Design Guidelines


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At the bottom of this page you will find a pdf copy of the current Mount Vernon Iowa Design Guideline Booklet – Preservation and Rehabilitation Dos and Don’ts for Commercial and Residential Structures.

The following content is the most recent addendum to the Design Guideline Booklet. The guidance in the addendum supersedes any offered in the Booklet.

Guide for Renovation, Additions, and New Construction

Rules of Thumb for Rehabilitating a Historic Building

The Design Guidelines for Mount Vernon Historic Districts are based on the Secretary of the Interior’s Standards for Historic Rehabilitation. The following, drawn from the Secretary of the Interior’s Standards for Rehabilitation, should be kept in mind when altering a property in the local historic districts. For more information, see

1. When adapting a property to a new use, distinctive materials, features, spaces, and spatial relationships shall be maintained.

2. The historic character of a property shall be retained and preserved. The removal of distinctive materials or alteration of features, spaces and spatial relationships that characterize a property shall be avoided.

3. Each property shall be recognized as a physical record of its time, place, and use. Changes that create a false sense of historical development, such as adding conjectural features or elements from other historic properties, shall not be undertaken.

4. Changes to a property that have acquired historic significance in their own right shall be retained and preserved.

5. Distinctive materials, features, finishes, and construction techniques or examples of craftsmanship that characterize a property shall be preserved.

6. Deteriorated historic features will be repaired rather than replaced. Where the severity of deterioration requires replacement of a distinctive feature, the new feature will match the old in design, color, texture and, where possible, materials. Replacement of missing features will be substantiated by documentary and physical evidence, such as early photographs of the structure, when possible.

7. Chemical or physical treatments, if appropriate, shall be undertaken using the gentlest means possible. Treatments that cause damage to historic materials shall not be used. Professional advice is recommended before using these processes.

8. Archaeological resources shall be protected and preserved in place. If such resources must be disturbed, mitigation measures shall be undertaken.

9. New additions, exterior alterations, or related new construction shall not destroy historic materials, features, and spatial relationships that characterize the property. The new work shall be differentiated from the old and shall be compatible with the historic materials, features, size scale and proportion, and massing to protect the integrity of the property and its environment, including the relation to the surrounding properties.

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.

Materials Standards in Historic Districts

The United States Department of the Interior provides principles for the treatment of historic structures: The Secretary of the Interior’s Standards for the Treatment of Historic Properties – Technical Preservation Services (U.S. National Park Service) ( In Mount Vernon those principles provide guidance concerning structures in our 3 historic districts that can also be applied to buildings elsewhere in the community. The Commission must issue a Certificate for exterior remodeling, new construction, and additions in the historic district and the principles below will guide our considerations.

“When deteriorated, damaged, or lost features of a historic building need repair or replacement, it is almost always best to use historic materials.” In Mount Vernon historic materials would include wood, limestone, cast iron, terracotta, and antique brick.

However, in some cases use of historic materials may not be desired by a property owner or required by the Commission:

  1. Because needed historic materials are generally not available or there are supply chain issues,
  2. Due to a lack of skilled craftspeople who can work with relevant historic materials,
  3. When historic materials are substantially more expensive than alternatives.

The property owner may also wish to avoid some of the work and cost required to maintain historic materials such as wood over time – however all materials require some sort of maintenance and can deteriorate over time. The Secretary of the Interior covers use of substitute materials in Preservation Brief 16: The Use of Substitute Materials on Historic Building Repairs: Preservation Briefs 16: The Use of Substitute Materials on Historic Building Exteriors (

The Secretary of the Interior requires that substitute materials must be compatible with the historic materials in appearance. More specifically: “In order to provide an appearance that is compatible with the historic material, the new material should match the details and craftsmanship of the original as well as the color, surface texture, surface reflectivity and finish of the original material.” Where the original material is not available for inspection, the materials should match the characteristics of what might have been there originally.

Vinyl products are not appropriate for use on historic structures in any of Mount Vernon’s historic districts because such products cannot mimic the surface texture or reflectivity of historic materials. The Mount Vernon Historic Preservation Commission discourages but may selectively allow vinyl products for more modern structures in the district or in cases in which vinyl has already been used on a historic structure.

Other substitute materials may, however, be appropriate for use in the historic districts. Preservation Brief 16 notes: “In the last few decades, however, and partly as a result of the historic preservation movement, new families of synthetic materials, such as fiberglass, acrylic polymers, and epoxy resins, have been developed and are being used as substitute materials in construction.” There are too many possible substitute materials for the Commission to provide a comprehensive list of what will and will not be allowed, and new materials are constantly becoming available.

The Commission will consider allowing substitute materials on a case-by-case basis. The application for a Certificate must clearly indicate how substitute materials used will mimic the use of historic materials in both shape and surface texture. Those who are considering the use of substitute material in new construction, repair or remodeling that affects the exterior of a structure, should consult with the Commission as early in the planning process as possible. This is especially true when non-historic materials are being

Solar Panel Guidelines

According to the Technical Preservation Services branch of the National Park Service: “Solar panels installed on a historic property in a location that cannot be seen from the ground will generally meet the Secretary of the Interior’s Standards for Rehabilitation. Conversely, an installation that negatively impacts the historic character of a property will not meet the Standards.” To meet the spirit of this guideline, the Mount Vernon Historic Preservation Commission requires property owners to install solar panels with the lowest possible profile to minimize visibility from the street. On a sloped roof, panels must lie parallel to the roof surface, and on a flat roof, the panels should be sloped such that they are not visible from the street. The preferred locations for solar panels are: 1) on a detached outbuilding or on poles at a distance from historic structures, 2) on the back of the historic structure, or 3) on the side of the historic structure. The MVHPC will consider approving placement on the front roof of a historic structure if that is the only feasible location for the solar panels. The solar panels and support rack systems should be a solid black color with no visible grid.

Current Mount Vernon Iowa Design Guideline Booklet – Preservation and Rehabilitation Dos and Don’ts for Commercial and Residential Structures

Click to Download/View (Design-Guide-Booklet-Scanned-Edited.pdf, 1.73MB)