Chapter 19.42

HISTORIC PRESERVATION AND INFILL IN THE HISTORIC ZONE

Sections:

• 19.42.010 Purpose.

• 19.42.020 Designation of a local historic resource or district.

• 19.42.030 Adaptive reuse.

• 19.42.040 Guidelines for preservation and adaptive reuse.

• 19.42.050 Guidelines for infill development.

This chapter is intended to safeguard the historic character of Sonoma by recognizing and preserving significant historic and cultural resources by providing incentives for the preservation and rehabilitation of historically and culturally significant resources, and by ensuring that new development in the historic overlay zone is architecturally compatible.

A. Officially Designated Historic Structures. This chapter establishes incentives, minimum standards, and guidelines for the preservation and adaptive reuse of officially designated historic structures to the greatest extent feasible, as well as a process for listing districts, sites, structures and other resources possessing local historic significance.

B. Potentially Historic Structures. This chapter establishes guidelines for the preservation of historic structures within the city, using the League for Historic Preservation’s inventory of historic structures as a guide for determining whether these provisions should be applied.

C. Infill Development. This chapter establishes guidelines to be used in review of infill development within the historic overlay zone for which a discretionary permit is required. (Ord. 06-2013 § 2(A) (Exh. B), 2013; Ord. 2003-02 § 3, 2003).

A. Purpose. In order to recognize and promote the preservation of sites, structures, and areas that are important to the history of Sonoma, this section provides for the nomination and designation of locally significant historic resources and districts.

The Sonoma Municipal Code is current through Ordinance 13-2025, passed December 3, 2025.

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B. Designation Process – Local Historic Resources. Local historic resources shall be designated by the historic preservation commission in the following manner:

1. Initiation of Designation. Designation of an historical resource may be initiated by the historic preservation commission or by the owner of the property that is proposed for designation. Applications for designation originating from outside the commission must be accompanied by such historical and architectural information as is required by the commission to make an informed recommendation concerning the application, together with the fee set by the city council.

2. Review, Notice and Hearing. The historic preservation commission shall conduct a public hearing on a nomination for local historic resource designation. Notice of the public hearing shall be provided, and the hearing shall be conducted in compliance with Chapter 19.88 SMC (Public Hearings), including mailed notice to the owners of any property proposed for such designation.

3. Findings, Decision. Following a public hearing, the historic preservation commission may approve or disapprove a nomination for designation as a local historic resource. The commission shall record the decision and the findings upon which the decision is based. The historic preservation commission may approve such designation only if it finds that the resource meets at least one of the following criteria:

• a. It is associated with events that have made a significant contribution to Sonoma’s history and cultural heritage; or

• b. It is associated with the lives of persons important in Sonoma’s past; or

• c. It embodies the distinctive characteristics of a type, period, region, or method of construction, or represents the work of an important creative individual, or possesses high artistic values; or

• d. It has yielded, or may be likely to yield, information important in Sonoma’s prehistory or history.

C. Designation Process – Local Historic Districts. Local historic districts shall be designated by the city council upon the recommendation of the historic preservation commission in the following manner:

1. Initiation of Designation. The designation of a local historic district may be initiated by the city council or the historic preservation commission.

2. Requirements for Designation. The designation of a local historic district is subject to finding by the review authority that all of the following requirements are met:

   • a. The proposed district is a geographically definable area.

• b. The proposed district possesses either a significant concentration or continuity of buildings unified by past events or aesthetically by plan or physical development.

  • c. Considered as a whole, a sufficient concentration of buildings within the proposed district demonstrates integrity of design, setting, materials, workmanship and association.

The Sonoma Municipal Code is current through Ordinance 13-2025, passed December 3, 2025.

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• d. The collective historic value of the buildings and structures in the proposed district is greater than the historic value of each individual building or structure.

• e. The designation of the area as a historic district is reasonable, appropriate and necessary to protect, promote and further the goals and purposes of this chapter and is not inconsistent with other goals and policies of the city.

