While many people believe preservation is expensive, experience has in fact shown that both buildings and budgets can best be preserved by using the proper process of investigation and inquiry. If the goal is to preserve, then we must begin with the building-centric approach of respecting existing systems and materials, not the design-driven process that guides construction of new buildings. If we fail to recognize that we cannot address existing buildings with a process that is different from how we design a new project based on our current needs, then preservation will continue to be seen as an expensive, risk-laden endeavor of limited value to society.
When we approach historic buildings without respect for the existing systems, imposing our modern perceptions of construction and aesthetic judgement without an understanding of the interrelatedness of what comes before, we risk making mistakes that will plague us for years to come. Understanding the existing building before beginning the design process is crucial to a successful outcome.
If we want buildings that will last beyond a quarter century - whether out of respect for the past, a desire to be environmentally-conscious, fiscal propriety, or a desire to pass something on to our descendents - then we must make decisions about materials and detailing of our building accordingly. When design leads investigation, building materials are incrementally replaced until nothing more can be claimed of an historic site other than "on this piece of ground once stood a building where some historic event happened."