His marriage ensured entry to French Canadian society, he was appointed diocesan architect for Montreal.

[2] This was followed by the McGill University Arts Building, 1839–1843, the oldest building on the McGill campus, extended 1860-1862 (formerly known as the McGill College Building, today renamed the McCall MacBain Arts Building); Asile des Soeurs de la Providence (aka Asile de la Providence), 1842 (demolished); High School of Montreal, 1845 (demolished); Protestant Orphan Asylum, 1848 (demolished); Palais episcopal (Episcopal Palace) 1849, burnt 1852; Eglise de Notre-Dame-de-Toutes-Graces, 1851; Church of St Anne, 1853 (demolished); Grand séminaire de Montréal, 1854; and the Old Montreal Court House, now known as the Édifice Lucien-Saulnier.1856-1859.

Ostell submitted designs for the new St. James Cathedral in Toronto in 1849, placing second in the competition to Frederick William Cumberland.

The house, which was abandoned for the past 30 years and falling apart, was restored recently (2019) to its original appearance by the real estate developer of the condominium complex now surrounding it.

The factory made doors and windows for export to Upper Canada (Ontario), Australia, the US and Britain.