Slate and tile are two of the oldest types of roofing materials that are still widely used today.  In fact, Celtic settlements located in the British Isles 4,500 years ago were roofed with slate.  Slate is a natural rock that consists of layers of glassy or micaceous materials that were pressed closely together under great pressure within the earth’s crust.  This rock is quarried, split into various thicknesses, and then sawed into squares ready for installation.

 Whereas slate begins as a natural rock, tile is completely man-made.  Originally, tile was created by baking clay, but in modern industrialized countries, it is manufactured by molding cementitious materials.  Historians believe that tile has been used for roofing since the oldest known civilizations located in the Middle East and China.  Many varied styles and designs of tile have characterized each culture and region.

 In North America, tile was originally used in the Spanish colonies located throughout Mexico, California, Texas, Florida, and the Caribbean.  Many fine examples of 17^th and 18^th century tile roofs remain perfectly functional, and tile roofs are part of the essential style and culture of Florida, California, and the Southwest.

 Slate, by contrast, was quarried in Europe and transported to the new American colonies on ships.  The slate was placed in the keels of merchant ships to provide stability during the often stormy voyages.  It, therefore, became the predominant roofing material in the colonial port cities of the East Coast.  After the Revolutionary War, American slate sources were developed, with the best slate coming from New England.  In the Spanish-influenced Southwest, meanwhile, tile kilns were built wherever clay and fuel were abundant.

 Although slate and tile are durable and long-lasting, wind, rain, and freezing will eventually age and deteriorate these wonderful materials.  The many layers which comprise slate offer the opportunity for water to be drawn by capillary action in from the edges.  In a process known as spalling, this water freezes in colder climates and eventually shatters the slate.  Tile is also porous and can be damaged by freeze-thaw cycles that will exploit any weaknesses and discontinuities within its structure.  Slate and tile can also suffer from “nail tiredness,” the enlarging of nail holes by intermittent vibrations caused by wind shear.  In addition, underlayments beneath tile and slate can decompose, allowing water blown under or drawn up by capillary action to leak into the building.  Historically, the answer to an aging and deteriorating slate or tile roof has been to perform a complete tear-off and replacement, but this can be very expensive and time-consuming.  Therefore, Andek’s Roof Restorer System was developed to economically and effectively restore slate and tile roofs.