Hardwoods & Clears
Hardwoods are mainly deciduous, or broad leaf, trees shedding their leaves in winter. There are two groups - temperate and tropical (some hardwoods are evergreen)
- Some 20,000 different commercial species
- Although generally more durable and stronger than softwood, they must be used in the correct way and environment
- Hardwoods tend to be deeper in colour and are often used decoratively
- The majority of hardwoods are usually denser than softwood, due to their comparative cellular structure. However, some hardwoods, particularly tropical species, grow fast enough to be of similar, or lower, density than slow growing softwoods.
- Hardwoods are usually supplied in random lengths and widths, but in standard thicknesses.
- Many hardwoods are used as veneers on softwood panel products.
Which species of wood do I choose?
This depends on a number of factors, but when selecting the timber species consider these points:
- The end use - for example, is the wood to be used as a structural material and then covered over with something else, i.e studding covered by plasterboard, or will it be exposed?
- What strength is required? Does the timber need to have a high bending strength, such as a joist, or a high tensile strength where the timber is stretched in the application?
- Is the wood to be used purely for a decorative effect? Is this to be a dark or light colour?
- Is the wood to be machined? Some species are more easily machined than others.
- Is the wood from a managed forest source, and certified, (i.e FSC or PEFC)
- Cost. It may look nice, but is it worth the additional cost, if another less expensive and more commercially available timber can do the same job?
- Durability and treatability: is it necessary to use preservatives?
How timber is graded
Strength grading is a way of assessing the strength of a piece of timber, which depends on its species as well as its grade. A low grade timber from a strong species may be equal in stength to a high
grade timber from a weaker species. Strength grading is needed to ensure timber is strong enough for a particular job, e.g. a floor joist or a roof truss. It also saves money by helping to avoid over-specification.
To make specifiying easier, species and grades are grouped into stength classes of similar strength. Strength classes range from C14 to C50 for softwood and D30 to D70 for hardwoods. The higher the number the stronger the timber. The most common grade for softwood carcassing is C16.