Warehouse Truss Collapse Risk and a Thin Documentation File
You are the origin and cause investigator for a 14,200 sq ft single-story warehouse storing aerosol products and palletized paper goods. The fire was knocked down at 02:10 after burning about 50 minutes. The building has 32 ft clear-span lightweight wood trusses; the east exterior wall bulges roughly 4 in at mid-height, the southeast corner has a 6 in diagonal crack, and 2 in of standing water covers the floor. A four-gas meter at the door reads 60 ppm CO and 5 ppm HCN; a thermal imager shows 380 F at a truss gusset plate over Aisle 12. The incident commander wants Aisle 12 photographed before the demolition contractor arrives at 06:00. Your own file is thin: the 22 exterior photos were shot at dusk without a scale or photo log, and the floor plan was drawn from memory two days later because the pre-fire drawings were never requested. Two firefighters describe a wall of fire at the west end.
1. Do you enter Aisle 12 before 06:00? Lay out your safety decision, the conditions you would set if entry is approved, and what you document before crossing the threshold.
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Do not treat the IC's timetable as a safety argument. The building is telling you it is compromised: a 4 in wall bulge and a 6 in corner crack indicate lateral displacement, the trusses are lightweight wood with metal gusset plates, and 380 F at a gusset over Aisle 12 means heated steel in a roof system that is already suspect. Lightweight truss systems fail without warning once a gusset is heated or a bottom chord is burned through. Aerosol storage also means you may have failed containers and a flammable propellant atmosphere.
Conditions I would set if entry is approved: a written safety briefing with names, times, and assigned tasks; two-person teams with a dedicated outside attendant; full PPE and SCBA regardless of the fire being out, because CO is 60 ppm and HCN is 5 ppm at the door; continuous four-gas monitoring with an evacuation trigger; a charged line at the entry; a collapse zone outside of at least 1.5 times wall height (about 48 ft); and an engineer's or the IC's explicit assessment of the truss and wall before anyone walks in.
Before entry I document exterior conditions with a scale, the crack and bulge measured, TI readings with time stamps, and the atmospheric readings, because those numbers are the record of why entry was limited if the building later fails.
2. Identify the documentation gaps in the file and how you would remediate each one before demolition.
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Photo set. Twenty-two exterior images shot at dusk with no scale and no log have limited evidentiary value. Remedy: reshoot in daylight with a scale and a directional reference, and build a photo log listing image number, date, time, photographer, location, direction, and subject. If the original 22 images are the only record of the pre-extinguishment exterior, log them with a note on the conditions under which they were taken rather than pretending they are something they are not.
Sketch. A plan drawn from memory two days later is not a measurement record. Remedy: redraw from an established baseline, take and record measurements, and label it as a measured sketch with the date and instrument used. The memory sketch can stay in the file as a working document, clearly labeled.
Missing records. Request the pre-fire drawings and the sprinkler and occupancy records immediately, plus the alarm log, dispatch times, and the suppression timeline. Those establish how long the fire burned and where suppression water went, which affects pattern interpretation.
Witness statements. Two firefighters describe a wall of fire at the west end. Take recorded, signed statements with date and time; memory fades and the statement is the evidence.
Demolition. Video the sequence with narration, and document the debris pile before it is hauled.
3. The demolition contractor wants to start at 06:00 and the IC supports it. What do you do?
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I do not try to stop a safety-driven demolition of an unsafe structure, because I cannot make that call and would not want to. What I negotiate is sequence and preservation.
Ask for a staging plan: demolition proceeds first in areas untouched by the fire so that Aisle 12 stays intact long enough for the exterior and roof-line documentation, measured sketch, and sampling. Get the agreement in writing, with times.
Explain the exposure plainly to the IC and the contractor: once the debris is commingled and hauled, the origin area is unrecoverable, which turns a defensible cause opinion into an undetermined classification and hurts every party in any later claim. I put that in a short written notice to the carrier and the fire department so the decision to proceed is documented as theirs.
If demolition must proceed anyway: video the entire operation, take representative samples from the debris pile as it is created, and document the sequence. I would also request the contractor preserve any identifiable aerosol containers or electrical components pulled from Aisle 12.
Escalation: if the demolition would destroy the origin area before any documentation, I ask the fire chief to make the call in writing. That protects the investigation and the chief.