What is the most common spacing for floor joists?

The most common spacing for floor joists is typically 16 inches on center. This standard spacing is widely used in residential construction because it provides a good balance between structural integrity and material efficiency. When joists are spaced 16 inches apart, it allows for a slightly flexible but stable structure that can support the weight of the floor above, including furniture and occupants. It also provides a suitable base for attaching flooring materials, ensuring that there are sufficient points of support.

While other spacings such as 12 inches or 24 inches can be used in specific situations—like in areas that require extra reinforcement or where heavier loads are anticipated—16 inches remains the most common choice due to its versatility and the overall performance it offers for most applications in home building. Spacing at 30 inches is less common for floor joists, as it may not adequately support typical loads.