Certification in the wood preservation sector

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Earth retaining structure, banks, supporting structure

Partly embedded, these are structures in landscaped areas. They are intended to hold back earth, embankments such as gardens, terraces, banks, slopes, etc.

The timber adapts easily to diverse topographies (simple and fast installation even if modifications are required). The products used for example are round timber of sawn timber.

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As they installed in the ground, these timbers are use class 4. Expected durability varies according to usage. Round timbers and sawn timbers that have been treated according to CTB-B+ specifications for a use class 4 are safe to use in use class 4. Expected service life is less than 10 years. For very long service lives or special circumstances, the retention treatment « Sp » for use class 4 provided for in the CTB-B+ certification, gives enhanced protection.

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CTB-B+ treated timber ensures the durability of these works. To guarantee their durability, ensure to :
• prohibit any machining after treatment.
• implement appropriate drainage on the part above ground in contact with the embankments
• avoid retentions and water traps on the part above ground
• also ensure the implementation of drainage adapted to the base if the embedded part has been cast in concrete
• prohibit the installation of onwoven geotextile in direct contact with the timber
In all cases, the design should ensure the mechanical stability of the structure.

logo entretien des bois certifiés CTB-B+


CTB-B+ treated timber does require the application of any additional products to ensure durability.
Its aesthetic appearance is maintained by cleaning using a brush and/or water jet (high pressure prohibited) Mechanical damage caused by clearing operations should be treated with a product appropriate for that purpose.

Universal use classes, specifications of different treatments :

Before choosing the timber species, please refer to the use class. Identical in every country, the uses classes define the situation of the timber in a particular structure. They do not, however, attest to its suitability for use. For the same use class, the treatment requirements may vary from country to country. Each species has its own characteristics in terms of natural durability (before treatment) and impregnability (capacity to retain the product). The allocation of a species to a use class determines how the timber should be treated. Its effectiveness depends on the selection of the timber, the quality and quantity of the product used and how the process is managed and controlled.
Tableau des classes d'emploi des bois classe 4
Schéma retenue de terre avec des bois certifiés CTB-B+

Fiche technique pour bien comprendre les classes d'emploi des bois



To help professionals make the right choices, holders of the CTB-B+ Mark publish a brochure entitled
« Fully understanding the classes of use ».

Download Fully understanding the classes of use