A Hardwood
Log Grading
Handbook
PB1772
$2.50
Contents
How Much Is a Log Worth? ..........................................1
Veneer, Sawlogs and Other Log Classes .................2
Log Scaling ................................................................3
Table 1. The Doyle Log Rule .......................................4
Log Grading — Relation to Lumber Grading ...........6
Table 2. Summary of the NHLA hardwood
lumber grading rules ............................................7
Log Grading Methods .................................................8
Defects .......................................................................8
USDA Forest Service Hardwood Sawlog
Grading System ...................................................11
Table 3. Summary of Forest Service
Hardwood Log Grading Rule ..............................12
Table 4. Total cutting lengths required
in each grade .....................................................15
Table 5. Sweep deduction (percent) .....................16
Grading a Log Using the Forest Service System ....17
Table 6. Scaling deduction factors .........................18
Clear Face Grading ................................................19
The Log Grading Rules Compared ..........................20
The US Forest Service Log Grading Rule .................20
Clear Face Rules .....................................................20
Weight Scaling .........................................................20
Tree Grading ...............................................................21
Table 7. Summary of US Forest Service Rule
for Tree Grading ...................................................21
Log Bucking Optimization ........................................22
Summary .....................................................................24
References ..................................................................25
1
A Hardwood Log Grading Handbook
Adam Taylor
University of Tennessee
A good understanding of log valuation will
help landowners, loggers, log buyers and saw
millers agree on the fair value for a load of logs.
This handbook briefly summarizes common log
grading rules for hardwoods. Basic concepts in
log scaling, lumber grading and log bucking
optimization are also discussed because each
of these topics relates to log grading.
How much is a log worth?
There are three main factors that buyers
and sellers use to determine the value of a
log: Grade, Scale and Species. Grade is a
measure of the quality of the log and the
lumber that will come from the log. Scale is
a measure of the quantity of lumber within a
log. Different species can be used for different
products and have inherently different value,
regardless of the quality of the lumber. Even
seemingly minor differences in grade or spe-
cies can mean a very different value for logs
– see below for an example:
Prices paid for logs of different species and
grade. An example from East Tennessee in 2009.
All values are in dollars per thousand board
feet, scaled using the Doyle rule.
Walnut Red Oak Poplar
High grade $930 $635 $380
Medium grade $505 $380 $260
Low grade $260 $230 $165
2
Log grading is important because it
helps buyers and sellers settle on a fair price
for a load of logs. Log grades can be used to
predict the proportion of high-quality lumber
that will be produced from that log. This log
grading can also be used to help measure
sawmill efficiency.
Veneer, Sawlogs and Other Log Classes
Some hardwood logs are reserved for the
production of veneer – thin sheets of wood
that are peeled or sliced directly from logs.
These logs are usually very high quality, with
few if any visible defects. Veneer logs may also
be judged on color, growth rate and amount
of sapwood versus heartwood. Veneer logs are
higher value than sawlogs. More information
on veneer, and the grading of veneer logs,
can be found in the publication Factors Affect-
ing the Quality of Hardwood Timber and Logs
for Face Veneer.
1
Sawlogs are those that are sawn into
hardwood lumber and the grading of saw-
logs is the subject of this handbook. These
logs are also called “factory” logs. Logs that
are not of sufficient quality to be a sawlog
may be used for cutting pallet stock or rail-
road crossties, where appearance is not im-
portant, or for pulpwood.
This handbook deals only with hardwoods.
Softwoods such as pine and spruce are gen-
1
Cassens, D.L. 2004. Factors Affecting the Quality of
Hardwood Timber and Logs for Face Veneer. Purdue
University publication FNR239. Available for down-
load from http://www.ces.purdue.edu/extmedia/
FNR/FNR-239.pdf
3
erally used for making structural products, for
example the studs used for framing a house.
Softwoods are graded using different rules that
focus on strength-reducing defects.
Log Scaling
Scaling is used to predict the amount of
lumber that will be sawn from a log. The amount
of lumber is measured in board feet, where one
board foot is 1” x 12” x 12”, or any dimension
with the same volume of wood. For example, a
board 2” x 6” x 8’ contains 8 board feet.
