Shaft Enclosure Fire Rated Walls On Roof Level

[Waleed Ali]

I have central AC system & air ducts are coming from roof through one big shaft. We have so many air ducts coming from roof through the same shaft. My questions are:
1. Shall this shaft on roof covered and constructed with fire rated walls?
2. Shall we install fire dampers on air ducts penetrating the shaft walls on roof?
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Much appreciated if you have a reference

 

[lukaiENG]

This will be code dependent but external walls/roofs do not typically need to be fire rated. Fire rating is normally required to limit the spread of fire within a building.
I have on occasion seen requirements for fire rated external walls but this would normally only be when there is a large fuel tank or transformer sited adjacent to the building which would be a risk to the building if it were to catch fire.

 

[MP Texas Engineering]

From working on a similar type of project just like your scenario, only the shaft wall penetrations require fire/smoke dampers.
You should ask your local code official for their opinion.