Jarrah is found only on lateritic soils in south-west Western Australia, in the 650 to 1250 mm rainfall zone. Under optimum conditions it is a tall tree attaining 30 to 40 m in height with diameter at breast heightup to 2 m. On poor sites the species is reduced to a mallee form.
Heartwood of mature trees is dark-red, although regrowth is pinkish-red, while sapwood is pale yellow. The texture of the wood is relatively coarse but even, with the grain slightly interlocked and sometimes producing a fiddleback figure.
Green density is the density of wood in the living tree, defined as green mass divided by green volume, and useful for estimating transport costs. It varies with season and growing conditions.
Air-dry density is the average mass divided by volume at 12 per cent moisture content (this is the average environmental condition in the coastal capital cities around Australia).
Basic density is oven-dry mass divided by green volume. This measure has the advantage that moisture content variations in the tree during the year are avoided.:
Green density is about 1170 kg/m3, air-dry density about 820 kg/m3, and basic density about 670 kg/m3.
Tangential and radial shrinkage before reconditioning are 7.5 and 5.0 per cent respectively, and after reconditioning 6.7 per cent and 4.6 per cent respectively.
The timber is relatively easy to work with sharp tools, although when dressing the planer angle may need to be reduced to 15°.
The CSIRO Durability Classes are based on the performance in ground of outer heartwood when exposed to fungal and termite attack.
|1||More than 25|
|2||15 to 25|
|3||8 to 15|
|4||Less than 8|
The ratings are not relevant to above-ground use. In late 1996, CSIRO published revised ratings, which include termite susceptibility. Ratings are now available for about seventy species for decay, and for decay plus termites.:
Durability Class based on the CSIRO 1996 ratings are 3/2 for decay, and 3/2 for decay + termites i.e. the wood is termite-resistant.
Minimum values (MPa) for strength groups for green and seasoned timber come from Australian Standard AS2878-1986 'Timber - Classification of strength groups'. In grading structural timber, each species is allocated a ranking for green timber of S1 (strongest) to S7, and for seasoned timber SD1 (strongest) to SD8.
MOR is modulus of rupture or bending strength, MOE is modulus of elasticity or 'stiffness', and MCS is maximum crushing strength or compression strength. Hardness refers to the Janka hardness test and is a measure of resistance to indentation.
Minimum values (Mpa) for green timber
Minimum values (Mpa) for green timber
Where test data were available, they are shown in bold print. Most values are from Bootle (1983), Wood in Australia. Types, properties and uses. (McGraw-Hill), or Julius (1906), 'Western Australian timber tests 1906: The physical characteristics of the woods of Western Australia'.
Where no strength data were available, air-dry density was used in accordance with the Australian Standard AS2878-1986 Timber - Classification of strength groups to predict the strength group. Consequently, the strength values quoted are from the above two tables.:
Green and dry strength groups are S4 and SD4 respectively. The most important strength properties are given in the table below.
|Modulus of Rupture||MPa||68||112|
|Modulus of Elasticity||MPa||10000||13000|
|Max Crushing Strength||MPa||36||61|
Jarrah is the major timber species in Western Australia, and readily available locally and interstate.
The major uses for jarrah are for joinery and furniture, panelling and flooring, although in the past the timber was used extensively for general construction, sleepers, poles and piles. In the 19th century it was widely used for cobbles.