The maximum span that can be supported by 2x4 floor joists depends on several factors, including the wood species, grade of lumber, spacing between the joists, and the type of load the floor will bear. However, it's important to note that 2x4 lumber is not typically used as floor joists in modern construction due to its limited load-bearing capacity.
In the past, 2x4 floor joists were more common in older construction methods, but they are now considered inadequate for most residential floor systems. They are more commonly used for shorter spans, such as in interior non-load-bearing walls or as bracing members.
For modern residential construction, 2x6 or larger lumber is generally used for floor joists to meet building codes and provide adequate strength and support. The specific maximum span for 2x6 floor joists will depend on the factors mentioned above, and it is crucial to consult with a structural engineer or refer to local building codes to determine the appropriate size and spacing of floor joists for your project.
If you are considering a floor joist project or any structural modifications to your home, it is best to consult with a licensed structural engineer or a qualified professional who can assess the specific requirements and ensure that the design meets the necessary safety and building standards.