Q: These corridor doors (i.e. patient rooms); if they are in a 1-hour fire barrier then is it okay for them to only be rated20-minute and not ¾ hour?
A: The answer is no. If a corridor door is part of a fire-rated barrier that serves some other function, such as a vertical opening, exit, or hazardous area, then it must meet the most restrictive requirements of either. In the scenario that you mentioned in your question, the corridor door must be at least a ¾ hour fire rated door, mounted in a fire-rated frame, with self-closing and positive latching hardware. Vertical openings are elevator shafts, mechanical shafts, stairwells, and the like. Exits are horizontal exits and exit passageways. Hazardous areas are storage rooms >50 sq. ft. containing combustibles, soiled utility rooms, fuel-fire heater rooms, laundries >100 sq. ft., paint shops, repair shops, trash collection rooms, laboratories, medical gas rooms (storage rooms with >3,000 cubic feet of compressed gas), and gift shops. I don’t see where a patient room door would be part of any of these fire-rated barriers. However, a patient room door could be part of a smoke compartment barrier. Even though the smoke compartment barrier is required to be 1-hour rated, it is not a fire rated barrier, because the doors in a smoke compartment barrier are only required to be 1¾ inch thick, solid-bonded, wood core doors, or of such construction to resist fire for at least 20 minutes, and must be self-closing. They are just like corridor doors, but must have closers on them.