Terms of the Trade: What are Dead Loads and Live Loads?

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The dead load of a building is the amount of static weight it has to support permanently, including all structural elements and non-moving components. The live (or "imposed") load of a structure or an element thereof is a calculation of temporary forces it may have to endure pressure, like the weight of people, vehicles, or equipment.

Together, the dead load and live load of a building at any given time are referred to as the "gravity load." Lateral loads considered distinct from dead and live loads for design purposes. They can operate on structures in other directions than that of gravity, and include forces like wind and shifting tectonic plates.

Environmental loads are technically live loads, but many have their own names and measurement formats, such as snow loads, wind loads, earthquake loads, ponding loads, and thermal loads. Maximum structural loads for various construction elements are governed by building design codes.