Detail for 2-hr fire-rated stair enclosure

[BayPointArchitect]

Hey there fellow code gurus.

Given that a steel beam is supporting a part of a two-hour fire-rated stair enclosure, and that the underside of this beam needs to be fire protected, does that level of protection need to be one-hour below the beam with the top side protected by a one-hour floor system? Or does the underside need to be two-hour fire-protected?

Four story building - fully sprinkled.

Thanks!

ICC Certified Plan Reviewer
NFPA Certified Fire Plan Examiner

 

[steveray]

IF....the penetration is allowed, it needs to be rated all the down to the foundation...jpoists/floor>beam>column>foundation...follow the load path.

1022.5 Penetrations. Penetrations into and openings through
interior exit stairways and ramps are prohibited except for
required exit doors, equipment and ductwork necessary for
independent ventilation or pressurization, sprinkler piping,
standpipes, electrical raceway for fire department communication
systems and electrical raceway serving the interior
exit stairway and ramp and terminating at a steel box not
exceeding 16 square inches (0.010 m2).

 

[BayPointArchitect]

Steve,

If I interpret your comment correctly, then you are saying that the beam needs to be two-hour fire-rated all around and the columns supporting the beam would also need to be two-hour fire-rated. And there is no credit or regard given to the concrete floor that goes over the top of the beam.

 

[steveray]

Correct....Stairs are protected with fire barriers....

707.5.1 Supporting construction. The supporting construction
for a fire barrier shall be protected to afford the required
fire-resistance rating of the fire barrier supported. Hollow
vertical spaces within a fire barrier shall be fireblocked in
accordance with Section 718.2 at every floor level.

The concrete floor could be a part of the 2 hr rated floor assembly, and itself could be 2 hr rated, but it is held up by unrated steel and that is the issue...

 

[mtlogcabin]

The beam does not need to be protected on the top if it is tight to the floor above. Remember the testing is done from the fire side which is below the floor.

 

[BayPointArchitect]

Thanks again gentlemen.