Identifying Primary and Secondary Interior Spaces in Historic Buildings

This document provides guidance on identifying and evaluating significant elements in the interior of a building, to clarify those elements that must be retained or minimally modified in a rehabilitation project, and those that can undergo greater change or modification.

This process has already been covered in some detail in Preservation Brief 18: Rehabilitating Interiors in Historic Buildings. This document complements that guidance, drawing from its terminology and general approach while providing more specific steps and questions it may be useful to ask, as well as a section covering typical elements to consider in specific building types.

A thorough evaluation of all historic elements of a building in the planning stages of a project will help ensure that the project can be completed successfully by maintaining the building’s historic character. Following the guidance below will help accomplish the evaluation. This review is part of a three-step process involving researching and documenting the building’s history, evaluating the building’s historic elements, and assessing changes to the building proposed in a rehabilitation project.

Evaluating the interior of a building involves two aspects: identifying which elements of the interior are historic, including those changes that have acquired significance; and evaluating the significance and physical condition of those elements. It is useful to note that determinations of historic significance for these evaluations are tied to the stated period of significance in the National Register nomination for the individual building or for the historic district in which the building is located.

Historic elements may be evaluated as either primary or secondary. Primary elements are those that are important in defining the historic character of a building and that should be retained or only minimally altered. Secondary elements are less critical in contributing to the historic character and may be able to undergo greater change without substantially impacting the building’s overall historic character. It should be recognized that these elements are more likely to lie on a continuum of most to least important, rather than simply falling into one category or the other, and the amount of acceptable change will have an inverse relationship to that importance, depending on other factors such as physical condition.

Elements can be categorized as pertaining to the building’s plan; the individual interior spaces or sequences of spaces; or architectural features, finishes or materials that may have sufficient importance and physical integrity to be retained or only minimally altered.

Differentiating between primary and secondary elements is very important. The following definitions may help in evaluating these elements.

Primary spaces are those that are essential in conveying the historic and architectural character of a building. They are most often associated with the primary use or purpose for which the building was designed or used during its period of significance and can vary greatly from building to building.

Where a public to private progression can be identified in the spaces of a building, the most public spaces will usually be the primary spaces. Entrance hall and parlor, and lobby and corridors are common examples of primary spaces. Similarly when spaces of a building vary in their architectural detailing, those that are the most elaborate are usually the primary spaces. This is not to say, however, that a private space or a simple unornamented space cannot be primary.

Some buildings, such as churches, theaters or gymnasiums, contain single large spaces that accommodate the principal use. These are easy to identify as the primary space of the building.

However, in some buildings such as hospitals, apartment buildings or other buildings consisting of multiple units that serve similar functions, it may be the sequences and interrelationships of spaces that are most important in defining the character of the building. Such buildings must be evaluated carefully to determine the importance of all the related elements in the context of the building being assessed.

Secondary spaces are less critical in defining a building’s importance within its period of significance. They often still help define the building’s significance and character, but because of their size, location, or function their impact is not felt as strongly when progressing through the building. Thus, altering these spaces may not significantly impair the ability of the overall building to convey its primary historic significance.

A secondary space is usually a more simply detailed space with restricted access – such as an office, hotel guestroom, or a bedroom – or a utilitarian space that serves a support function within a building – such as a kitchen or bathroom. Generally, these spaces are less architecturally detailed and subordinate in character to the primary spaces to which they relate.

The physical condition of interior elements will frequently affect their historic character and how they contribute to the historic significance of the building. If an interior plan has been heavily altered, it may no longer adequately convey its importance to the building’s character, and further changes may be more acceptable. Conversely, if a bedroom in a rowhouse still retains many of its features such as moldings, fireplaces and doors, then significant alterations in the space may not be appropriate. And, while secondary spaces such as offices behind a corridor typically may be able to accept major plan changes, if features such as historic trim and woodwork around the perimeter wall of the building are still extant they should be retained.

To aid in evaluating the significance and integrity of each of these categories of elements it may be helpful to ask the following questions about a building's plan, spaces, features, and finishes and materials.. These are not comprehensive but, instead, suggest how an evaluation may proceed in order to cover the significant elements of any building.

Plans

Does the building have a floor plan that is an important characteristic of the building type, style, or period of construction or historic function?

