There's a building with groups E, B and I4. The E wants to expand into some of the B space. Fully sprinkled, IIB,1-story, I'm using 2015 IBC and 2015 IEBC. In IEBC 1012.5.1.1, they'd meet the 1st and 3rd condition, but I'm not certain I'm understanding the interpretation of #2 to know it's met. If they put a 2hr fire barrier between the new E area and the neighboring uses (here it's remote from the rest of the E, it's 'neighbors' are B), does the old school area need to be evaluated as NS for it's area limitation then? If so, the old E portion is well over, would they need to subdivide it as well? My first thought is that if it's a "Fire Wall Alternative", it's first a fire wall, then, as a separate building, it's ok in area (it's under 14,500 SF) and the old E portion is a 'separate building' and didn't have a change of use, so it (being like 50,000 SF single fire area) is still ok to remain as is. Does condition #2 really intend that there be 2hr fire barriers put in throughout the old part to make it into 14500 SF chunks? And what about the B areas- they'd need separated out the same also? It would seem then that the 'alternative' isn't much help, and a full fire wall instead would be best.