Quick answer The most common causes of water leaks in Sydney apartment buildings are failed sealant joints around windows and expansion joints, cracked or porous render on the façade, blocked or poorly sloped balcony drains, and ageing waterproof membranes around windows and balcony doors, most of which can be identified and fixed with targeted high rise water leak repairs Sydney building owners can arrange without needing major structural work. If you've noticed a damp patch