Westman attended Enskilda Gymnast and graduated from the KTH Royal Institute of Technology in 1945.

He acted as chief architect at Stockholm's city planning office between 1973 and 1985 and was involved in several controversial construction works.

In this position, he became involved in the continued Norrmalm regulation, whose first stage with Hötorgscity and Sergels torg was completed in 1966.

The 1962 city plan was the basis for the continued work south of Sergels torg.

Torsten Westman, together with Anders Nordberg and Åke Hedtjärn, was the mastermind behind this city plan.