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.
Hardwood species found in temperature regions have an annual growth cycle, whereas tropical hardwoods grow throughout the whole year.
Service conditions and durability are important factors when specyfing the species. Risks include attack by fungi, wood-boring insects and marine borers.