Is the plan symmetrical and is this symmetry an important characteristic of the building type or style? Conversely, is the asymmetry an important characteristic?

Has the plan been altered over time? Have the alterations been additive (large rooms subdivided into smaller ones); or have the alterations been subtractive (walls removed)?

Does the plan retain its basic integrity?

Spaces

Are there rooms or spaces that are architecturally or historically significant?

Have rooms survived that are characteristic of the building type or style or that are associated with specific persons or patterns of events?

Is there a sequence of spaces that has been consciously designed or that is especially important to the understanding and appreciation of the building or the architect? Examples might include a foyer opening into a large hall; front and rear parlors connected by pocket doors; office lobby opening into an elevator hall; hallway to stairwell to upper hallway, etc.

Does the space have distinctive proportions – ceiling height to room size, for example?

Are the room shapes or volumes in any way unusual? Examples may include rooms with curved walls, rooms with six or eight walls, or rooms with vaulted ceilings.

Are the rooms a consciously designed “whole,” that is, are the space, features, and finishes part of an integral design?

Have the spaces retained their architectural integrity, despite alterations and deterioration?

Do the spaces reflect the exterior design, e.g., tall windows indicating an assembly space on the second floor?

Features

Are there architectural details that are characteristic of the period of significance, construction or historic function? Examples might include wainscoting, parquet flooring, picture molding, mantels, ceiling medallions, built-in bookshelves and cabinets, crown molding, arches, as well as simpler, more utilitarian features, such as plain window and door trim.

Are there features that indicate later changes and alterations that have gained significance over time? Examples might include lobby alterations, changes to wall and floor finishes, and later millwork.

Are there features that were worked by hand, or that exhibit fine craftsmanship or are characteristic of the building style or type?

Have the features survived intact in one or more rooms?

Is the ceiling vaulted, coffered, decorated with plasterwork, domed, or otherwise embellished?

What is the condition of the features: can they be retained and preserved?

Finishes/Materials

Are there surviving historic finishes that can reasonably be retained and preserved? Examples might include plaster, tile, flooring, and marble?

What is the condition of the finishes, e.g., has water damage been so severe as to render the finishes unsalvageable?

Are there finishes such as graining that are characteristic of a period or style of architecture?

Evaluating Interior Elements – Typical Building Types

Certain building types tend to have common types of plans, spaces, features, and finishes; for example, most schools can be expected to have auditoriums and most rowhouses can be expected to have a front parlor. Assessing the importance and condition of these architectural elements is the essential component of evaluating any interior rehabilitation proposal.

In virtually all cases, a project will not meet the Secretary of Interior’s Standards for Rehabilitation if, as a result of the rehabilitation, the interior has lost all vestiges of its past; in these cases, the sense of time and place has been lost that was associated both with the building and the district in which it is located. Radical transformations of the sequence of spaces, or of the trim and finishes can be justified only in exceptional cases, where the interior deterioration is so extreme that the building can be said to retain its significance only by virtue of a high degree of integrity on the exterior.

Listed below are major building types that are commonly rehabilitated, with general statements about the relative importance of architectural elements often found in them. The guidance is not intended to be comprehensive, but rather is intended to help make consistent decisions about interior rehabilitation treatments in keeping with the Standards for Rehabilitation. A certain degree of repetition may be noted from building type to building type – for instance, it is always recommended to retain historic window and door trim.

Despite generalizations about certain building types, it is important to keep in mind that what may be an acceptable rehabilitation approach for one building may not be acceptable for another. For example, in one school, subdividing a simple, unadorned auditorium with no association with important persons or events may be an appropriate treatment, while in another, the elaborately detailed auditorium (space, features, and finishes) may warrant retention or minimal alteration. It is also important to recognize that a plain, simply detailed 19th-century worker’s house is neither more nor less significant than a highly ornamented, high-style townhouse of the same period. Both resources, if equally intact, deserve the same careful rehabilitation that respects the qualities for which designation as “certified historic structure” was granted.

Each evaluation is unique, taking into account the facts and circumstances of the building in question.

Houses, Rowhouses, and Duplexes

These elements tend to be character-defining interior elements and should be retained.