There are different log rules that are used
for scaling in different regions and for different
products. The three most common log scales
are the Doyle rule, the Scribner rule and the
International ¼” Rule. By tradition, the Doyle
Scale is the most commonly used scaling rule
used in Tennessee (Table 1.)
2
The Doyle Rule often underestimates the
yield of lumber for small logs and for modern,
more efficient sawmills (e.g. band mills). This
underestimating can lead to “overrun”, when
the actual yield is more than the scaling pre-
dicted. Figure 1 shows a comparison of the
Doyle scale to the International ¼” Rule, which
more accurately predicts the true yield.
Log prices are normally different depend-
ing on the rule used, reflecting the differences
in the scale resulting from each rule. Thus, the
2
For more information on scaling, and conversions
among the log rules, see Understanding Log Scales
and Log Rules by Brian Bond. University of Tennessee
Extension PB1650. Download available at www.
utextension.utk.edu/publications/pbfiles/Pb1650.pdf
4
Table 1. The Doyle Log Rule.
Log Length (feet)
8 10 12 14 16
Scaling
Diameter
(inches)
------------Yield of Lumber ------------
(board feet)
8 8 10 12 14 16
9 13 16 19 22 25
10 18 23 27 32 36
11 25 31 37 43 49
12 32 40 48 56 64
13 41 51 61 71 81
14 50 63 75 88 100
15 61 76 91 106 121
16 72 90 108 126 144
17 85 106 127 148 169
18 98 123 147 172 196
19 113 141 169 197 225
20 128 160 192 224 256
21 145 181 217 253 289
22 162 203 243 284 324
23 181 226 271 316 361
24 200 250 300 350 400
25 221 276 331 386 441
5
average log value will be the same regardless
of the scaling rule that is used.
Special rules for certain species or prod-
ucts are used in some locations. For example,
some buyers use a “cedar rule” for predicting
the lumber yield from eastern redcedar logs,
which are small and irregularly shaped.
Species is another important factor in
determining log value. For example, top grade
walnut, cherry or hard maple logs can be
worth two- or three-times as much as hickory,
soft maple or poplar logs of the same size and
quality. This is because the products made
from those species are worth more and there
are fewer top quality logs of the high-value
species available. Species differences may
Figure 1. The predicted lumber yield using the Doyle scale compared
to the International ¼” rule. The International Rule is fairly accurate for
all log diameters, while the Doyle Rule underestimates the true yield
of lumber for smaller logs. The actual yield of lumber from a scaled
log will vary with mill technology, wood species and other factors.
Log Diameter (inches)
10 15 20 25 30
Predicted Lumber Yield
(percent)
40
50
60
70
80
90
100
D
o
y
le S
c
a
le
International 1/4" Rule
Overrun
6
be stated explicitly in some log grading rules.
Other log grading rules grade all species of
logs in the same way, with buyers paying dif-
ferent prices for logs of the same grade but of
different species.
There are regional differences in pricing
of logs and lumber products, because the
wood quality of certain species is thought to
be superior in some areas. For example, cherry
logs from the northeastern United States are
believed to contain higher-quality lumber and
thus higher prices are paid for cherry logs from
that area. There are also local variations in log
prices. For example, if there are many sawmills
within a reasonable hauling range of a timber
harvest, this can increase the demand – and
thus the price paid – for logs. Finally, prices
paid for logs can vary substantially with fluc-
tuations in demand due to seasonal changes
and overall economic trends.
3
Log Grading —
Relation to Lumber Grading
Most hardwood logs are sawn into lumber.
The value of this lumber, and thus of the log, is
determined in part by the lumber grade. The
grade of hardwood lumber is determined by
a visual inspection of each board according
to rules developed by the National Hardwood
3
Information on prices trends in log and lumber
markets are available from a number of sources
including the including Tennessee Division of
Forestry (www.state.tn.us/agriculture/forestry/
tfbp.html), the Hardwood Market Report (www.
hmr.com/), the Hardwood Review (www.
hardwoodreview.com/) and TimberMart South
(www.tmart-south.com/tmart/)
7
Lumber Association (NHLA - Table 2). The most
important factors in determining lumber grade
are width, length and yield of defect-free
wood (“clear cuttings”).
