What creates air space between the roof sheathing and roof covering?

The creation of air space between the roof sheathing and roof covering is primarily achieved through the use of nailing strips. Nailing strips, typically utilized in roofing applications, are horizontal boards that are fastened to the roof structure. When the roofing material is applied over these strips, a gap is formed between the sheathing and the roof covering itself. This air space is crucial as it allows for ventilation, helping to regulate temperature and moisture levels. Proper ventilation can prevent issues such as mold growth and enhance the overall durability and performance of the roofing system.

While vapor retarders, base flashing, and head lap contribute to a roof's performance and moisture management, they do not specifically create an air space between the sheathing and the covering. Vapor retarders are designed to limit moisture movement, base flashing helps direct water away from critical areas, and head lap refers to the overlap of shingles or roofing materials to prevent water infiltration. None of these components facilitate air flow in the way that nailing strips do, making them not suitable for creating the specific air space mentioned in the question.