Section R701 requires water-resistive barriers behind exterior wall coverings to protect the building from moisture infiltration. Water-resistive barriers include felt, synthetic membranes, or foam sheathing. The barrier must be lapped horizontally with upper portions overlapping lower portions to shed water. Flashing at window and door openings extends past the water-resistive barrier and is integrated with the exterior cladding. Air space behind brick veneer permits water drainage and prevents water backing up into the wood frame. Drainage systems including gutters and downspouts direct water away from foundations.