Springy Floor, Separated Baseboard, and Two Civilians on the Third Floor
You are the second-arriving company at a three-story Type V garden-style apartment building built in 2003. Fire started in a first-floor kitchen and has been burning about 18 minutes. As you reach the second-floor landing, the floor feels springy underfoot and the carpet is hot. In the hallway, the baseboard has pulled about an inch away from the wall, and smoke is pushing from the electrical outlets. The building has engineered wood I-joists with a 16-inch open web and a single layer of 5/8-inch drywall on the ceiling below. The first-floor crew reports no visible fire on their level but heavy heat. Two occupants are reported still on the third floor, and the interior stair is the only means of egress.
1. What do those four indicators tell you about the floor system, and what do you do about the crews above the fire?
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Each indicator alone is worth a pause; together they are a single conclusion.
A springy floor means the joist has lost stiffness. A hot carpet means heat is coming up through the assembly, not just through the doorway. Baseboard pulled away from the wall means the sill plate or the rim has shrunk or charred, letting the wall assembly move. Smoke from outlets means the concealed space is charged with products of combustion and the drywall is no longer a barrier.
Engineered I-joists have no redundancy and fail early and without the sag that gives a solid-sawn joist its warning. An 18-minute fire in a first-floor kitchen under a 16-inch open-web I-joist floor is a collapse profile, not a caution.
So: withdraw all crews from the second and third floors immediately, notify the IC that you believe the floor assembly is involved, and treat the interior stair as unusable for firefighting. Report over the radio in plain language - "floor system compromised, crews coming out, do not send anyone up" - before you finish the conversation.
2. How do you verify the floor before committing anyone, and what are the limits of that verification?
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You can verify from a position you can retreat from, and only in a limited way.
Sounding with the flat of a tool from a doorway or off the stair landing, a thermal imager sweep of the floor from a protected position, and a look at the ceiling below for sag, cracking, or discoloration all give information. Listening and reading smoke movement in the concealed space helps too.
The limits are the point. Sounding tells you about the small area you struck, not the span you are about to walk across. It does not detect a joist whose web has been eaten out mid-span under the drywall. And it cannot be done from a place you cannot safely reach - if the only way to sound the floor is to stand on it, you have already answered the question wrong.
Given the indicators in this building, no amount of sounding converts that floor into a working platform. Verification is used to decide whether a quick grab-and-go at the top of the stairs is survivable, not to justify a search team above the fire.
3. What do you recommend to the IC about the two civilians and the overall strategy?
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Recommend switching the effort above the fire to the outside and going defensive on the fire floor.
For the two occupants: the interior stair is the only egress and it is directly over the compromised floor. Ground ladders to the third floor on the side away from the smoke, or an aerial if available, make the rescue independent of the stair. That is the fastest safe route, and it does not put a crew on the second-floor span. Simultaneously, a crew at the third-floor stair door can pull occupants down only if the second-floor landing is still sound at the moment - which you cannot promise.
For the fire: big water from outside into the first floor, with the master stream directed into the fire compartment, not into the attic, while a handline holds the stair and the exposure. Request a second alarm for relief and for the ladder work, and start accountability. The strategic fact is that the building has already told you its floor is failing - believe it and stop trading firefighters for a fire that is not going anywhere.