We don't have a lot of split-level houses around here...I guess because it's so flat. The ones I have done elevation certs for have been textbook examples.
Today, I did one with a crawlspace below the next higher level.
To me, it's a no-brainer that the first floor, which is slab at grade is C2.a.
My question is regarding the next higher floor(C2.b), which is over a 3.8' crawlspace. The crawlspace is vented, but the vents start 2' above grade AND they are above BFE...So, no vents.
Should I use this next higher floor as C2.b, and note in the comments that it is not vented? Or, use the crawlspace dirt floor as the next higher, since it is not vented? (The crawlspace elevation is the same as C2.a.)
I'm guessing the first option.
If the crawlspace is the same elevation as the slab then wouldn't it make sense to consider it the same floor? Next higher floor would be the next step up. Just note the crawlspace and include the size of the enclosure. I'm also guessing the first option. The lowest floor guide, if you haven't already checked, might have a building diagram that matches what you are describing. http://www.fema.gov/pdf/nfip/manual201105/content/07_lfg.pdf