What is a "girder" typically used for in construction?

A girder is primarily used as a main support structure in construction. It acts as a horizontal support beam that transfers loads from the roof, floors, and walls down to the foundation of a building. Essentially, girders bear significant weight and help distribute this weight across other structural members, ensuring the stability and integrity of the overall building. This often makes them critical components in large structures like bridges, commercial buildings, and industrial facilities.

The other choices do not accurately reflect the role of a girder. While decorative elements and finishes can enhance a building's aesthetic appeal, they do not contribute to its structural support. Additionally, insulation serves a very different purpose, focusing on temperature regulation and energy efficiency rather than structural integrity. Therefore, the distinction of girders as primary support structures highlights their essential role in construction.