As shown in Table 2, high-grade lumber
must be relatively long, wide and clear of de-
fects. Therefore high grade logs must be long,
large in diameter and contain mostly clear
wood. Larger logs are also preferred in log
grading because they cost less to process per
unit of lumber produced.
Table 2. Summary of the NHLA hardwood lumber
grading rules. Adapted from NHLA, 2003.
Grade
Lumber Requirements
Min.
Board
Length
(feet)
Min.
Board
Width
(inches)
Clear cuttings
(poor face)
Total
yield
Min.
size
Max.
number
FAS (the
top grade)
8 6 83.3% 4” x 5’
3” x 7’
4
*
Selects 6 4 83.3%
(good
face)
1 Common 4 3 66.6% 4” x 2’
3” x 3’
5
*
2 Common 4 3 50% 3” x 2’ 7
*
3 Common
(the lowest
grade)
4 3 33.3% 3” x 2’ --
*
The maximum number of cuttings allowed depends
on board size. The actual number is usually fewer.
8
Although low-quality logs will produce
some high-grade lumber, higher-grade logs pro-
duce a higher proportion of better quality lum-
ber. That is why high-grade logs have a higher
value. An example is given in the table below.
Log Grading Methods
Unlike lumber grading, there is no one
system that is widely accepted for grading
logs. The United States Forest Service has de-
veloped a log grading system based on the
yield of “clear cuttings” from faces of the log.
Alternatively, many buyers use a “clear face”
system, where the number of clear (defect-
free) faces on the logs is the basis for deter-
mining quality. Some sawmills also buy logs on
the basis of weight. Buying by weight assumes
an average grade for the whole load.
Defects
Defects are features that reduce the qual-
ity or quantity of the lumber that will be sawn
from the log. For the US Forest Service log grad-
ing rule, defects are defined as follows:
Grade and value of lumber produced from
black cherry logs of different grades. Expressed
as board feet of 4/4 (1” thick) lumber sawn from
16” diameter, 12’ long logs, based on prices
for Appalachian hardwoods in 2009.
Log Grade
FAS &
Select #1 C #2 C #3 C
Total
Lumber
Value
High (F1) 59 20 17 12 $111
Medium
(F2)
28 38 22 20 $79
Low (F3) 15 46 23 23 $65
9
● Grade defects include anything that re-
duces lumber value. These include stem
bulges, splits, rot and insect or bird holes.
Abnormalities on the surface of a log must
extend into the log more than 15% of the
diameter to be considered a defect (see
“Quality Zones” in Figure 2). Knots, and bark
distortions where the tree has grown over
old knots, are the most common defects.
These are also the most important defects
because knots extend to the center of the
log and will appear on all the lumber sawn
from that part of the log.
Small bark distortions, that do not clearly
indicate an overgrown knot, are not consid-
ered to be a defect in 15”+ diameter logs.
Horizontal breaks in the bark are not defects.
Abrupt bumps are defects, but clear cuttings
can extend ¼ of the length of the bump.
Bumps with gradually sloping sides (length
12+ times the height) can be ignored.
● End defects are determined by looking at
both ends of the log. Any abnormality in
the “heart center” (the innermost 1/5 of
the diameter) can be ignored for grading
purposes. End defects are classified in the
following three categories:
■ Unsound end defects include knots, de-
cay (rot) and shake. If the defect extends
more than half the distance from the
heart zone to the bark (both Quality zones
– Figure 2), then a clear cutting cannot be
taken over it. The distance up the log that
10
the defect extends should be estimated;
a clear cutting can extend over 1/3 of the
estimated length of the defect.
■ Sound end defects include stain and
slight dote (the beginning of rot) and are
restricted in Grades 1 & 2.
• Grade1–notmorethan½ofeitherend
• Grade2–notmorethan3/5ofeither
end(limitedto½of16”diameterand
smaller logs.
■ Specific end defects include bird peck,
wormholes, spots and streaks. If these de-
fects cover more than half the distance
from the heart center to the bark under
three or more faces at one end, or two
faces at both ends, lower Grade 1 & 2
one grade.
● Scaling defects reduce the amount, or vol-
ume, or useable lumber. Rot and large holes
Figure 2. Quality
zones in a hardwood
log. Abnormalities
must occur in both the
inner and outer quality
zones to be consid-
ered a defect for grad-
ing purposes. Defects
in the heart center are
ignored for grading
purposes. Adapted
from McKenna, 1981.
