Ch. 9 Flat Roof Collapse

Question 1

Lightweight construction like unprotected steel bar joists can fail in how many minutes of fire exposure?

Answer 1

5-10 minutes

Question 2

To determine roof collapse at a flat roof bldg. 3 facts need to be known. What are the 3 facts?

Answer 2

• Type of roof system(solid wood, C-joists, wood I-beams, lightweight wood truss, unprotected steel bar joists)
• How the joists are connected to the wall (Simple supported joist system or a Fixed system)
• Is the roof deck directly attached to the main roof beams (or is it a inverted or raised roof)

Question 3

Open web steel bar joist are non combustible but not fire resistive, they can be provided some fire protection by what 2 things?

Answer 3

• Covered by spray on fireproofing
• Fire retarded by a membrane ceiling-This barrier only provides protection if installed correctly, with no panels removed, damaged, or improperly set.

Question 4

When a Bldg. has steel bar joists supporting the roof, what type of ventilation is preferred?

Answer 4

Horizontal ventilation of the windows and doors in advance of the hose lines is preferred to vertical roof ventilation, which requires FF’s to operate on the roof above the fire.

Question 5

Lightweight wood truss is another dangerous roof. They are widely used in Private dwellings and stores. Experience has shown that lightweight wood truss construction can fail within how many minutes of fire exposure?

Answer 5

5-10 minutes

Question 6

Members on the roof must be continuously aware of an emergency escape route. The escape route must be available for the entire operation. Fire should never get in between the escape route and roof position. If ordered to evacuate the roof immediately and there are 2 escape routes available which one should the FF take?

Answer 6

Do not always take the quickest path if another route is available. Take the safest way even if it is longer.