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3/13/2012 10:33:28 AM
Table 503 lists the allowable building heights and areas for specific occupancy classifications base on contruction type. My question is this: Under construction types, what does the A and B stand for? What is the difference between say Construction Type IIA and Type IIB? Where in the code does it define what A and B are?
Thanks for your help.
3/13/2012 10:55:23 AM
See Table 601
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3/13/2012 11:20:08 AM
Table 601 does not indicate what A and B are.
3/13/2012 11:27:24 AM
It is my understanding that A and B does not mean anything other than there are two different catagories under each construction type. The differnce being how the differnt components are rated.
3/13/2012 11:38:01 AM
Table 601 does tell you what A and B are because it gives the fire-resistance rating required for the two categories. In the old UBC, there was a Type and a Type NR, eg Type V-1 hour versus Type V-NR for "not rated". The IBC uses A and B possibly recognizing that fire-resistance rating requirements are a bit more complex. Even in the UBC, unrated construction had requirements for rated assemblies which confused some people.
Anyway, basic differences between Type A and Type B are shown in Table 601. One must also check Table 602 and specific requirements in other sections, however.
3/13/2012 11:43:55 AM
Type "A" typically have a higher fire resistance rating on some of the building components. See Table 601 and I believe the footnotes give some clarification. I don't have the IBC in front of me, but table 601 should be self explanitory.
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3/13/2012 5:11:24 PM
What it boils down to is that A is protected and B is unprotected.
"A" means that all structural members of a building or structure has additional fire rated coating or cover by means of sheetrock, spray on, or other approved methods. This additional fire rated coating or cover extends the fire resistance rating of structural members. This is why 601 shows (for instance) the structural frame of Type IA 3 hour whereas Type IB is 2.
"B" means that all structural members of a building or structure has not additional fire rated coating or cover. Easy way to remember - always think B stands for "burn" and you got it.
2/3/2014 3:10:13 PM
Okay, so most code guys are trying to work the table in reverse, i.e. they are looking at the table with a preconceived notion of what the construction type is to determine what the required separation or level of protection will require in order to be compliant. You should be looking at a detail of each of the listed components in order to establish what level of protection is provided for each component, then you classify it as either a Type A or B construction.
2/4/2014 10:03:36 AM
Design professional specifies type of construction and code guy reviews for conformance to code.