1

 14 PRESERVATION

BRIEFS

New Exterior Additions to Historic 

Buildings: Preservation Concerns

Anne E. Grimmer and Kay D. Weeks

A new exterior addition to a historic building should 

be considered in a rehabilitation project only after 

determining that requirements for the new or adaptive 

use cannot be successfully met by altering nonsignificant interior spaces. If the new use cannot be 

accommodated in this way, then an exterior addition 

may be an acceptable alternative. Rehabilitation as a 

treatment “is defined as the act or process of making 

possible a compatible use for a property through repair, 

alterations, and additions while preserving those portions 

or features which convey its historical, cultural, or 

architectural values.”

The topic of new additions, including rooftop additions, 

to historic buildings comes up frequently, especially as it 

National Park Service

U.S. Department of the Interior

Technical Preservation Services

Figure 1. The addition to the right with its connecting hyphen is compatible with the 

Collegiate Gothic-style library. The addition is set back from the front of the library and 

uses the same materials and a simplified design that references, but does not copy, the 

historic building. Photo: David Wakely Photography.

relates to rehabilitation projects. It is often discussed and 

it is the subject of concern, consternation, considerable 

disagreement and confusion. Can, in certain instances, 

a historic building be enlarged for a new use without 

destroying its historic character? And, just what is 

significant about each particular historic building 

that should be preserved? Finally, what kind of new 

construction is appropriate to the historic building?

The vast amount of literature on the subject of additions 

to historic buildings reflects widespread interest as well 

as divergence of opinion. New additions have been 

discussed by historians within a social and political 

framework; by architects and architectural historians 

in terms of construction technology and style; and 

by urban planners as successful or 

unsuccessful contextual design. However, 

within the historic preservation and 

rehabilitation programs of the National 

Park Service, the focus on new additions 

is to ensure that they preserve the 

character of historic buildings. 

Most historic districts or neighborhoods 

are listed in the National Register of 

Historic Places for their significance within 

a particular time frame. This period of 

significance of historic districts as well 

as individually-listed properties may 

sometimes lead to a misunderstanding 

that inclusion in the National Register may 

prohibit any physical change outside of a 

certain historical period—particularly in 

the form of exterior additions. National 

Register listing does not mean that a 

building or district is frozen in time and 

that no change can be made without 

compromising the historical significance. 

It does mean, however, that a new 

addition to a historic building should 

preserve its historic character. 
2

Guidance on New Additions

To meet Standard 1 of the Secretary of the Interior’s 

Standards for Rehabilitation, which states that “a 

property shall be used for its historic purpose or be 

placed in a new use that requires minimal change to 

the defining characteristics of the building and its site 

and environment,” it must be determined whether a 

historic building can accommodate a new addition. 

Before expanding the building’s footprint, consideration 

should first be given to incorporating changes—such as 

code upgrades or spatial needs for a new use—within 

secondary areas of the historic building. However, this 

is not always possible and, after such an evaluation, 

the conclusion may be that an addition is required, 

particularly if it is needed to avoid modifications to 

character-defining interior spaces. An addition should 

be designed to be compatible with the historic character 

of the building and, thus, meet the Standards for 

Rehabilitation. Standards 9 and 10 apply specifically to 

new additions:

(9) “New additions, exterior alterations, or related 

new construction shall not destroy historic 

materials that characterize the property. The new 

work shall be differentiated from the old and 

shall be compatible with the massing, size, scale, 

and architectural features to protect the historic 

integrity of the property and its environment.” 

(10) “New additions and adjacent or related new 

construction shall be undertaken in such a manner 

that if removed in the future, the essential form 

and integrity of the historic property and its 

environment would be unimpaired.”

The subject of new additions is important because a 

new addition to a historic building has the potential to 

change its historic character as well as to damage and 

destroy significant historic materials and features. A new 

addition also has the potential to confuse the public and 

to make it difficult or impossible to differentiate the old 

from the new or to recognize what part of the historic 

building is genuinely historic. 

The intent of this Preservation Brief is to provide 

guidance to owners, architects and developers on 

how to design a compatible new addition, including a 

rooftop addition, to a historic building. A new addition 

to a historic building should preserve the building’s 

historic character. To accomplish this and meet the 

Secretary of the Interior’s Standards for Rehabilitation, a 

new addition should:

• Preserve significant historic materials, 

features and form;

• Be compatible; and 

• Be differentiated from the historic building. 

