Video
Applying the Standards: Post-World War II Office Buildings – Webinar #4
Transcript
Hello! I’m Jennifer Bailey, an Architectural Historian with Technical Preservation Services. This training is part of a series dealing with the interpretation and application of the Secretary of the Interior’s Standards for Rehabilitation. This webinar specifically focuses on applying the Standards to Post World War II office buildings. This is an advanced training intended for those already familiar with the Rehab Standards, and we assume everyone watching this webinar series already comes to it with that basic knowledge. However, additional information and training about the Standards are available on our website. The content of today’s training, like other guidelines, publications, training, and information available from the National Park Service, is intended to assist in the interpretation and application of the Standards but is not regulatory or binding. For the purposes of the tax incentives program, the program regulations and the Standards themselves take precedence in any decision-making and should always be consulted first.
The project examples included in this webinar are not necessarily case studies. Some have had their facts and circumstances as described in the presentation simplified or adapted to more clearly express the concepts being discussed. Also, in using the information contained in this training, it should be considered in its entirety, and portions not taken out of context. Likewise, the TPS website should always be consulted to make sure you are using the most current version of any published guidance and information. The rehabilitation of the post-war office building is a particularly hot topic as of late. What many people may not realize is that we’ve been seeing this building type in the tax credit program for at least fifteen years.
Today we will discuss this building type, exterior and interior character defining features, and common rehabilitation issues, specifically as they relate to housing conversions. Additionally, the presentation will provide you with a series of questions to ask as you evaluate these buildings for rehabilitation in the context of a tax credit project. Before we dive in, it is important to remember that these buildings share characteristics with a pre-war office buildings, such as hierarchy of interior spaces, and that applying the Standards and the analysis of these buildings within the context of a tax credit project use the same overall treatment approaches.
Often, we encounter two main types of post-war office buildings in the tax credit program: headquarters and speculative or spec. Both can be architect-designed, high-style, and be a stand-alone building or multiple building complexes. Both types can be as low as one story, or as high as the sky, and they are found in rural and urban settings. The office building on the left in Houston, TX was constructed as the headquarters building of a bank, while the building on the right is in Atlanta and constructed as a speculative office space. Both are examples of high-rise versions that are architect-designed and in more urban settings, but their purpose, cladding, and fenestration patterns are different.
Meanwhile, the Kankakee Title and Insurance Company, Clintonville Savings and Loan Association, and the Citizen’s State Bank, shown on the screen, are excellent examples of low-rise office and bank buildings. Projects may involve one or more buildings or features that are part of a larger complex like an office park or a civic center. Office parks are usually located in a more suburban setting, like Office Park Circle in Mountain Brook, AL seen here. This complex features many office buildings all designed for different tenants over a relatively short period of time, reflecting different styles of modernism. It also features designed landscapes that incorporate fountains, plazas, and greenspace, while the overall layout and design of the park works in harmony with the hilly topography. Fun fact: in this example some of the fountains were an integrated part of the adjacent building’s heating and cooling system.
Another complex type is the civic center, where governmental and civic functions are concentrated into a larger designed district. These are not specific to the post-war era, but there are numerous examples from this time period, such as Civic Center Plaza in Tulsa, seen here. It incorporates an auditorium, the police headquarters, city hall, the federal courts building, and the library, all in different styles of modernism. It also incorporates statues, fountains, and subterranean parking.
Now, let’s turn to character defining features, starting from the outside and working our way inside. The primary exterior character-defining elements that need to be taken into consideration include such features as the construction system, fenestration pattern, and cladding material. The buildings on the previous slides all demonstrate the variety of construction systems and fenestration patterns that are found in these types of buildings. Curtain walls and windows are systems that are often integrated and create a single overall feature. For this building in Cleveland, the curtain wall introduces elements that emphasize both verticality and horizontality, which results in the curtain wall and fenestration pattern creating the building’s most significant exterior element.
Which brings us to cladding material. While this building in Ohio was constructed of glass and aluminum, the cladding materials on these buildings can be vast and varied. The lists on the screen are typical, but not exhaustive. While cladding materials and structural systems are important, these buildings can incorporate a multitude of exterior features. We regularly see plazas, retaining walls, parking lots and garages, tower bases, and podiums. Parking can be below ground or above ground. Site features can be designed landscapes or courtyards. The buildings pictured here are “all about that base.” The building at 100 N Main in Memphis shown on the left incorporates the parking into a base that extends out from the bottom of the building podium, while the Mercantile Bank and Trust Building in Kansas City on the right uses a spaceframe truss to raise the shaft of the building above the sidewalk.
