With roofs, as with many other home systems, there is often no problem until something changes. It may be relatively sudden changes, such as may happen with alterations or repairs to the roof in which workmanship has been poor, or it may be long-term, such as weathering/aging of the roofing system or one/some of its components. From the time they are first produced, every system, component, and material in a home is deteriorating. For most components and materials exposed to weather, deterioration is relatively rapid for a short time and then slows dramatically. Over most of its design life, a well-built, well-designed, and properly installed roofing component will deteriorate slowly. Toward the end of its life span, deterioration will accelerate until failure occurs.
Due to the extend and complexity of a roof system it is not possible to discuss in detail what problems may be encountered but only a few will be mentioned in this section.
Most roof structures will consist of manufactured trusses. Manufactured trusses are designed by a structural engineer and built in a facility under controlled conditions. Trusses are typically designed for a specific home and will vary in design.
Types of Tiles
The materials most commonly used for roofing tiles are clay and concrete. In the past, tiles made from fiber cement contained asbestos. Due to legislation enacted to limit the use of asbestos in products, sisal has been substituted for asbestos. There are also tiles made from recycled plastic.
Parts of a Tile
The parts of interlocking tiles have the same names no matter what material they’re made from:
The different tile parts are as follows:
- Face– is the side of the tile facing up when the tile is in place.
- Back– is the side of the tile facing the roof cavity when the tile is in place.
- Head– is the end of the tile farthest uphill when the tile is in place. When you walk the roof, the tile heads are hidden beneath the butts of the ties in the course above. From the roof cavity, they should be hidden by the underlay.
- Butt– is the end of the tile farthest downhill when the tile is in place.
- Underlock– forms the under-part of the interlocking portion of two tiles. It’s designed to act as a water channel to direct any water that enters the interlock back onto the surface of the roof.
- Coverlock– forms the upper-part of the interlocking portion of two tiles. It covers the underlock and is the most fragile part of an interlocking tile. It’s the part most easily broken by foot traffic.
Tiles on the Roof
Tiles on the roof are named according to their position and the purpose they serve:
- Starter course– is the first course of tiles, installed at the eve.
- Finish course– is the last course of tiles before the ridge cap tiles.
- Ridge cap tiles– protect the roof at the gap between finish courses.
- Hip cap tiles– protect the roof at the hip at the gap where field tiles on different slopes meet.
- Verge tiles– protect the roof at the verges where the field tiles end.
- Field tiles– are the tiles covering the main portion of the roof. They include all the tiles on the roof except for the starter and finish tiles, and the ridge-, verge- and hip- cap tiles.