Fire Size-Up Checklist For A House Fire (12 Inputs Most Officers Miss)

Most company officers who have run more than fifty residential fires can tell you exactly which inputs they trust on arrival and which ones lie. A residential structure looks deceptively simple from the curb. One story, two stories, smoke from a window, fire showing somewhere. You think you have it read in three seconds. Then the 360 reveals the basement fire, the missing occupant, the propane grill in the breezeway. Now your three-second read is a problem.

The checklist below is the one that holds up across modern residential fires. It reflects UL-FSRI's flow path research, NFPA's reporting on residential fireground tactics, and the standard references in IFSTA and Norman's tactics. It is in priority order. Skip the early inputs and the later ones will not save you.

Run this checklist on every house fire you respond to. Practice it on photographs. Practice it on YouTube videos with the sound off. By the time you have done two hundred mental reps, you will not have to consciously run it. You will just see the fire and the inputs will be there.

Time of day tells you presumed occupancy and presumed survivability. A residential fire between 2200 and 0600 is presumed occupied with sleeping victims. Search priority is high. A residential fire at 1400 on a weekday is presumed unoccupied to partially occupied. Search priority is still real but the math on commit and risk is different.

Day of week matters for working-age residences. Weekday daytime fires in family homes tend to have lower adult occupancy and higher child or elderly occupancy. Weekend fires have higher full-occupancy presumption. Holiday fires tend to be loaded with extended family, more sleeping in unusual spots (couches, basements, finished attics), and more cooking and heating risk factors.

Construction era is the single biggest predictor of how the building will behave under fire load. Pre-1970 construction in most of the country is heavier dimensional lumber, plaster walls, slower fire spread, longer collapse timelines. Post-2000 construction is heavily engineered lumber, lightweight trusses, OSB sheathing, drywall, fast fire spread, dramatically shortened collapse timelines.

The UL-FSRI floor collapse studies on engineered lumber show structural failure in as little as 6 minutes of direct fire exposure on unprotected I-joists. Solid sawn lumber under the same conditions holds substantially longer. Your interior commitment decision has to account for which one is under your crew.

Balloon frame versus platform frame matters too. Balloon frame (typically pre-1940) allows fire to travel uninterrupted from basement to attic in the wall void. A basement fire in a balloon frame is an attic fire in waiting. Plan ventilation and resource allocation accordingly.

The Dodson framework. Volume tells you fire size. Velocity tells you internal pressure and fire intensity. Density tells you fuel load in the smoke (flashover indicator). Color tells you what is burning and how completely.

Thick, black, turbulent smoke pushing hard from multiple openings is a fire ready to flash or already in the rollover stage in the involved compartment. Lazy gray smoke from a single opening is a contents fire still in growth stage. Brown smoke from structural areas (eaves, gable end, attic vents) suggests structural wood pyrolysis and is a collapse warning.

Read all four dimensions together. Reading one in isolation will fool you.

Where is the fire visible from the outside, and where is it likely to go next? A first-floor fire in a two-story will extend up the stairs and into the second floor sleeping areas unless the door is closed. A basement fire will extend up the wall voids in balloon frame and up the stairs in platform frame. An attic fire from below has already passed through the second floor in most cases.

Note any visible auto-exposure paths. Eaves above a first-floor window. A failed window that exposes the room above. A second-story window above a porch roof. These predict your second alarm assignment and your exposure protection priorities.

Cars in the driveway. Plural cars suggest multiple occupants. Single car at 0300 still suggests at least one adult home. Lights on inside. Toys, bikes, swings, basketball hoops, accessibility ramps. Pet bowls, dog houses, cat doors. Christmas lights still up in February (less likely to be modernized residents). A wheelchair ramp signals presumed limited-mobility occupant and changes your search plan.

A vehicle running in the driveway at the time of arrival is a hard sign. Someone tried to leave or someone just arrived. Either way, account for them.

