Structural screws are designed and tested to do hard work, but that doesn’t make them hard to use. In this post, Simpson Strong-Tie structural engineer Bryan Wert explains how the load-rated strength, versatility and easy installation of the code-listed Strong-Drive® SDWC Truss screw and SDWF Floor-to-Floor screw make it a cinch to create a continuous load path to resist wind uplift.
Winter’s finally shedding her blanket and unveiling springtime in Texas. There’s now a short window of picture-perfect weather where my purchases at Home Depot are no longer foam hose bib covers to protect outdoor faucets from freezing temperature, but aren’t quite yet tiki torches and floats for the pool for hot and humid summer days. I find myself in the garden center looking at the freshly delivered trees, shrubs and flowers, along with just about every other adult in my city. This year, my wife’s decided we need to surround our outdoor living space with hanging planters displaying perky red, purple, yellow and blue flowers.
Upon returning home to get started on the honey-do list I find that instead of simple screw-in hooks for the hanging planters, we’ve instead purchased extension arms with S-hook do-hickeys and — lucky me — they come with their own installation screws. I try installing the screws through the predrilled bracket into the wood cedar beam at my patio’s perimeter and the screw turns maybe two revolutions before refusing to embed further. Now I have to find a drill bit to match the undefined screws. At best, this will double my time for installation and at worst cost me a second trip to the store to replace the common Phillips-head screw as it cams out upon installation. In the end, I find myself somewhere in between — predrilling holes, then hand-driving each screw into place.
This project deepened my appreciation for the full line of Simpson Strong-Tie® structural screws with either hex-head or 6-lobe drive-heads. The Simpson screws make driving easy, thanks to their proprietary SawTooth™ point that helps them start fast with reduced torque, and, the best part, require absolutely no predrilling.
One of the most exciting product groups in the growing Strong-Drive® line is the combination of the SDWC Truss screw and the SDWF Floor-to-Floor screw with TUW take-up washer. Models within these two lines of screws create a new and innovative method of creating a continuous load path for wind uplift resistance.
The Strong-Drive SDWC screw is suited for a plethora of fully tested and load-rated connection types. These include ledger-to-rim, sole-plate-to-rim and almost all connections needed to complete a load path to resist uplift forces. The SDWC is load rated for stud-to-bottom-plate or stud-to-top-plate connections, as well as fastening trusses and rafters to top plates. The fully threaded shank engages the entire length of the fastener providing a secure connection. It’s tested in accordance with ICC-ES AC233 (screw) and AC13 (wall assembly and roof-to-wall assembly), is code listed under IAPMO-UES ER-262 and meets 2012 and 2015 IRC® and IBC® code requirements for several common framing applications.
Where the SDWC Truss screw’s capabilities end, the Strong-Drive SDWF Floor-to-Floor screw’s begin. This screw’s designed to simplify the wind uplift–restraint floor-to-floor connection while providing superior performance over the life of the structure. The unique design of the SDWF enables it to attach upper and lower walls together from the top, spanning the floor system, and requires no predrilling to provide a secure connection within the continuous uplift load path of the structure.
The innovative take-up washer (TUW) plays a key role in the long-term performance of the SDWF when installed between the screw head and the sole plate of the upper floor. The specialized threaded portion under the head of the screw ratchets up through the matching threaded tabs of the TUW as the structure settles in response to shrinkage and construction loading. The interlock between the tabs of the take-up washer and the threads under the head of the SDWF prevents the screw from sliding back under load, providing a simple yet reliable means of shrinkage compensation up to 3/4″ per story.
As I sit back on my patio with a cold drink in my hand and admire my handiwork, I dare not tell my wife about the versatile, labor-saving SDWC and SDWF screws. Revealing the existence of these innovative wind uplift–resisting continuous load path screw connections might result in a much longer honey-do list that could even include deploying Strong-Drive® fasteners to build a whole new house. But while I won’t be telling my wife about it, if you’re an engineer, builder or code official interested in learning more about how to use fastener systems for uplift restraint, check out our one-hour webinar.