About mid-19th century, an increased sensibility to colour in Gothic architecture was encouraged in new interpretations of the Gothic Revival by Toronto roofing company such as William Butlerfield and George Edmund Street and the writing of the influential aesthete John Ruskin. Butterfield’s All Saints’ Church, Margaret Street, London (1850-53) built of red brick banded and patterned with black brick, introduced polychromy into English Gothic Revival architecture just at the time Ruskin was urging the importance of colour and the study of Italian Gothic models. In 1855 Street’s Brick and Marble Architecture in the
North of Italy focused attention on the possibilities of geometric mosaics in these and other materials. Polychrome soon became the principal symbol of the new High Victorian Gothic and, coupled with the high pointed roots, large scale and bold silhouettes that were also features of this phase, it opened the way for colour effects in many materials, including slate.
In Canada the taste for polychrome effects in slate roofing initially appeared in High Victorian Gothic institutional and governmental architecture. University College, Toronto (1856-59) was one of the earliest examples. Inspired in composition by the newly completed Oxford Museum, the College incorporated Norman as well as Gothic elements and was crowned by mansard pavilions and a medium-pitched roof with wide bands of alternating slate colours. On the roof of the west elevation slates were worked into rows of zigzags and diamonds enclosed by parallel horizontal lines. Similar geometric patterns had recently been employed by Butterfield in the brick walls of All Saints’ Church. The diamond or quincunx had been used before in 14th-century French slating but in the new Gothic spirit, the banding, bordering and zigzags of University College recall medieval models.
Within a few years polychrome pattern slate roofing was used on the Parliament Buildings in Ottawa. The “noble civic buildings of the Low Countries and Italy” provided suggestions for the design, but the High Gothic interpreted here liberally mixed its models of inspiration producing a vigorous composition of mixed Gothic, Second Empire and other sources enriched by the colorful treatment of building materials. The slate roof of Fuller and Jones’ central Parliament Building was striped in contrasting bands of plainly cut yellow and green slates. Repeated a decade later on the conical tower of the chapter-house Library of Parliament, the roof stripes capped a building complex unparalleled in its picturesque effect. In their design of the Departmental Buildings that flanked the legislature, architects Stent and Laver used similar slate colours but created a more whimsical roof pattern alternating bands of plain and hexagonally cut slates and punctuating the latter by rosettes. These ministerial offices were more informal in character and their polychrome floral slate patterns paralleled ornamental slating in contemporary domestic architecture.