Wood shingles are machine cut, while wood shakes are hand split or mechanically split. Wood shakes are thicker and have a much more uneven surface. Most wood shingles are cedar; however, some are redwood. Wood shingles can be used on roofs with a pitch as low as four in twelve; however, six in twelve or more is recommended. Wood shingles vary in length between sixteen inches and twenty-four inches. On a good quality installation, no more than one third of the shingle is exposed to the weather.

The life expectancy of wood shingles is generally thirty to forty years;in splitting and cupping of the shingles. Too much shade and moisture causes however, low quality shingles have been known to deteriorate badly in fifteen to twenty years. The rate of wear depends largely on exposure (the amount of shingle which is exposed to the weather) the pitch (the steeper the better) the grade of shingle (there are three) and the amount of sun and shade. Too much sunlight dehydrates the shingles, causing them to become brittle. This results in splitting and cupping of the shingles. Too much shade and moisture causes rot and moss to grow. Wood shingles and shakes can also suffer mechanical damage from tree branches, foot traffic, snow shoveling, etc.

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Figure 3. Shingle Application

Another factor which affects the life of wood shingles is their ability to dry quickly. It is preferable to put wood shingles over spaced roof sheathing boards rather than plywood sheets. Some experts say the use of plywood will halve the life of the shingles.

As a general rule, when more than ten to fifteen percent of the roof requires repair, it is best to replace the roof covering.