Fire Code Question for Dwelling Construction

[jlab]

I recently noticed a new style of residential building being constructed on Staten Island. Previuosly if the builder wanted to use a lot to accomodate two families the two houses would be built next to each other with a 2 hour sheetrock fire wall in between the two dwellings. Recently I noticed new houses for two families built on top of each other rather than next to each other. That means that the only separation between the two dwellings is the floor and not the 2 hour fire wall. My question is, does the floor between the two dwellings have to conform to a 2 hour fire resistance or can the builder now provide less protection of the dwelling above from a fire in the second floor dwelling ?

 

[manlt]

They are technically different. The first building you talk about is “semi attached “ private dwelling. The two share the wall, but are two separate buildings. Separate address, certificate of occupancy, etc. It’s not considered a one building. Bigger semis do have an apartment, making that a two family.
The second is a straight up two family. As far as I know, they are built the same as a one family. They were common construction in the ‘70s. 6 over 6. 6 rooms on 1 st floor, 6 on second.