If you own a 40-year-old house that’s never been remodeled, you probably want to make some changes. Compared with most households in 1970, you have more clothes, a bigger bed, spend more time on personal grooming and use vastly more hair- and body-care products, and you regard cooking as a family activity, not something that happens behind closed doors.

Translating this into three dimensions, you want to add a master suite with space to accommodate a king- or queen-size bed, a walk-in closet and a bigger bathroom, and you want a bigger kitchen that opens to both dining and living areas.

It sounds modest enough. But in many parts of the country, especially in the Washington area, you may discover that restraints have been imposed on what you can do, either because you’re in a historic district or your local homeowners association has been empowered to pass judgment on residents’ remodeling proposals.

This can come as an unpleasant surprise, especially to those who live in historic districts but assume that their 40-year-old “builder’s special” is not historic. Within most such districts, all houses are considered historic and all modifications are subject to review by the district’s design review board.

What restraints are imposed on homeowners? They’re usually limited to what the public can see, but this can include the elevations facing the back and side yards as well as the one facing the street.

Historic districts generally follow the guidelines for preservation that were established in 1966 and maintained and updated by the National Park Service. A historic district is an entirely local entity, however, created and managed by individual jurisdictions. It may be only a few blocks in area or an entire section of a city such as Georgetown in the District or Old Town in Alexandria.

The purpose of the National Park Service’s guidelines is to maintain the historic character of a neighborhood. To accomplish this, it recommends that the exterior of a proposed addition be designed in a style that is “sympathetic” to the original house, but also clearly “identifiable” by incorporating an “articulation” between the old and the new, so that an observer can easily distinguish between them. The addition should have the same scale, so as not to dwarf the older portion of the house, and it should be built with the same or similar materials. Interestingly, the guidelines support designs for additions that are contemporary in style, and they specifically advise again an exact duplication of the older structure.

Most historic districts have a professional staff that will initially review your design proposal and possibly suggest changes that more closely conform to the district’s regulations. Final approval is determined by a design review board in a public meeting.

It sounds very straightforward, but District architect Norman Smith, who has overseen many renovations in historic districts, likened the process to navigating troubled waters.

“In sailing through historic waters to a safe beach, you may encounter unforeseen obstacles lying just below the surface,” Smith said. “Architects and owners understand the need to be ‘sympathetic to the original design,’ but this has no precise definition. It’s a nonobjective call that’s full of interpretation, and it can lead to disagreements between the homeowners and their architect and the board.”

Bethesda-based architect Tom Manion, who has also shepherded many projects through historical review boards, said that success has depended not only on his knowledge of the nuances of a given architectural style. He also has had to be strategic, researching the biases of the review board. “Some boards are very open to a new interpretation of a historic style and think it enriches the neighborhood, and some think this destroys the neighborhood.” Manion also noted that the bias can change without warning. “One week it’s very contemporary, [the] next week it must look like it was built in 1851.”

Manion said that even when there’s no historic preservation issue to deal with, a house can be located in an area with a homeowners association that is empowered to review the designs for new additions. In most cases, the HOA was established by the original builder or developer to ensure that the houses would not change in character before the subdivision was built out and to prevent homeowners from altering their houses in ways that could negatively affect the value of neighboring properties.

The neighborhood HOA design review boards, which are not guided by any historical precedents, tend to be much more subjective in their evaluations, Manion said. Unlike the review boards in historic districts, some HOAs meet in private, so it can be hard for homeowners to get a sense of which way opinions are going and how to rectify things if a board denies approval.

And while a historic district’s review board encourages variety within historic parameters, an HOA design review board can favor uniformity, insisting that the front of every house look exactly the same, right down to the smallest detail, Manion said. For example, a proposal he made for a covered overhead above a front door was denied, he said, “because it wasn’t exactly identical to all the other ones in the neighborhood.”

Does the need to get a review board’s approval affect what an architect might design for your house? Both Manion and Smith said yes.

“An architect always has different ways to accomplish the same goal, but the number of ways to accomplish this is more limited in a historic neighborhood,” Smith said. “For example, there’s a de facto limitation on windows because an older house has more wall than windows.”

In some respects, however, remodeling projects in older neighborhoods with design review boards are like all the other jobs that he designs, Smith said. At least half the challenge is helping the homeowners figure out what they need. The issue is usually not the size of the rooms in the existing house, it’s how those rooms relate to each other. The clients often assume the solution to their problem lies in building more space, but often a judicious removal of a wall here and there may be all that’s needed.

Katherine Salant has an architecture degree from Harvard. A native Washingtonian, she grew up in Fairfax County and now lives in Ann Arbor, Mich. If you have questions or column ideas, she can be contacted at salanthousewatch@gmail.com or www.katherinesalant.com.