Tasmanian oak

Scientific name

Eucalyptus regnans, E. delegatensis, E. obliqua. Family: Myrtaceae.

Local names

Mountain ash, Victorian ash (E. regnans), alpine ash, woollybutt (E. delegatensis), messmate stringybark, brown-top stringybark (E. obliqua)

Description and natural occurrence

The three species in this group are large trees, attaining heights up to 90 m and stem diameters up to 2.5 m at the butt. Tree trunks are free of branches to a considerable height. Bark is rough and persistent to the small branches on E. obliqua but only on the lower half of the trunk of the other species. Above this it is smooth.

E. regnans occurs abundantly in eastern Victoria and Tasmania.

E. delegatensis has a wide distribution in south eastern Australia, found at elevations of 600-900 m in Tasmania and 900-1200 m in Victoria.

E. obliqua has a wider distribution extending into parts of southern Queensland.

Wood appearance

Colour. The heartwood is pale brown to white brown and often with pinkish tints. Generally there is no noticeable colour difference between sapwood and heartwood.

Grain. Generally moderately open to coarse, but even and straight. Growth rings are often noticeable.

Wood properties

Density. 675-770 kg/m3 at 12% moisture content; 1.3 to 1.5 m3 of seasoned sawn timber per tonne.

Strength groups. S4 unseasoned; SD4 seasoned.

Stress grades. F7, F8, F11, F14 (unseasoned), F11, F14, F17, F22 (seasoned), when visually stress graded in accordance with AS 2082:2000, Timber - hardwood - visually stress-graded for structural purposes.

Joint groups. J3 unseasoned; JD3 seasoned.

Shrinkage to 12% MC. E. regnans: 13.3% (tangential); 6.6% (radial). E. delegatensis: 8.5% (tangential); 5.2% (radial). E. oblique: 11.3% (tangential); 5.1% (radial).

Unit shrinkage. E. regnans: 0.36% (tangential); 0.23% (radial). E. delegatensis: 0.35% (tangential); 0.22% (radial). E. obliqua: 0.36% (tangential); 0.23% (radial). These values apply to timber reconditioned after seasoning.

Durability above-ground. Class 3 - life expectancy 7 to 15 years.

Durability in-ground. Class 4 - life expectancy 0 to 5 years.

Lyctine susceptibility. Untreated sapwood of E. delegatensis and E. obliqua is susceptible to lyctid borer attack. Untreated sapwood of E. regnans is non susceptible. Because Tasmanian oak, as marketed, normally comprises a mixture of the three species it is classed as lyctid susceptible.

Termite resistance. Not resistant.

Preservation. Sapwood readily accepts preservative impregnation but penetration of heartwood is negligible using currently available commercial processes.

Seasoning. Needs care in seasoning because these species are prone to collapse and internal checking. They are also prone to surface checking on the tangential surfaces.

Hardness. Firm to moderately hard (rated 3 and 4 on a 6 class scale) in relation to indentation and ease of working with hand tools.

Machining. Machines and turns well to a smooth surface.

Fixing. No difficulty has been experienced with the use of standard fittings and fastenings.

Gluing. Can be bonded satisfactorily using standard procedures.

Finishing. Will readily accept stain, polish and paint.

Uses

Decorative. Furniture, linings, parquetry flooring, laminated beams, joinery, turnery.

Other. Sawn timber in general house framing, internal flooring, joinery.

Identification features

General characteristics

Sapwood. Similar to the heartwood.

Heartwood. Pale brown to white-brown and often with pinkish tints.

Texture. Texture varies from open to moderately open. Usually straight grained. Gum veins sometimes prominent in E. regnans.

Wood structure

Growth rings. Prominent in some samples of E. regnans and E. delegatensis and occasionally in E. obliqua.

Vessels. Single, medium to large in all three species, often forming oblique chains in E. obliqua. May be more common in the early wood. Tyloses occurrence varies from very few in E. regnans to common in E. obliqua. Vessel lines prominent on dressed longitudinal surfaces of all species.

Parenchyma. Indistinguishable, even with a lens.

Rays. Fine, not prominent.

Other features

Burning splinter test. All three timbers burn to charcoal, sometimes with small amounts of grey or black ash.

Figure. Generally lacking but occasionally wavy on quarter-sawn surfaces.

Further reading

Boland, DJ, Brooker, MIH, Chippendale, GM, Hall, N, Hyland, BPM, Johnston, RD, Kleinig, DA and Turner, JD 2006, 'Forest trees of Australia', 5th edn, CSIRO Publishing, Collingwood Australia.

Bootle, K 2005, 'Wood in Australia: types, properties and uses', 2nd edn, McGraw-Hill, Sydney.

Hopewell, G (ed.) 2006, 'Construction timbers in Queensland: properties and specifications for satisfactory performance of construction timbers in Queensland, Class 1 and Class 10 buildings', books 1 and 2, Department of Primary Industries and Fisheries, Brisbane.

Ilic, J 1991, 'CSIRO atlas of hardwoods', Crawford House Press, Bathurst, Australia.

Standards Australia, 2000, 'AS 2082-2000: Timber - hardwood - visually stress-graded for structural purposes', Standards Australia.

Last updated 25 August 2010