3. Historic Preservation Commission Hearing and Recommendation. The historic preservation commission shall conduct a public hearing on a nomination for local historic resource district. Notice of the public hearing shall be provided, and the hearing shall be conducted in compliance with Chapter 19.88 SMC (Public Hearings), including mailed notice to the owners of any property proposed for such designation. Following the public hearing, the commission shall recommend approval in whole or in part or disapproval of the application for designation in writing to the city council, setting forth the reasons for the decision. The historic preservation commission may approve a recommendation for a local historic district only if it makes the findings set forth in subsection (B) of this section.

4. City Council Hearing and Decision. The city council shall conduct a public hearing on a nomination for local historic district. Notice of the public hearing shall be provided, and the hearing shall be conducted in compliance with Chapter 19.88 SMC (Public Hearings), including mailed notice to the owners of any property proposed for such designation. Following the public hearing, the city council shall by resolution approve the recommendations in whole or in part, or shall by motion disapprove them in their entirety. The city council may approve a designation as a local historic district only if it makes the findings set forth in subsection (B) of this section. If the city council approves a local historic district, notice of the decision shall be sent to property owners within the district.

D. Amendment or Rescission. The historic preservation commission and the city council may amend or rescind any designation of an historical resource or historic district in the same manner and procedure as are followed for designation.

E. Previously Designated Historic Resources. The sites and structures previously designated by the city council as having local historic significance through the adoption of Resolution 18-2006 are hereby designated as local historic resources as defined in this chapter.

F. Register. The historic preservation commission shall maintain a register of designated local historic resources and districts. (Ord. 10-2025 § 2 (Exh. A), 2025; Ord. 06-2013 §§ 2(A) (Exh. B), 3, 2013).

The adaptive reuse of historic structures within the historic overlay district, involving uses not otherwise allowed through the base zone, may be allowed subject to the approval of a conditional use permit, in compliance with SMC 19.54.040 and as set forth below.

• A. Eligible Structures. The following types of structures are eligible for adaptive reuse:

The Sonoma Municipal Code is current through Ordinance 13-2025, passed December 3, 2025.

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1. Officially Designated Structures. Those structures of officially designated historical significance as indicated by (a) listing with the State Office of Historic Preservation, or (b) listing as a locally significant historic resource, regardless of whether they are located within the historic overlay zone.

2. Structures with Potential Historical Value. In addition to officially designated structures, there are other structures that may have historical value because of their age (usually more than 50 years old), and their contribution to the overall historic character of the community due to their unique architectural scale and style, use of design details, form, materials, or proportion, as may be documented through listing on the Sonoma League for Historic Preservation’s inventory of historic structures. Such structures shall only be eligible for adaptive reuse if located within the historic overlay zone and shall not be eligible for consideration as a vacation rental.

B. Allowable Use. The following uses may be considered in an application for the adaptive reuse of a historic structure:

1. Residential Uses and Densities.

   • a. Allowable Residential Uses. Single- and multifamily dwellings and residential condominiums.

   • b. Allowable Residential Densities. The allowable residential density within the historic overlay district may exceed the normally allowable density under the subject general plan designation and zoning district, subject to the approval of the planning commission.

2. Nonresidential Uses.

   • a. Bed and breakfast inns;

   • b. Hotels;

   • c. Limited retail;

   • d. Mixed use (residential over commercial) developments;

   • e. Professional and service-oriented offices;

   • f. Restaurants (with or without outdoor dining facilities); and

   • g. Vacation rentals (limited to structures listed or eligible for listing on the State Register of Historic Places); and

   • h. Wine tasting facilities.

C. Retention of Residential Character, Scale, and Style. Adaptive reuse projects shall retain a residential character, scale, and style (e.g., off-street parking areas would be prohibited in the front and street side setbacks, new construction would have a residential appearance, signs would be limited, etc.). The guidelines set forth in SMC 19.42.040 shall be considered by the planning commission in applications for adaptive reuse.

The Sonoma Municipal Code is current through Ordinance 13-2025, passed December 3, 2025.

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D. Compliance with Parking Standards. The above-listed uses shall be provided with suitable parking, in compliance with Chapter 19.48 SMC (Parking and Loading Standards).

