To waterproof a balcony with existing flooring, apply a high-quality waterproof coating or membrane to the subfloor and walls. Fill cracks with epoxy filler, then seal joints and edges using a silicone or polyurethane sealant. For added protection, install a drainage system, such as a sloped surface or French drain, and ensure proper ventilation. Regularly inspect and maintain the waterproofing system to prevent moisture buildup.

The primary goal is to create a continuous barrier against water渗透, which prevents wood rot, mold growth, and structural damage. According to a 2021 study by the Journal of Building Engineering, 30% of balcony failures in the U.S. are linked to water ingress, costing property owners an average of $5,000 in repairs. Waterproof coatings form a durable, flexible layer that adapts to thermal expansion, while sealants address gaps and joints. The EPA highlights that mold remediation costs can exceed $10,000 if unchecked, emphasizing proactive maintenance. A drainage system diverts water away from the structure, reducing hydrostatic pressure. Data from the American Society of Civil Engineers (ASCE) shows that properly waterproofed balconies have a 90% lifespan reduction compared to untreated ones. Combining these methods ensures compliance with building codes and extends the balcony’s lifespan by up to 20 years. Regular inspections every 6–12 months are critical, as even minor cracks can compromise the system.