In the ongoing project of adding to the recently built, or more specifically the problem of additions to postwar icons, the issues have proven more slippery. (In this context, I use “project” to mean a larger theoretical endeavor or task of investigation rather than an architectural proposal.) First, what, in this context, is postwar? To focus this thesis, I define it as the period in American architecture from the end of World War II to the dissolution of the modern movement into the splintered ‘isms’ of the late 1970’s and early 1980’s that were bubbling up in the decades before. And why icons? Rather than the “low road” buildings of recent heritage – the dysfunctions of which are most often happily mitigated by additions – postwar icons would seem to pose a distinct set of challenges. This premise is born out even anecdotally by the evidence: numerous additions by high profile design talents with sincere intentions that amount to ambiguous results. The particular provocations of the task, in most cases, remain unacknowledged and unmet. In this thesis I mean to investigate the challenges and parameters posed through these types of projects, and the degree to which the circumstances are unique to ‘their’ (modern) movement and ‘our’ contemporary moment. (While Modernism is an admittedly loaded and imprecise term, I will use it as shorthand for the various ideologies in mainstream architectural practice in the midtwentieth century.) First, how does the consideration of the “recent past” as short temporal distance play a role, and second, how might this be complicated further by modernism’s own ambivalent relationship with history? And then what of our own ambivalent relationship with modernism as history? What are the specific theoretical questions at hand as regards changing conceptions of time, author, and artifact? The working thesis of this paper is that, indeed, in the broader spectrum of additions to significant historic buildings, the project of adding to a postwar icon is unique on two levels. The first is that these icons necessitate a sophisticated approach, distinct from the broader addition paradigm as it is now understood in conservation and preservation design. By virtue of the moderns’ era, our era, and the relationship therein, postwar icons stipulate an ‘ethic’ that may prove to have some surprising tolerances but nonetheless demands a unique approach and demonstrable design rationale. The second argument is that a requisite ethic largely remains out of sight, discourse, and widespread use. The paradigms of current practice, through their failures and ambiguities, make the case for a critical reconsideration of this project within our complementary and combined fields of architecture and preservation design.