He graduated from a technical college specializing in civil engineering and, in 1912, began studying architecture under J. Plečnik at UMPRUM. In the summer of 1914, he was drafted to the front in Galicia with the 102nd Infantry Regiment from Benešov; he was taken prisoner in late 1915. In March 1918, following his application, he was assigned to the 5th Czechoslovak Rifle Regiment. In August 1918, his commanding officers assigned him to work as a clerk in the office of the prisoner-of-war camp in Vladivostok. It was not until June 1919 that he was assigned to the painting workshop of the Information and Education Department of the branch of the Czechoslovak National Council in Russia. In Vladivostok, he organized his first exhibition of watercolors. At that time, painting became his sole means of self-expression. In July 1920, he embarked on a study trip to China and India, from which he gathered a wealth of artistic material for his drawings, watercolors, and oil paintings. Upon his return, he worked at the Liberation Memorial (he was demobilized with the rank of first lieutenant), from 1920 to 1921 he studied part-time at UMPRUM in P. Janák’s class; from 1924 to 1927 he studied under J. Gočár at the Academy of Fine Arts in Prague (AVU) and continued to work in his studio; in 1930 he established his own practice as an architect. From 1931, he was a member of the Mánes Union of Fine Artists (SVU Mánes), the Association of Architects, and the Union of Czechoslovak Art.

From 1948 to 1950, Grus worked as an interior designer at the Central Office for Folk Art Production; from 1951 to 1958, he was a professor at the Academy of Arts, Architecture and Design. He also made a name for himself as an exhibition designer (the 1939 World’s Fair in New York and the 1948 exhibition marking the 600th anniversary of Charles University). After the liberation, he devoted himself primarily to urban planning; among his most significant works was the 1949 design for the National Memorial at Dukla. In 1963, Grus was named an Honored Artist. His son, Pavel Grus (1935–1993), was a designer.

Martin Kučera, Biografický slovník českých zemí 20, Praha 2017, s. 795.