Additions

Placement

9.1    Addition should be placed where they are minimally visible from the public right-of-way and generally are not appropriate on the fronts of buildings.

9.2    Where possible, functions and services required for new uses (such as elevators and stairways) should be placed internally. If not feasible, they should be on secondary and non-character defining elevations, limited in size and scale in relationship to the historic building.

Design

9.3   The addition should result in the least possible loss of original materials and avoid obscuring, damaging, or destroying character defining features.

9.4    The addition should be subordinate and secondary to the historic building and compatible in massing, scale, materials, relationship of solids to voids, and color.

a. Additions should be smaller than the original building to avoid overwhelming the historic character.

b. Duplication of the exact form, material, style and detailing of the historic building in the addition would create a false sense of history.

c. The use of a hyphen or link can accomplish differentiating new and old while preserving the historic wall.

9.5    Materials used for the addition should be similar in scale, color, texture, and finish to the original materials on the structure or in the area.

a. Building materials in the same color range or value as those of the historic building should be used.

b. Glass may be appropriate for small-scale additions, such as an entrance on a secondary elevation or a connection between an addition and the historic building.

c. Standard brick sizes should be used. Thin brick veneer is not allowed. In commercial or industrial districts, standard brick embedded into precast panels may be used.

d. Stone, cast stone, and masonry materials that replicate the look found in the district are allowed.

e. Stucco should be cementitious and a minimum 7/8 inch thick. EIFS is not an allowable alternative. Fiber cement panels may be used on secondary facades but is not recommended on primary facades.

f. Architectural metals should not be used on residential buildings in locations visible from the public right-of-way but may be used when designed with a matte finish in commercial or industrial districts.

g. Wood siding, shingles, and shakes should be installed with orientations and reveals (exposed widths) that are similar to what is found in the district or on the original portion of the building.

h. New materials that have characteristics similar to historic materials may be approved when they have a similar size, shape, and texture.

i. The number of materials on the addition should be limited to one or two, depending on the scale of the addition.

9.6    Base the alignment, rhythm, and size of the window and door openings of the new addition on those of the historic building.

a. Window and door materials should be similar to the historic building. For example, wood, aluminum clad wood, and fiberglass are appropriate window materials for residential additions.

b. Windows should have either true divided lights or simulated divided lights with a spacer bar, not muntins between glass panes.

c. Glass should be clear or near clear low-e glazing with frosted glass allowed on secondary elevations or bathrooms.

d. Doors should be a more simplified design, not replicating the exact design of the historic structure entrance.

9.7    Retain the appearance and orientation of the original primary entrance.

9.8    Distinguish the old and new portions of the building so the new construction blends with the old, but doesn’t create an exact replica or creates a false sense of history.

a. Incorporating a simple, recessed, small-scale hyphen, or connection, to separate the addition physically and visually from the historic building helps to distinguish new from old.

b. Setting the addition back from the wall plane of the historic building by at least four inches is another approach.

9.9    The addition stylistically should fit the building type (ex: residential, commercial, etc.) using a simplified version of the architecture style of the original or a compatible, contemporary style.

9.10    In addition to the relationship with the historic building, the design should reflect its location in the historic district, neighborhood, and setting.

a. Porch eaves, roof lines, overall height, and other features should relate and align with adjacent structures when possible.

9.11    The roof configuration of the addition should be compatible with the original structure including the pitch, orientation, and complexity.

a. Roof materials should be compatible with the historic structure roof materials in terms of visual impact, texture, and architectural style compatibility.

Rooftop Additions

9.12    When necessary, rooftop additions should be set back at least one full bay, but no less than a distance equal to the proposed height of the addition, from street adjacent elevations.

9.13    Additions should only be one story in height to minimize its visibility and impact on the historic character of the building. The height should be inconspicuous when viewed from surrounding streets.

a. Care should be given to the design of the addition on low-rise, one to three story building to ensure it does not overwhelm the building and negatively impact the district.

9.14    Historic features should not be obscured or removed when adding a rooftop addition.

9.15    Rooftop additions with amenities (such as a raised pool deck with plantings, HVAC equipment, or screening) should be set back and designed in a manner to avoid impacting the historic character of the building.

9.16    When feasible, mockups should be erected on the roof to demonstrate the visibility of the addition as viewed from the surrounding streets. At a minimum, a diagram or rendering showing the building addition site line impact shall be submitted.

a. Generally, rooftop additions to small residential homes should be limited to dormer additions and not the addition of a full story (see Rooftop Alterations for guidance on dormer additions). In limited cases where the home is on a small lot with no opportunities for a ground floor addition, a rooftop addition may be considered.  

Appropriate One-Story Addition	Inappropriate One-Story Addition
The one-story addition is inset from the side walls of the original dwelling and the roofline is below the original roofline.	The inappropriate approach on this one-story addition is the extension of the home without any differentiation between old and new as the side walls of the addition extend back from the original with no set back.

Appropriate Two-Story Addition	Inappropriate Two-Story Addition
The minimum visual impact of the two story addition is created by insetting it from the side walls oft he original home and scaling it down to be less than half the size of the original home.	Similar to the one-story addition, this two-story addition extends continuously from the original home and overwhelms the original with its mass and scale and gives an impression that the home was always this large.

Helpful Links

• ITS Bulletin 3: New Additions: New Additions to Mid-Size Historic Buildings (1999)

• ITS Bulletin 18: New Additions: New Additions to Mid-Size Historic Buildings (2001)

• ITS Bulletin 34: Additions: Completing Never-Built Portions of a Historic Building

• ITS Bulletin 36: Rooftop Additions

• ITS Bulletin 37: Rear Additions: Rear Additions to Historic Houses

• ITS Bulletin 47: Rooftop Additions on Mid-Size Historic Buildings (2007)

• ITS Bulletin 53: Designing New Additions to Provide Accessibility

• NPS Brief 14: Exterior Additions to Historic Buildings: Preservation Concerns.

• ITS Bulletin 10: Stair Tower Additions: Exterior Stair/Elevator Tower Additions