Wood is a marvelously adaptable structural building material. When treated with a compatible preservative to prevent early decay deterioration, it is an economical and practical structural material for many short-span bridges (spans in the range of 15 to 60 ft). Timber's inertness to deicing chemicals, as well as some new design developments, such as glued-laminated deck panels and prestressed laminated decks, make it more attractive than ever for use in highway structures, Important factors in assuring long, useful lives for timber bridges include designing to avoid water-trapping details, use of effective and compatible preservative treatment, and following a systematic inspection and maintenance program. Attention to these factors will provide a lifespan that is competitive with other structural materials, such as steel and concrete, and will, in most cases, dramatically increase the useful life of timber bridges.

Timber bridges are remarkable structures--when properly designed, built, and maintained, they can (a) carry heavy loads without showing material fatigue,(b) resist the deteriorating action of deicing chemicals,(c) be constructed by unskilled labor, and (d) last for long periods of time. Timber is particularly adaptable to short-span bridges (spans up to 60 ft) and can be economically designed to carry heavy highway loads. For example, some timber bridges in western Canada routinely carry logging trucks and machinery weighing in excess of 100 t. Wood was one of man's first building materials. However, as modern technology has yielded its wonders in mass-produced steel, aluminum, concrete, and plastic construction materials, wood has been largely overlooked as a primary structural material for bridges. Wood is still a marvelously adaptable structural material. For example, structural wood