Simpson Strong-Tie, the leader in engineered structural connectors and building solutions, announced today that the RTUD and ATUD take-up components of its high-performance Strong-Rod® anchor tiedown and uplift restraint systems are now UL listed as through-penetration firestop solutions when used in conjunction with Simpson Strong-Tie bearing plates.
Designed for securing mid-rise wood-framed buildings against forces caused by seismic and wind events, Strong-Rod systems include ratcheting take-up devices (RTUD) and expanding, screw-style take-up devices (ATUD) that work with the threaded rod assembly to compensate for wood shrinkage, providing a constant, continuous load path for maximum resilience to seismic and high-wind events.
Similar to electrical conduits and utilities that travel up, down, and through the framing of a building, continuous rod systems run vertically from the foundation to the roof line, penetrating through the sill plate, subfloor, and double top plate. For years, the most common means of closing these penetrations has been to apply fire caulking that cures around holes to create a firestop.
However, the grip of cured fire caulk on threaded rod assemblies can lead to the buckling of rods, which can compromise take-up devices. Fire caulking that cures and hardens inside the take-up device can also damage its moving components, and some fire caulking can even be corrosive to the steel or aluminum components of the rod assembly.
“As part of a complete tiedown system, Strong-Rod take-up devices have been engineered for easy installation and reliable performance when connecting floors in mid-rise wood-framed buildings,” says Sam Hensen, vice president of Connectors and Lateral Systems for Simpson Strong-Tie. “We continually challenge our product designs through rigorous testing and are excited that the RTUD and ATUD can also provide adequate fire protection without the need to install costly and time-consuming fire caulking.”
In order to obtain data and fire-rating coverage on multiple hour-rating assemblies, Simpson Strong-Tie, partnering with RectorSeal, a UL-certified testing laboratory, constructed wood-framed floor-to-ceiling assemblies per UL and ASTM standards and then had them set on fire inside a high-capacity, industrial furnace for one-hour and two-hour rating tests.
After independent UL analysis of the test data and observations, the Simpson Strong-Tie take-up devices and bearing plates have been listed under UL Fire Resistance Directory R40313 for F, T, and L ratings without the need for fire caulking that could compromise system effectiveness.