HEART
CENTER
R = 20% D
INNER QUALITY
ZONE
R = 15% D
OUTER QUALITY
ZONE
R = 15% D
QUALITY ZONE
(Inner plus outer)
R = 30% D
11
produce no lumber and thus can reduce
not only the grade (quality) of the lumber
produced from a log but also the quantity
(scale). Scaling deductions can be made
to account for these defects when scaling
the log but these defects are also consid-
ered in log grading.
USDA Forest Service Hardwood Sawlog
Grading System – a clear cutting method
The Forest Service has developed a system
to organize sawlogs into one of three grades.
Grade 1 (or “F1”, where F stands for ‘factory’) is
the highest (top quality), grade 2 (F2) the next
best, and grade 3 (F3) is the lowest grade.
The Forest Service grading system predicts the
yield of 1 Common and better grades of lumber
produced from the log. This is estimated based
on the whether the log is a butt or upper cut,
the log length and diameter, and the number
and location of defects on the log.
Table 3 summarizes the requirements for
each of the three grades. The factors used in
grading are listed in the left-hand column.
● Position in tree. “Butt” logs come from the
base of the tree and are preferred because
there is usually more clear wood in that part
of the tree stem. Butt logs can be identified
by the flare at the base of the log and the
presence of the notch that was used to di-
rect the falling tree. Upper logs are also ac-
ceptable for all three grades, except smaller
grade 1 logs (13” – 15” diameter), which must
be butt cuts only.
12
Table 3. Summary of Forest Service Hardwood Log Grading Rule.
Adapted from McKenna, 1981.
Grading Factor Grade 1 (F1) Grade 2 (F2) Grade 3
(F3)
Position in tree Butt
only
Butt or upper Butt or upper Butt or
upper
Diameter 13”-
15”
16”-
19”
20”+ 11” 12”+ 8”+
Length 10’+ 10’+ 8’-
9’
10’-
11’
12’+ 8’+
Clear cuttings
on 3
rd
best/2
nd
worst face
Length 7’ 5’ 3’ 3’ 2’
Number 2 2 2 2 3 No limit
Yield 5/6 2/3 3/4 2/3 2/3 ½
Sweep
If < ¼ of end in
sound defects
15% 30% 50%
If > ¼ of end in
sound defects
10% 20% 35%
Total scaling deduction 40% 50% 50%
13
● Diameter. The diameter of a log for grad-
ing (and scaling) is the diameter inside
the bark at the small end. Most logs are
not truly round, so two (or more) diameter
measurements should be made and the
average value used. The grading rule speci-
fies minimum diameters because larger
diameter logs tend to contain a higher pro-
portion of defect-free wood and because
high-grade lumber must be wide.
● Length. The length of a log for log grading
and scaling is the length in feet, without
trim. Most log buyers require 4” or 8” of trim
allowance.
● Clear cuttings. As in the lumber grading
rules, clear cuttings are the basis of the For-
est Service log grading system. Clear cut-
tings are sections of the log that are free
from defects. Clear cuttings are determined
on the grade face.
■ Choosing the grade face. The grade face
is determined by dividing the surface of
the log into four equal faces. This should be
done such that one face is the “worst” – i.e.
it contains the most defects (Figure 3). The
next best face is the grade face. The other
two faces should be at least as good, or
better, than the grade face
■ Clear cutting length. The minimum
length of a clear cutting is specified. High-
er grade logs require longer cuttings. All
cuttings must be the full width of the face.
14
■ Maximum number of clear cuttings. For
grade 1 (F1) logs, only two cuttings are
allowed on the grade face. Some F2, and
all F3 logs, can have 3 cuttings.
■ Clear cutting yield. The yield of clear cut-
tings on the grade face is calculated as
the total length of the cuttings divided by
the total length of the log (no trim). High-
er grade logs must have a higher yield.
Table 4 provides calculations of total clear
cutting lengths for different log lengths.
● Maximum Sweep. Curved logs are more
difficult to process and they produce a lower
yield of good-quality lumber. Therefore the
log grading rule specifies the maximum
Divide the log into four faces…
…ignore the worst face and grade
the next worse face.
Figure 3. Determining the grade face of a log.
