What is the minimum thickness required for roof sheathing when framing is at 600 mm centers?

The minimum thickness for roof sheathing when framing is spaced at 600 mm centers is 15 mm (5/8 inch). This requirement is established to ensure sufficient structural integrity and load distribution across the roof. When the framing is closer together, as is the case with 600 mm spacing, a moderately thinner sheet than would be required at wider spacings can provide adequate support.

Using a thickness of 15 mm allows for a balance between structural strength and material efficiency. It is capable of supporting typical loads, including snow or wind, while still being light enough for manageable handling and installation.

Thicker options like 18 mm might provide extra strength but are generally unnecessary for standard applications unless specified by unique structural or load-bearing needs, thus leading to increased material costs. Similarly, options below 15 mm, such as 12 mm, would not meet code for sheathing at this framing interval, potentially compromising safety and structural performance. Therefore, 15 mm is identified as the appropriate minimum thickness in this context.