Stress Grades and Design Properties of Wood

The Stress Grades and Design Properties of Wood online PDH course is part of our Structural Design Category and provides guidance on stress grades and design properties for lumber, round timber, and ties.

Round timbers, ties, and lumber sawn from a log, regardless of species and size, are quite variable in mechanical properties. Pieces may differ in strength by several hundred percent. For simplicity and economy in use, pieces of wood of similar mechanical properties are placed in categories called stress grades, which are characterized by (a) one or more sorting criteria, (b) a set of properties for engineering design, and (c) a unique grade name. The most familiar system is that for lumber. Sorting criteria have also been established for round timbers and ties.

This course is based on Chapter 7 of the United States Department of Agriculture, Forest Service, Forest Products Laboratory, General Technical Report FPL–GTR–190 “Wood Handbook: Wood as an Engineering Material”.

This course is intended for use by civil and structural engineers, design and construction professionals, students and others interested in learning about stress grades and design properties of lumber, round timber and ties.

Learning Objectives

Upon completion of this course, you will be able to:

• List the sawn lumber grading agency
• Understand the sawn lumber grading process, grouping of species and classification criteria
• Describe the visual and machine grading process and classifications
• Explain how properties of lumber are adjusted for design use
• Understand the design properties and stress grades for round timbers and ties