Wind is the input that decides whether you have a routine room and contents fire or a wind-driven event that will move fire faster than your crews can move. UL-FSRI's wind-driven fire research is unambiguous: a sustained wind of 10 mph or more pushing through a failed window on the windward side will create a flow path that floods the unburned side of the structure with fire and heat within seconds.

Note the wind direction on arrival. Note where the failed openings are. If the wind is pushing into the fire compartment and out the door your crew is about to enter through, you have a flow path problem. The tactical answer is to control the door, control the flow path, and consider exterior application before interior commit.

Other structures within reach of radiant heat or flying brand. Vehicles in driveways. Propane tanks (grills, RV tanks, residential propane). Natural gas meters. Electrical service drops. Overhead power lines that may fail. Fences that act as fire-spread paths. Detached garages. Sheds with stored gasoline.

The exposure check is not abstract. Name them in your size-up. "Charlie exposure is a wood fence and a detached garage at 25 feet. Bravo exposure is a 2-story residential at 12 feet." That gives the second-due crew their assignment without you having to say it.

Front door deadbolted versus open. Storm door present. Security bars on windows. Burglar bars on doors. Gates around the property. Cars blocking driveway access. Hose lay length to nearest hydrant and grade between hydrant and engine.

Forcible entry conditions affect the timeline from arrival to water on fire. If your front door is going to take 45 seconds to force, your interior crew is taking on smoke and heat for an additional 45 seconds before they can advance the line.

Hydrant location and distance from your apparatus. Hydrant condition (if known from pre-plan or visual). Tanker shuttle distance if rural. Drafting source if no hydrants. The water supply input is what makes the difference between sustained suppression and running your booster dry at minute six.

A working residential fire requires sustained flow of at least 100 to 150 gpm on the attack line, with backup line at equal or greater flow. Your second-due engine establishing supply is not optional. Name it in your size-up.

Walkout basements are the most missed input on Side Alpha size-ups. A house that looks like a single story from the street may have a fully exposed basement on the Charlie side. That basement may contain the fire. Without the 360, you are about to commit an interior crew above an unknown basement fire condition. That is a floor-collapse scenario waiting to happen.

Grade changes also affect apparatus positioning, hose lay routing, and aerial access if needed for ventilation or rescue.

If dispatch was 8 minutes ago and the fire is fully involved on arrival, the fire is in late free-burn stage and you are looking at structural involvement timelines, not contents fire timelines. If dispatch was 90 seconds ago and conditions are already heavy, the fire was advanced before the call was even made.

The elapsed time check changes your interior commitment decision more than most officers realize. NFPA 1700 and the modern command references reflect that residential fires in modern fuel loads transition fast. Time stamps matter.

This is the input most officers skip because they trust the screen. The screen said "smoke in the kitchen" but you see fire through the second floor. The screen said "everyone is out" but there is a car running in the driveway. The screen said "single family" but you are looking at what is clearly a converted multifamily with three meter banks.

Update the picture out loud. The on-scene report and the strategy declaration have to reflect what is actually in front of you, not what dispatch told you was supposed to be.

This is twelve inputs and you have about 30 to 60 seconds from stop to on-scene transmission to integrate them. The only way that happens reliably is repetition. You do not consciously walk through the list on the fireground. You see the fire and the list runs in the background and the relevant outputs surface in your transmission.

The reps come from drill ground exercises, from pre-plan walks, from running the checklist mentally on every photograph and video you watch, and from graded practice on simulators that score whether you caught the inputs. StruckBox's tactical fire sim puts a real photograph of a working residential fire in front of you, asks for your size-up out loud or typed, and grades you on which inputs you covered, which ones you missed, and how a panel or a deputy chief would score your transmission against the standard rubric.

The officers who run clean size-ups on house fires are not smarter than the rest. They have done the reps. Run the list cold a few hundred times and the checklist becomes the way you see structures. Then the badge does the rest.