1 hour fire rated ceiling/floor assembly?


Treehouse2339
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So I am designing a separate rental unit in the basement of a home.  The city fire department wants a 1 hour fire rated ceiling for the lower unit, floor of the upper home.  Right now there are conventional 2x10 floor joists separating the two units with 3/4" T&G ply on the floor above.  Is anyone aware of the easiest layer makeup to achieve the 1 hour rating?  I would like to see most of the required layering be on the lower ceiling so that additional material layers would not have to be at different elevations on the top layer ends where it does not need to be 1 hour.  My initial thought that 5/8 x rated rock on the lower ceiling might work but i think there needs to be the equivalent of 5/8 x rock on both surfaces.  Then I was thinking cut 5/8 first and install it between joists close to the upper sub floor.  but tenably I think since the top of the floor joist would not be covered it may not work.  The good thins is there are no wires or ductwork in the way at this point.  Hope that made sense.  Thanks in advance.

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3 hours ago, Treehouse2339 said:

So I am designing a separate rental unit in the basement of a home.  The city fire department wants a 1 hour fire rated ceiling for the lower unit, floor of the upper home.  Right now there are conventional 2x10 floor joists separating the two units with 3/4" T&G ply on the floor above.  Is anyone aware of the easiest layer makeup to achieve the 1 hour rating?  I would like to see most of the required layering be on the lower ceiling so that additional material layers would not have to be at different elevations on the top layer ends where it does not need to be 1 hour.  My initial thought that 5/8 x rated rock on the lower ceiling might work but i think there needs to be the equivalent of 5/8 x rock on both surfaces.  Then I was thinking cut 5/8 first and install it between joists close to the upper sub floor.  but tenably I think since the top of the floor joist would not be covered it may not work.  The good thins is there are no wires or ductwork in the way at this point.  Hope that made sense.  Thanks in advance.

Your answers lie in googling "Section 721.6 " :)

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Not only does the fire protection need to work from both top and bottom sides of the floor assembly, when you create a 2nd dwelling unit below, you will need to meet upgraded acoustical separation requirements per the building code. Also, the new unit will need its own mechanical system. You should pay attention to the details of any penetrations of the fire-rated assembly. Recessed lights will need their own fire protection, for example.  Also, the current stairs between the units will have to be detailed correctly, and in some cities, removed. Check with your planning department.

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