Writing to fellow architect Benjamin Labtrobe seven months after retiring from the presidency, Jefferson described Monticello as his "essay in architecture." Always balancing practicality with beauty, Jefferson noted his essay "has been so much subordinated to the law of convenience, & affected also by the circumstance of change in the original design, that it is liable to some unfavorable & just criticisms." One manifestation of the conflict between Jefferson's classical design and "convenience" is Monticello's south façade. Sharp-eyed guests have long noticed that Jefferson ignores symmetry—a fundamental tenet of classical architecture—by designing a south face that does not mirror the north façade's appearance.
Jefferson first mentions this departure from classicism in an 1806 letter directing joiner James Dinsmore to hurry along work on the "Porticle of the S.E. Piazza." The "porticle" or Venetian porch, as Jefferson occasionally termed it, was one of two wooden structures that enclosed two small terraces on the south and east corners of the house. In contrast, the north and west corners on the north façade remained open.Replying to Dinsmore's inquiry about installing a Chinese railing on top of the porticles to match those on the roof of the main house, Jefferson demurred, saying "it would make them more conspicuous" and distract the eye. The intention, explained, was "that they [the porticles] should be as obscure as possible that they might not disturb the effect of their principal."
Jefferson's writings yield nothing about the porticles' purpose, but they most likely served to shield his library and study from the unrelenting Virginia sun. They would have also provided him with more privacy and a quiet place to read.