What is the exterior layer of an exterior wall called?

The exterior layer of an exterior wall is commonly referred to as siding. Siding serves both a functional and an aesthetic purpose, providing a protective layer against the elements such as rain, wind, and solar exposure, while also contributing to the overall appearance of the building. It is typically available in various materials, including wood, vinyl, fiber cement, and metal, each offering different benefits in terms of durability, maintenance, and style.

In contrast, sheathing refers to the board or panel materials that are attached to the framing of the wall beneath the siding, providing structural support and a surface to attach the siding. Overlayment often relates to roofing applications or additional layers that provide extra protection or insulation and is not specific to exterior wall finishes. Membrane, frequently found in roofing systems, serves as a barrier to moisture but does not qualify as an exterior layer of a wall in the context of traditional siding.