A floor joist can be cantilevered beyond the foundation a distance of up to what proportion of their length?

When considering the cantilevering of floor joists, building codes typically allow for a maximum cantilevered length that is proportionate to the overall length of the joist. According to common practice, a floor joist can safely be cantilevered up to one-third of its total length. This balance ensures the structural integrity and stability of the joist while providing sufficient support for loads placed on it, preventing issues such as sagging or undue stress.

The one-third rule allows for adequate load distribution back to the supported portion of the joist, ensuring that the cantilevered portion can effectively handle the forces it will encounter without compromising safety. This is particularly important in residential and commercial construction, where proper load management is critical for the longevity and durability of the structure.

Other options, such as one-quarter, one-half, and two-thirds of the joist length, do not align with standard building practices and could lead to scenarios where the joist may be subject to excessive bending or failure under load. Hence, the choice that reflects the industry standard is the one-third proportion of the joist length for cantilevering beyond the foundation.