• E. Findings and Decision. The planning commission shall approve, with or without conditions, the adaptive reuse of an historic structure only if all of the following findings can be made, in addition to those identified in SMC 19.54.040 (Use permits). The alteration or adaptive reuse would:

  1. Enhance, perpetuate, preserve, protect, and restore those historic districts, neighborhoods, sites, structures, and zoning districts which contribute to the aesthetic and cultural benefit of the city;

  2. Stabilize and improve the economic value of historic districts, neighborhoods, sites, structures, and zoning districts;

  3. Preserve diverse architectural design reflecting phases of the city’s history, and encourage design styles and construction methods and materials that are compatible with the surrounding neighborhood(s);

  4. Promote and encourage continued private ownership and utilization of structures now so owned and used; and

  5. Substantially comply with the applicable Secretary of the Interior Standards and Guidelines for the Treatment of Historic Properties as well as the applicable requirements and guidelines of this chapter.

The following additional finding is required for applications for adaptive reuse as a vacation rental:

6. Restore and rehabilitate a historic structure and/or property, excluding second units, which is listed or eligible for listing on the State Register of Historic Places, that has fallen into such a level of disrepair that the economic benefits of adaptive reuse are necessary to stem further deterioration, correct deficient conditions, or avoid demolition as implemented in the conditions of project approval. (Ord. 03-2016 § 1 (Exh. A), 2016; Ord. 06-2013 § 2(A) (Exh. B), 2013; Ord. 06-2009 §§ 1 – 3, 2009; Ord. 2003-02 § 3, 2003. Formerly 19.42.020).

A. Purpose. The purpose of these guidelines is to implement general plan policies related to the preservation and adaptive reuse of officially designated historic structures throughout the city and of structures having potential historical value within the city’s historic overlay zone.

B. Applicability. These guidelines are to be utilized during the development/design review process as criteria against which to review new construction within the historic overlay district requiring discretionary approval and adaptive reuse projects.

C. Preservation and Rehabilitation of Existing Structures. In general, preservation and rehabilitation efforts should aim toward protecting the essential architectural features of a structure that help to identify its individual style and thereby further its contribution to the historic character of the surrounding neighborhood.

The Sonoma Municipal Code is current through Ordinance 13-2025, passed December 3, 2025.

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1. General Rehabilitation Principles.

a. Historic structures should be recognized for their own time and style. Rehabilitation should not try to create a preconceived concept of history, but should reuse existing or appropriate features.

b. Rehabilitation of historic structures should try to retain and restore original elements first. If damage or deterioration is too severe, the element should be recreated using original materials to match the color, design, texture, and any other important design features.

c. When replacement is necessary and original material cannot be obtained, substitution material should incorporate the color, design, and texture that conveys the visual appearance of the original material.

2. Doors.

a. Older structures almost always had solid wood doors that fit the particular style of the structure. The front door of the structure was the most ornate with secondary doors usually more utilitarian in appearance. The shape, size, and style of doors are an important feature of all historical architectural styles and the original design/type should be maintained.

b. Original doors should be repaired in place whenever possible. When replacement is necessary, the replacement door should match the original design and materials as close as possible.

c. If the original door is missing, appropriate design and materials should be selected by studying the doors of similar structures in the surrounding neighborhood or consulting books on architectural styles. Many older style panel doors are still available from material suppliers and may match the original doors very closely.

3. Exterior Materials.

a. The original exterior building materials should be retained whenever possible. It is not desirable to use mismatched materials of different finishes, shapes, sizes, or textures.

b. Structures with original wood siding should not be stuccoed in an attempt to modernize their appearance. Likewise, plastic shingles should not be used to replace wood siding or shingles.

c. Replacing wood siding with aluminum siding of the same shape and size as the original siding can be an alternative, but care shall be taken to use siding of the appropriate size.

d. Brick surfaces should not be sandblasted in an attempt to remove old paint. Sandblasting would damage the natural fired surface of the brick, and cause it to lose its water repellent qualities. Also, mechanical grinders should not be used to remove mortar as this can damage the brick surrounding the joint.

4. Ornamentation and Trim.

The Sonoma Municipal Code is current through Ordinance 13-2025, passed December 3, 2025.

