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Dane County. The garage addition is appropriate as it separates itself from the original house with a reveal, has a lower roof and relates to the historic house in design and materials. Source: WHS - State Historic Preservation Office. View the property record: AHI 5769

If you want to add more living space to your historic house, there are several ways you can construct an appropriate-sized addition while preserving the character of your house. With careful planning, it is quite possible to design and build an addition that blends beautifully with the original part of your house. To accomplish this goal, you should follow these general guidelines:

• Design your new addition to be compatible with the architectural character of your building.
• Plan your new addition so it does not significantly alter the original distinguishing qualities of your house, such as the basic form, materials, fenestration and stylistic elements.
• Construct your new addition so that if it is removed in the future, the essential form and integrity of your original house could be restored. 

Evaluate the Need for an Addition

Before you make plans to increase the footprint of your house, complete an inventory of your existing and potential space. You might have space available for expansion in the attic or basement. Historic houses often have a large attic or full basement. You might find it easier or less expensive to renovate these spaces than to build an addition. For example, you might be able to renovate your attic space by installing a new staircase and add light with a dormer window or skylight on the rear roofline. Likewise, you could renovate your basement into a variety of uses.

Address Primary Design Concerns

When you plan an addition, you will have two primary design concerns, which are:

• How the addition can be designed to complement rather than detract from your house’s historic character.
• The extent to which the addition will be visible from the street.

The location of your addition will have a big impact on these concerns. In most cases, the best location for your addition will be at the rear of your house. A properly planned side addition may also be appropriate. You should never place an addition on the front of your house. The front of your house displays the main decorative and design features that define your house’s architectural style. It is difficult to make even a small addition on the front of your house that is compatible with its original design.

The size and scale of your addition is also of particular importance. You do not want the new addition to overwhelm your house’s original character-defining features so your house undergoes “demolition by addition.” Your addition should also be in keeping with the size and scale of your neighborhood.  A well-designed addition will add value to your property and to your neighbors’ properties.

Consider the Most Common Additions: Wings, Garages and Roofs

The most common means of adding space to historic houses are wings for additional living space, attached garages and rooftop additions, such as additional stories or dormers.

Wing. Often the simplest and easiest method of adding living space is to attach a wing at the rear of the house. Many houses built in the 19^th century had a new kitchen, bathroom or sun porch added in the early 20^th century. In recent years, master suites and family rooms have been popular additions for historic houses.

Garage. Many historic houses do not have a garage, so a garage addition is a popular choice for many people. Since garages are non-historic features to 19^th- and early 20^th-century houses, your garage addition should be located out of sight as much as possible. The front of your garage addition should face the secondary side of your lot so the doors do not face the street. If your house is on a corner lot, your garage addition should face the side street.

Rooftop addition. If you are renovating your attic space and need more light and headroom, you should consider adding dormer windows. Dormers have been used for years to introduce light into upper floors and attics. Dormers are a much better option than adding an extra story, which would likely significantly alter the original appearance of your house. You can preserve the character on the front face of your house by placing your dormers at the rear or designing them so they are not readily visible from the street.

Consider Making an Alteration

You might need to make an alteration to your historic house to meet a new use or provide more flexible space. Exterior and interior alterations are sometimes needed to ensure a historic building’s continued use. Some common alterations include:

• Adding a new entrance or windows on a rear or side elevation.
• Installing an entirely new mechanical system.
• Adding an accessibility ramp.

Another type of alteration is the removal of previously added non-historic building materials that detract from your house’s architectural integrity and historic character.

Determine Applicable Design and Zoning Requirements

Before you start designing your addition, you need to find out if your house is located in a historic district and subject to design review by your community’s historic preservation commission. You can find out this information from your community’s planning department. If your house is in a historic district, you will likely be required to have your plans for an addition approved by your HPC.

You should also review your community’s zoning or historic preservation ordinance to check rear and side yard setback regulations. Most Wisconsin communities that have a zoning code require any addition or new construction to be set back a certain distance from neighboring properties. The size and scale of your addition will need to comply with these setback requirements unless you request a variance from your local zoning board. 

Consult Standards for Rehabilitation

Most Wisconsin HPCs use the Secretary of the Interior Standards for Rehabilitation as the standards for their design review process. These standards should form the basis of principles you should follow when you are designing an addition. 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.”

Follow Good Design Principles  

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The rear addition to this historic house is appropriate. The addition is small and located at the rear of the historic house not affecting the historic appearance. Source: Phil Thomason.

When you are designing your addition, you should follow these principles:     

• Design your addition to be smaller in mass and scale than your original structure.
• Construct your addition at the rear of your house where it will have less visual impact. Consider a lateral or side addition only if a rear addition is not practical. A side addition should be recessed back from the front of your house.
• Design your addition to be different from, but compatible with, your original structure. Your addition should not be an exact “copy” of the materials and details of the original house. Instead, it should be clearly of its time but compatible with the original structure. You do not want to create a false sense of history by making your new addition appear old. For example, for an older brick house, do not use old reclaimed bricks to construct your new addition; use new bricks or an alternative but compatible material. Consider using a small connecting wing to connect your original house and the addition. A connecting wing will clearly identify where the original dwelling ends and the new one starts, thus maintaining the scale and size of your house. Build your addition in such a way that it does not destroy or remove original building materials or features from your house. In other words, if someone in the future were to remove your addition, your original structure would still be intact. Consider attaching the addition through an existing doorway or by enlarging an existing window.
• Recess your addition so that you maintain the outer edges of your house, even if the square footage of your addition approaches the size of the original house. Avoid simply extending gable ends at their full width, which would erase the historic corners of your house.
• Do not design an addition that would change the roofline on the front of your house. A rooftop addition such as a dormer may be appropriate at a rear elevation. The rear rooftop addition should be recessed in from the sides to reduce its visual impact from the street. 
• Design your addition’s roofline lower than that of your original house to help maintain the prominence of your original house and keep the addition in proper scale.  

Avoid These Actions

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The rear addition to this historic house is not appropriate. The addition is too large and is also visible from the public right of way, greatly altering the house's original appearance. Source: Phil Thomason.

When you are designing an addition or alteration to your historic house, you should avoid the following actions:

• Expanding the size of your house by constructing a new addition when the new use could be met by renovating available interior space.
• Building an addition so that important character-defining features of your house are concealed, damaged or removed.
• Designing a new addition whose scale and size overwhelms the original structure.
• Imitating the original design, materials, style and detailing of your house so that you cannot tell where the original house ends and the addition begins.
• Designing an addition in a false style or time period that is not in keeping with the style of the original structure, such as adding a Colonial style addition onto a Bungalow style house.
• Constructing additional stories so that the historic appearance of your house is radically altered.