The continuity and integrity of air-barrier systems play a critical role in the performance of exterior envelopes in controlling airflow and vapor transmission. Continuity is essential, particularly in locations along the coast where climates with elevated humidity and high winds exist. In new construction, a continuous air barrier can be achieved by applying materials on the exterior of wall systems, including sheet membranes, fluid-applied membranes, rigid insulations, and spray polyurethane foams (SPF). This method is generally preferred due to the ease of installation and limited detailing concerns. However, in developing and implementing repairs for existing buildings, the application of an air barrier can require repair solutions from the interior due to site conditions, budget constraints, building occupants, or other factors. Sealants, in combination with SPFs, have been successfully utilized in the creation of interstitial (cavity) air-barrier systems along exterior walls. After the construction of three mid-rise multifamily condominiums located in Morehead City, NC, interior damage related to air infiltration began to be reported by building occupants and maintenance staff. Issues included microbiological growth on interior walls and ceilings; condensation along ductwork, registers, and exhaust vents; and air infiltration around windows, electrical fixtures, and wall terminations. The investigation to determine causes of air infiltration, as well as the development and implementation of repairs, are discussed herein. The investigation revealed inadequate detailing around window openings and penetrations in the building envelope, along with incomplete construction of the exterior walls and walkway expansion joints. The improper construction allowed unconditioned exterior air to infiltrate the building envelope. Repairs to create a continuous air barrier included sealing of exterior walls, ductwork, joints between wall framing members, and expansion joints with sealants and SPFs from the interior along with localized reconstruction of exterior walls. Isolated repairs to the existing weather barrier and flashings were also implemented to address moisture infiltration issues.