What parameter controls the thickness of walls in Revit?

The thickness of walls in Revit is primarily controlled by the Wall Type parameter. Each wall type defined in the project has specific characteristics, including its thickness, material composition, and any associated structural properties. When you create or modify a wall in Revit, you're essentially selecting a wall type from the available types in the project, which directly determines how thick that wall will be.

While wall layer configuration defines how layers within a wall type are arranged and can affect the overall thickness if you modify those layers, it is not the primary parameter used to control thickness at a high level. The structural layer pertains to specific components within a wall but does not inherently define the thickness of the wall as a whole. Wall height, while important for defining how tall a wall is, has no impact on its thickness. Therefore, selecting the Wall Type correctly identifies the main method by which wall thickness is established in Revit.