A review of the Canadian federal buildings built in the Second Empire mode from 1871 to 1881 shows the tendency to polychrome slating in its plainer examples. An important exception was the Toronto Custom House (1873-76), seen by architectural historians as probably the most pompous example of the Second Empire style erected by the Department of Public Works. While it was slated with two colours of plain and round cut slates worked into diamonds between the dormers, the polychrome pattern is dominated by the elaborately carved stonework of the main facades. Most fine examples of the style with very broken or complex rooflines such as the Montreal Post Office , Toronto Post Office (1871-74), and Saint John Custom House (1872-74) used plain or common slate work on the slopes and in the latter two, tin for the domes. In contrast, unusually austere Second Empire designs were dressed up by slate floral motifs or banding in two or more colours that appeared in the towers as well as the slopes. In Ottawa such colour banding on the slate mansards of the Post Office (1872-76) and Supreme Court (converted from workshop 1881) was part of a conscious effort to make these buildings accord with the High Victorian Gothic structures on Parliament Hill.
It was in the residential expression of the Second Empire that the full potential of roof slate for coloured picturesque effect was realized by re roofing industry. The more fanciful roofs were probably inspired less by federal architecture than by the pattern books that circulated across the country. The French roofed (man-sarded) villas or suburban residences that appeared in Ilobb’s Architecture of 1873 invariably called for slates in two or more tints cut to ornamental shapes. An advertisement for a slate design in Cummings and Miller’s Architecture  revealed that some American architectural firms actually patented specific patterns, but a review of patents here shows there was no Canadian parallel to this practice.В В Good slaters could emulate most designs and imitation of the examples illustrated in Bicknell’s Village Builder (1871)В В made their appearance on Canadian mansards.
The majority of polychrome slate mansards that adorned Canadian Second Empire homes displayed one-of-a-kind patterns using common motifs assembled in unique ways. Round forms took precedence over the jagged geometric patterns of the Gothic. The floral motif used on the east and west blocks of Parliament Hill was one of the most popular. It appeared as a simple line of rosettes on round or hexagonally cut slalework, flowers within contrasting colour bands, or the central motif in an intricate design framed by patterned borders. In one instance, colour banding was worked into a refined lacelike pattern which echoed the delicacy of iron cresting.