Laprade's work reflected many of the changes in 20th-century architecture during his long career, but he always remained true to the principles of aesthetics, balance and proportion.[2] He and other architects of his time struggled with the challenge of building modern structures in Paris without destroying the harmony of the city's architecture. In 1931 he created a series of photomontages that illustrated the problem, showing skyscrapers emerging from among 19th-century buildings.[24]