Jarrah
Eucalyptus marginata
Botanical Eucalyptus marginata
Revision history
- — Data re-verified in site-wide audit (formulas, sources, durability classes)
- — Working properties and comparable-species data cross-checked against listed sources
About Jarrah
Jarrah (Eucalyptus marginata) is a hard, wear-resistant timber that is heavy going on tools, with a Janka hardness of 1,910 lbf (8,496 N) and a density of about 0.82 g/cm³. It grows in Australia.
Radial 4.6% against tangential 6.6% is an unusually even T/R ratio of 1.43 — Jarrah shrinks close to uniformly, which is why it holds a flat panel in exterior joinery and cladding. Its fibre saturation point is near 26%. Below it the wood shrinks steadily — 6.6% tangential, 4.6% radial. Ordinary territory: design the gaps rather than hoping the finish will hold it.6% tangential against 4.6% radial, quartersawn stock will behave noticeably better than flatsawn.
At 820 kg/m³ a cubic metre of Jarrah weighs about 820 kg air-dry — that figure, the 6.6% tangential and 4.6% radial movement and the 1,910 lbf hardness are the three inputs the calculators below actually consume. Select Jarrah in any of them to get species-specific results for weight, moisture, shrinkage and hardness.
Working properties
How Jarrah behaves at the bench and on the machine, drawn from WoodSolutions Australia, Australian government timber data and the USDA Forest Products Laboratory.
Durability & use classification
Jarrah is rated very durable (EN 350 Class 1), resisting decay, termites and even marine borers, and its density gives genuine fire resistance (meeting Australian bushfire ratings). The narrow sapwood is vulnerable to powder-post (lyctid) beetle attack, and the heartwood is effectively impermeable to preservative.
Typical applications & suitability
Indoor Outdoor — Equally at home indoors and out. Durable enough for wharves, sleepers and marine work, yet bought for its deep red colour in premium flooring, furniture and joinery.
Documented end-uses: heavy engineering (wharves, bridges, railway sleepers, poles, piles), structural framing, flooring, decking and cladding, high-quality indoor and weatherproof outdoor furniture, turnery, joinery and parquetry, marine structures and boatbuilding, and musical instruments.
Comparable species
Species closest to Jarrah by density, hardness, stiffness and bending strength, computed directly from the Vriksai species dataset rather than hand-picked.
Trade alternatives. Comparable durable hardwoods include Merbau and, for a similar reddish tone, Shisham (Sissoo); for exterior decking, South-American Cumaru and Ipe compete directly.
Alternatives to Jarrah
Jarrah measures 1,910 lbf Janka at 0.82 g/cm³, EN 350 durability Class 1, movement rated Excellent. Anything replacing Jarrah outdoors has to hold Class 1 durability and carry the load — so nothing below that class appears here, however well it matches on hardness. Read the numbers against the Janka scale and EN 350 durability classes.
For decking, marine work and structural exposure where the surface takes impact as well as weather. Expect slower machining, faster tool wear and more weight to handle on site.
Lighter sections, easier fixing and lower freight per m³ — while holding the exterior durability class. Useful where the spec is over-engineered for the actual load.
Exterior sections move most, and a dense timber that moves takes fixings and joints with it. These hold their dimension better in the same durability class. Size the gaps with the shrinkage predictor and EMC calculator.
If Jarrah is unavailable and the specification cannot change, these are the nearest substitutes across hardness, density, movement, stiffness, bending strength and durability class together — not on any single property. Lower distance means a closer match.
Computed from measured properties only — hardness, density, movement, stiffness, bending strength and EN 350 class. Price, availability and appearance are never inputs. Figures are representative values, not consignment absolutes: two species within a few percent are equivalent until verified on the material. Full method and the rules the engine cannot break.
Substituting outdoors is a match on durability class and movement first. Colour and grain can be matched later; a wrong durability class shows up as a callback in three monsoons. Where two candidates are close, compare them directly before specifying.
Compare Jarrah side by side
The pairings below are the ones that actually come up in exterior and structural tendering. Every pairing shows the measured figures side by side; full matrix in the comparison index.
Calculators relevant to Jarrah
Sized for exterior and load-bearing work in Jarrah — spans, fixings, weathering gaps and freight weight. Full set in the tool index.
Understand the figures
ThermoWood species guide — Thermo-D/Thermo-S treatment classes · Janka hardness scale — how the lbf figure is measured · Wood density reference — oven-dry vs air-dry basis · Moisture content — EMC, FSP and service conditions.
Further reading. Wood moisture content explained · How to calculate board feet.
Common questions about Jarrah
unverified no published source for this figure · FPL USDA FPL Wood Handbook GTR-190 · WD The Wood Database (Eric Meier) · calc derived from the figures above