Structural use of hardwoods

Although the vast majority of structural timber in the UK is softwood, there is a significant interest in hardwoods from both temperate and tropical regions for structural applications. When using hardwoods in structures, the specifier may need to take more interest in the species, its origin and its moisture condition than would be the case in the routine specification of softwoods.

The term hardwood designates wood from angiosperm trees, which are flowering broad-leaved trees with enclosed seeds called fruit. Hardwood trees have a natural distribution that extends throughout the tropical and subtropical regions to the outer edges of the northern and southern temperate zones, although the range of species varies tremendously between continents and regions.

This Wood Information Sheet (WIS) covers a number of topics relating to the structural use of hardwoods including the strength properties of some of the most common hardwood species, the drying and storing process and some of the more service condition and durability factors which must be considered when specifying the species.

Contents:

• Hardwood
• Applications
• Wood drying and storing
• Specifying hardwoods
• Structural design with hardwoods
• Determining structural design values

This Wood Information Sheet was revised in January 2017. Major changes have been made to reflect new and updated standards, including BS EN 350, BS 5756, BS EN 16737, BS EN 14080 and BS EN 14081-1. One of the significant changes is to strength grading, where the grade designation HS has been updated to STH, which is harmonised across Europe. The section on the marking of structural timber has also been revised to include the process of CE marking as required by the Construction Products Regulation 2011. Updates have also been made to the strength classes section to reflect changes in the standard BS EN 338.