Generally, what is the minimum size for spaced sheathing?

The minimum size for spaced sheathing is indeed 1 x 4 boards. This dimension is significant because it ensures that there is adequate support for materials applied above the sheathing, such as roofing. Spaced sheathing is typically used to allow air circulation and help prevent moisture buildup, which can lead to issues like rot or mold.

Using 1 x 4 boards specifically provides the balance between strength and the necessary spacing that allows for ventilation. Smaller sizes might not provide sufficient structural integrity, while larger sizes might not allow for proper ventilation. The 1 x 4 size is also consistent with the requirements often found in building codes and guidelines for roofing applications, making it a standard choice for roofing contractors focusing on ventilation and structural support.

In contrast, other board sizes might either be too weak, too wide, or not commonly recommended for the specific purposes that spaced sheathing serves.