Bangkirai
Shorea laevis
Also known as yellow balau, selangan batu · Botanical Shorea laevis
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 Bangkirai
Bangkirai (Shorea laevis) is a hard, wear-resistant timber that is heavy going on tools, with a Janka hardness of 1,798 lbf (7,998 N) and a density of about 0.85 g/cm³. It grows in Southeast Asia and the Pacific.
Tangential movement of 9.3% against 4.2% radial puts the T/R ratio at 2.21. That is the ratio to watch: it predicts cupping in wide flatsawn boards better than either figure alone. Its fibre saturation point is near 26%. Below it, movement is the governing constraint on this species: 9.3% tangential against 4.2% radial, a T/R ratio of 2.21. Flatsawn boards will cup; quartersawn stock is worth the premium here. — wide boards need real expansion room, not a token gap.
At 850 kg/m³ a cubic metre of Bangkirai weighs about 850 kg air-dry — that figure, the 9.3% tangential and 4.2% radial movement and the 1,798 lbf hardness are the three inputs the calculators below actually consume. Select Bangkirai in any of them to get species-specific results for weight, moisture, shrinkage and hardness.
Working properties
How Bangkirai behaves at the bench and on the machine, drawn from CIRAD Tropix, WoodSolutions Australia and European timber-protection references.
Durability & use classification
Bangkirai heartwood is rated durable (EN 350 Class 2) and resistant to termites, and its sheer density puts it among the few tropical hardwoods used for permanent salt-water immersion. Worth knowing: bangkirai and Yellow Balau are the same trade timber — the name simply follows the country of export, Indonesia versus Malaysia. Both are trade groups rather than one species: Shorea laevis is the principal source, but heavy Shorea species such as S. glauca, S. atrinervosa and S. maxwelliana are sold under the same names, so durability varies between parcels. The sapwood is not durable, offers insufficient resistance to marine borers, and the heartwood is practically impossible to treat.
Typical applications & suitability
Indoor Outdoor — A premium exterior decking and heavy-structural hardwood whose mechanical performance rivals ipe and cumaru — one of the most specified South-East Asian timbers worldwide.
Documented end-uses: decking, terraces and screens, heavy construction, bridges and bridge piles, railway sleepers, sheet piling, poles and beams, boat building, industrial floors, loading ramps, wagon and container floors, garden furniture and fencing.
Comparable species
Species closest to Bangkirai by density, hardness, stiffness and bending strength, computed directly from the Vriksai species dataset rather than hand-picked.
Trade alternatives. It sits in the same group as Balau (its Malaysian trade twin) and competes directly with Merbau, Garapa and, at the denser end, Ipe and Cumaru.
Alternatives to Bangkirai
Bangkirai measures 1,798 lbf Janka at 0.85 g/cm³, EN 350 durability Class 2, movement rated Moderate. Anything replacing Bangkirai outdoors has to hold Class 2 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 Bangkirai 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 Bangkirai 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 Bangkirai
Sized for exterior and load-bearing work in Bangkirai — spans, fixings, weathering gaps and freight weight. Full set in the tool index.
Understand the figures
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 · Strength properties — MOR, MOE and what they govern.
Further reading. Wood moisture content explained · How to calculate board feet.
Common questions about Bangkirai
unverified no published source for this figure · PROSEA PROSEA 5(1), Plant Resources of South-East Asia · calc derived from the figures above · — no published source found
Where these figures come from. Hardness, density and shrinkage are checked against PROSEA 5(1): Timber trees — major commercial timbers (Kochummen, Wong, Fundter & Sosef, 1993), the standard reference for South-East Asian timbers. PROSEA gives the balau group 8,010–9,520 N side hardness and 850–1160 kg/m³ at 15% MC; the figures above sit at the lower edge of both bands — which is what you would expect for S. laevis specifically. Shrinkage now follows PROSEA’s green → oven-dry values. MOR and MOE are not verified: PROSEA quotes those at 40% moisture content and the panel above is a 12% figure — different conditions, not comparable. Treat those two as indicative.