Part 4: Identify, Retain and Preserve
Under guidelines published by the National Park Service, historic rehabilitation is a three-step process of identifying, retaining, and preserving the form and detailing of architectural materials and features that are important in defining the historic character.
Recommended: Repair if possible,
or replace with like materials
Actions that are most apt to diminish or destroy the buildings's historic character are not recommended.
A word of caution, however. Loss of character is just as often caused by the cumulative effect of a series of seemingly minor actions. Thus, undertaking any changes that are not recommended must be viewed in that larger context, e.g., for the total impact on a historic building.
These steps should be followed in rehabilitating any historic building.
Step 1: Identify
- First, identify materials and features that are important and must be retained.
Step 2: Protect and Maintain
- Protection generally involves the least degree of intervention and is preparatory to other work.
For example, protection includes the maintenance of historic material through treatments such as rust removal, caulking, limited paint removal, and re-application of protective coating; the cyclical cleaning of roof gutter systems; or installation of fencing, protective plywood, alarm systems and other temporary protective measures. Although a historic building will usually require more extensive work, an overall evaluation of its physical condition should always begin at this level.
Step 3: Repair
- When the physical condition of character-defining materials and features warrants additional work, repairing is recommended.
Guidance for the repair of historic materials such as masonry, wood, and architectural metals again begins with the least degree of intervention possible. This might include:
- or otherwise reinforcing or upgrading them according to recognized preservation methods.
Repairing also includes the limited replacement in kind--or with compatible substitute material--of extensively deteriorated or missing parts of features when there are surviving prototypes (for example, brackets, dentils, steps, plaster, or portions of slate or tile roofing).
Although using the same kind of material is always the preferred option, substitute material is acceptable if the form and design as well as the substitute material itself convey the visual appearance of the remaining parts of the feature and finish.
Step 4: Replace
- Following repair in the hierarchy, is replacing an entire character-defining feature with new material.
This is acceptable when the the original materials are too deteriorated or damaged to repair. Examples might include an exterior cornice; an interior staircase; or a complete porch or storefront.
If repair is not possible, the next best thing to do is replace the feature with new material of the same kind.
If the essential form and detailing are still evident and can be used to re-establish the feature as an integral part of the rehabilitation project, then its replacement is appropriate.
Like the guidance for repair, the preferred option is always replacement of the entire feature in kind, that is, with the same material. Because this approach may not always be technically or economically feasible, provisions are made to consider the use of a compatible substitute material.
It should be noted that, while the National Park Service guidelines recommend the replacement of an entire character-defining feature under certain well-defined circumstances, they never recommend removal and replacement with new material of a feature that--although damaged or deteriorated--could reasonably be repaired and thus preserved.
Step 5: Recreate missing features
When an entire interior or exterior feature is missing -- for example, an entrance, or cast iron facade; or a principal staircase -- it no longer plays a role in physically defining the historic character of the building unless it can be accurately recovered in form and detailing through the process of carefully documenting the historical appearance.
Where an important architectural feature is missing, its recovery is always recommended in the guidelines as the first or preferred, course of action. Thus, if adequate historical, pictorial, and physical documentation exists so that the feature may be accurately reproduced, and if it is desirable to re-establish the feature as part of the building's historical appearance, then designing and constructing a new feature based on such information is appropriate.
However, a second acceptable option for the replacement feature is a new design that is compatible with the remaining character-defining features of the historic building. The new design should always take into account the size, scale, and material of the historic building itself and, most importantly, should be clearly differentiated so that a false historical appearance is not created.
Step 6: Carefully consider any additions or alterations
Some exterior and interior alterations to historic building are generally needed to assure its continued use, but it is most important that such alterations do not radically change, obscure, or destroy character-defining spaces, materials, features, or finishes.
Alterations may include providing additional parking space on an existing historic building site; cutting new entrances or windows on secondary elevations; inserting an additional floor; installing an entirely new mechanical system; or creating an atrium or light well. Alteration may also include the selective removal of buildings or other features of the environment or building site that are intrusive and therefore detract from the overall historic character
Avoid new construction
The construction of an exterior addition to a historic building may seem to be essential for the new use, but it is emphasized in the guidelines that such new additions should be avoided, if possible, and considered only after it is determined that those needs cannot be met by altering secondary, i.e., non character-defining interior spaces.
If, after a thorough evaluation of interior solutions, an exterior addition is still judged to be the only viable alterative, it should be designed and constructed to be clearly differentiated from the historic building and so that the character-defining features are not radically changed, obscured, damaged, or destroyed.
Additions to historic buildings are referenced within specific sections of the guidelines such as Site, Roof, Structural Systems, etc., but are also considered in more detail in a separate section, New Additions to Historic Buildings.
To see a list of all of the stories in this series, click here.
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