the floor assembly below/above the floor area / the story , there is no floor assembly above

[sunyaer]

In Ontario building code, there is numerous locations where "there is no floor assembly above" and "the floor assembly below the floor area / the story" are used. Now assume a five story building with no rooftop enclosures, no basement, could you please explain in which floor ""there is no floor assembly above" is true? If I am standing on 3rd floor, does the floor assembly that I am stepping on refer to "the floor assembly below the floor area / the story"?

 

[tmurray]

In Ontario building code, there is numerous locations where "there is no floor assembly above" and "the floor assembly below the floor area / the story" are used. Now assume a five story building with no rooftop enclosures, no basement, could you please explain in which floor ""there is no floor assembly above" is true? If I am standing on 3rd floor, does the floor assembly that I am stepping on refer to "the floor assembly below the floor area / the story"?

This can depend on the context, but since we dealt with 3.4.4.2. in another post, we can use it here. The intent in that clause is to ensure that there is no possibility for a minimally rated fire separation in an exit enclosure. If the 3.2.2. classification resulted in an unrated roof, the exit enclosure would otherwise default to a 45 minute rating. However, if the floor rating in the 3.2.2. classification was an hour or more, the enclosure would need to meet this higher rating because of the "if there is no floor assembly above" term.

 

[sunyaer]

.. If the 3.2.2. classification resulted in an unrated roof, the exit enclosure would otherwise default to a 45 minute rating..

Does the roof of the exit enclosure separate the exit from any adjacent floor area as per OBC 9.9.4.2.(1)? It looks to me it doesn't, so there is not required to be a 45 minute rating as per OBC 9.9.4.2.(1), though the roof of the exit enclosure separates the exit from the open rooftop.

 

[tmurray]

No, the roof would normally be unrated, unless the building classification under 3.2.2 requires the roof for the whole building to be rated.