  • Basic floor plan
  • Features and details that are characteristic of the architectural style of the house
  • Entertaining and living spaces, such as entry halls or foyers, parlors and dining rooms
  • Primary staircase
  • Floor-to-ceiling height in primary rooms
  • Fireplaces, mantelpieces, and finishes on chimney breasts
  • Architectural detailing including window and door trim, baseboards, picture rails, cornices, etc.
  • Doors and windows
  • Historic floors
  • Historic hardware and fixtures, sometimes including lighting, radiators (if distinctive), knobs, pulls, and hinges

These elements tend to be of less importance and may be able to accept greater intervention in the process of rehabilitation.

  • Bedrooms, assuming the basic floor plan is retained
  • Bathrooms and kitchens
  • Secondary staircases
  • Attached garages
  • Utilitarian spaces such as closets and laundry rooms
  • Basements and attics

Apartment Buildings and Tenements

These elements tend to be character-defining interior elements and should be retained.

  • General plan of the building including location of hallways, circulation patterns, arrangement of apartments off central hallways (or entries)
  • Overall character of design, spaces, details, and finishes–whether simple and utilitarian or highly decorative
  • Historic public entrance(s) and lobbies
  • Primary staircase(s)
  • Elevator lobbies including space, features and finishes
  • Corridors and doors off corridors
  • Principal spaces within apartments, such as the foyer, living room, dining room, etc.
  • Architectural detailing including window and door trim, baseboards, picture rails, cornice, etc.
  • Doors and windows
  • Historic floors

These elements tend to be of less importance and may be able to accept greater intervention in the process of rehabilitation.

  • Room dimensions, unless rooms are detailed or carefully proportioned
  • Kitchens and bathrooms
  • Utilitarian spaces such as laundry rooms, storage areas, boiler rooms, etc.
  • Secondary staircases
  • Secondary spaces within individual units

Shotgun Houses

These elements listed below tend to be character-defining interior elements and should be retained.

  • Linear floor plan
  • Sequence of spaces
  • Basic floor-to-ceiling height
  • Architectural detailing including window and door trim, transom lights, baseboards, etc.
  • Doors and windows

These elements tend to be of less importance and may be able to accept greater intervention in the process of rehabilitation.

  • Kitchens and bathrooms
  • Actual dimensions in rear rooms

Schools

These elements tend to be character-defining interior elements and should be retained.

  • Historic public entrances
  • Configuration and width of corridors
  • Main staircases
  • Generous floor-to-ceiling heights
  • Auditoriums, gymnasiums or other large assembly spaces where space, features and finishes create an architectural statement or where the space is of historic importance
  • Architecturally-detailed spaces such as the principal’s office or library
  • Unusual ceiling treatments such as vaults, coffers, etc.
  • Architectural detailing including wainscoting, marble, beaded board, decorative plaster, window and door trim, baseboards, etc.
  • Windows, doors, and transom lights

These elements tend to be of less importance and may be able to accept greater intervention in the process of rehabilitation.

  • Large assembly spaces that are not architecturally distinguished or historically important, or have been altered
  • Secondary staircases
  • Kitchens and bathrooms
  • Utilitarian spaces such as cloakrooms, janitor’s closets, boiler rooms, and storage areas
  • Classroom size and actual room dimensions
  • Blackboards

Factories, Industrial Buildings, and Warehouses

These elements tend to be character-defining interior elements and should be retained.

  • Generous floor-to-ceiling height
  • Structural systems such as wood beams, cast iron or steel columns, and truss systems
  • Main stairs and stair towers
  • Company offices
  • Historic equipment, such as cranes and pulleys
  • Architectural detailing including wainscoting, window and door trim, baseboards, etc.
  • Doors and windows

These elements tend to be of less importance and may be able to accept greater intervention in the process of rehabilitation.

  • Full sense of open space if some sections are maintained
  • Actual floor-to-ceiling height, if new ceilings are set above or significantly back from windows
  • Secondary stairs

Fraternal and Lodge Halls

These elements tend to be character-defining interior elements and should be retained.

  • Entrance, lobby and general arrangement of spaces
  • Main meeting rooms
  • Floor-to-ceiling height
  • Main staircases
  • Proscenium arch and stage
  • Architectural detailing including wainscoting, ornamental ceilings, wall finishes, window and door trim, baseboards, fireplace mantels, etc.
  • Windows and doors
  • Historic floors

These elements tend to be of less importance and may be able to accept greater intervention in the process of rehabilitation.

