Professorville has always held a special place among Palo Alto's dozens of neighborhoods -- a thriving section of downtown that doubles as a national historic landmark.

The area, which is roughly bounded by Emerson Street, Addison Avenue, Cowper Street and Embarcadero Road, harkens back to the city's earliest days in the late 19th century, when Stanford University faculty began settling the area. When the Professorville Historic District won its spot on the National Register of Historic Place in 1979, the nomination credited it with reflecting "the unique background or the area's origins and its early ties to the founding of both the University and Palo Alto itself."

Now, the City Council is embarking on an effort to protect Professorville's special status. On Monday night, the council will consider adopting a new set of design guidelines for Professorville, a document that has been five years in the making and that lays out in detail what type of construction is allowed in the neighborhood and what type is frowned upon.

The goal of the new Professorville Historic District Design Guidelines is to help manage new development in the area. A report from the Department of Planning and Community Environment calls the document "a tool for members of the community to evaluate the compatibility of proposed development with the historic character of Professorville." For homeowners, the document will provide "advice on everything from ordinary maintenance and repair of existing buildings to major new construction." For architects, it will aim to reduce the "guesswork" involved in designing architecturally compatible improvements, the report states.

"The Guidelines will also give the public a basis for understanding how decisions are made regarding the appropriate treatment of properties in Professorville," the staff report states.

Created by the consulting firm Page & Turnbull, the document does not advocate for any particular architectural style. That's largely because of the eclectic nature of Professorville's architecture, which includes Queen Anne, Spanish Colonial and Craftsman styles.

Nor is it intended to be the final arbiter of architectural decisions. The guidelines, according to staff, are intended to be suggestions rather than decrees. Unlike development standards or zoning codes, which set clearly defined rules, guidelines are intentionally squishy. The staff report calls them "a starting point for a conversation about historically compatible development." The reason staff is proposing guidelines rather than the more prescriptive development standards is to "allow for interpretation and flexibility in decision making, based on specific circumstances."

At the same time, many of its proposals are fairly clear-cut and leave little room for discretion. For example, the guidelines plainly prohibit the demolition of any homes built before 1930, calling the early homes the "critical components of the historic district." If an early residence is heavily altered or damaged, an attempt should be made to rehabilitate it or repair it rather than pursue demolition and replacement, the guidelines state.

Similarly, residents are discouraged from demolishing any building that, while not itself historic, is "complementary to the district" by reinforcing historical development patterns.

Where a building or accessory-dwelling unit is constructed in Professorville, it should be placed on a lot with a similar location, setback and orientation as nearby residences, the document states. The new home's distance from the street, for instance, should be similar to that of surrounding residences and its primary facade should also face the street, according to the new document.

Furthermore, the new guidelines encourage architects and builders to construct new residences in such a way that these structures "are not more prominent in the district than properties built during the historic period." Additions to existing buildings should be "subordinate" to the historic buildings when it comes to location, scale and detailing. And features of existing buildings that are deemed to be "character defining" should be retained and rehabilitated whenever possible, with an emphasis on those elements that can be seen from the public right-of-way, according to the guidelines.

The dominant underlying theme of the new document is compatibility. Though it acknowledges that change is inevitable and, in many cases, desirable, new construction should not detract from the historical feel of Professorville. Thus, it offer tips for installing solar panels (they should be placed on roof slopes that are less visible from the public right-of-way), encourages "muted colors" for primary exterior walls and encourages residents to "recreate" historical features on buildings where they once existed and were later removed.

The document also discourages residents from introducing new stylistic elements "based on conjecture rather than research" and states that a residence should not have "new features added that represent a different historic period or architectural style than existing property."

At the same time, the guidelines stop well short of encouraging uniformity. Its chapter on altering existing structures in fact encourages "differentiation" features that allow new construction to be distinguished from the original buildings so as to avoid creating "a false sense of historical development."

"New construction should not be radically different in style or materials; however, minor differences can be used effectively to distinguish new from old," the guidelines state.

One way to achieve this, according to the guidelines, is to use "similar but simplified decorative details at the addition, which would allow the addition to read as subordinate to the historic building." And if the addition has the same number of stories as the original structure, the builder is encourage to place the eave heights of the addition slightly lower to indicate the beginning of new construction and to indicate the primacy of the original residence."

For new homes (a rare occurrence in the mostly built-out neighborhood), builders are challenged to balance the overarching mandate for "compatibility" with this call for differentiation.

"As opportunities for new residential construction arise, it is critical to design buildings to be compatible with the neighborhood's early residences, yet also differentiated in some way in order to continue the physical record of historical development in the district," the guidelines state. "The most important considerations for compatibility include site placement, general form and massing, size and height, and fenestration patterns."

"Designing a home that takes into consideration these aspects of the historic character of surrounding homes would ensure that the overall appearance and feeling of Professorville remain distinguishable."