Final answer:
The most suitable option for bridging/blocking in a non-engineered floor is squash blocks, as they provide additional vertical support to help distribute loads more effectively.
Step-by-step explanation:
The most appropriate bridging/blocking for a non-engineered floor is squash blocks. Squash blocks are short pieces of lumber installed vertically between the joists at mid-span or where heavy loads are anticipated, providing additional support and helping to distribute the load over a wider area. They are typically used in conjunction with other flooring components to enhance the structural integrity of the flooring system. Unlike X-bracing, which is used to prevent lateral movement, or metal strapping, which is often employed for tensile resistance, squash blocks are effective in resisting compression from above. Firestops are used to prevent the spread of fire and are not primarily for structural support. Therefore, given the options listed, squash blocks are the best choice for additional support in a non-engineered flooring system.