If the first row of roof sheathing is started with a full sheet of plywood, how should the second row start?

Starting the second row of roof sheathing with a half sheet is the correct approach because it helps in staggering the joints between the rows. Staggering the joints is crucial in roofing systems as it enhances the structural integrity and stability of the roof by preventing seams from aligning directly above each other. This technique also helps in distributing the load more evenly across the sheathing and reduces the likelihood of water infiltration at the seams.

By using a half sheet for the second row, the seams are offset from the first row's seams, which minimizes the risk of leaks and makes the roof stronger overall. Proper staggering is a standard practice in construction to ensure that roofing and sheathing materials perform optimally under various weather conditions and stress.

Using a full sheet for the second row would not achieve the necessary stagger, potentially leading to weaker structural performance and increased risk of leaks over time. Similarly, starting with a quarter or three-quarter sheet would not provide the optimal offset needed for effective load distribution and waterproofing. Thus, beginning the second row with a half sheet is the best choice for achieving a durable and reliable roof.