In the first half of the 19th century tin roofing also spread to commercial and public building to the exclusion of slate. An agent of the Phoenix Fire Insurance Company wrote from Montreal in 1809 “in the covering of houses in this country they never employ Tiles or Slates, which are not thought to stand the Climate, as well as Tin or Sheet Iron.” In its recommendations on the form and nature of building best adapted for barracks and storehouses, the 1825 Smith Commission on the defense of British North America reasserted the prevailing belief in the superiority of tin or iron over slate roofing: The roofs of the principal buildings in this country are covered with plank, upon which sheets of Tin or Iron are nailed. We think this an excellent sort of roof, much less liable to be out of order and to require repair, than slate or tiles. We are of opinion that the roofs of all Barracks, Storehouses or Government Buildings in the Canada’s ought to be covered in this way.
Contrary to British military practice in Quebec, the Atlantic colonies of British North America during this period saw general use of slate for stone public and commercial buildings. In her study of roofing materials used by the Royal roofing contractor in Canada, Elizabeth Vincent has found that while spurning slate in the upper colonies the Engineers preferred the material on the east coast. Duchess slates (slates 12 inches by 24 inches) were adopted for covering the magazines of the Halifax citadel and its dwelling casements and the original slates of the south magazine covered in the 1840s are still intact. Many Maritime public buildings were roofed with slate: Province House, Halifax, 1811-18; Admiralty House, Halifax, 1819; Province House, Charlottetown, 1843-47; and Government House, St. John’s, 1827. The major seaports of Saint John, Halifax, and St. John’s were predominantly wood built, shingle-roofed towns. However, through the century numerous fires eventually made brick or stone buildings roofed with slate the norm for waterside warehouses and stores.