angeles County has thousands of commercial parcels whose buildings no longer support the business that built them. An auto parts store, a repair garage or a small warehouse that closes becomes a structure with an owner, a mortgage and no occupant. The utilities are sometimes shut off and sometimes not. The roof develops leaks. The plaster falls away from the walls, and the fire protection systems, if there were any, are not tested again.

Then the building fills. Vacant commercial structures accumulate discarded furniture, pallets, tires and whatever else is left behind or brought in, and the interior that was designed to hold shelving is holding a fuel array. The fire load of an empty building is frequently higher than the fire load of a working one.

The other condition is access. Boarded windows and doors keep people out and also keep hose streams and ventilation out. A fire in a sealed building produces a hotter, more pressurized interior, and when a window or a roof opening fails, the result is a sudden change in the fire that can reach anyone working near it.

Where a roof fire becomes a wall problem

An auto parts building is typically a single-story masonry or tilt-up box with steel bar joists spanning to the walls and a built-up roof over a metal deck. The roof assembly in older buildings is often the weakest structural element, carrying ponding water and years of patching.

Heat from below attacks the joists at their bearing points on the wall. When a bar joist fails, the roof deck over it drops, and the load redistributes to the members beside it. That sequence is why a burning roof is a collapse indicator rather than simply a ventilation problem, and it is why the collapse zone at a defensive fire is set at a distance that equals the height of the building plus a margin, not at the curb.

Fire venting aggressively through a roof also creates an exterior exposure problem. In a commercial corridor, the building on the other side of a lot line is close enough to be pre-wetted, and the radiant heat from a fully involved roof can ignite a neighbouring fascia before the first line is even in position.

What happens to the site after the fire is out

The building is not gone, and the property is now a liability. Los Angeles County and the cities within it have procedures for dangerous buildings: an inspection, an order to secure or demolish, and a schedule. Until the structure is removed or repaired, it is a vacant building with a damaged roof, an open perimeter and no protection.

That is a security condition as much as a code condition. Fire-damaged commercial buildings are entered for scrap metal, for fixtures and wiring, and for shelter. The drywall and debris left after a defensive fire are combustible, and a second fire in the same structure is a normal outcome rather than an unusual one.

Where a building's fire protection systems are out of service and the property remains in use or in the care of a contractor, the impairment rules in the applicable code require notification and, beyond the permitted interval, a fire watch. Los Angeles County's own hot work and fire watch requirements sit within a regulatory framework that is set out in the county's adopted code, and the countywide framework is summarised in the Los Angeles fire watch and hot work regulations volume published by this newsroom.

The economics that produce vacant commercial buildings

A vacant commercial building is usually the residue of a business decision rather than a fire protection decision. Small commercial parcels in Los Angeles County carry taxes, assessments and code obligations, and the cost of a compliant repair or a demolition frequently exceeds what the owner can recover from redevelopment in the near term. Leaving the building closed and paying the minimum is a rational choice from inside that arithmetic.

The consequence lands on the fire department. Vacant and abandoned structures account for a disproportionate share of arson fires in national fire data, and they are over-represented in the fires that injure firefighters, because the interior has been altered by people who were not building anything. Holes cut through floors, stairs removed for scrap, and doors that no longer exist are conditions that turn a routine interior attack into a trap.

Cities have tools for this, and Los Angeles County uses them. Boarding and securing orders, nuisance abatement, receivership and demolition orders each address a different part of the problem, and each takes time that a burning building does not provide.

What the site needs in the next thirty days

Three tasks sit ahead of any redevelopment conversation, and they are the same three whether the owner intends to rebuild or sell.

The first is stabilization. Either the structure is made safe to leave standing with an engineer's assessment behind it, or it comes down under permit. A burned building left open with a damaged roof does not stabilize; the deck continues to corrode, water continues to enter, and the walls continue to lose the bracing the roof provided.

The second is the perimeter. Boarding is a delay rather than a barrier, and a chain-link fence with a locked gate is only as good as the frequency of the checks behind it. A fire-damaged commercial parcel is entered for metal, for wiring, for anything salvageable, and for shelter. The people who enter also light fires, frequently in the same building.

The third is the record. Photographs, an inventory of what remained on site, and a log of every person who entered after the fire department released the property protect the owner in an insurance claim and protect the contractor from an accusation.

During any of that work the site needs a presence at night, and where a building's fire protection is out of service while repairs are under way the impairment rules apply. A fire watch assigned to a property of this kind covers the structure and the lot, and its purpose is to catch the second fire before it becomes the second incident.

What a defensive decision costs the owner

Writing off a building is a life-safety decision with a financial consequence attached. An interior attack is attempted while there is a survivable space and something to protect inside it. Once crews move to the exterior, the water goes onto the roof and through the openings rather than onto the seat of the fire, and the contents of the building are treated as a total loss.

That decision belongs to the incident commander and is not a judgement about the value of the property. It follows the condition of the structure, the volume of fire and the presence of anything inside worth risking a crew for. In a vacant building there is nothing to search for and nothing to save.

For the owner, the practical result is a total loss claim, an adjuster's inspection, and a salvage question about what can be removed from a building that may still collapse. For the street, the result is a prolonged operation with road closures and a smoke column that draws calls from several miles away.

The second fire is the one to plan for

Fire-damaged commercial buildings burn again. The reasons are structural and human: a roof that no longer sheds water, debris that stays on site, and a perimeter that cannot be kept closed.

Planning for that means treating the parcel as an active site rather than a finished incident. A fence, a locked gate, documented checks, and a presence during the hours when nobody is working are the measures that prevent the second call. Where the building's protection systems are confirmed out of service, the impairment provisions of the fire code apply, and a fire watch assigned to the property is the interim measure that the authority having jurisdiction will recognize.

The USPA position

USPA Nationwide Security provides emergency fire watch coverage for properties whose suppression or alarm systems are out, and uniformed officers for access control at commercial buildings that are damaged, vacant or under demolition. Coverage is opened through the emergency desk and sustained until the property is released or secured by other means.

Related reporting from the newsroom: Fire crews in Kansas City battled a vacant apartment building fire in the Wabash block, and a Hampton commercial fire disabled the electrical core and handed the building to investigators.