There are many reasons a shower or balcony may be leaking. A common problem is slight building movement. This is especially problematic in second story or larger apartment complexes. Any movement will cause separation between the wall and floor tiles allowing water to leak under the base. Another major reason for a leaking shower can be caused by the incorrect installation of shower screens. Most screens are manufactured by wardrobe companies with very little understanding of waterproofing. A shower screen must have every junction and chanel sealed internally.