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• a. Most often it is the authentic decoration and trim on a structure that lends character and identifies the structure with its particular architectural style. Original ornamentation should be preserved whenever feasible.

b. If the material needs to be removed to be repaired or copied, determine how the piece is attached and carefully plan the work to be sensitive to the material. Any prying action should be slow and careful, with a minimal amount of force.

c. If the ornamentation or trim is comprised of several layers of materials, it is helpful to sketch the components as they come apart to ensure proper reassembly. If the pieces are beyond repair, a skilled finish carpenter should duplicate the original work.

5. Porches and Stairs.

a. During rehabilitation efforts, the design integrity of the front porch should not be compromised. Front porches should not be enclosed with walls or windows.

b. If enclosing the porch is the only viable means of adding needed space, care should be taken to use decoration(s), doors, siding materials, trim details, and windows that match the facade of the structure surrounding the porch.

6. Roofs.

a. Roofs are important both functionally and aesthetically. Great care should be taken to ensure that roofs are watertight and that roofing materials are compatible with the original style of the structure. Oftentimes roofs only need repairs, but when replacement is necessary roofing materials should be selected that are appropriate to the structure’s architectural style.

b. It should be recognized that fire safety requirements may preclude reroofing a structure in its original material. The determination of what material to use for the replacement of wood shingles or shakes in historic structures should be based on compatibility with the colors and materials used elsewhere on the structure.

7. Windows.

a. Most older/historic structures had wood framed windows that were either casement, double hung, or fixed. The shape, size, and style of windows are an important feature of most architectural styles and the original type window should be maintained.

b. When window replacement is necessary, it is preferred that the new window be an exact match of the original.

c. An alternative to special milling may be the use of an “off-the-shelf” standard window that closely matches the original.

The Sonoma Municipal Code is current through Ordinance 13-2025, passed December 3, 2025.

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• d. Aluminum or plastic frame windows should not be used as replacements on any part of an historically valuable structure without justification. The use of such materials is highly visible and the contrast of materials and styles can permanently affect the architectural integrity of the structure. The use of traditional materials is preferred.

D. Additions to Existing Structures. Additions to historically valuable structures may be necessary to ensure their continued use. Modifications (e.g., additions, new entrances and exits, parking facilities, handicap facilities, and seismic strengthening) should be made with care so as not to compromise a structure’s historically valuable features, finishes, or materials.

1. Site Plan Considerations. Additions should be carefully placed to minimize changes in the appearance of the structure from the public right-of-way. Whenever possible, additions should be placed to the side or rear of the structure and should not obstruct the appearance of the structure from the public right-of-way.

2. Architectural Compatibility.

• a. Additions to historically valuable structures should incorporate the distinctive architectural features of the original structures including:

  • i. Door and window shape, size, and type;

  • ii. Exterior materials;

  • iii. Finished floor height;

  • iv. Roof material, pitch, and style; and

  • v. Trim and decoration.

b. Refer to the rehabilitation guidelines, subsection (C) of this section, Preservation and Rehabilitation of Existing Structures, for discussion of appropriate exterior doors, porches, wall materials, windows, etc.

3. Roof Pitch and Style.

   • a. The roof of a structure, especially its pitch and style, is an important architectural element that should be taken into consideration when planning an addition.

   • b. Whenever possible, the pitch and style on the addition should match the original.

   • c. Roof materials should also match as close as possible.

4. Second-Story Additions.

a. Because adding an additional story to an existing structure will always change the structure’s proportions, such additions should be carefully designed to follow similar two-story examples of the particular style that may be found in the surrounding neighborhood.

The Sonoma Municipal Code is current through Ordinance 13-2025, passed December 3, 2025.

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• b. Integrating the new second-story addition into the original design of the structure may be easier if the addition is set back from the front facade so that it is less noticeable from the public right-of-way.

(Ord. 06-2013 § 2(A) (Exh. B), 2013; Ord. 2003-02 § 3, 2003. Formerly 19.42.030).

A. Purpose. These guidelines are intended to encourage new infill development in the historic overlay district to be compatible in scale and treatment with the existing, older development and to maintain the overall historic character and integrity of the community. At the same time, these guidelines are intended to promote the visual variety that is characteristic of Sonoma, to allow for contemporary architectural designs, and to provide reasonable flexibility in accommodating the tastes, preferences and creativity of applicants proposing new development, especially individual single-family homes. As stated in the 2020 General Plan:

Sonoma should continue to be characterized by variety in terms of land uses, building types, and housing, and this diversity should be consistent with preserving the town’s small-scale and historic character.

