Window seepage is the most common defects in building maintenance.

Practically, an opening is left during construction and window frame is fixed later. The gap is usually back filled with cement mortar and workmanship is becoming the most crucial factor in determining the possible seepage. Moreover, crack on the window corners is also the common cause of window seepage because shear force is usually exerted on this location. Beside the visible cracks directly exposed on external wall, water seeps through various ways from steel bars, wall plastering and then goes through the porous cement mortar to window lintel/sill and even spread out the whole window frame.

Unless the seepage is obviously located, it is not easy to rectify it wholly on the external wall because the seepage may come from somewhere far above the window. The situation may be even worse if a layer of waterproofing material is not properly and exactly applied on location of seepage on external wall because it just only seals the surface that prevent the water from going out. As a result, it becomes more cost-effective to carry out waterproofing works internally if condition is allowed.

Epoxy injection is the most effective method to seal the cracks and fill up the porous cement mortar around the windows. Special treatment to the window frame, external wall and replacement of defective sealant are also necessary, depending to different site conditions.