At mid century slate was still a forgotten roof covering in central Canada. In the mercantile part of the city of Montreal which included “the most elegant and substantial of the public Buildings” nineteenths of the buildings had roofs of tin or sheet iron. Insurance reports pointed out that “Tiles or Slates being nowhere used in the Colony.” The prevailing disregard of slate was reiterated in a Quebec Gazette article on various kinds of roofing used in Lower Canada. The feature on 10 June 1846 reported, “Slates are at present but little appreciated in this country although they have stood the test of climate.” The negative attitude toward slate roofing in pre – Confederation Ontario and Quebec is most practically and quantitatively illustrated by G.F. Baillairge’s 1867 report describing the public buildings of Upper and Lower Canada. The document which summarizes most major construction since 1830 lists about 115 buildings including houses of parliament, observatories, custom houses, post offices, court houses, jails and drill sheds. Four buildings have slate roofs, the most significant being the houses of parliament just completed in the capital of the new Dominion of Canada.
The choice of slate for roofing the Ottawa Parliament Buildings, a construction project of unprecedented magnitude in British North America, was the result of several circumstances that dramatically changed builders’ attitudes toward the use of this material in the 1850s and 1860s.
The rapid settlement stimulated financial and commercial development of Toronto and Montreal, and created an increased demand for building materials of all kinds. Railway improvements contributed to the urban growth and made possible commercial slate quarrying in the United States and Canada by linking cities with quarries away from ship routes. Hence forth a supply of roofing installation slate was readily available and reasonably priced. Finally a shift from conservative Neoclassical public building that de accentuated roofing to the Gothic Revival and Second Empire styles featuring steeply pitched, colored, patterned roofs encouraged the use of slate as it could be readily fitted to complex roof forms and lent itself to fanciful designs.