Marja Petäjä (née Koskelo, 1923–) studied architecture at the Technical University of Helsinki. Her brother, Heikki Koskelo, was also an architect. She established a shared office with his architect husband Keijo Petäjä in 1950, after they won the architecture competition of the Central Finland vocational school. Marja and Keijo Petäjä designed home and office for themselves to Lauttasaari, Western Helsinki. Bringing domestic and workspaces together was a common choice for architect couples in the 20th century, to combine work and family life, Aino Marsio-Aalto and Alvar Aalto being pioneers of this choice. One of Marja and Keijo Petäjä’s main works is Lauttasaari Church. Marja Petäjä was named as the honory member of the association of Finnish female architects, Architecta in 2011. Architects Käpy Paavilainen (née Petäjä) and Juha Petäjä are Marja and Keijo Petäjä’s children. After Keijo Petäjä’s death, their son Juha has been running the office, which operates in the same premises since 1957.