The maximum size penetration that can be made in steel deck without the need of reinforcing is______.

The correct answer is based on standard construction practices regarding the structural integrity of steel decks. In the context of steel deck construction, penetrations such as openings or holes must be carefully managed to maintain the deck's strength and load-bearing capabilities.

A #12 penetration is the maximum size that can typically be made in a steel deck without requiring additional reinforcing. This size is established by industry codes and structural engineering principles, ensuring that the integrity of the steel deck is preserved while still allowing for necessary utility lines or other components to pass through.

Larger penetrations, such as #14 or #16, often necessitate reinforcing measures to prevent weakness in the structure, as they could compromise the load distribution and overall stability of the steel deck. A #10 penetration falls below the threshold where reinforcing is needed but is not the maximum limit allowed. Therefore, a #12 penetration represents the maximum opening standard that maintains the required structural performance without the need for reinforcements.