Iroko — Density, Movement, Workability & Cost

Sold across Europe and Africa as "African teak," iroko (Milicia excelsa) earns that comparison honestly on the numbers — 8.8% volumetric shrinkage with a tangential:radial ratio under 1.4 is genuinely exceptional stability, in teak's own territory, at a price that undercuts true teak significantly.

Teak-level stability, with a hazard teak doesn't have

At 41.2 lb/ft³ and 1,190 lbf on the Janka scale, iroko is comparable in weight and hardness to teak, but it lacks teak's oily, silica-free working feel. What it has instead is a different and more destructive hazard: hard calcium carbonate deposits, sometimes called "stone," embedded inside the grain of a meaningful fraction of iroko logs. Hit one with a planer knife and the edge is instantly ruined — sounding each board by tapping and listening, and staying alert for an unexpected hard spot mid-cut, is standard practice rather than excessive caution.

Movement, and what a wide panel actually weighs

Radial shrinkage of 2.8% against a tangential figure of 3.8% gives a 1.4 ratio — both absolute numbers are low, among the more stable species on this site regardless of the ratio. A 24"-wide panel moving from a 12% moisture content to a dry 6% loses about 0.182" (4.6mm) across its width; narrower boards run through the wood movement calculator. A 1"-thick, 24"-wide, 7-foot tabletop blank weighs about 48.1 lb at iroko's milled density; the wood weight calculator covers other slab and panel sizes.

Gluing without teak's oil problem, and a golden finish

Iroko is meaningfully less oily than teak, so a solvent wipe before gluing an older, oxidized surface is a sensible precaution rather than the near-necessity it is with true teak. It finishes to a golden brown that darkens further toward a deep coffee tone over time, and the pores may want filling for a fully smooth film finish, though many finishers leave them open for texture.

Durability, cost, and a genuine occupational hazard

Iroko's heartwood is very durable and termite-resistant — a genuine exterior wood, which is exactly why it competes directly with teak for laboratory benches, exterior joinery, and boatbuilding at a meaningfully lower price. It sits at about $13 per board foot on this site's premium tier — still well under true teak. Exterior joinery, boatbuilding, laboratory benches, decking, and furniture round out its markets. The dust is a strong, well-documented sensitiser — asthma, dermatitis, and in some workers, boils are all recorded reactions, making iroko one of the more hazardous common African hardwoods to machine regularly.

The teak substitute relationship, examined honestly

Iroko genuinely delivers teak-comparable stability and durability at a real cost saving, which is exactly why it earned the "African teak" name in commercial trade. What it doesn't replicate is teak's naturally oily, silica-free working feel or teak's UV-resistant golden colour retention — iroko darkens further with age rather than bleaching pale grey-silver the way teak does outdoors, so the two age visibly differently even where their structural performance overlaps.

What people actually ask about iroko

What exactly is the "stone" that damages tools when working iroko? It's mineral deposits, mainly calcium carbonate, that form inside the wood's cell structure as the tree grows — genuinely hard enough to chip or dull a cutting edge on contact, and undetectable from the wood's surface appearance alone.

Given how close iroko's durability is to teak's, does it also share teak's tendency to weather to a silvery grey when left unfinished outdoors? It weathers differently — iroko tends to darken further toward deep coffee brown with age and light exposure rather than bleaching pale silver-grey the way teak does, so a buyer choosing iroko specifically to mimic teak's weathered look outdoors will be disappointed even though the underlying durability is comparable.

Why is iroko dust considered more hazardous than teak dust? Iroko's sensitising compounds are more consistently and severely documented across exposed workers than teak's, producing asthma and skin reactions at a notably higher reported rate — dust extraction and a proper respirator matter more here than with many comparably priced tropical hardwoods.

FPL's Table 4-4 (Wood Handbook, FPL-GTR-190, 2010) lists iroko under its older name, Chlorophora excelsa, and is the source for the shrinkage figures above; The Wood Database's own 12%-moisture-content testing gave density and Janka hardness.