EN 13145: Quality Standards for Wooden Railway Sleepers

What is EN 13145?

EN 13145 is the European Standard titled “Railway applications – Track – Wood sleepers and bearers.” This standard defines the requirements for wood species, quality grading, dimensions, and durability for timber components used in the Permanent Way (P-Way).

Despite the widespread use of concrete and steel sleepers, wooden sleepers remain vital for specific applications, such as turnouts (bearers), bridges, and historic lines. EN 13145 ensures that the wood used can withstand the high static and dynamic loads of passing trains while resisting biological decay in harsh outdoor environments.

Material Selection and Wood Species

Not all wood is suitable for railway use. EN 13145 categorizes acceptable species based on their mechanical strength and natural durability. The choice typically depends on the availability of local resources and the required lifespan of the track.

• Hardwoods: Species like Oak (Quercus spp.) and Beech (Fagus sylvatica) are preferred for high-traffic lines due to their density and resistance to mechanical wear (rail seat abrasion).
• Softwoods: Species like Pine (Pinus sylvestris) or Larch are often used on secondary lines. These usually require intensive chemical treatment to achieve the necessary durability.
• Tropical Woods: Species such as Azobé are sometimes utilized for their extreme natural resistance to rot without the need for preservatives.

Technical Requirements and Grading

The standard sets strict limits on natural defects that could compromise the structural integrity of the track. Inspection criteria include:

• Knot Size: Excessive or loose knots are restricted as they act as stress concentrators.
• Fissures and Checks: While some cracking is normal in wood, deep longitudinal splits that reach the rail fastening zone are grounds for rejection.
• Wane: The presence of bark or missing wood on the corners of the sleeper is limited to ensure a stable bearing surface on the ballast.

Preservation and Durability

A core aspect of EN 13145 is the reference to durability classes. Since wood is a biological material, it is prone to fungi and insect attacks. To reach a service life of 20-30 years, most sleepers must be treated with preservatives such as creosote or copper-based alternatives, following the penetration requirements specified in the standard.

Comparison: Wood vs. Concrete Sleepers

Why EN 13145 Remains Relevant

Wooden sleepers are the “shock absorbers” of the rail world. Engineers prefer EN 13145 compliant timber for bridges because it reduces the impact loads on the bridge structure and for turnouts where complex shapes (bearers of varying lengths) are easier to manufacture from wood than from pre-stressed concrete.