Every historic building is different and each 

rehabilitation project is unique. Therefore, the guidance 

offered here is not specific, but general, so that it can 

be applied to a wide variety of building types and 

situations. To assist in interpreting this guidance, 

illustrations of a variety of new additions are provided. 

Good examples, as well as some that do not meet the 

Standards, are included to further help explain and 

clarify what is a compatible new addition that preserves 

the character of the historic building. 

Figure 2. The new section on the right is appropriately scaled and 

reflects the design of the historic Art Deco-style hotel. The apparent 

separation created by the recessed connector also enables the addition 

to be viewed as an individual building.

Figure 3. The red and buff-colored parking addition with a rooftop 

playground is compatible with the early-20th century school as 

well as with the neighborhood in which it also serves as infill in the 

urban setting.
3

Preserve Significant Historic 

Materials, Features and Form

Attaching a new exterior addition usually 

involves some degree of material loss to 

an external wall of a historic building, 

but it should be minimized. Damaging 

or destroying significant materials and 

craftsmanship should be avoided, as 

much as possible. 

Generally speaking, preservation of 

historic buildings inherently implies 

minimal change to primary or “public” 

elevations and, of course, interior 

features as well. Exterior features that 

distinguish one historic building or 

a row of buildings and which can be 

seen from a public right of way, such 

as a street or sidewalk, are most likely 

to be the most significant. These can 

include many different elements, such 

as: window patterns, window hoods 

or shutters; porticoes, entrances and 

doorways; roof shapes, cornices and 

decorative moldings; or commercial 

storefronts with their special detailing, 

signs and glazing patterns. Beyond a 

single building, entire blocks of urban 

or residential structures are often closely 

related architecturally by their materials, 

detailing, form and alignment. Because 

significant materials and features should 

be preserved, not damaged or hidden, 

the first place to consider placing a 

new addition is in a location where 

the least amount of historic material 

and character-defining features will 

be lost. In most cases, this will be on a 

secondary side or rear elevation. 

One way to reduce overall material 

loss when constructing a new addition 

is simply to keep the addition smaller 

in proportion to the size of the historic 

building. Limiting the size and number of openings 

between old and new by utilizing existing doors or 

enlarging windows also helps to minimize loss. An 

often successful way to accomplish this is to link the 

addition to the historic building by means of a hyphen 

or connector. A connector provides a physical link 

while visually separating the old and new, and the 

connecting passageway penetrates and removes only a 

small portion of the historic wall. A new addition that 

will abut the historic building along an entire elevation 

or wrap around a side and rear elevation, will likely 

integrate the historic and the new interiors, and thus 

result in a high degree of loss of form and exterior walls, 

as well as significant alteration of interior spaces and 

features, and will not meet the Standards.

Compatible but Differentiated Design

In accordance with the Standards, a new addition must 

preserve the building’s historic character and, in order 

to do that, it must be differentiated, but compatible, 

with the historic building. A new addition must retain 

the essential form and integrity of the historic property. 

Keeping the addition smaller, limiting the removal 

of historic materials by linking the addition with a 

hyphen, and locating the new addition at the rear or on 

an inconspicuous side elevation of a historic building 

are techniques discussed previously that can help to 

accomplish this. 

Rather than differentiating between old and new, it 

might seem more in keeping with the historic character 

Figure 4. This glass and brick structure is a harmonious addition set back and connected 

to the rear of the Colonial Revival-style brick house. Cunningham/Quill Architects. 

Photos: © Maxwell MacKenzie.
4

simply to repeat the historic form, material, features and 

detailing in a new addition. However, when the new 

work is highly replicative and indistinguishable from 

the old in appearance, it may no longer be possible to 

identify the “real” historic building. Conversely, the 

treatment of the addition should not be so different that 

it becomes the primary focus. The difference may be 

subtle, but it must be clear. A new addition to a historic 

building should protect those visual qualities that make 

the building eligible for listing in the National Register 

of Historic Places. 

