By KENNETH MORGAN
We have all read about or heard of the dangers of engineered wood joists—or I-joists—when exposed to fire, but they don’t need to be on fire to degrade. Developed in 1969, I-joists have become a construction staple because of their economic value and ability to shoulder large loads over large spans. Originally constructed of a plywood web and solid flanges (chords), the flanges were replaced with laminated wood in 1977. The switch to orientated strand board (OSB) webs occurred in 1990.1
Just how much does it take to damage these engineering marvels? When exposed to heat, they degrade rapidly,2 so the importance of knowing the structures in your first-due response area becomes alarmingly evident.
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