It has always been part of the design of the fire-resistance rating for the UL Design of the fire-resistance rated system.
However, the top would be sealed/caulked with a specified sealant/caulk (fire-resistive rated) and an intumescent sealant similar to these examples:
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http://www.stifirestop.com/product_info ... alant.html )
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http://solutions.3m.com/wps/portal/3M/e ... PCLC0PX0gl )
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http://www.firesealants.com/?a=prod )
Here is the Gypsum Association Fire Resistance Design Manual (
http://www.gypsum.org/GA60006.html ), download the higher resolution files - page 58 (in
http://www.gypsum.org/pdf/Section%203.pdf ) shows typical wood framed interior partitions with 16 inch on center studs and 24 inch on center studs and references a commonly used UL Design: UL Design U309.
UL Design U309 (
http://database.ul.com/cgi-bin/XYV/temp ... sequence=1 ) shows number 3 pointing to joints/nails/screws and states: (underlining and bold are mine)
- 3. Joints and Nailheads — Wallboard joints covered with paper tape and joint compound.
Nailheads covered with joint compound. Gypsum plaster not more than 1/8 in. thick may be applied over the wallboard in addition to the specified joint treatment.
Additionally, the question is now raised about protecting the roof sheathing.
As old apartments it is apparent that the fire separation was not addressed as fully as fire separation is addressed today, and with the apartments having been converted into condos (recently, I presume you mean), the simplest way to address the fire separation between units was to extend the walls in the attic above each units walls rather than make the ceiling/roof system a fire-resistance rated system.
In doing the above, though, they have now exposed part of the structure to the fire-resistance protected "interior" of the condo, meaning the roof sheathing needs to be protected. As the roof sheathing is not fire-retardant treated, the minimum which needs to be done would be to protect the roof sheathing and trusses for a minimum of 4 feet from each side of the fire partitions which have been added in the attic.
Those are the first things I have thought of and should work for starters, and may cover much of what it needed.