Reclaimed ulin ironwood, specified properly

Why ulin, and why reclaimed

Ulin (Eusideroxylon zwageri, Bornean ironwood) is the most durable structural timber Indonesia produces. It is rated Class I for both durability and strength under the Indonesian timber classification, is naturally resistant to termites, marine borers and rot, and has served for generations as bridge decking, shipbuilding timber and roof shingles across Kalimantan. Density is roughly 1,000 kilograms per cubic metre once seasoned, which is why it sinks in water and why fixings need pre-drilling.

New-growth ulin is slow growing and heavily restricted, so responsible projects specify reclaimed stock: timber recovered from decommissioned bridges, warehouses, jetties and village structures, then re-milled into decking, cladding, structural sections and joinery. Reclaimed ulin that survived fifty years in service has already proven itself, and its recovery gives an exceptional material a second life without touching standing forest.

The three questions that decide a specification

One: where was it reclaimed from, and can the supplier show the paper trail? Legitimate reclaimers document the source structure and hold SVLK legality paperwork for the recovered timber. If the documentation is vague, the timber may not be reclaimed at all.

Two: has it been re-milled and graded, or just cleaned? Proper stock is denailed, re-sawn to consistent sections, and graded so that structural pieces and appearance pieces are separated. A stack of cleaned bridge planks is not yet a specification-ready product.

Three: what is the moisture content now, not when it was salvaged? Ulin moves little once seasoned, but recovered stock that has been sitting in a yard through a Balinese wet season needs checking. Ask for readings at the point of dispatch; below roughly 15 to 18 percent is the working range for external decking in Bali's climate.

Where it performs in a project

Decking and pool surrounds are the classic use, where its density and rot resistance outlast every alternative. It is equally strong as exposed structural posts and beams, external cladding and screens, stair treads, and heavy outdoor furniture. For fine internal joinery its weight and hardness make machining slower and blunter, so many projects pair ulin outside with lighter species inside.

Expect colour to weather from warm brown to silver grey if left uncoated. Many designers let it silver deliberately; where the brown is wanted, a penetrating oil maintained annually holds the tone.

Sourcing it properly in Bali

The gap between good and bad reclaimed ulin is invisible in a photograph, which is why we vet suppliers on documentation, re-milling capability and delivered project references before they enter the directory. Build Supply Indonesia lists reclaimed timber specialists with factories in Bali, including reclaimed ulin decking, structural sections and custom architectural works.