Now let’s zoom in on the actual building sites. Whether the property is an urban high rise, or a suburban office park, they can have designed landscapes that incorporate a single large feature or a multitude of smaller features such as plazas, courtyards, seating, water features such as fountains and lakes, and greenspace in the form of a lawn or planter boxes. Plazas themselves can also incorporate features that are either functional or decorative. Courtyards located below grade were designed to allow for much-needed daylighting inside subterranean entry floors. While the existence of balconies, hyphens, skybridges, and rotating restaurants are not common features seen in the rehabilitation program, they do exist, as seen here.
It’s now time to go inside. This is about office space, the character of which is finished space. Per Standard 2, the features and spaces that characterize a property should be retained and preserved. Often, headquarter buildings will exhibit more consistent finishes and features throughout, so it is important to ask these questions. First, what finishes and features are extant? Two, are they modular? And three, are they consistently found on each floor?
Meanwhile, spec office buildings will often have been constructed with a minimum or standard finish, as illustrated in these advertisements, but were changed over time depending on the preference of the tenant. Thus, the existing finishes at the start of a rehab project might vary. We have also seen post-war office buildings constructed as both headquarters and spec office space, where the company constructing the building will occupy some floors and then lease the remaining floors to other businesses. In these instances, finishes and features might be consistent on some floors and then vary on others.
Our document, “Identifying Primary and Secondary Spaces in Building Interiors” provides a basic list of character-defining elements in the commercial office building. As with pre-war office buildings, post-war office buildings, regardless of type, style, location, or architect, have a hierarchy of spaces and interior character-defining features. Often, the primary spaces in the post-war building type are the entry floor or lobby, as well as the upper floor elevator lobbies and corridors, or a centralized circulation core. Additionally, there are often special-use or assembly spaces, such as an executive office suite, a cafeteria, an auditorium, a banking hall, or a boardroom. As with the pre-war type, the features and finishes within these spaces, which include walls, ceilings, doors, and door opening rhythm, can add to the significance of the building.
Now we’re going to start at the bottom of these buildings and work our way up. Often, high-rise office buildings had an entry floor with monumental features, such as stairs, mezzanines, atriums, courtyards, or fountains. They can also have multiple lobbies for different purposes, such as a hotel and office. These spaces can have one feature, or they can combine multiple features. It is important to note too that sometimes; the entry floor can be the second floor. Both of these office buildings in Ohio have two-story, grand halls that incorporate several mezzanines.
It’s safe to say that most entry floors in a high-rise office building have at least one lobby or vestibule, but in smaller office buildings, not all lobbies or vestibules take up an entire floor. The photograph on the left is a small bank building lobby in Illinois, while on the right is an example of a smaller vestibule in a realtor office in South Carolina. The corridor and circulation plan for any office building is considered a character-defining feature. And just like the pre-war building type, post-war office buildings can exhibit double- or single-loaded corridors, such as the building on the left.
In high-rise office buildings, often a centralized circulation core will include elevators, elevator lobbies, stair halls, bathrooms, and mechanical chases with a corridor that allows one to access all these common areas. The only regularity about the two floor plans on the right is that the corridor wraps around the circulation core; the partitioning behind the corridor wall varies from one floor to another. Corridor finishes in headquarters are often consistent throughout each floor, while finishes in spec office buildings can vary due to the intent to adapt to the needs of the tenant occupying the space.
Which brings us to finishes and features. The primary finishes and features to pay attention to are walls, doors, ceilings, and flooring. For each of these items, their locations and their materials are important. Often, headquarter buildings have a regular upper floor corridor pattern, so the location of the corridor walls are important since we consider corridors primary spaces. In a spec office building, the location of the circulation core and the walls that define that core are important. Historic wall materials in these buildings included plaster, gypsum board, and concrete and featured various coverings such as granite, marble, wallpaper, and grass cloth.
Doors and door placement can be character defining features in all office building types. For ceilings, an acoustical panel ceiling is often the historic ceiling and is the most common type of ceiling finish in the post-war office building. An acoustical panel ceiling or APC is a type of suspended ceiling with a modular system of T-frames and solid lay-in panels, hung from the structure above. Light fixtures and grilles, vents, and diffusers for mechanical systems could be easily integrated into the system. The panels could be used to create a sense of uniformity, scale, pattern, or direction in the space, as seen in both photographs on the screen.
