Search:


Home > Species > Properties explanation

Explanation of Species Properties


Table showing Summary of Species Properties

Properties
The species guides all have a table showing the various properties of the timber. The following information explains these properties.
DENSITY
Measured in kg/m3 and given for both Green Density (GD) and Average Dry Density (ADD)
HARDNESS
Measured in kN – a standard test is carried out (Janka Test) which measures the penetration into the timber of a common load and projectile. The results relate back to a hardness capacity of the material. This information is useful where the timber may be subject to potential damage from impacts – i.e. a dance floor.
DURABILITY CLASS
All timber is assigned a durability classification (Classes 1- 4) following inground testing. This ensures adequate life expectancy when exposed to both fungal and insect attack. The lower the number the higher the performance in terms of durability. This information is also useful for specifying material for external or exposed applications.
STRENGTH GROUP
Timber of various species is assigned into a strength group based on the mechanical properties of the material (in a clear state free of strength reducing characteristics). There are seven strength groups for unseasoned timber (S1 to S7) and eight strength groups for seasoned timber – i.e. with a moisture content of 12% (SD1 to SD8). The lower the group number, e.g. SD1, the higher the mechanical properties.
JOINT GROUP
Timber of various species are also assigned into a Joint Group, for unseasoned timber J1 to J6 and for seasoned timber JD1 to JD6. These groups have a relationship to the timber species density – the higher the density the higher the capacity and the lower the Joint Group number.
STRUCTURAL GRADES
Timber grading is done to set appropriate structural limitations on individual pieces of timber. Each species has structural properties assigned to it following tests conducted on clear small sections of timber. Timber may then be graded visually for any faults or characteristics which may reduce the ‘clear’ sample’s capacity, e.g. a knot hole. Alternately, timber may be machine graded or proof graded where the individual timber element has a known load applied and its reaction to this load measured, thus reflecting its capacity in bending. The higher the grade number assigned, e.g. F17 etc, the higher the structural capacity.
TOUGHNESS
This is a measure of a timbers ability to resist impact forces such as shocks and blows. Generally we have specified either Light, Medium or High in regards to these properties. Typically, each species has a Nm capacity in regards to toughness:

  • Light: up to 15Nm
  • Medium: 15 – 25Nm
  • High: greater than 25Nm

EARLY FIRE HAZARD INDICES
These indices relate to the Ignitability, Spread of Flame and Smoke Development for various species of timber. Not all species have been tested – where this is the case it should be noted that there is some strong relationship to density to give a comparison result, although this is not completely reliable. The requirements vary with regard to the application and the Class of Building and this information is covered within the Specifying Guide and the Building Code of Australia.
TERMITE RESISTANCE
Some species of timber offer higher resistance to incidence of termite attack than others. These species have been nominated in AS3660.1 as being naturally termite resistant.
COLOUR
Colour Species
Blond Ash (Silvertop, Mountain and Alpine), Blackbutt, Messmate, White Mahogany
Brown Brown Barrel, Brushbox, Grey Box, Manna Gum, New England Blackbutt, Spotted Gum, Stringybark (Yellow, Red, Silvertop), Grey Ironbark
Yellow Cypress, Tallowwood
Red Forest Red Gum, Flooded Gum, Grey Gum, Red Ironbark, River Red Gum, Sydney Blue Gum, Turpentine, Red Mahogany, Bloodwood