08 Timber Truss Roof Collapse Flashcards
Three ways FFs can die when operating at fires involving timber truss construction?
- FFs operating outside the building: When trusses collapse, they can cause a secondary collapse and push out a masonry wall.
- FFs operating on the roof: Can fall through when burning timber trusses fail
- FFs operating inside: Can be crushed and burned to death when the collapsing truss roof falls
Timber is wooden construction larger than __________ but not large enough to be classified as heavy timber of mill construction.
2x4
A timber truss roof can be built in a variety of shapes.
- Inclined Plane Truss (gable shape)
- Parallel Chord Truss (flat roof)
- Bowstring Truss (arch roof)
What is the most common of truss designs?
Bowstring Truss
What is the most dangerous roof system that a FF will encounter?
Truss construction
It is known to collapse during the _____________ of a fire, and it will often cause a secondary collapse of the masonry enclosure walls.
early stages
When an IC receives conflicting reports (interior size up vs roof size up), the chief should rely on the ______ report.
Roof. (The roof size-up is more accurate than the interior)
In a timber truss building, the main fire will be in the ___________________, not in the content below.
roof structure
Three size-up indicators for a truss roof in a building:
- Large open space without columns
- A mounded roof (bowstring truss only)
- Certain occupancies that frequently use truss construction (supermarkets, bowling alleys, garages, theaters, places of worship, auto dealerships, piers, and armories)
The fire strategy of a first-arriving engine company at a timber truss roof building without a ceiling should be to do what?
Attack the fire directly with a large-diameter hoseline.
In a bowstring truss-roofed building which does not have the web members enclosed with plasterboard, where can vent openings be made?
In the front and rear sloping portions of the roof - providing horizontal cross-ventilation of the entire roof.
When a truss roof appears weakened by fire, FFs ordered to evacuate the roof should retreat in what direction?
Perpendicular to the roof trusses (get to another truss section that hasn’t been burned out)
What is the key to safety when operating at a fire in a truss constructed building?
Communications
What is the most unstable structure in a community?
Places of worship
What is the most unstable part of a place of worship?
The steeple and tower.
What percentage of fires are extinguished by the first attack hoseline?
95%
What is the one window at a church or temple that is high enough and big enough to vent smoke and heat at the upper reaches of a burning place of worship?
The Rose Window
What are three reasons to vent the side stained-glass windows at a church?
- If it remains closed up, it may suffer a smoke explosion that could raise the roof and push out the walls.
- Fire may flash over when FFs are operating inside
- Smoke and heat may bank down on FFs searching and operating inside
Window venting should start where?
At the top and work down.
Can handheld hoselines put out a fire that has reached the attic spaces of most places of worship?
No.
Highest collapse hazards at places of worship
- Bell towers
- Steeple
- Ceiling
- Sidewalls
- Roof
Apse
Part of the church that is a semicircle or U shape wall
Chancel
A space reserved for the clergy that includes the altar and the front choir area
Nave
A main seating area of the church
Rose Window
A large round window at the front of Gothic churches
Triforium
A middle story of a church (side balconies)
Transept
A space that runs at right angles to the nave and chancel
Gothic
Church architecture of 12th century that features a pointed arch
