Installation errors can affect the load capacity of framing connectors and — if not corrected — cause long-term problems, such as cracking and separation of finishes or failure in weather or seismic events. Here are some of the most common problems and how to avoid them.
Misplaced Anchor Bolts
In seismic regions, codes typically require that foundation bolts have 3-inch-square bearing plates instead of washers. An incorrectly placed bolt can cause the bearing plate to extend beyond the edge of the sill or to conflict with the framing, as shown to the left.
Do not notch the stud. Instead, use a slotted plate, such as the one shown in the photo to the left, which can be offset to accommodate an anchor bolt near a stud.
Another way to reduce framing conflicts is to use strap anchors instead of bolts.
Spalling at Embedded Straps
If a hold-down is wet-set or bent while the concrete is still green, it can cause spalling in the concrete. Spalls less than an inch tall will not affect the hold down's load capacity, but those between 1 and 4 inches will reduce capacity by 10 percent and should be checked by the engineer or designer. If spalling is severe, you may be able to retrofit the connection with an epoxied threaded rod or mechanical anchor, code permitting.
Excessive Bends in Strap-Tie Offsets
Strap-tie hold downs installed over the sheathing may need to be bent horizontally, but the offset should not exceed 5/8 inch. Easing or lightly notching the panel edge, and nailing from the bottom of the strap upward will prevent the strap from bulging and keep wall movement to a minimum. More than one 90-degree bend is not allowed.
Hold-Down Bolts Too Short
When an anchor bolt is set too low in the concrete, there may not be enough exposed thread to properly connect the hold down. To achieve full strength the bolt must, at a minimum, be flush with the top of the tightened nut.
Anchor Bolt Misaligned For a Hold Down
If a bolt is too far away from the framing it can sometimes be salvaged by extending it with a coupling nut, then gradually offsetting it to meet the raised hold down. As a general rule the rod should be within 5 degrees of plumb, or no more than a 1/4-inch of offset for every 3 inches of additional height. However it’s best to check with the hold down manufacturer.
Missed Holes
A gun-driven nail that misses the factory-punched hole and makes its own reduces the connector's shear capacity. Framing connectors should not be installed with a regular framing nailer, but rather with a specialty nailer that advances the nail first so it can be registered in the hole before firing the trigger.
Overdriven Pneumatic Nails
Overdriven fasteners cause excessive dimpling and weaken the hardware by fracturing the steel around the nail hole. The solution is to use a specialty framing-connector nailer that allows you to properly set the driving depth.
Visit the JLC Field Guide for more guidance on installing framing connectors.
