Technical information and regulations

Below you will find information about properties and regulations regarding the use of Bilinga. Reference is made to various official documents. Due to licensing rights, we are unable to make copies of these standards available to you through the website. If you have specific questions, please contact us directly.


Name: Opepe/Bilinga
Growing area: Tropical West Africa
Botanical name: Nauclea diderrichii (De Wild.) Merr. (= Nauclea trillesii, Sarcocephalus diderrichii), Nauclea
gilletii (De Wild.) Merr.
Heartwood durability class: 1
Usage class: 5
Strength class: Origin West Africa, grading class HS (BS 5756) is classified in D50 (NEN-EN 1912).
Kiln dried: N/A
Density:  (660-)750(-900)kg/m3 at 12% moisture content, 900-1150kg/m3 (moisture content about 55%).
Suitable for: Widely used for building structures both indoors and outdoors. In hydraulic engineering for lock gates, barriers, weirs, jetties, purlins, bridges and bridge decks. Decking parts and garden wood.
To machine: Despite the great hardness, Opepe can be machined quite well.

Bilinga Constructiehout

Strength class Opepe

In the Netherlands, the European strength classes according to NEN-EN 338 are used. A strength class is indicated by the letter C for softwood and D for hardwood, followed by a number. That number corresponds to the representative value for the bending strength parallel to the fiber (material property). These values ​​form the starting point for the constructor to determine the design value of the material. For class A/B Bilinga is classified in class D50. This makes it one of the wood species with the highest calculation values ​​for bending, tensile and compressive strength, modulus of elasticity, and so on.


Opepe is divided into three quality classes, namely A, B and C (NEN 5480). Class A sets the highest demands on strength and/or appearance, such as thread drift, knots, cracks and deformations.

In the Dutch Standard NEN 5493 (formerly NPR 5493), Quality requirements for hardwood in ground, road and hydraulic engineering works and other constructive applications, 8 application categories are defined:

– Walking decks/deck parts
– Bridge decks and planking for landing stages;
– Construction wood
– Horizontal handrails
– Studded piles
– Sawn piles
– Round posts

It’s established for each category which imperfections may occur and to what extent. Defects such as heart, tassels, mechanical damage, cracks, sap and deformation measured over the entire length. Standards have also been laid down for the moisture content and the performance of batch inspections.

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