The PFCB and PFC post frame column bases and angles are our newest post base products and part of an expanding line of post frame construction solutions. These dry-set parts connect your glulam, nail-lam, or solid sawn post to the foundation with either an angle bracket pair (PFC) or a mechanically clinched assembly (PFCB) sized for a variety of widths. The wood side takes 1/4″-diameter SDS screws and the anchorage side takes 5/8″-diameter anchors. Installation is fast and easy with no through-bolts. They’re G90 galvanized, and HDG or black powder coat is available by special order.
The PFCB and PFC are fully tested and code listed for uplift and lateral loads. Check the product pages for installation instructions, load tables, and code report. For the PFC, which requires two individual angle brackets, standard installation is with the angle brackets on opposite faces of the post. If you want to install them on adjacent faces instead, see the corner condition table. We also offer a concrete anchorage table to guide your PFC or PFCB installation into a stem wall, turndown edge, and round pier. Anchorage values are calculated per ACI 318-19 and use Titen HD® heavy-duty screw anchors or SET-3G® adhesive anchors. Allowable load should always be the lesser of the connector allowable load and the anchorage allowable load.
PFCB vs. PFC, what’s the difference? The PFCB comes in sizes A, B, and C. A is for 1 3/8″–ply southern yellow pine, the typical size for glulam. B is for planed, multi-ply posts targeting 1 7/16″ plies (uncommon, used to be made by Ohio Timberland). C is for 1 1/2″–ply (2x nominal) nail-laminated, non-planed lumber or built-up sections in the field. PFC can go on anything that meets the minimum size. If you want the highest lateral capacity and your lumber fits those sizes, go for PFCB. If you want the installation sequence flexibility of individual brackets, need to install in the corner condition (perhaps a doorjamb), have wider lumber, are retrofitting, or want the low-cost option, go for PFC.
The PFCB design features a mechanical clinch holding the angle brackets to the base plate. The metal of the bottom plate is punched into the angle plate and deformed to create an interlock in four locations. The connection design of these parts was one of the big decisions we had to make during the R&D phase. We could weld it, but welding comes with corrosion concerns and quality control considerations. We could add fasteners, but more components add additional cost and complexity. Clinching is a simple and cost-efficient manufacturing method that accomplishes exactly what we need.
A very prominent feature on the PFC5, PFC6.5, and PFCB models is the detachable washer. This is a required washer for the anchor head that you can easily remove by hand. PFC3 is the only model that doesn’t have a detachable washer — a standard–cut washer is still required but not supplied. If you’re using a 1/2” anchor instead of the standard 5/8“ anchor, you’ll need to add a 1/2” cut washer on top of the normally required washer. Check the load table footnotes for the 1/2” anchor reduction factor. Proper washer installation looks like the picture below, where the washer sits between the stiffeners and doesn’t overhang.
Testing complied with ICC-ES AC13 Joist Hangers and Similar Devices. We tested three configurations: angle pair, clinched part, and corner angle pair. It would be conservative to test just the angle pairs and use that data for everything, but we saw an opportunity to get better loads by also testing the assembly. The clinched base plate provides extra stiffness, which improves lateral loads. So we tested angle pair configurations in uplift and lateral, and clinched assemblies in lateral. Additionally, we performed an uplift test with 1/2″ anchors to determine the reduction factor.
In the testing photos, you’ll see we used a custom fixture, a large 2″ steel plate with hole patterns, as the anchoring surface. Uplift testing was done by pulling up on the post. For lateral testing, we opted to turn the part sideways and push down on the post with a set of parts on each end for symmetry.
One of the footnotes on the anchorage load table references the prying amplification factor. This factor is baked into the table to account for the increase in anchor tension caused by prying action on the metal. We determined this through finite element analysis (FEA) and physical testing. We performed a physical test on steel substrate that isolated prying behavior, taking special care to control pretension on the anchor. We did FEA both with the part anchored to steel and with embedded anchors bonded to concrete. Our theory was that steel substrate would yield higher prying forces because it’s a harder material than concrete, so it will have less give when the part is leveraging against it. On the other hand, anchor stretch length should reduce the forces somewhat. A lot of data was collected, and then we had to decide what to do with it. Ultimately, we chose to look at average prying amplification force from 50%-100% of allowable load and the worst case of FEA and lab testing to come up with the final prying ratio.
The PFCB and PFC were designed to meet the needs of modern post frame builders. Post frame construction used to be called “telephone pole barn” or “pole barn,” a term that came about during the Great Depression when old round utility poles were repurposed to build barns. Pole barns were built with rule-of-thumb designs and little to no engineering, which mostly worked out because structures used solely for agriculture don’t have the strictest regulations. Today, it’s no longer pole and only sometimes barn. Post frame design is realizing its potential across the commercial and residential sectors. Demand has increased for a clear, standardized engineering methodology to justify designs to building officials. The first widely recognized engineering reference for post frame design is the Post-Frame Building Design Manual published by the National Frame Building Association (NFBA), published in 2000. The second edition remains the primary industry reference today.
If you’re interested in learning more about PFCB and PFC, feel free to ask a question in the comments and visit the product pages for the PFCB and PFC at strongtie.com.
