Why joists fail 👎 #carpentry #electrical #plumbing #learn #testing

Joists are a main component in your flooring system. They're used for spanning between two bearing points, and the depth is determined by the span and the load that is on the joist. Your joists will either sit on a mudsill that sits on top of a foundation or on an I-beam or a bearing beam. It's common that holes get drilled for plumbing and electrical. Holes can be drilled the full length of the joist other than a couple inches at the ends and 2 inches below the top and above the bottom of the joist. The hole size needs to be less than 1/3 of the joist depth. It should be spaced two to three times the hole's diameter. Notches can only be installed on the outside 30 or joist. So, if this joist is 12-ft long, you can only do it in the outside 4-ft sections, not the center four. Depending on the situation, notches for bearing points could be 1/4 the depth. In other locations other than the center, they can be 1/3 of the depth. Always check local codes. Keep in mind, any notching on the bottom is not a great idea. When your joist gets loads applied, the top is in compression and the bottom is in tension. Let's test this. As a downward force is applied, you'll see these curves want to close with compression. Let's make a cut down here and load it to 2 tons again. As you see, the load didn't even make it to a ton. Notches are one of the main cause for joist failure, and it's why you never want to notch your joist in the center. Thanks for watching.