  • Secondary or altered meeting spaces
  • Secondary staircases
  • Kitchens and bathrooms
  • Utilitarian spaces such as storage areas, coat rooms, etc.

Commercial Office Buildings

These elements tend to be character-defining interior elements and should be retained.

  • Historic corridor plan, including upper floors
  • Historic public entrance(s) and lobby
  • Main staircases
  • Elevator lobbies: space, features and finishes (including upper floors)
  • Executive office suites, board rooms, other meeting rooms and banking rooms
  • Generous floor-to-ceiling heights
  • Office doors, particularly those with transom lights above
  • Light fixtures in public spaces
  • Windows in corridors
  • Architectural detailing including elevator doors, ornamental ceilings, wainscoting, wall finishes in public areas, window and door trim, baseboards, etc.
  • Doors and windows

These elements tend to be of less importance and may be able to accept greater intervention in the process of rehabilitation.

  • Full length of corridors
  • Office wall partitions on upper floors, if undistinguished architecturally
  • Exact floor-to-ceiling heights on upper floors, if new ceilings are set above or significantly back from windows
  • Secondary staircases
  • Utilitarian spaces such as storage rooms, boiler rooms, etc.

Churches

These elements tend to be character-defining interior elements and should be retained.

  • Historic public entrance(s) and vestibule
  • Sanctuary space and volume
  • Balcony
  • Vestry hall
  • Stairs to balcony space
  • Doors and windows (configuration, size, and glazing)
  • Architectural detailing including columns, ornamental ceilings, flooring, lighting fixtures, stairways, wainscoting, window and door trim, baseboards, etc.

These elements tend to be of less importance and may be able to accept greater intervention in the process of rehabilitation.

  • Secondary public spaces
  • Sunday school classrooms
  • Sacristies
  • Fellowship halls
  • Offices
  • Kitchens and bathrooms
  • Utilitarian spaces such as storage rooms, coat rooms, boiler rooms, etc.

Hotels

These elements tend to be character-defining interior elements and should be retained.

  • Historic public entrance(s) and lobby
  • Configuration and width of corridors
  • Main stairs and elevator lobbies
  • Commercial arcades on ground floor
  • Floor-to-ceiling heights on ground floor
  • Main ballrooms and reception rooms
  • Architectural detailing including registration desks, columns, lighting elements, fountains, fireplaces, mantels, ornamental ceilings, wainscoting, door surrounds and transoms, window trim, baseboards, etc.
  • Doors and windows

These elements tend to be of less importance and may be able to accept greater intervention in the process of rehabilitation.

  • Full length of corridors, depending on circumstances
  • Secondary gathering spaces
  • Individual guest rooms off corridors
  • Service elevators
  • Secondary staircases
  • Kitchens and bathrooms
  • Utilitarian spaces such as service pantries, laundries, coatrooms, service corridors, etc.
  • Parking facilities

Hospitals

These elements tend to be character-defining interior elements and should be retained.

  • Historic public entrance(s) and lobby
  • Reception office or alcove
  • Main stairs and elevator lobbies
  • Configuration and width of corridors
  • Entrances to wards
  • Daylight rooms or solariums
  • Chapel
  • Operating theaters
  • Dining rooms
  • Floor-to-ceiling heights in public areas
  • Architectural detailing including decorative plaster, ornamental ceilings, columns, wainscoting, chair rail, window and door trim, baseboards, etc.
  • Historic floors, such as terrazzo
  • Windows and doors

These elements tend to be of less importance and may be able to accept greater intervention in the process of rehabilitation.

  • Full length of corridors, depending on circumstances
  • Secondary staircases
  • Ward or room dimensions
  • Operating rooms
  • Cafeterias
  • Kitchens and bathrooms
  • Utilitarian spaces such as laundries, boiler rooms, and storage rooms

Additional guidance »

Preservation Brief 18: Rehabilitating Interiors in Historic Buildings – Identifying Character-Defining Elements

Preservation Brief 17: Architectural Character – Identifying the Visual Aspects of Historic Buildings as an Aid to Preserving Their Character.