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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 restuls 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
in-ground testing. This ensures maximum life expectacies when
exposed fungal and insect attack. The lower the number the higher
the perfromance 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 mechancial
properties of the material (in a clear state free of strength
reducing characteristics). There are seven strength groups fro
unseasoned timber (S1 to S7) and eight strength groups for seasoned
timber - ie with a moisture content of 12% (SD1 to SD8). The lower
the group number, eg SD1, the higher the mechancial
properties.
Joint Group Timber of various species
are also assigned into a Joint Group. for unsesoned 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 test conducted on clear small sections of timber. Timber
may then be graded visually for any faults or characteristics which
may reduce the 'clear' samples capacity, eg a knot hole.
Alternatively, timber ay 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, eg
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 Nm capacity in regards to
toughness; Light: up to 15Nm Medium: 15-25 Nm High:
>25Nm
Early Fire Hazard Indicies These indicies
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 attackl than
others. These species have been nominated in AS3660.1 as being
naturally termite
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