Illustration of the cutting dimensions of a log

Photo Credit © Jeff Strobel

Determining the value of a log

The process for determining the value of individual logs is complex and involves a number of variables.

As is nearly always the case, a family disagreement took place while we were working in the woods.  Now it may seem like we are always disagreeing in the woods, but that is not true at all.  In fact, we agree on many things including who drives the tractor out to the woods (the family elders), and who rides in the trailer (me).  I know which arguments to have and which points to concede.

The latest disagreement revolves around the value of the trees being grown.  Some in the family (who shall remain nameless) believe that there is a gold mine in the woods due to the abundance of large trees.  When I noticed him paging through a catalog for speed boats, I knew it was time for a reality check as to the true value of the family trees.

Now, there is a lot that goes into what a logger will pay for any trees in your woods, including the size of the sale (acreage and volume of timber), price of fuel, how accessible the trees are, and many more.  For determining the value of individual logs (trees can be made up of more than one log), the three main factors are grade (quality), scale (an estimate of the quantity of lumber within a log), and species.  So, even though we have a lot of big trees on the property, that is only part of the calculation for determining a dollar value for a tree.

The grade can make the difference between a red oak log fetching $600 per thousand board feet (MBF) and one worth only $200 MBF.  The log grade scale is very short and standardized throughout the US, even though there is some subjectivity in determining which category a log falls into.  “Veneer” is the highest quality followed by No. 1, No. 2, No. 3, and cull.

The process for determining which of these categories your logs fall into is not that complicated.  The first step is to evaluate the log from all sides.  The highest quality logs are free from defects like knots, branches, fractures/seams, decay, and sweep (a curving of the log).  Most trees have some defects, and these may not cause your log to be downgraded from the highest grade.

Then divide your log into four equal sides with one side having the most defects on the log (also called the worst face).  After doing that, identify the best side (with the fewest defects), the second best side, and finally the third best side.  You will be grading the log based on the quality of the third best side.

The next step is to measure the number and length of “clear cuttings” on the grading face of your log.  These are sections of your log that are free from defects, and the longer these sections are, the higher the grade.  Another way to think about it is as the proportion of the log in clear cuttings.  For No.1 logs it is 5/6, for No. 2 logs it is either 3/4 or 2/3 depending on the diameter of the log, and for No. 3 logs it is 1/2.

To finish the calculation you will need the total length of the log you are evaluating, the diameter of the log at the small end and inside the bark (also called scaling diameter), and the percentage of sweep.  You can determine the scaling diameter by multiplying the diameter at breast height (DBH and 4.5 feet off the ground) by 0.8.

Here is an example to give you an idea of how this works (see the figure on this page).  Say you have a large tree where the bottom or “butt” log is 16 feet long and 28 inches DBH.  The log is nearly perfectly straight, so the sweep is nearly zero.  On the third best side there is one defect near the middle of the tree and so you have identified two clear cuttings.  One cutting is seven feet long and the other is 8 feet long.  Based on this information, you have a No. 1 log.

Check out “Guidelines for Grading Hardwood Logs” to see the table that lays out the characteristics of each log grade and much more.

The family member with the big dreams was a bit let down after I explained the grading process and we evaluated some of our trees.  However, it did start to click for him as to why we prune some of the trees and manage the way we do.  And he has switched to a catalog for canoes rather than speed boats.