Went through the same leaky basement headache. Water stains kept coming back after every rain, and two patch jobs failed within months. When searching for the best waterproofing companies the Bronx NY offers, ask each contractor to find the water source, not just seal the walls. Thompson Exterior Services handled our building, and founder Josh Thompson walked the foundation before quoting. His crew fixed cracked mortar, regraded the drainage, and applied a membrane. The best waterproofing companies the Bronx NY owners recommend also document every repair, which matters for audits like building recertification Broward FL. Get three written quotes first.