Building construction for Firefighter I recruits

Rapid cooling of steel is not what makes soaked stock dangerous.

Absorbent stock soaks up water and expands against the walls, while the added water weight loads the floors.

Runoff is a property damage issue; the collapse threat comes from the stock taking on water.

Bales drying and reigniting is a real problem, but it is not the structural collapse hazard.

A cantilever leaves floor sections projecting from a standing wall, so a wall must still be up.

When both bearing walls fail, the floors drop nearly flat on one another, leaving only small voids.

A lean-to keeps one end of the floor supported, but here both walls failed.

A V-shape forms when the floor fails in the middle while both ends stay supported.

The sill is at the bottom of the opening and supports nothing above it.

The sash holds the glass and is not a structural member.

The lintel spans the top of the opening and carries the masonry above; when it fails, the brickwork over the window drops.

Jambs form the sides of the frame and do not carry the wall above.

A parapet is the section of an exterior wall that rises above the roof line.

A soffit is the underside of a roof overhang, below the roof line.

Fascia is the board along the roof edge, not part of an exterior wall rising above it.

A cornice is a decorative projection at the top of a wall, not the wall's extension above the roof.

Poured concrete walls do not need these anchors; the plates mark older masonry.

Fire escape anchors sit along the escape's own frame, not as plates spread across the wall at floor levels.

Roof beams are not marked by plates scattered over the face of the wall.

Stars and plates are the ends of rods run through the building to tie masonry walls to the floors; heated rods stretch and can let a wall move.

The cockloft between the top ceiling and the roof often runs unbroken over a row of stores, so fire travels across the row unseen.

A crawl space is under the first floor and is not usually shared along a row.

Each store's stairs serve only that store and do not connect the row.

Stud channels run inside one store's own walls and do not pass from one store to the next.

Smoke color reports fire conditions, not structural stability.

Runoff from a doorway is normal during an attack.

A wall bulging out is being pushed or losing support, a collapse sign command needs at once.

Failing glass shows heat, not that the structure is about to give way.

Wind direction matters for smoke, not for where a wall falls.

Standing in front of a wall puts the crew in the path of that wall's fall.

Corners are the strongest point and walls tend to fall straight out from the middle, so apparatus goes at the corners, outside the collapse zone.

A wall can break up and scatter farther than its own height, and mid-wall is where the debris lands.

Steel is already noncombustible; the danger is the strength it loses when hot.

Keeping steel from rusting is the job of a different coating; this material is for fire resistance.

Steel loses strength as it heats, so the coating insulates it and keeps it carrying load longer in a fire.

An insulating coating does not seal smoke paths.

A hot floor area over a basement fire may be close to failing, so the crew stays off it and tells command.

Sounding cannot detect joists burning from below; a floor can feel solid just before it fails.

Cooling the top surface with fog does nothing for the fire under the floor and keeps the crew on it.

Cutting keeps the crew on a weakened floor and opens a path for fire to come up.

Steel expands when it heats, so it does not shrink.

Heated steel expands, and a long beam can lengthen enough to push bearing walls out and bring them down.

Heat does not add strength to steel; the hazard in this case is the expansion that shoves walls out.

Steel deforms and moves long before it melts.

Veneer is an outside facing and gives no path between floors.

Concrete floor slabs separate one story from the next and resist vertical spread.

Self-closing rated doors are built to keep fire out of the stairs.

Vertical chases and shafts often pierce many floors with poorly sealed openings, letting fire appear far above its origin.

A rating is the time an assembly held up in a standard laboratory fire test; real fires and damaged walls can do worse.

Fire resistance and smoke tightness are measured separately.

A rating does not make an assembly fireproof; it measures how long it resisted fire passage in a test.

A real fire can be hotter or longer and penetrations weaken walls, so the rating is no guarantee.

Type III has noncombustible exterior walls with wood inside; it is not the mass timber class.

The 2021 IBC placed mass timber in Types IV-A, IV-B and IV-C, alongside traditional heavy timber.

Type I is fire-resistive construction of protected noncombustible materials.

Type V is light wood frame of small-dimension lumber, the tempting pick because the members are wood.

Steel reinforcement weakens in fire but does not melt at normal fire temperatures.

Cracking of the floor slab is not what endangers crews when the roof goes.

Heat can flake the concrete surface, but spalling does not by itself bring the panel down.

Tilt-up panels rely on the roof to hold them upright, so when the roof fails the unbraced panels can fall and a collapse zone is needed.

An impact load is applied suddenly, like a firefighter dropping onto a roof.

Wind load is the force of wind pushing on the building, not the building's own weight.

Dead load is the fixed weight of the structure and permanent equipment; it is always present, so weakened supports can fail under it alone.

Live load is weight that moves or changes, such as people, furniture and firefighters.

A fire cut is a collapse-control detail, not a fire stop, and does nothing to keep fire out of the wall.

The cut sits at the joist end inside the wall pocket and has no drainage role.

The cut does the opposite of locking: it lets the joist drop free so the wall stays standing.

The angled end lets a burned-through joist rotate out of its wall pocket and drop, without prying the masonry wall apart.

The top chord is in compression and carries the roof load; every member is needed, which is why one failure can drop the truss.

The steel connector plates grip only a shallow layer of wood; as that wood chars, the plates pull out and the truss comes apart early in the fire.

Truss roofs carry ordinary sheathing; deck weight is not what makes them fail early.

Trusses are built from small-dimension lumber, usually 2x4s, not larger members, so this reverses the facts.