I'm looking at a '72 built school for re-roof, they intend to remove the
existing built-up roofing system and replace it with a new ballasted
membrane roofing system.
In order to check the capacity of the steel joists, I looked into the
50-Year Steel Joist Digest by the SJI. Unfortunately, the joists shown on
the original building plans are not listed. First of all, can anything be
learned from these non-standard spec numbers - second if so, what or how??
Obviously, the alternative is to analyze the joists, but the ceiling finish
would have to go.
Here are the numbers listed (they are shown clearly on the plans):
20DH8 (6'-6" o.c. & span 37'-8")
26DH9 (6'-6" o.c. & span 35'-8")