Metal Bldg has no bearing walls - Is it always a type III-B?

[JBI]

I was told by Code Congress some time ago that the Construction Type is based on the size of the building and its occupancy use group. If you have a small building, say constructed as a Type II-B and it could be classified as a lower construction type, then per the Building Code you are suppose to classify it for the minimum Construction Type allowed for the Occupancy Use Group allowed. However, if the building is ever to be expanded then the Architect should take that into consideration and list the Construction Type desired. If the building is an existing building then its actual construction type and its actual size with any allowable increases in area and building height requires evaluation to see if the intended occupancy use group can be in the building. The building's location to the property lines does not have anything to do with the building's construction classification. You have to comply with any ratings required as you get closer to the property lines.

I would question the opening statement. 'Construction type' is not based on the size or occupancy class, rather those two factors may limit size based on construction type.
'Construction type' is based on the materials of construction and fire resistance ratings.
An applicant/design professional MAY elect to assign a lower construction type for any number of reasons.

 

[steveray]

I was taught at the same school as Paul....I THOUGHT that the reason you got type IIIB about the same as IIB was because the exterior was rated and didn't allow it to spread to adjacent structures...Although that is not really how it reads these days....If it ever did....

 

[jsnock]

I’ve seen several plans in our area which are PEMB submitted as III-A or III-B and I do not agree. One could argue that the building frames are part of the exterior load bearing walls and further the girts are certainly load bearing. Load bearing isn’t just gravity, but lateral, wind, uplift, shear, etc. Therefore I would submit in type III that the frames should be rated to the exterior wall requirement. It just doesn’t pass the logic test that if I you have exterior load bearing masonry walls they would have to be rated, but the building frames which support the exterior wall would not need to be rated, regardless of the ‘primary structural frame’ requirement.