Another type of acoustical ceiling of the same period is tiles that were not part of a suspended system. Instead, they were adhered directly to the ceiling or with furring strips. Similar to acoustical panels in material, acoustical tiles were typically more utilitarian and plain in character, although some were designed with distinctive patterns or textures.
And now it's time for our final finish, Flooring. The flooring materials in these buildings can be as vast and varied as the exterior cladding material, as illustrated in the photographs on the screen. Additionally, historic flooring material can differ throughout the building, depending on the location, primary or secondary. Like with ceilings, a first-floor lobby and upper-floor elevator lobby might have a higher quality material than what is found in office or other secondary spaces. However, that does not mean that carpet was never historically installed in primary spaces.
The next section of the presentation addresses common rehabilitation issues for reusing these buildings. Specifically, basic treatment approaches to exterior systems, interior finishes and features, hazardous materials, and conversions to housing. One common issue is maintaining the overall visual appearance and visual uniformity of an exterior system, which might require replacing historic materials. For the Executive Office Building, also known as “The Flashcube” in Kansas City, the curtain wall’s reflective glazing is the building’s primary character-defining feature. Previous efforts to replace single pieces of broken glazing fell short of providing a true match to the original glass, resulting in a patchwork of noticeably different shades of blue, pink, and green-tinted glass outlined by the red boxes on the left. When the developer converted the 1970s building to housing, they presented all options in terms of incremental versus full replacement of the glass, and we agreed with their assessment that the visual uniformity created by the glass was the salient characteristic of the building, not the authenticity of the remaining historic glass material. To achieve the visual uniformity, the applicant replaced over 2,300 panes of reflective glass with panels that matched the historic glazing units, as seen on the right.
The organization of a building or its sequence of spaces and circulation patterns is important in conveying the historic context, character, and development. For this reason, corridors in office buildings are almost always primary spaces and should be retained. We should also evaluate the circulation pattern itself in order to determine what makes it distinctive. The identification of distinctive or significant spaces, features, and finishes helps us to establish a continuum of importance. The less distinctive a space, the more change it can accommodate.
The two floor plans on the left illustrate the pre-rehabilitation conditions of two upper floors in the same building. Because this is a spec office building, we can reasonably expect the centralized elevator core with elevators, communal restrooms, stair halls, and mechanical space outlined in red to be the only commonality between these floors. Outside the red box, we expect partition locations and wall, floor, and ceiling finishes to vary at the start of the project since they were intended to be readily adaptable according to a tenant's needs. Thus, there is more flexibility in the spaces outside the core, and they can accommodate more change in the context of rehab, as seen in the floor plan on the right.
In 2024, we issued information on acoustical panel ceiling or APC systems. Like plaster, beadboard, and pressed metal ceilings that came before them, APC systems will often be considered character-defining features that should be retained as part of a rehabilitation project, consistent with Standard 2. When evaluating proposals, there are three questions to ask. First, where is it located; is it a primary versus secondary space? Two, what is its condition, and three how significant or distinctive is the ceiling to the overall space?
In historic primary and circulation spaces where historic acoustical panel ceilings remain, they should be retained. We recognize that it’s not always feasible or practical to retain these features, however, in which case they should be replaced to match, as in this example. It is also important to pay attention to the size of the individual panels, as well as the exposure of grid or splines, and if the panel retains a distinctive design, pattern, orientation, texture, color, and lighting. Distinctive lighting patterns as seen on the left can be common. Sometimes, acoustical panel ceilings can be important to the exterior character of a building, depending on how visible they are from the outside, such as at the Inland Steel Building on the right.
What if the ceiling finish is missing as seen on the left? The same approach for all other building types applies here: there is no requirement to restore the missing feature. This is not a restoration program, after all. If the building exhibited various non-historic ceiling finishes at the start of the project as seen on the right, then the applicant can keep them.
In either of these cases, if the proposal is to install a new ceiling where one is missing, or to replace the extant non-historic ceiling, then a new, compatible ceiling configuration, including flat gypsum, depending on the proposed locations, could be appropriate. Generally, in spaces that historically had an APC system, but that system has been replaced with a non-historic APC system that exists at the beginning of the project, the APC system still contributes to the character and appearance of the building.
