UL Classified and Listed Assembly Design Considerations

Definitions:

1. Nominal Gap – distance between installed “starting” position of wall sheathing and lowest point of overhead structure
2. Movement Capabilities:
• Class II (Wind Sway) – 10 Cycles/min (500 cycles)
• Class III (Seismic) – 30 Cycles/min (500 cycles)
3. Extension – wall sheathing being pulled away from “starting” position and overhead structure increasing the overall width of installed joint
4. Compression – overhead structure pushed toward wall sheathing decreasing the overall width of the installed joint
5. L-rating – Air/Smoke Leakage Rating at .30 inch (7.47 Pa) of water IBC 2006 Section 713.6 – Max 5 cfm/lft in rated joints
6. Encumbered Joint – systems requiring materials to be located in “gap” between wall sheathing and overhead or limited by elasticity, compressibility, or adhesive characteristics of coating materials overlapping both overhead and wall sheathing
7. Unencumbered Joint – “gap” between wall sheathing and overhead free of any material (joint protection typically resides inside or outside “gap” and is not connected to both overhead and wall sheathing)
8. Compression Only Design – joint designed to accommodate compression of overhead structure from “installed/starting” position with possible return to no more than “installed/starting” position – Typical design would be one story structure
9. Combined “Overall” Movement Capability (MC) multi-story – joint designed to accommodate both compression and extension at head of wall joints. Typical design would be multi-story structure joints experiencing either compression or extension on different levels due to loads or deflecting forces placed on individual levels

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