Species > Properties explanation
Explanation of Species Properties
Table showing Summary of Species Properties
The species guides all have a table showing the various properties of the timber. The following information explains these properties.
Measured in kg/m3 and given for both Green
Density (GD) and Average Dry Density (ADD)
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.
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.
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.
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.
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
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.
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 || 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|