His work focuses on the formal relationship between a building and its surroundings. Platt viewed the garden as an outdoor room. He used straight lines and geometric structures. He also relied on formal axes. His etchings of coastal scenes and European towns show a mastery of light and shadow. He preferred clean compositions over the cluttered styles common in the late nineteenth century. This approach is evident in his designs for the Freer Gallery of Art.

Modern collectors value Platt for his architectural precision. His prints offer a sense of order. The etchings provide a glimpse into a period of American design that valued classical proportions. These works suit contemporary interiors because they are understated. They provide a calm visual experience without unnecessary ornamentation. His etchings of the New England coast are particularly sought after for their clarity.