11.   Used as substitutes for plywood sheeting and solid wood floor joists and beams, these products make a house stronger and quieter.

12.   What is done is that the duct goes from the ceiling of the bathroom, then between the attic floor joists and into the soffit.

13.   Another suggests that the exterior columns pulled inward, giving in to floor joists weakened by raging fires.

14.   Another theory suggests that the exterior columns pulled inward, giving in to floor joists weakened by raging fires.

15.   Those floor joists are thought to have been the first parts of the buildings to fail as intense fires heated and weakened them.