Details for joist repair and strongback installation

Knowledge is power, as the saying goes. I was called into a jobsite recently and found a damaged joist. You can see by the picture that the bottom chord got an undue amount of downward force on it, resulting in a split. A joist repair was in order.

Stepped on the bottom chord

In this particular instance, the GC admitted that someone had stepped on the bottom chord when setting the joists. Sometimes people tell me the joist was delivered damaged. Had this GC told me something like that, it would have surprised me. Firstly, because he’s not the kind of person to install a damaged joist. Secondly, because it is very unlikely that he had received the joist in that condition. The open joist TRIFORCE® manufacturing process is 100% automated and also includes several QA steps before packaging and shipping. Finally, as they are shipped in sealed bundles, it is just about impossible to have one damaged this way before arrival at a jobsite.

To remedy the situation, we used this joist repair detail.

Repairdetail_cut_bottom_chord

Repair detail for cut bottom chord

Improper strongback installation

The second thing you’ll notice in the photo is that the Strongback (running perpendicular to the joists) is installed improperly.

Strongbacks are an excellent way to improve the overall rigidity of a floor system. They help eliminate vibration and make the floor more stable and coherent. They are inexpensive and can be easily installed. So easy in fact, that workers can get casual and install it lying on its side as shown, instead of vertically. We call this type of horizontal installation a rat run because it adds nothing to the floor system. When vertical, the Strongback can properly resist deflection and vibration. We recommend the following installation for best results.

Strongback_detail

Strongback installation detail

Finally, you’ll notice that the Strongback cuts through the wall framing, but it doesn’t need to. The Strongbacks can be stopped to allow HVAC and walls as long as three (3) consecutive joists are attached.

If you’d like to know more about the TRIFORCE® product, download our spec. guide or contact us. We’ll be happy to help.

Triforce Spec Guide

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