Outdoor timber decking is subjected to very harsh conditions, being exposed to rain, hard sunlight and other weather over the course of its lifetime. Harder Timber will withstand these conditions much longer than lesser quality woods.
The hardness of timber is measured by the Janka Test, which gives a numerical value to the hardness of each type of timber. This test pushes a small steel ball half way into the wood surface. The amount of pressure required to push the ball to this half way mark is measured in Kilo Newtons (kN). This Number in Newtons is the Janka number. The higher the Janka number the harder the timber.
Building timber usually have a Janka hardness number between 5kN and about 12kN, occasionally some timbers rate at 16kN. Indoor timbers for floors require a reasonable hardness of at least 6.0kN if they are expected to last. Outdoor structures should be 8kN or higher.
There are several species of wood grown or available in Australia that are suitable for outdoor decking, gazebos and other small structures.
- Jarrah 8.5kN Janka
- Blackbutt 9.1kN
- Spotted Gum 11kN
- Merbau (Asian wood) 8.56kN
- Stringybark 8.1kN
- Sydney Blue Gum 9.0kN
- Turpentine 12.0kN
- Ironbark 14kN The hardest and most durable option.
Another option is treated pine. Though raw pine is fairly soft it can be chemically treated to increase its hardness. This treated pine is an inexpensive option for outdoor building, and has an advantage in that it can be stained or painted in many different styles. It must be oiled on a yearly basis.
Cypress Pine has a Janka rating of about 6.1kN
We supply timber for DIY or professional building projects. This includes timber suitable for outdoor structures as well as internal floor.