The U.S. Secretary of the Department of the Interior has a series of standards to abide by regarding the maintenance, replacement, and repairing of historic materials, as well as the design of new additions and alterations to a property.
In addition, there are also Department of the Interior guidelines that recommend how the standards can be applied to a specific property when it comes to design and technical treatment. Together, they serve as a frame of reference in the decision-making process about the changes to a historic property.
These standards and guidelines cover historic properties of all types, materials, sizes, construction styles, and uses (both interior and exterior). They can be applied to a property’s landscape features, environment, site, or other related new construction as well.
There are four specific, but interrelated approaches to the treatment of historic properties: