Laboratory setup for wood strength testing with timber samples under bending load
Laboratory setup for wood strength testing with timber samples under bending load

Wood Strength Testing

Wood Strength Testing – was revised on January 19, 2026

  • Wood strength testing data and design specifications answer different questions and should not be mixed.

  • An 8 inch mat made from a stronger species can have roughly the same bending strength as a 12–14 inch mat made from a weaker mixed hardwood.

  • Contractors, owners, and EPCs can use publicly available references to compare species and make better engineering decisions.

Wood strength testing is not guesswork. Well-established standards and handbooks give you consistent data. That way you can compare species and understand how strong a mat can be. You’ll also need to know when you must use design values instead of raw test numbers.

Why Understanding Wood Strength Matters

For mat users, stronger results generally mean better mat life and fewer disruptions in the field because of failed mats. All else equal, stronger materials tend to produce stronger results.

Species choice and quality matter. An 8 inch mat made from a high-strength species can have roughly the same bending strength as a 12–14 inch mat made from a weaker mixed hardwood species. This is why understanding wood strength testing and design values is so important.

Key Sources For Wood Strength Data

Three well-respected standards bodies have already done the heavy lifting on wood strength testing.

  • US Forest Service – Forest Products Laboratory (FPL): Publishes the Wood Handbook: Wood as an Engineering Material. It’s the definitive free reference for species properties, including many domestic and imported woods.

  • American Wood Council (AWC): Publishes the National Design Specification for Wood Construction (NDS) and its Supplement. The Supplement list design values such as bending strength and compression for most North American species.

  • Eurocode 5: Classifies structural timber into strength classes (for example D30, D40). Eurocode includes both European and important exotic species (including Eucalyptus) making it easier to compare species and grades at a glance.

Most secondary sources and online tables draw wood strength testing data from these primary references.

This is where you see, for example, that a stronger species used in one size mat can deliver similar design bending capacity to thicker mat, once everything is normalized.

For USA species this is an easy comparison but:

  1. You need to use the American Wood Council National Design Specifications Supplement and
  2. You need to know the grade and species of the timbers involved. 

This does not replace formal engineering, but it helps explain why thickness alone does not tell you how strong a mat really is.

For example, look at Northern Red Oak, Posts and Timbers, Select Structural vs. # 2 timber bending strength: 1500 psi vs. 700 psi. 

USFS clear wood samples data. NOT design data!
USFS clear wood samples data. NOT design data!
AWC NDS 5x5 timbers - design specifications
AWC NDS 5x5 timbers - design specifications

 

Testing Data Versus Design Specifications

There is a critical difference between test data and design specifications in wood strength testing.

  • Testing data (like those in the FPL Wood Handbook) report how small, clear wood samples performed under controlled tests. These values show raw bending, compression, and other properties.

  • Design specifications (like NDS and Eurocode 5) generate allowable design value. That happens through a recognized system to use clear wood samples first. Secondly, design specifications apply safety factors, duration of load adjustments, moisture factors, and other real-world considerations.

Testing data answer questions such as “How strong is this species in a lab sample?” 

Design specifications answer questions such as “How big does this member need to be to hold up a roof or support a crane mat under real conditions?”

Using Strength Classes To Compare Species

Eurocode 5 and similar systems group species and grades into strength classes. Higher classes generally mean higher design strengths.

For example:

  • A typical oak used structurally in Europe might be in a class like D30.

  • A higher strength species like Eucalyptus could be in a stronger class such as D40.

When a mat is made from a D40-class species at 8 inches thick, its design bending strength could be roughly in the same range as a 12–14 inch mat made from a lower class mixed hardwood, once engineering adjustments are applied. 

Practical Takeaways For Contractors, Owners, And EPCs

For day-to-day project work, a few practical rules help keep wood strength testing and design values straight.

  • Use test data (FPL, similar) to understand relative species strength and to compare options at a high level.

  • Use design specifications (NDS, Eurocode 5) when doing any engineering work or when your project has formal design or stamping requirements.

  • Remember that species, grade, moisture, and defects all matter as much as nominal thickness. An 8 inch mat from a stronger species can be roughly equivalent in bending strength to a much thicker mat from weaker mixed hardwood.

If you are comparing mat options with engineering requirements, your team should always work from design values, not just lab test numbers.

See the learning center content on timber mats and wood properties.

Next Steps: How To Use This Information

If you want to compare different mats or species, start by pulling the appropriate tables from the FPL Wood Handbook, the AWC NDS Supplement, or Eurocode 5. Then ask your engineering department or consultant to translate those numbers into the design values needed for your specific condition.

For quick reference on appropriate values for engineering comparisons, you can also use resources such as https://eucmat.is/Facts alongside the primary standards listed above.

If you would like additional educational materials or links on wood strength testing and design specifications for mats, contact World Forest Group for more information.