B. Guidelines for Compatibility. The single most important issue of new infill development is one of compatibility, especially when considering larger structures. When new structures are developed adjacent to older single-family residences, there are concerns that the bulk and height of the infill structures may have a negative impact on the adjoining smaller-scale structures. The following considerations are intended to address this concern:

1. Site Plan Considerations.

   • a. New development should continue the functional, on-site relationships of the surrounding neighborhood. For example, common patterns that should be continued are entries facing the public right-of-way, front porches, and garages/parking areas located at the rear of the parcel.

   • b. Front setbacks for new infill development should follow either of the following criteria:

     • i. Equal to the average front setback of all residences on both sides of the street within 100 feet of the property lines of the new project; or

     • ii. Equal to the average front setback of the two immediately adjoining structures on each side of the new project.

c. In cases where averaging between two adjoining existing structures is chosen, the new structure may be averaged in a stepping pattern. This method can work especially well where it is desirable to provide a large front porch along a portion of the front facade.

2. Architectural Considerations.

The Sonoma Municipal Code is current through Ordinance 13-2025, passed December 3, 2025.

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a. New infill structures should support the distinctive architectural characteristics of development in the surrounding neighborhood, including building mass, scale, proportion, decoration/detail, door and window spacing/rhythm, exterior materials, finished-floor height, porches, and roof pitch and style.

b. Because new infill structures are likely to be taller than one story, their bulk and height can impose on smaller-scale adjoining structures. The height of new structures should be considered within the context of their surroundings. Structures with greater height should consider providing greater setbacks at the second-story level, to reduce impacts (e.g., blocking or screening of air and light, privacy, etc.) on adjoining single-story structures.

c. The incorporation of balconies and porches is encouraged for both practical and aesthetic reasons. These elements should be integrated to break up large front facades and add human scale to the structures.

d. The proper use of building materials can enhance desired neighborhood qualities (e.g., compatibility, continuity, harmony, etc.). The design of infill structures should incorporate an appropriate mixture of the predominant materials in the surrounding neighborhood whenever possible. Common materials are brick, horizontal siding, shingles, stone, stucco, and wood.

e. Color schemes for infill structures should consider the color schemes of existing structures in the surrounding neighborhood in order to maintain compatibility and harmony. Avoid sharp contrasts with existing building colors.

3. Single-Family Residences.

a. The design of an individual single-family residence is typically of great significance to the homeowner. Changes required through the design review process should be the minimum necessary to achieve compatibility with the overall character of the historic overlay district.

b. Historic architectural styles (e.g., craftsman, Victorian, bungalow, etc.) are not mandated. However, contemporary architectural treatments proposed for new residences should complement and not detract from the qualities of the historic overlay district and the neighborhood setting of the proposed development.

c. To the extent that a proposed residence is not readily visible from a public street, other public vantage point, or a significant historic resource, greater design flexibility should be allowed.

4. Sustainable Construction Techniques.

a. Building forms that reduce energy use may be radically different than traditional architectural types. Careful and sensitive design is required in order to produce a contrast that is pleasing rather than jarring. The use of appropriate colors and textures on exterior materials is one method of linking a contemporary building design to a traditional neighborhood context.

b. Roof gardens, solar panels, and other sustainable construction features should be fully integrated into the design of new construction, rather than applied at the conclusion of the design process.

The Sonoma Municipal Code is current through Ordinance 13-2025, passed December 3, 2025.

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5. Accessory Structures.

a. New accessory structures (e.g., garages, second units, sheds, etc.) that are visible from the public right-of-way should incorporate the distinctive architectural features (e.g., color, materials, roof pitch and style, etc.) of the main structure.

• b. Design features should be applied with less detail on the accessory structure so that it does not compete with the main structure and is clearly subordinate to it. (Ord. 06-2013 § 2(A) (Exh. B), 2013; Ord. 07-2007 § 1 (Exh. B), 2007; Ord. 2003-02 § 3, 2003. Formerly 19.42.040).