In primary spaces, if the non-historic ceiling is to be replaced as part of the rehab project as seen on the left, then the new ceiling should be an acoustical panel ceiling compatible in overall design, material, and appearance with the historic character of the building, its period, and style. In this case, the extant ceiling on the left was not historic, but the historic ceiling type was an APC system. Thus, the owner installed a new APC system that combined solid and illuminated panels with a similar and compatible grid size, and it was installed in a compatible direction as seen on the right.
When there are non-historic APC ceilings in secondary spaces, then there is more flexibility. As stated earlier, if a non-historic feature or finish exists at the start of the project, then the applicant can keep it. But if it’s to be modified, then the new finish or feature simply must be compatible. The images on the screen show the pre-and post-rehab conditions of the upper floors at 55 Public Square in Cleveland. This building was a speculative office building with irregular floor plans outside of a main elevator block and with non-historic APC ceiling finishes on the upper floors at the start of the project as seen on the left.
Because we know there was an APC ceiling in the primary spaces, the applicant replaced the non-historic ceiling with a compatible new APC ceiling as seen in the center. In the secondary spaces, the applicant installed smooth drywall ceilings and hard surface floors on the interior of new residential units, as seen on the right. The same questions asked for ceiling finishes applies to flooring finishes. Where is it located? Is it in a primary or secondary space? What is its condition, and is it distinctive?
I want to emphasize two key concepts. First, historic flooring that is significant or distinctive, in repairable condition, and in primary spaces should be retained and repaired. If it is beyond repair, then the flooring material should be replaced to match the visual characteristics of the historic flooring, including size, shape, design, direction, and where possible, material, per Standard 6. Second, if a non-historic finish is extant, then it can be replaced with a flooring material that is compatible with the character and appearance of the building.
For the Tower Building in Richmond, VA, which was a bank building rehabilitated into housing, the Part 2 indicated the extant tile and carpet were non-historic, and that the historic flooring was originally vinyl tile, which is what was installed, as seen in the photo on the right, though we would have allowed another compatible material. Please remember that for buildings that had a finished character historically and at the start of the project, they should have a finished character at the end of the project. Mitigation of hazardous historic materials contaminated with asbestos or polychlorinated biphenyls or PCBs is a concern regardless of the new use of a property. Both asbestos and PCBs were used in the original construction of the Armstrong Rubber Company Building in New Haven, CT, a brutalist office building designed by Marcel Breuer. Not only was asbestos found in the wall materials, but also PCBs were found in the fluorescent lighting ballasts and the exterior window caulking. The project abated the PCBs when it retrofitted historic fixtures with LEDs, and the exterior window caulking was abated when they replaced the windows. The applicant maintained acoustical tile ceilings, distinctive lighting patterns, and fixtures in public and primary spaces. The applicant also retained and repaired the historic executive office suites and finishes on the top floor and converted the suites into hotel rooms, as seen in the photograph on the right.
Finally, let’s discuss some common issues that might arise when converting post-war office budlings to housing. Specifically, we’ll discuss open air and ventilation needs, the installation of MEP systems, and life-safety or code issues triggered by a change in use. The need for increased ventilation and therefore the need for operable windows is another aspect to consider when converting post-war office buildings to housing. Fenestration patterns are character defining. Because these buildings were often climate controlled, window operation was not necessarily needed. However, when the use changes to housing or hotel, the need for operable windows might arise. When the Harry Weese-designed Mercantile Bank & Trust Building in Missouri was converted from office to housing, the change to residential use required an update to the ventilation system. Because a new fresh-air system was too expensive, the applicant and consultant worked with the SHPO and NPS to find a way to make the inoperable windows operable. The solution was a beefier internal frame that appeared nearly frameless from the exterior, and that opened outward to provide fresh air. The building’s historic tinted glass camouflaged the thickened framing from the outside and maintained the appearance of the exterior facade. Clear Lucite panels were installed on the inside to prevent objects from falling out.
The Charles Luckman-designed Ten Main Center in Missouri is another example of an office to housing conversion that required changes to the windows on the upper floors. In order to achieve the ventilation requirements, the historic single-pane fixed windows were replaced with casement windows and frames that closely matched the historic assemblies, as seen in the drawing on the right. As stated previously, these buildings had historically finished spaces; thus, they should remain finished if there were ceiling, wall, and floor finishes at the beginning of the project. Exposing, removing and eliminating historic ceiling finishes and running exposed ducts and pipes to create an unfinished character is an incompatible treatment, even if a building’s historic ceilings have been replaced previously with non-historic suspended ceilings. Rehabilitated office buildings should have concealed ducts, pipes, and chases.
