There’s a difference between a building being old and historically significant. By far the most common reason for listing is embodiment of an architectural style. The rule of thumb for embodiment is a combination of characteristic form, decorative elements, and materials (e.g., steep roofs, pointed windows, and board-and-batten siding in Gothic Revival). In Historic Resources Surveys, poor understanding of architectural styles by hastily-trained volunteers have often resulted in old, or large, or interesting buildings being listed rather than ones that embodied a style, or the overlooking of changes that had already altered the design, materials, and workmanship beyond the building’s ability to communicate its significance.

The types of buildings that never embodied an architectural style were often hurriedly built for utility, on spec, or by less reputable developers, often in a standard form with no more than a nod to fashionable decorative detail.

Common reasons for deeming an originally significant building unable any longer to communicate that significance include the removal of historic or addition of nonhistoric porches, enclosure of historic porches by glass or wall, addition or alteration of windows, loss of decorative elements, additions and removals of stories and extensions, enclosure of garages, and addition of aluminum siding or replacement of historic siding—particularly as they affect the appearance from the street (views from which are the legal underpinning for municipal control over historic preservation, from a 1926 Supreme Court case, Village of Euclid v. Ambler Realty Co., ruling that zoning was constitutional if it had relation to health and welfare).