Hi all,

I'm currently working on a mixed use project consists of 200,000 SF Data center (S2) and 68,000 SF of office (B), but I'm having difficulty understanding mixed-use occupancies and the area calculation. (508.3 and 508.4).

I thought that I need to follow the Separated Occupancy method since 508.4 requires a 1HR fire separation in between S2 and B occupancies.  Because the office portion is larger than 10% of the data center, I don't think auxiliary occupancy would work here.  

If there isn't any fire separations required in between occupancies, then is it possible to go with non-separated occupancies?  

I need to consider following factors (also client requests):

1. Construction type is IIIA, Fully Sprinklered

2. Data center - 212000 SF | 2 Levels | 42'

3. Office - 76800 SF | 5 levels | 72'

To calculate the area, I followed the method listed in 506.2.4 and 508.4.2, so I calculated area per level.  This is little tricky because  2 levels of the office floor are same height as 1 level of the data center.  

= [ (B Proposed area/B tabular Allowable area At) + (S2 Proposed Area/S2 tabular allowable areat) ] < 1

=12000/28500 + 106000/117000 = 0.91 < 1

I also used the sprinkler increase in two different areas (i'm not sure if this is ok).  As for B occupancy, I followed At under height increase (S), while I used 'SM' for S2 occupancy. 

I don't feel confident about the allowable area calculation and the steps I followed.  I would be really grateful if you can chime in and offer any insights and know-hows.