Designing MEP systems that are properly sized, located, and coordinated becomes more important when you have a lower ceiling height, which was the historic condition in many post-war office buildings. One solution might not work for all spaces, so it might result in a combination of treatments such as soffits and painted sprinkler lines.
In the case of 655 Broadway in Denver, the non-historic APC ceiling seen on the upper left was removed, and the historic ceiling heights restored in the apartments. Units were laid out in a way that allowed for the HVAC ducts to be enclosed in a soffit held well away from the windows. In order to preserve the historic, though still rather low, ceiling height, sprinkler lines and conduit were allowed to be exposed but painted to match the surrounding surface as seen on the right. Another interesting feature of this project was that the new MEP system reused the building’s historic fan coil unit location and venting, as seen in the center.
Sometimes these buildings will have an extant, historic heating and air system, which can come in the form of a fan coil unit or a packaged terminal air conditioner or PTAC unit. As you can see from the photograph on the left, these offices had historic fan coil units located along the windows at the start of the project. NPS did not require them to be kept as part of the rehabilitation as seen in the photo on the right. While fan coil and PTAC units are not required to be retained in secondary interior spaces, the appearance of the unit might be a character-defining feature in a primary space, such as a built-in case in a boardroom or it might be important to retain the appearance of a PTAC unit’s vent on the building exterior if it is considered a distinctive architectural feature.
The Lincoln Plaza Historic District is a collection of hotel and office buildings near the capitol building in Oklahoma City. It was constructed in the 1970s in the New Formalist style. As part of the rehabilitation, the applicant simply replaced PTAC units in the hotel building, which allowed them to keep the appearance of the historic PTAC unit vent on the exterior, as seen at the bottom of the solid panel between the two panes of glass in each bay. The applicant maintained visual characteristics of the rhythm and pattern of vertical and horizontal elements that characterized the hotel building’s exterior.
Which brings us to our final point of discussion for today: Life-safety and other code issues triggered by a change in use, which are common to all rehabilitation projects, and post-war office buildings are no exception. South Tower in Atlanta is a spec office building, and each floor’s ceiling, wall, and floor finishes had been changed over the years, including in the central elevator lobby. However, the one thing that was intact on each floor was the overall configuration of the centralized circulation pattern delineated by the red box and the blue arrows.
Basic code requirements called for a number of divisions for fire separation within the primary circulation and lobby spaces of South Tower, delineated by the pink bubbles.
In consultation with the design team and fire marshal, the number of proposed fire separation divisions were able to be reduced in order to better preserve the character defining features and spaces in this building. As always, we encourage you to have discussions with us as early as possible in the design process if any code requirements are at odds with preserving the historic features, spaces, and materials.
There is a lot of additional information available on our website regarding office building rehabilitations, and using the Preservation by Topic section of the website can help you find it easily. In summary, whether you have a pre-war art deco gem in a commercial main street district, or a post-war, New Formalist complex on the outskirts of town, Post War Office Buildings are generally headquarters or speculative types that are found in all settings. They incorporate a variety of features and materials on the exterior and interior. They have a hierarchy of spaces that may or may not have distinctive wall, flooring, and ceiling finishes. They are approached the same as with the pre-war office building type when applying the Standards. And they present some challenges when being converted to housing. Today’s examples illustrated how the standards are flexible. They can be applied to all styles and types of office buildings taking into consideration the unique facts and circumstances of the property, technical and economic feasibility, and the cumulative effect of the rehabilitation.
A project that is effective at preserving the historic character of a property overall can often absorb the effect of some treatments that would generally not be recommended. The work may have different levels of impact depending on how far any given treatment diverges from what would normally be recommended and how much of the building is affected.
In closing, we understand the challenges that a post-war office building can present, especially when converting them to housing. We support reusing these buildings for new uses, while still preserving the historic exterior and interior character of the building. Thus, we encourage you to use the preliminary consultation process through the SHPOs in situations where there are particularly unique features and finishes or in instances where an unconventional treatment option is being proposed. Thank you.
Description
This webinar focuses on historic post-World War II office buildings and complexes, including the identification of character-defining features and primary and secondary spaces and the treatment of acoustical panel ceilings, windows, curtain walls, and MEP systems.
Duration
30 minutes, 17 seconds
Date Created
04/28/2026
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