Due to corrosion and/or leakage at joints, water supply lines routed through wall cavities may have tiny pinholes. These can leak continuously or intermittently, soaking insulation within walls, saturating wood and drywall structure. Uninsulated copper cold water pipes can also sweat condensation in sufficient quantities to cause damage within walls. Especially if structural cracks and gaps allow moist outdoor air to infiltrate the cavity of the wall.