Karri is one of Australia's tallest hardwoods, with height from 45 to 70 m. It is native to south-west Western Australia on site-specific soils around Manjimup, about 300 km south of Perth. The mean annual rainfall in the area of occurrence is mainly from 900 mm to 1300 mm, and occurring in winter. Outlying forests, away from the main karri belt, occur between Karridale and Forest Grove, and other smaller ones are at Mount Many Peaks, Torbay, Rocky Gully and the Porongorup Range.
Heartwood of timber from mature trees is pale pink to reddish brown, although regrowth heartwood is a lighter colour. The sapwood is white and usually easy to distinguish.
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 1200 kg/m3, air-dry density about 900 kg/m3, and basic density about 690 kg/m3.
Tangential and radial shrinkage before reconditioning are 10.0 and 4.5 per cent respectively, and after reconditioning 8.5 and 4.0 per cent respectively.
Karri is less easy to work than jarrah, even with sharp tools. Whendressing the timber, the planer angle may need to be reduced to 15°. It generally requires additional sanding after moulding.
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 is 3/2 for decay and 4 for decay + termites. Sapwood is Lyctus-susceptible.
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 S3 and SD2. The more important strength properties are given in the table below.
|Modulus of Rupture||MPa||73||132|
|Modulus of Elasticity||MPa||14000||19000|
|Max Crushing Strength||MPa||36||72|
The species has been one of the major timber species of Western Australia and available both locally and interstate. Availability will be restricted considerably with most of the resource now in conservation reserves.
Karri is now being used more extensively for flooring and panelling, and has potential for fine design furniture because of its high strength. It has been used extensively for general construction, shipbuilding, sleepers, guides or side beams in mines, structural plywood, roofing timbers and pulp and paper. Greater lengths are available than from any other Western Australian hardwood.