Deflection Capabilities of UL listed Dynamic Assemblies
Approved deflection of firestop materials protecting dynamic Head of Wall (HOW) joints listed through UL are based on two major factors. The first, “Nominal Joint Width” refers to a joint created by an installed gap distance between the top of the wall sheathing and the overhead structure. The second, “Movement capabilities” refers to the maximum percentage of the nominal joint width that joint materials can deflect without compromise or failure at a given cycle rate based on three levels.
- Level I – 1 cycle/min for total of 500 cycles (Thermal)
- Level II – 10 cycles/min for total of 500 cycles (Wind Sway)
- Level III – 30 cycles/min for total of 500 cycles (Seismic)
The following illustration displays deflection capabilities and required nominal joint widths using the majority of mastic joint systems which are limited to class II movement. These systems being reliant upon compressibility, elasticity, and bond strength of fill, void, or cavity materials (mineral wool and fire caulk/spray) are restricted to common UL ratings of +/- 25% movement capabilities:
| Nominal Joint Width | 25% Compression | 25% Extension | Deflection = Compress. + Ext. | Compression Only |
| 1/2" | 1/8" | 1/8" | 1/4" | 1/8" |
| 1" | 1/4" | 1/4" | 1/2" | 1/4" |
| 2" | 1/2" | 1/2" | 1" | 1/2" |
| 4" | 1" | 1" | 2" | 1" |
In comparison, UL listed dynamic HOW assemblies utilizing Firestik™ profiles are provided 100% movement capabilities during compression or extension for class I, II, or III movement. The following illustration shows deflection capabilities provided using Firestik™ as the HOW joint fire stop material:
| Nominal Joint Width | 100% Compression | 100% Extension | Deflection = Compress. + Ext. | Compression Only |
| 1/2"(FS1) | 1/2" | 1/2" | 1" | 1/2" |
| 3/4"(FS1)* | 3/4" | 1/4" | 1" | 3/4" |
| 1"(FS2) | 1" | 1" | 2" | 1" |
| 2"(FS2)* | 2" | - | 2"* | 2" |
The proprietary design and use of Firestik™ enables assemblies to be installed with smaller nominal gap joints and achieve superior movement. The unencumbered movement allows for unequal compression and extension designs when overall deflection requirements are within parameters of total deflection capabilities of individual profiles.