The preservation and conservation of deteriorated historical structures is always a difficult but challenging task. Theoretically, all significant historic structures should be conserved and saved from being removed or discarded. Practically, this ideal may not always be achievable for all decayed components of the historic structures. Sometimes their conditions are too bad to be reasonably repaired to a safe state. On the other hand, replacement is not the only resort for all the damaged relics. There are situations that these relics should better be preserved, though more resources will have to be invested and greater challenge might be encountered in the course of work. This paper attempts to illustrate the deliberation with a case study - the preservation of wooden structures of Chik Kwai Study Hall in Hong Kong, and addresses the considerations in making decision between repair and replacement. Scientific or structural analysis has played a key role in directing our way to the final decision. Methodology used for guiding the whole conservation process will also be discussed.