Final answer:
Old guidelines suggested a spacing of 5 diameters side-to-side and 7-8 deep for sheathing and the back of veneer, but newer recommendations propose a larger gap of 8 diameters side-to-side and 15 diameters deep.
Step-by-step explanation:
A nominal 1-inch air space is required to drain the water as well as keep the brick and mortar from coming into direct contact with the sheathing. If air spaces are less than 1 inch, mortar bridging will occur too frequently. Air spaces can be as large as 4h inches, if wire wall ties are used.
The appropriate space to maintain between sheathing and the back of veneer can depend on various factors including the specific project requirements and the materials used. Historically, an older "rule of thumb" might have recommended maintaining a gap of 5 diameters side-to-side and 7 to 8 diameters deep. However, more recent findings suggest that a larger space might be necessary, possibly as much as 8 diameters side-to-side and 15 diameters deep for optimal performance and stability. This increase acknowledges the need for sufficient space to accommodate potential expansion, contraction, and movement of the building materials over time.