I tried to find the answer to your question by downloading the Chicago Building Code but found no reference to stud or rafter spacing. Are you sure that a maximum spacing requirement exists in the Chicago area?
Why wouldn’t that involve the use of the std. NDS and AF&PA literature, regular structural design methods, good engineering judgement, and std. sizes of sheathing sheet goods, etc. If there is something raising your suspicions, don’t keep it a secret from us; alternatively, it’s your job, call them.
It is the City of Chicago Building Code.... If you don't have experience with this then you may not understand why it is even a question and it is possible that the NDS can't help. It is one messed up code.
focuseng:
Enlighten us a little bit. You don’t have to attach the entire code, verbatum. A number of the big, older, cities have a bunch of history, bureaucracy and negative inertia which really complicates things. Their City Bldg. Code is probably one of the oldest bldg. codes in North America. And, when asked nobody can even explain where this or that came from or why. I’ve never used the City Bldg. Code there, but I’ve done work with the City Transit Authority and their codes and specs are plenty convoluted.
dheng, I am not trying to imply you specifically, or anyone else, doesn't have knowledge of Chicago code. Just that the question may be valid despite what the NDS says (and what year version is applicable) because of the items you mentioned. I personally don't know of anything which limits this, but it wouldn't surprise me if there was. ChigCago does have antiquated rules regarding fire ratings and wood structure.
Perhaps it is time for each state to adopt a building code and remove all city codes. Even better, adopt a building code across the entire country complete with climatic information pertaining to all parts of the country. This would be a hard sell, however.
I guess to get back to the OP: Try calling the WoodWorks rep in the Chicago area. Mrs. Ciecko, the midwest regional director, is the one you want to speak with:
