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What is okan?

The Wood Guide · The wood register

Tropical hardwood · reference

Okan

Sixty metres tall and a trunk up to three metres thick. A giant from the West African forests that yields wood nothing gets through.

  • Cylicodiscus gabunensis
  • Up to 60 m tall
  • Trunk up to 3 m thick
Cylicodiscus gabunensis
Okan wood sample: golden to dark brown with a coarse, wavy grain (Cylicodiscus gabunensis)
Okan wood sample: golden to dark brown with a coarse, wavy grainCylicodiscus gabunensis
Okan wood sample: golden brown with light and dark stripes (Cylicodiscus gabunensis)
Okan wood sample: golden brown with light and dark stripesCylicodiscus gabunensis
In pictures · Okan1 / 7
Chapter 1 · The species

Okan

Sixty metres tall and a trunk up to three metres thick. A giant from the West African forests that yields wood nothing gets through.

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Summary

Okan in brief

One of the largest trees of the West African rainforest, and the source of one of the hardest hardwoods on the market.

The dimensions alone are remarkable: a height of up to sixty metres and a trunk diameter of up to three metres. Trees like that are centuries old, and that is exactly what gives the wood its density.

The wood is golden brown to reddish brown and is among the heaviest traded. Where most hardwoods reach their limit — permanent ground contact, heavy wear, mechanical load — okan is only just getting started.

Where you come across it

Okan is a civil engineering timber: sheet piling, bridge decks, fender works, lock gates and heavy floors. You rarely see it in a private garden, and rightly so — it is too heavy and too coarse for that.

Botanical
Cylicodiscus gabunensis
Origin
West Africa
Height
up to 60 metres
Trunk diameter
up to 3 metres
Colour
golden brown to reddish brown
Strength in
density and wear resistance

Fair is fair: okan is hard to work and heavy to carry. Pre-drilling is a must, saw blades wear quickly, and the dust can irritate the skin and airways. It is not a pleasant material for DIY work.

Measurable

Why it makes the grade for hydraulic engineering

Extremely dense

Among the heaviest commercial timbers. Water barely penetrates it, and without water there is no fungus.

Very hard-wearing

A bridge deck or industrial floor in okan withstands heavy loads for years without wearing down.

High durability

Even in ground contact and in water, where most species give up.

High bending strength

Large spans without deflection — the reason it is used in bridges.

Uses

What okan is used for

Use Why okan Alternative
Sheet piling and bank revetments Durable in permanent ground contact Azobé, bilinga
Bridge decks Bending strength and wear resistance Azobé, ipé
Lock gates and fender works Mass and resistance Azobé, bilinga
Industrial floors Extreme wear resistance Jatoba, massaranduba
Railway sleepers Load-bearing capacity and service life Azobé, concrete
Garden furniture Unsuitable — too heavy and coarse Teak, acacia
The heavy class of the register

Okan belongs to the same group as azobé and bilinga: wood species you do not choose for their looks but because the structure has to stand for decades in conditions where nothing else lasts.

Quick answer

Frequently asked questions about okan

How big does an okan tree grow?

Up to sixty metres tall with a trunk diameter of up to three metres. It is one of the largest trees of the West African rainforest.

What is okan used for?

Mainly in hydraulic engineering and heavy construction: sheet piling, bridge decks, lock gates and industrial floors. It is too heavy and too coarse for garden furniture.

Is okan the same as azobé?

No, but it plays in the same league. Azobé is Lophira alata, okan is Cylicodiscus gabunensis — both extremely heavy and both hydraulic engineering timbers.

Can I work okan myself?

With carbide-tipped tools and pre-drilled holes, yes, but it is not easy. The dust can also cause irritation — work with extraction and a mask.

More in The Wood Guide

Okan in perspective

A reference species in our register — the wood of bridges and sheet piling.

To The Wood Guide Azobé Tropical hardwood

Have a question about your project? Just ask — we're happy to help.

Photos via Wikimedia Commons: Cylicodiscus gabunensis — Cirad, Xylothèque (via Gallica/BnF), Public domain · Cylicodiscus gabunensis — Cirad, Xylothèque (via Gallica/BnF), Public domain

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