A client who reports a defect in building work to the contractor does not have to know its cause. The Federal Court of Justice has held this for many years under what is called the Symptomtheorie, the symptom theory. The client is not required to name the causes of the defect in detail. A description of the symptoms that such a defect typically produces is enough. For example, a homeowner may report a damp patch on the basement wall without knowing why it is damp.