Mechanical damage causes water leakage
Most times, before the application of cementitious waterproofing, polyurethane waterproofing or bitumen waterproofing careful considerations may not be given to the equipment that would be installed such as AC, Chillers, DSTV etc. And so they end up drilling holes, damaging/breaking through these membranes to install these equipment thereby causing leakages.
Poor product specification
In areas that are prone to high hydrostatic pressure, crystalline water proofing admixtures are meant to be specified for such areas, but in cases where water-repellent admixtures are specified for these areas. Waterproofing may fail hereby causing leakage
Cracks, Joint holes can cause water leakage
Water can penetrate through cracks, joints holes, joints that are weak, movement, pipes that are not properly fixed. Bad installation of sanitary fittings and sealants faulty internal plumbing.
During the original construction of your home in many cases, the concrete forms were hand-built form wood and held together during the cement pour with 5/8 steel roads. These rods are placed in 2 horizontal rows, every 1.5feet, with one row about a foot off the ground and the other 4 feet above theat. Upon completion of the walls, the roads are removed leaving rod holes. Also holes are created on concrete if it is not properly mixed. The holes paves way for water to enter into use mortar LN.
Poor waterproofing at the time of construction
A building can be properly designed, the material used may be of high quality but without being applied by qualified hands following industry standards. The water proofing membrane fail. Waterproofing is very dependent on the application. Error in application is the most common cause of water ingress problems in a building.