The site for the new school was the former Christie mansion property on Bronson Avenue at the corner of Lisgar Street, which was purchased for $25,000.

[1] By 1929, enrollment had increased to 160 students, and a new building with five classrooms, a science lab and a small library was constructed.

A home economics department and nine new classrooms were added in 1939 to meet the needs of the enrollment of 300 students, taught by nine Sisters.

In 1952, an addition to the Kearns Memorial Wing added three new classrooms, a students’ library and a principal’s office.

When Immaculata marked its 60th anniversary in 1988, James J. Shea was appointed as the school’s first lay principal, overseeing an enrollment of 870 students.

[1] After Immaculata celebrated its 65th anniversary in September 1994 (after 2 years of major renovations), the school moved to the current location at 140 Main Street.

[citation needed] The high school's current location was originally built in 1929–1930 to house both St. Patrick's High School and St. Patrick's College (Ottawa), a now defunct Catholic post-secondary institution administered by the Oblate Fathers.

In January 2002, the program, now called St. Mary’s Home Community Outreach, moved into 780 rue de l’Eglise.