The National Park Service policy concerning new 

additions to historic buildings, which was adopted in 

1967, is not unique. It is an outgrowth and continuation 

of a general philosophical approach to change first 

expressed by John Ruskin in England in the 1850s, 

formalized by William Morris in the founding of the 

Society for the Protection of Ancient Buildings in 

1877, expanded by the Society in 1924 and, finally, 

reiterated in the 1964 Venice Charter—a document that 

continues to be followed by the national committees 

of the International Council on Monuments and 

Sites (ICOMOS). The 1967 Administrative Policies for 

Historical Areas of the National Park System direct that 

“...a modern addition should be readily distinguishable 

from the older work; however, the new work should be 

harmonious with the old in scale, proportion, materials, 

and color. Such additions should be as inconspicuous as 

possible from the public view.” As a logical evolution 

from these Policies specifically for National Park 

Service-owned historic structures, the 1977 Secretary 

of the Interior’s Standards for Rehabilitation, which may 

be applied to all historic buildings listed in, or eligible 

for listing in the National Register, also state that “the 

new work shall be differentiated from the old and 

shall be compatible with the massing, size, scale, and 

architectural features to protect the historic integrity of 

the property and its environment.”

Preserve Historic Character 

The goal, of course, is a new addition that preserves the 

building’s historic character. The historic character of 

each building may be different, but the methodology of 

establishing it remains the same. Knowing the uses and 

functions a building has served over time will assist in 

making what is essentially a physical evaluation. But, 

while written and pictorial documentation can provide 

a framework for establishing the building's history, 

to a large extent the historic character is embodied in 

the physical aspects of the historic building itself—

shape, materials, features, craftsmanship, window 

arrangements, colors, setting and interiors. Thus, it 

is important to identify the historic character before 

making decisions about the extent—or limitations—of 

change that can be made. 

Figure 5. This addition (a) is constructed of matching brick 

and attached by a recessed connector (b) to the 1914 apartment 

building (c). The design is compatible and the addition is 

smaller and subordinate to the historic building (d).

b c

a

d
5

Figure 6. A new addition (left) is connected to the garage which separates it from the main block of the c. 1910 former florist shop (right). The 

addition is traditional in style, yet sufficiently restrained in design to distinguish it from the historic building. 

A new addition should always be subordinate to the 

historic building; it should not compete in size, scale 

or design with the historic building. An addition that 

bears no relationship to the proportions and massing 

of the historic building—in other words, one that 

overpowers the historic form and changes the scale—

will usually compromise the historic character as 

well. The appropriate size for a new addition varies 

from building to building; it could never be stated 

in a square or cubic footage ratio, but the historic 

building's existing proportions, site and setting can 

help set some general parameters for enlargement. 

Although even a small addition that is poorly 

designed can have an adverse impact, to some extent, 

there is a predictable relationship between the size of 

the historic resource and what is an appropriate size 

for a compatible new addition. 

Generally, constructing the new 

addition on a secondary side or rear 

elevation—in addition to material 

preservation—will also preserve the 

historic character. Not only will the 

addition be less visible, but because 

a secondary elevation is usually 

simpler and less distinctive, the 

addition will have less of a physical 

and visual impact on the historic 

building. Such placement will help to 

preserve the building's historic form 

and relationship to its site and setting.

Historic landscape features, including 

distinctive grade variations, also 

need to be respected. Any new 

landscape features, including plants 

and trees, should be kept at a scale 

and density that will not interfere with 

understanding of the historic resource 

itself. A traditionally landscaped 

property should not be covered with large paved 

areas for parking which would drastically change the 

character of the site.

Despite the fact that in most cases it is recommended 

that the new addition be attached to a secondary 

elevation, sometimes this is not possible. There simply 

may not be a secondary elevation—some important 

freestanding buildings have significant materials and 

features on all sides. A structure or group of structures 

together with its setting (for example, a college campus) 

may be of such significance that any new addition 

would not only damage materials, but alter the 

buildings' relationship to each other and the setting. 

An addition attached to a highly-visible elevation of a 

historic building can radically alter the historic form 

or obscure features such as a decorative cornice or 

window ornamentation. Similarly, an addition that fills 

Figure 7. A vacant side lot was the only place a new stair tower could be built when this 

1903 theater was rehabilitated as a performing arts center. Constructed with matching 

materials, the stair tower is set back with a recessed connector and, despite its prominent 

location, it is clearly subordinate and differentiated from the historic theater. 
6

in a planned void on a highly-visible elevation 

(such as a U-shaped plan or a feature such as a 

porch) will also alter the historic form and, as a 

result, change the historic character. Under these 

circumstances, an addition would have too much 

of a negative impact on the historic building and 

it would not meet the Standards. Such situations 

may best be handled by constructing a separate 

building in a location where it will not adversely 

affect the historic structure and its setting. 

In other instances, particularly in urban areas, 

there may be no other place but adjacent to the 

primary façade to locate an addition needed for 

the new use. It may be possible to design a lateral 

addition attached on the side that is compatible 

with the historic building, even though it is a 

highly-visible new element. Certain types of 

historic structures, such as government buildings, 

metropolitan museums, churches or libraries, 

may be so massive in size that a relatively largescale addition may not compromise the historic 

character, provided, of course, the addition is 

smaller than the historic building. Occasionally, 

the visible size of an addition can be reduced by 

placing some of the spaces or support systems in 

a part of the structure that is underground. Large 

new additions may sometimes be successful if 

they read as a separate volume, rather than as an 

extension of the historic structure, although the 

scale, massing and proportions of the addition 

still need to be compatible with the historic 

building. However, similar expansion of smaller 

buildings would be dramatically out of scale. In 

summary, where any new addition is proposed, 

correctly assessing the relationship between 

actual size and relative scale will be a key to 

preserving the character of the historic building.

Figure 8. The rehabilitation of this large, early-20th century warehouse (left) into affordable artists’ lofts included the addition of a compatible glass 

and brick elevator/stair tower at the back (right). 

Figure 9. A simple, brick stair tower replaced two non-historic additions 

at the rear of this 1879 school building when it was rehabilitated as a 

women's and children's shelter. The addition is set back and it is not visible 

from the front of the school. 

Figure 10. The small size and the use of matching materials ensures that 

the new addition on the left is compatible with the historic Romanesque 

Revival-style building. 
7

Design Guidance for Compatible 

New Additions to Historic Buildings

There is no formula or prescription for 

designing a new addition that meets the 

Standards. A new addition to a historic 

building that meets the Standards can be any 

architectural style—traditional, contemporary 

or a simplified version of the historic 

building. However, there must be a balance 

between differentiation and compatibility in 

order to maintain the historic character and 

the identity of the building being enlarged. 

New additions that too closely resemble the 

historic building or are in extreme contrast to 

it fall short of this balance. Inherent in all of the 

guidance is the concept that an addition needs to 

be subordinate to the historic building.

A new addition must preserve significant 

historic materials, features and form, and it 

must be compatible but differentiated from 

the historic building. To achieve this, it is 

necessary to carefully consider the placement 

or location of the new addition, and its size, 

scale and massing when planning a new 

addition. To preserve a property’s historic 

character, a new addition must be visually 

distinguishable from the historic building. 

This does not mean that the addition and the 

historic building should be glaringly different 

in terms of design, materials and other visual 

qualities. Instead, the new addition should 

take its design cues from, but not copy, the 

historic building.

Figure 11. The addition to this early-20th 

century Gothic Revival-style church provides 

space for offices, a great hall for gatherings 

and an accessible entrance (left). The stucco 

finish, metal roof, narrow gables and the 

Gothic-arched entrance complement the 

architecture of the historic church. Placing the 

addition in back where the ground slopes away 

ensures that it is subordinate and minimizes 

its impact on the church (below). 

A variety of design techniques can be effective ways to 

differentiate the new construction from the old, while 

respecting the architectural qualities and vocabulary of the 

historic building, including the following:

• Incorporate a simple, recessed, small-scale hyphen 

to physically separate the old and the new volumes 

or set the addition back from the wall plane(s) of the 

historic building.

• Avoid designs that unify the two volumes into 

a single architectural whole. The new addition 

may include simplified architectural features that 

reflect, but do not duplicate, similar features on the 

historic building. This approach will not impair 

the existing building’s historic character as long 

as the new structure is subordinate in size and 

clearly differentiated and distinguishable so that the 

identity of the historic structure is not lost in a new 

and larger composition. The historic building must 

be clearly identifiable and its physical integrity must 

not be compromised by the new addition.
8

• Use building materials in the same color range 

or value as those of the historic building. 

The materials need not be the same as those 

on the historic building, but they should be 

harmonious; they should not be so different 

that they stand out or distract from the 

historic building. (Even clear glass can be 

as prominent as a less transparent material. 

Generally, glass may be most appropriate for 

small-scale additions, such as an entrance on a 

secondary elevation or a connector between an 

addition and the historic building.)

• Base the size, rhythm and alignment of the 

new addition’s window and door openings on 

those of the historic building. 

• Respect the architectural expression of the 

historic building type. For example, an 

addition to an institutional building should 

maintain the architectural character associated 

with this building type rather than using 

details and elements typical of residential or 

other building types. 

These techniques are merely examples of ways to 

differentiate a new addition from the historic building 

while ensuring that the addition is compatible with 

it. Other ways of differentiating a new addition from 

the historic building may be used as long as they 

maintain the primacy of the historic building. Working 

within these basic principles still allows for a broad 

range of architectural expression that can range from 

stylistic similarity to contemporary distinction. The 

recommended design approach for an addition is one 

that neither copies the historic building exactly nor 

stands in stark contrast to it. 

Figure 12. This 1954 synagogue (left) is accessed through a monumental entrance to the right. The new education wing (far right) added to it features 

the same vertical elements and color and, even though it is quite large, its smaller scale and height ensure that it is secondary to the historic resource. 

Figure 13. A glass and metal structure was constructed in the 

courtyard as a restaurant when this 1839 building was converted 

to a hotel. Although such an addition might not be appropriate in 

a more public location, it is compatible here in the courtyard of this 

historic building. 

Figure 14. This glass addition was erected at the back of an 1895 

former brewery during rehabilitation to provide another entrance. 

The addition is compatible with the plain character of this 

secondary elevation. 
9

Revising an Incompatible Design for a New Addition to Meet the Standards

Figure 15. The rehabilitation of a c. 1930 high school auditorium for a clinic and offices proposed two additions: a one-story entrance and 

reception area on this elevation (a); and a four-story elevator and stair tower on another side (b). The gabled entrance (c) first proposed was not 

compatible with the flat-roofed auditorium and the design of the proposed stair tower (d) was also incompatible and overwhelmed the historic 

building. The designs were revised (e-f) resulting in new additions that meet the Standards (g-h).

a b

c d

e f

g h
10

Incompatible New Additions to Historic Buildings

Figure 18. The expansion 

of a one- and one-half story 

historic bungalow (left) 

with a large two-story rear 

addition (right) has greatly 

altered and obscured its 

distinctive shape and form. 

Figure 17. The small addition on the left is 

starkly different and it is not compatible with 

the eclectic, late-19th century house. Figure 16. The proposal to add three row houses to the rear ell of this early-19th century 

residential property doubles its size and does not meet the Standards.. 

Figure 19. The upper two floors of this early-20th century 

office building were part of the original design, but were 

not built. During rehabilitation, the two stories were finally 

constructed. This treatment does not meet the Standards 

because the addition has given the building an appearance it 

never had historically. 

Figure 20. The height, as 

well as the design, of these 

two-story rooftop additions 

overwhelms the two-story 

and the one-story, low-rise 

historic buildings. 

New Addition

New Addition
11

New Additions in Densely-Built 

Environments

In built-up urban areas, locating a new 

addition on a less visible side or rear 

elevation may not be possible simply 

because there is no available space. In this 

instance, there may be alternative ways to 

help preserve the historic character. One 

approach when connecting a new addition 

to a historic building on a primary elevation 

is to use a hyphen to separate them. A 

subtle variation in material, detailing 

and color may also provide the degree of 

differentiation necessary to avoid changing 

the essential proportions and character of 

the historic building. 

A densely-built neighborhood such as 

a downtown commercial core offers a 

particular opportunity to design an addition 

that will have a minimal impact on the 

historic building. Often the site for such 

an addition is a vacant lot where another 

building formerly stood. Treating the 

addition as a separate or infill building 

may be the best approach when designing 

an addition that will have the least impact 

on the historic building and the district. In 

these instances there may be no need for a 

direct visual link to the historic building. 

Height and setback from the street should 

generally be consistent with those of the 

historic building and other surrounding 

buildings in the district. Thus, in most 

urban commercial areas the addition 

should not be set back from the façade of 

the historic building. A tight urban setting 

may sometimes even accommodate a larger 

addition if the primary elevation is designed 

to give the appearance of being several 

buildings by breaking up the facade into 

elements that are consistent with the scale of 

the historic building and adjacent buildings. 

Figure 21. Both wings of this historic L-shaped building (top), which 

fronts on two city streets, adjoined vacant lots. A two-story addition was 

constructed on one lot (above, left) and a six-story addition was built on 

the other (above, right). Like the historic building, which has two different 

facades, the compatible new additions are also different and appear to be 

separate structures rather than part of the historic building. 

Figure 22. The proposed new addition is compatible with the historic buildings that remain on the block. 

Its design with multiple storefronts helps break up the mass. 

New Addition
12

Rooftop Additions

The guidance provided on designing a compatible new 

addition to a historic building applies equally to new 

rooftop additions. A rooftop addition should preserve 

the character of a historic building by preserving historic 

materials, features and form; and it should be compatible 

but differentiated from the historic building.

However, there are several other design principles that 

apply specifically to rooftop additions. Generally, a 

rooftop addition should not be more than one story in 

height to minimize its visibility and its impact on the 

proportion and profile of the historic building. A rooftop 

addition should almost always be set back at least one full 

bay from the primary elevation of the building, as well as 

from the other elevations if the building is free-standing or 

highly visible.

It is difficult, if not impossible, to minimize the impact 

of adding an entire new floor to relatively low buildings, 

such as small-scale residential or commercial structures, 

even if the new addition is set back from the plane of 

the façade. Constructing another floor on top of a small, 

one, two or three-story building is seldom appropriate 

for buildings of this size as it would measurably alter 

the building’s proportions and profile, and negatively 

impact its historic character. On the other hand, a rooftop 

addition on an eight-story building, for example, in a 

historic district consisting primarily of tall buildings 

might not affect the historic character because the new 

construction may blend in with the surrounding buildings 

and be only minimally visible within the district. A 

rooftop addition in a densely-built urban area is more 

likely to be compatible on a building that is adjacent to 

similarly-sized or taller buildings.

A number of methods may be used to help evaluate the 

effect of a proposed rooftop addition on a historic building 

and district, including pedestrian sight lines, threedimensional schematics and computer-generated design. 

However, drawings generally do not provide a true 

“picture” of the appearance and visibility of a proposed 

rooftop addition. For this reason, it is often necessary to 

construct a rough, temporary, full-size or skeletal mock up 

of a portion of the proposed addition, which can then be 

photographed and evaluated from critical vantage points 

on surrounding streets. 

Figure 23. Colored flags marking the location of a proposed penthouse 

addition (a) were placed on the roof to help evaluate the impact and 

visibility of an addition planned for this historic furniture store (b). 

Based on this evaluation, the addition was constructed as proposed. 

It is minimally visible and compatible with the 1912 structure (c). 

The tall parapet wall conceals the addition from the street below (d). 

a

b

c

d
13

Figure 24. How to Evaluate a Proposed Rooftop Addition.

A sight-line study (above) only factors in views from directly across the 

street, which can be very restrictive and does not illustrate the full effect 

of an addition from other public rights of way. A mock up (above, right) 

or a mock up enhanced by a computer-generated rendering (below, 

right) is essential to evaluate the impact of a proposed rooftop addition 

on the historic building. 

Figure 25. It was possible to add a compatible, three-story, 

penthouse addition to the roof of this five-story, historic bank 

building because the addition is set far back, it is surrounded 

by taller buildings and a deep parapet conceals almost all of the 

addition from below. 

Figure 26. A rooftop addition 

would have negatively 

impacted the character of the 

primary facade (right) of this 

mid-19th century, four-story 

structure and the low-rise 

historic district. However, a 

third floor was successfully 

added on the two-story rear 

portion (below) of the same 

building with little impact to 

the building or the district 

because it blends in with the 

height of the adjacent building. 
14

This guidance should be applied to help in designing 

a compatible new addition that that will meet the 

Secretary of the Interior’s Standards for Rehabilitation:

• A new addition should be simple and 

unobtrusive in design, and should be 

distinguished from the historic building—a 

recessed connector can help to differentiate the 

new from the old.

• A new addition should not be highly visible from 

the public right of way; a rear or other secondary 

elevation is usually the best location for a new 

addition.

• The construction materials and the color of the 

new addition should be harmonious with the 

historic building materials. 

• The new addition should be smaller than the 

historic building—it should be subordinate in 

both size and design to the historic building.

The same guidance should be applied when 

designing a compatible rooftop addition, plus 

the following:

• A rooftop addition is generally not appropriate 

for a one, two or three-story building—and 

often is not appropriate for taller buildings.

• A rooftop addition should be minimally visible.

• Generally, a rooftop addition must be set back 

at least one full bay from the primary elevation 

of the building, as well as from the other 

elevations if the building is freestanding or 

highly visible.

• Generally, a rooftop addition should not be 

more than one story in height.

• Generally, a rooftop addition is more likely to 

be compatible on a building that is adjacent to 

similarly-sized or taller buildings.

Designing a New Exterior Addition to a Historic Building

Figure 27. Although the new brick stair/elevator tower (left) is not visible from the front (right), it is on a prominent side elevation of this 1890 stone 

bank. The compatible addition is set back and does not compete with the historic building. Photos: Chadd Gossmann, Aurora Photography, LLC.

Figure 28. A small addition 

(left) was constructed when 

this 1880s train station was 

converted for office use. The 

paired doors with transoms 

and arched windows on the 

compatible addition reflect, but 

do not replicate, the historic 

building (right). 
15

Summary

Because a new exterior addition to a historic building can damage or destroy significant materials and can change the 

building's character, an addition should be considered only after it has been determined that the new use cannot be 

met by altering non-significant, or secondary, interior spaces. If the new use cannot be met in this way, then an attached 

addition may be an acceptable alternative if carefully planned and designed. A new addition to a historic building should 

be constructed in a manner that preserves significant materials, features and form, and preserves the building’s historic 

character. Finally, an addition should be differentiated from the historic building so that the new work is compatible 

with—and does not detract from—the historic building, and cannot itself be confused as historic.

Additional Reading

Byard, Paul Spencer. The Architecture of New Additions: Design 

and Regulation. New York, NY: W.W. Norton & Company, 1998.

Day, Steven, AIA. “Modernism Meets History: New 

Additions to Historic Structures.” Preservation Seattle [Historic 

Seattle’s online monthly preservation magazine.] May 2003. 

www.historicseattle.org/preservationseattle/publicpolicy/

defaultmay2.htm.

Incentives! A Guide to the Federal Historic Preservation Tax 

Incentives Program for Income-Producing Properties. “Avoiding 

Incompatible Treatments: New Additions & Rooftop 

Additions.” Technical Preservation Services Branch, National 

Park Service. Online at www.nps.gov/history/hps/tps/.

Interpreting the Standards Bulletins (ITS). Technical Preservation 

Services Branch, National Park Service. Online at 

www.nps.gov/history/hps/tps/.

New Additions to Historic Buildings. Technical Preservation 

Services Branch, National Park Service. Online at www.nps.

gov/history/hps/tps/.

O’Connell, Kim A. “Making Connections.” Traditional Building. 

March/April 2004. (Vol. 17, No. 2), pp. 12-15. 

The Secretary of the Interior's Standards for Rehabilitation and 

Guidelines for Rehabilitating Historic Buildings. Washington, 

D.C.: U.S. Department of the Interior, National Park Service, 

Preservation Assistance Division, rev. 1990. 

The Secretary of the Interior's Standards for Rehabilitation & 

Illustrated Guidelines for Rehabilitating Historic Buildings. 

(Authors: W. Brown Morton, III, Gary L. Hume, Kay D. Weeks, 

and H. Ward Jandl. Project Directors: Anne E. Grimmer 

and Kay D. Weeks.) Washington, D.C.: U.S. Department of 

the Interior, National Park Service, Preservation Assistance 

Division, 1992. Online at www.nps.gov/history/hps/tps/.

Semes, Steven W. “Differentiated and Compatible: The 

Secretary’s Standards revisited.” Traditional Building. February 

2009. (Vol. 22, No. 1), pp. 20-23.

Semes, Steven W. The Future of the Past: A Conservation Ethic for 

Architecture, Urbanism, and Historic Preservation. (In association 

with The Institute of Classical Architecture and Classical 

America.) New York, NY: W.W. Norton & Company, 2009.

Figure 29. This simple 

glass and brick entrance 

(left) added to a secondary 

elevation of a 1920s 

school building (right) 

is compatible with the 

original structure. 

Figure 30. The small addition on the right of this late-19th century 

commercial structure is clearly secondary and compatible in size, 

materials and design with the historic building. 
16

Acknowledgements

Anne E. Grimmer, Senior Architectural Historian, Technical Preservation Services Branch, National Park Service, 

revised Preservation Brief 14, written by Kay D. Weeks and first published in 1986. The revised Brief features all new 

illustrations and contains expanded and updated design guidance on the subject of new additions that has been 

developed by the Technical Preservation Services Branch since the original publication of the Brief. Several individuals 

generously contributed their time and expertise to review the revision of this Preservation Brief, including: Sharon 

C. Park, FAIA, Chief, Architectural History and Historic Preservation, Smithsonian Institution; Elizabeth Tune and 

Karen Brandt, Department of Historic Resources, Commonwealth of Virginia; and Phillip Wisley and David Ferro, 

Division of Historical Resources, Florida Department of State. The Technical Preservation Services professional staff, in 

particular Michael J. Auer, Jo Ellen Hensley, Gary Sachau and Rebecca Shiffer, also provided important guidance in the 

development of this publication. All illustrations are from National Park Service files unless otherwise credited. Front 

cover image: Detail of new addition shown in Figure 4. Photo: © Maxwell MacKenzie.

This publication has been prepared pursuant to the National Historic Preservation Act of 1966, as amended, which 

directs the Secretary of the Interior to develop and make available information concerning historic properties. The 

Technical Preservation Services Branch, National Park Service, prepares standards, guidelines and other educational 

materials on responsible historic preservation treatments for a broad public audience. Additional information 

about the programs of Technical Preservation Services is available on the website at www.nps.gov/history/hps/tps. 

Comments about this publication should be addressed to: Charles E. Fisher, Technical Preservation Publications 

Program Manager, Technical Preservation Services-2255, National Park Service, 1849 C Street, NW, Washington, DC 

20240. This publication is not copyrighted and can be reproduced without penalty. Normal procedures for credit to the 

author and the National Park Service are appreciated.

ISBN: 978-0-16-085869-7

U.S. Government Printing Office Stock Number: 024-005-01280-0 August 2010

Figure 31. An elevator/stair tower 

was added at the back of this 

Richardsonian Romanesque-style 

theater when it was rehabilitated. 

Rough-cut stone and simple 

cut-out openings ensure that 

the addition is compatible and 

subordinate to the historic building. 

Photo: Chuck Liddy, AIA. 
17

 roF ueht yb elas netnirep tned oG .S.U ,stnemucoD fo nrev eciffO gnitnirP tnem

ohP vog.opg.erotskoob :tenretnI 68( eerf llot :en 15 )6 aera CD ;0081-2 02( 15 )2 0081-2

02( :xaF 15 )2 4012-2 potS :liaM notgnihsaW ,CCDI 0402 CD , 1000-2

 S

ISBN 978-0-16-085869-7

I S B N 978-0-16-085869-7

9 7 8 0 1 6 0 8 5 8 6 9 7

9 0 0 0 0

 August 2010

Acknowledgements

Anne E. Grimmer, Senior Architectural Historian, Technical Preservation Services Branch, National Park Service, 

revised Preservation Brief 14, written by Kay D. Weeks and first published in 1986. The revised Brief features all new 

illustrations and contains expanded and updated design guidance on the subject of new additions that has been 

developed by the Technical Preservation Services Branch since the original publication of the Brief. Several individuals 

generously contributed their time and expertise to review the revision of this Preservation Brief, including: Sharon 

C. Park, FAIA, Chief, Architectural History and Historic Preservation, Smithsonian Institution; Elizabeth Tune and 

Karen Brandt, Department of Historic Resources, Commonwealth of Virginia; and Phillip Wisley and David Ferro, 

Division of Historical Resources, Florida Department of State. The Technical Preservation Services professional staff, in 

particular Michael J. Auer, Jo Ellen Hensley, Gary Sachau and Rebecca Shiffer, also provided important guidance in the 

development of this publication. All illustrations are from National Park Service files unless otherwise credited. Front 

cover image: Detail of new addition shown in Figure 4. Photo: © Maxwell MacKenzie.

This publication has been prepared pursuant to the National Historic Preservation Act of 1966, as amended, which 

directs the Secretary of the Interior to develop and make available information concerning historic properties. The 

Technical Preservation Services Branch, National Park Service, prepares standards, guidelines and other educational 

materials on responsible historic preservation treatments for a broad public audience. Additional information 

about the programs of Technical Preservation Services is available on the website at www.nps.gov/history/hps/tps. 

Comments about this publication should be addressed to: Charles E. Fisher, Technical Preservation Publications 

Program Manager, Technical Preservation Services-2255, National Park Service, 1849 C Street, NW, Washington, DC 

20240. This publication is not copyrighted and can be reproduced without penalty. Normal procedures for credit to the 

author and the National Park Service are appreciated.

Figure 31. An elevator/stair tower 

was added at the back of this 

Richardsonian Romanesque-style 

theater when it was rehabilitated. 

Rough-cut stone and simple 

cut-out openings ensure that 

the addition is compatible and 

subordinate to the historic building. 

Photo: Chuck Liddy, AIA.