 Due to the clay sediments of the former lake bed that Toronto is built upon, and but more prominently the shale layer underlying this area of North America, brick has been an especially cheap and available material for almost the city's entire history.Much of it was provided by the Don Valley Brick Works, Domtar's brick division, Canada Brick and Brampton Brick, whose output can still be found in thousands of structures across the city and throughout the surrounding regions.Throughout the city, most homes from all eras are made of brick or brick and cinder block.