Mission Tile

Mission tile is a curved clay roof tile laid in two layers: a row of concave pans (or "nuns") with their edges turned up, and a row of convex covers (or "monks") laid over the joints between them. The result is the deeply ribbed, wavy roof associated with Mediterranean, Spanish Colonial and California Mission architecture. In English the system is also known as barrel tile, and in German as Mönch und Nonne.

Shape

Each tile is a tapered half-cylinder, slightly wider at one end so that each tile fits into the next one up the slope. The same tile can be used as either pan or cover simply by turning it over, although many modern systems make the two parts in different sizes. A popular story says early tiles were shaped over a worker's thigh; whatever the truth, the hand-made tapered form produced the irregular look many people associate with old roofs.

History

The two-piece pan-and-cover principle goes back to ancient Greece and Rome, where flat tegulae were combined with half-round imbrices. Fully curved pans and covers became the standard form around the Mediterranean and were carried to the Americas by Spanish and Portuguese settlers. In California, mission-style clay tile was first produced in 1780 for the Franciscan missions, which gave the tile its English name. In Germany, flat beaver-tail tiles gradually replaced two-piece curved tiles from the late Middle Ages.

Performance

Mission tile roofs are heavy and use more tiles per square metre than one-piece pantiles or interlocking tiles. The curved shape creates an air space under the tiles that helps reduce heat gain, which is one reason the form is common in hot climates. In high-wind regions the covers must be mechanically fixed with nails, wire, clips or approved adhesives, since loose covers can be lifted by the wind.

Modern versions

Two-piece clay mission tiles are still manufactured, along with one-piece "S" tiles and concrete imitations that reproduce the look at lower cost.