Lumber Design Properties

Lumber Design Properties

Wood has different strength properties when loaded in different manners. In fact, there are six main design values that are published for lumber and timbers in order for engineers to appropriately design a structure.

Bending: Two values are published for bending properties. The fiber stress in bending, Fb, is related to the breaking strength of a piece when loaded in bending. The Modulus of Elasticity, MOE, or E, is related to the stiffness of a piece loaded in bending. The stiffness is considered a “serviceability” factor and determines how much a piece bends as well as the magnitude of vibrations, say when someone walks across a floor. The following figure shows an example of a beam loaded with a bending load:

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Behind The Mark – A Look At The SPIB Treated Wood Inspection Process

SPIB Treated Wood Quality Mark

OK, we’ve covered a ton of information in our first two Treated Wood Inspection blogs!

Essentially, the plant inspection has been completed…records were reviewed, in-plant QC was assessed, product was evaluated for penetration and retention analyses have all been completed and uploaded into the plant’s database.

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What is Wood Grain – Part 2

In our first Blog, “What is Wood Grain’’, (May 12, 2016), we learned that one way the term “wood grain” can be used is to describe the density of the wood as it relates to structural properties of dimension lumber.  We learned that the closer together the annual rings are, and the higher the percentage of summerwood, the greater the density and the greater the strength of the wood. Higher wood density is a grading rule requirement for certain higher grades of Southern Yellow Pine Dimension Lumber, whereas low-density pieces may have to be segregated into lower grades of dimension lumber.

Now let’s look at some other ways that the words “wood grain” are used to describe several other characteristics of wood.

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Behind the Mark – Part 2 – The SPIB Laboratory

The SPIB Laboratory

During last month’s Blog, we looked at the Treated Wood Field Inspection Process…so what happens next?

As we learned previously, core samples are taken by the SPIB Inspector as part of the routine audit process of a given treating plant and the number of charges to be sampled is based on the plant’s production and/or performance.  Charges found non-conforming for penetration are isolated for correction while charges found conforming are accepted.  

But that is just half the story!

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What is Wood Grain

Wood grain is the longitudinal arrangement of wood fibers [1] or the pattern resulting from this.[2] R. Bruce Hoadley wrote that grain is a “…confusingly versatile term…” including the direction of the wood cells (straight grain, spiral grain), surface appearance or figure, growth-ring placement (vertical grain), plane of the cut (end grain, quarter sawn, flat sawn, etc.), rate of growth (narrow grain), relative cell size (open grain), and other meanings.[3]

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Behind the Mark: A Look at the SPIB Treated Wood Inspection Process

Inspection Practices for Treated Lumber Products

There are many questions about the different treated wood products in our market today. Although there may appear to be many differences in what options to use for your next project, there may be more similarities than you know. Treated wood products must meet very specific quality requirements to meet the building code. These requirements are initially checked by the producing treating plant, but are ultimately verified by independent, third-party agencies that ensure plants produce treated wood products in accordance with industry standards.

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How to Grade Displaceable Knots

How to Grade Displaceable Knots

Grading Knots Away From the Edge

Learning to grade edge knots and combination knots in dimension lumber takes a fair amount of study and practice. These type knots most often limit the grade of a piece. Once the grader has a complete understanding of how these knots are measured and limited it becomes a matter of closely judging the size of what you see and comparing this to a known limit for a known knot size. This makes it relatively easy to estimate the size, and grade accurately on edge and combination knots.

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What every Dimension Lumber Grader Trainee Should Know

What Every Dimension Lumber Grader Trainee Should Know

If you are learning to grade Dimension Lumber for the first time, there are some basic facts and skills that you should study and practice before working with your trainer. Following is a list of these along with some tips, and further clarifications of rules that have proven vital to mastering the art of lumber grading. Studying, practicing, and memorization of these will speed up your training process.

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Lumber Size Categories

This blog is the second in a series of articles intended to provide information about softwood lumber, including grade-marking, design properties, testing, and continued monitoring of the lumber resource.

American Softwood Lumber Standard
There are several ways to classify lumber which are spelled out in the American Softwood Lumber Standard – Voluntary Product Standard PS 20-15. This standard is published by the National Institute of Standards and Technology (NIST) which is under the US Department of Commerce. The most recent version of PS 20 was approved and published in 2015. This American Softwood Lumber Standard was developed by the American Lumber Standard Committee (ALSC). From the abstract of PS 20: “This standard established standard sizes and requirements for development and coordination of the lumber grades of the various species, the assignment of design values when called for, and the preparation of grading rules applicable to each species. … It establishes principal trade classifications and lumber sizes for yard, structural, factory and shop use and provides for the classification, measurement, grade marking of rough and dressed sizes of lumber items.”

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