Clay tile roofs - Canal tiles

This document completes the and deals specifically with the installation of clay canal tile roofs.

The canal tile is one of the oldest shaped roofing materials. Today's tiles seem to derive from the "imbrex", which covered the edges of two flat-bottomed tub-shaped tiles (the "tegulae"), and was widely used by the Romans. Over the centuries, the two elements evolved into the unique terracotta half-cone shape that characterizes the majority of canal tiles in use today. Some under-tile models once again feature a flat base, others have tenons on the underside to allow them to be laid on battens, and under-tiles (or running tiles) and over-tiles (or roof tiles) can feature "stop" devices that lead to a fixed overlap of the elements whatever the conditions of application. From the 1960s onwards, channel tiles were also combined with profiled sheet roofing supports.

Geographically, canal tiles are mainly used in France on the Atlantic seaboard and in the Mediterranean basin, but they are still used in Lorraine, in a climatic context that is not conducive to the use of this technique, and for which the tradition brought by the Romans seems to be the only accepted determining factor.

Among clay tile roofs, canal tile roofs are probably the most varied in terms of installation techniques (supports, laying, fixing, etc.), with regional and sometimes even very local variations. This peculiarity made it difficult to draw up harmonized national provisions – in the form of DTU 40.22, which is widely referred to below –, and obliged the drafters of this document to take account of local provisions whose use was deemed satisfactory, while retaining the scope of their original use.