Jarrah — Density, Movement, Workability & Cost

Nineteenth-century wharves and bridges around the world were built with jarrah (Eucalyptus marginata) shipped from Western Australia specifically for its resistance to marine borers — a genuinely global export trade built on one Australian eucalyptus species long before "sustainable sourcing" was a phrase anyone used, because the wood simply outlasted everything else available for underwater piling.

A deep red hardwood that fights you during drying, not after

At 52 lb/ft³ and 1,860 lbf on the Janka scale, jarrah is hard, heavy, and deep red, deepening further toward burgundy as it ages. The genuine difficulty with this species sits almost entirely in seasoning: collapse, checking, and honeycomb are all routine drying defects in jarrah, common enough that commercial dryers routinely recondition it by steaming partway through the schedule as a standard, expected step rather than a rescue measure for a problem batch.

Movement, and why sourcing dry stock matters more than usual

Radial and tangential shrinkage figures here are drawn from FPL's Table 4-4 (7.7% radial, 11% tangential, giving a 1.4 ratio) — notably higher than The Wood Database's own alternate figures for this species, a genuine discrepancy worth knowing about since either version points to real, substantial movement either way. A 6"-wide board seasoning from a wet 16% down to a drier 10% loses about 0.132" (3.4mm) across its width; other widths run through the wood movement calculator. A 3/4"-thick, 6"-wide, 8-foot flooring board weighs about 13 lb; the wood weight calculator covers other flooring sizes.

Working it once it's actually dry, and living with gum veins

Once properly seasoned, jarrah is stable enough in service and machines well with carbide, though interlocked sections still tear under a plane. Gum veins — pockets of natural resin trapped within the grain — are frequent and simply won't bond; gluing across one is a wasted effort, so identify and work around them rather than through them. Away from gum pockets, gluing is otherwise reliable once the surface is properly prepared.

Durability, cost, and its historical wharf-piling reputation

Jarrah's heartwood is very durable, including genuine resistance to marine borers, which is exactly the property that built its historical export trade to ports around the world. It's priced around $16 a board foot — premium, on this site's own scale. Flooring, decking, furniture, wharf and bridge timbers, and turnery round out its markets — the historical structural-timber uses have given way somewhat to flooring and decking as the dominant modern markets, though the underlying durability that made the historical trade possible hasn't changed.

The drying discipline that actually determines success

More than most species on this site, jarrah rewards buying properly kiln-dried, reconditioned stock rather than attempting to season it casually — the checking and collapse defects genuinely are routine at commercial scale, and a hobbyist without access to steam-reconditioning equipment is taking on real risk trying to dry thick jarrah stock from green.

What people actually ask about jarrah

Can a hobbyist with a small home kiln realistically recondition jarrah themselves, or is it strictly a commercial-scale process? It's genuinely difficult without commercial steam-reconditioning equipment — a home kiln can approximate the humidity and temperature spike involved, but the margin for error on a wood this collapse-prone is narrow enough that most hobbyists are better served buying already-reconditioned stock from a supplier equipped for it.

Is jarrah as durable as ipe for an outdoor deck? Both are very durable species with real marine-timber histories, though most direct comparisons still rate ipe's overall density and hardness somewhat higher — jarrah remains a very credible decking choice, particularly where its striking deep red colour is specifically wanted.

Which of the two cited jarrah shrinkage figures should a builder actually plan a wide panel around, the FPL number or the lower Wood Database one? Planning around the higher FPL figure is the more conservative and safer approach for anything genuinely wide, since building an expansion allowance for the smaller number and getting the larger real-world movement risks a cracked panel, while the reverse mistake only costs a slightly wider gap than strictly necessary.

Jarrah's shrinkage figures come from Table 4-4 of the USDA Forest Products Laboratory's Wood Handbook (FPL-GTR-190, 2010); The Wood Database supplied density and Janka hardness at 12% moisture content and separately publishes a lower shrinkage set (6.3% radial, 9.4% tangential, 16.4% volumetric).