What is the purpose of doubling joists under load-bearing walls?

Doubling joists under load-bearing walls serves the critical purpose of supporting structural loads. When a load-bearing wall is present, it transfers weight from the roof and upper floors down to the foundation. Joists play a key role in distributing this weight evenly across the structure. By doubling the joists, you effectively increase the load-bearing capacity of that section of the floor system. This added support helps to prevent sagging or failure in the joists due to excessive weight, ensuring that the structural integrity of the building is maintained. It is essential for the safety and durability of the overall construction, especially in areas where significant loads are anticipated. In contrast, increasing flexibility, saving materials, or reducing costs are not primary considerations when it comes to the structural necessity of doubling joists for load-bearing walls.