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Archive for May, 2009

Elevator Lobbies

May 11th, 2009


On a recent visit of a renovation of a high rise building, I noticed smoke dampers installed in transfer openings in a wall which formed a required elevator lobby.  As the construction documents were approved under 2006 Michigan Building Code, an elevator lobby is required at each floor where an elevator connects 3 or more  stories.  Previously, International Building Code and Michigan Building Code required these lobbies only when the elevator opened into a rated corridor.

elevator-shaft

Existing 2-hr masonry walls formed 3 sides of the lobby and approximately 6 ft of metal stud wall made up the remaining wall which I was inspecting.  2 HVAC penetrations were made in this wall one was ducted and the other was the transfer grille.

IBC/MBC 2006 require the walls that make up this elevator lobby to meet the requirements of fire partitions.  There is an exception, when the building has an NFPA 13 or 13R fire suppression system, that allows these walls to be smoke partitions.  The design professional chose to take this exception.  Let’s review the requirements for both.

fire-smoke-chart

As you can see, the fire partition will require a 20 min door, a fire damper and some firestopping, but by using the exception and denoting the wall as a smoke partition a smoke damper will be required for the transfer grill.  Smoke dampers are a more costly item, not only for materials but for labor charges because of its motorization and activation requirements.  The cost of the smoke damper would greatly outweigh the costs of upgrading to a fire door and joint/penetration firestopping.

It Pays To Know $$$