1. Field of the Invention
The invention relates to a tile particularly for installation on a sloping roof, but the tile could have applications elsewhere, for example on a vertical wall.
2. Prior Art
Conventional interlocking roof tiles or shingles have been known for many years, and are commonly found as two main types, namely relatively thick clay tiles, or sheet tiles, which are made from sheet metal or other similar thin material. The clay tiles are heavy, mechanically relatively weak and are limited in mechanical complexity due to manufacturing difficulties and material limitations. Metallic sheet tiles also have problems, for example a tendency to bend and be permanently deformed after a person has walked over the roof, due to insufficient backing support for the tile. Also, if a relatively thin material is usued, the tile might lack adequate stiffness to resist bending under strong wind forces blowing up the roof and bending the tile upwardly, thus permitting water to penetrate under the tile. While attempts have been made to stiffen relatively thin tiles using raised ribs, commonly the ribs do not extend continuously along the length of the tile between upper and lower ends, and thus there is an area of weakness between the ribs. Also, the use of stiffening ribs or corrugations in a metallic tile can increase difficulty of installation of the tile because some designs of tile do not permit much variation or tolerance to the "fit" between adjacent tiles. Commonly, with prior art ribbed metallic tiles, fitting errors during installation of a series of tiles can accumulate to such an extent that unsightly gaps can exist between adjacent tiles, which can permit entry of water into the roof. Typical metallic tiles are shown in U.S. Pat. No. 279,487 issued to Jones; U.S. Pat. No. 361,031 issued to Thorne; U.S. Pat. No. 397,298 issued to Lee, and U.S. Pat. No. 2,202,830 issued to Bussey. These four patents disclose metallic roofing tiles with corrugations to cooperate with adjacent tiles, and partially to stiffen the tile. However, some of the edge fitting structure is quite complex and would likely present difficulties when installing the tiles. Also stiffening ribs in these tiles do not extend continuously down the tile.
Some of the prior art tiles have interfitting edge portions which cooperate closely with complementary edge portions of adjacent tiles such that a relatively small gap exists between the tiles. This gap can be sufficiently small as to cause water to be drawn by capillarity through the gap, around corrugations and into the roof, giving the impression of a leaking roof.