California- CBC 709.1.6 Fire Partitions between tenants in high-rise

[miguele3]

California added the following section regarding fire partitions: "6. Walls separating enclosed tenant spaces in high-rise buildings and ...."

For many years in California we have had our high rise buildings NOT require a 1 hour partition between tenants. There are two concerns: The first is the difficulty of building a 1 hour partitions between tenants can be very difficult because of all the stuff above the ceiling. The second concern is the bigger one. If I interpret this correctly, we will need fire-smoke dampers between tenants for our plenum return air. But I'm wondering about section 1018.1 which allows non-rated corridors if we have a fully automatic sprinkler system. If we don't need the 1 hour corridor for the tenants, do we then run all our plenum air out into the corridor? If so, how is this an improvement to the code?

 

[mark handler]

Part of the Post 9/11 High Rise Safety codes

Exceptions:

1. The wall need not be extended into the crawl space below where the floor above the crawl space has a minimum I-hour fire-resistance rating.

 

[pete_t]

Mark

You're confusing me, his reference is to 790.1 #6, yours is to 709.4 x1.

 

[miguele3]

I should say it's a B occupancy and a high-rise.

 

[mark handler]

Yes. I am giving exceptions to the rule.

Where the corridor ceiling is constructed as required for the corridor walls, the walls shall be permitted to terminate at the upper membrane of such ceiling assembly.

 

[JPohling]

Ok, lets revisit this because i am a bit perplexed when I read thru these code sections. Project : California high rise type 1 construction NON Sprinklered. 709.1.6 would require that the tenant demise wall assemblies be fire partitions. 709.3 would require the fire partition to be a minimum one hour partition as the building is non sprinklered and exception #3 does not apply. 709.4 Continuity. Exception 1. The wall need not extend into the crawl space below where the floor above the crawl space has a minimum 1-hour fire resistance rating. These floors are two hour rated so the exception applies. What is confusing to me is that a 1-hour fire wall is required, but it is able to terminate at the ceiling and not pass thru the plenum and terminate at the rated deck above. That just does not seem correct? Is that really the intent here?