Due to the many facets of window design, assembly and installation, window defects are common and can result in water intrusion. Problems may be caused by improper flashing installation, paper application, and improper use of sealants. Also, it is possible that the window itself is defective. Damage can be severe if not remedied immediately. Damages range from staining and cracking of interior drywall surfaces (especially on top of window sills), to structural member damage and ultimately dry-rot and mold infestation, if not addressed.