Which of the following is essential to avoid weakening a joist when creating holes?

To ensure that a joist maintains its structural integrity when creating holes, it is crucial to place those holes strategically to avoid compromising the joist's strength. Placing holes near the center of the joist, away from the flanges, is the most effective method to minimize the risk of weakening the joist. This is because the central portion of a joist generally experiences the least amount of bending stress, thereby maintaining the load-bearing capacity while allowing for the necessary perforations.

When holes are placed near the top or bottom flanges, they can directly impact the integrity of the structural support provided by those flanges, which are critical for resisting bending and shear forces. Furthermore, creating multiple small holes throughout a joist may also contribute to a reduction in strength, as it increases the potential for weakness in various locations, rather than concentrating the alteration in a less critical area. Hence, maintaining the overall structural capacity of the joist necessitates careful consideration of hole placement, making the approach of drilling near the center a more appropriate choice.