Adapted from Rast et al, 1973.
Grade Determining Face
15
amount of sweep that is allowed for each
grade. Sweep is measured as the maximum
deviation of the log from a straight line
(Figure 4). The sweep deduction can be
determined using Table 5. The rule permits
less sweep allowance for logs with sound
defects covering more than 1/4 of either end.
Example: A 14’ long log, with a 20” scaling
diameter, has 8” of sweep. The sweep de-
duction is 30% (Table 5).
● Total scale and sweep deduction. The
rules limits the amount of unusable wood in
a log. The defect length factor multiplied
by the defect cross-section factor equals
Figure 4. Measuring sweep on a curved log. This log has 8” of
sweep. From McKenna, 1981
8”
16’
20”
Table 4. Total cutting lengths required in each grade.
Adapted from McKenna, 1981.
Log length
(feet)
Grade 1 (F1)
(5/6 yield)
Grade 2 (F2)
(2/3 yield)
Grade 3 (F3)
(1/2 yield)
8 -- 6’ (3/4 yield) 4’
10 8’4” 6’8” 5’
12 10’ 8’ 6’
14 11’8” 9’4” 7’
16 13’4” 10’8” 8’
16
Table 5. Sweep deduction (percent). Adapted from McKenna, 1981.
Sweep (inches) Diameter at the small end inside the bark (inches)
8-10 foot logs 14-16 foot logs 8 10 12 14 16 18 20 22 24 26 28 30
- 3 12 10 8 7 6 6 5 5 4 4 4 3
3 4 25 20 17 14 12 11 10 9 8 8 7 7
4 5 38 30 25 21 19 17 15 14 12 12 11 10
5 6 50 40 33 29 25 22 20 18 17 15 14 13
6 7 50 42 36 31 28 25 23 21 19 18 17
7 8 50 43 38 33 30 27 25 23 21 20
8 9 50 44 39 35 32 29 27 25 23
9 10 50 44 40 36 33 31 29 27
10 11 50 45 41 38 35 32 30
11 12 50 45 42 38 36 33
12 13 50 46 42 39 37
13 14 50 46 43 40
14 15 50 46 43
15 16 50 47
16 17 50
11-13 foot logs
3 19 15 12 11 9 8 8 7 6 6 5 5
4 31 25 21 18 16 14 12 11 10 10 9 8
5 44 35 29 25 22 19 18 16 15 13 12 12
6 45 38 32 28 25 22 20 19 17 16 15
7 46 39 34 31 28 25 23 21 30 18
8 46 41 36 32 30 27 25 23 22
9 47 42 38 34 31 29 27 25
10 47 42 39 35 33 30 28
11 48 43 40 37 34 32
12 48 44 40 38 35
13 48 44 41 38
14 48 45 42
15 48 45
16 48
17
Table 5. Sweep deduction (percent). Adapted from McKenna, 1981.
Sweep (inches) Diameter at the small end inside the bark (inches)
8-10 foot logs 14-16 foot logs 8 10 12 14 16 18 20 22 24 26 28 30
- 3 12 10 8 7 6 6 5 5 4 4 4 3
3 4 25 20 17 14 12 11 10 9 8 8 7 7
4 5 38 30 25 21 19 17 15 14 12 12 11 10
5 6 50 40 33 29 25 22 20 18 17 15 14 13
6 7 50 42 36 31 28 25 23 21 19 18 17
7 8 50 43 38 33 30 27 25 23 21 20
8 9 50 44 39 35 32 29 27 25 23
9 10 50 44 40 36 33 31 29 27
10 11 50 45 41 38 35 32 30
11 12 50 45 42 38 36 33
12 13 50 46 42 39 37
13 14 50 46 43 40
14 15 50 46 43
15 16 50 47
16 17 50
11-13 foot logs
3 19 15 12 11 9 8 8 7 6 6 5 5
4 31 25 21 18 16 14 12 11 10 10 9 8
5 44 35 29 25 22 19 18 16 15 13 12 12
6 45 38 32 28 25 22 20 19 17 16 15
7 46 39 34 31 28 25 23 21 30 18
8 46 41 36 32 30 27 25 23 22
9 47 42 38 34 31 29 27 25
10 47 42 39 35 33 30 28
11 48 43 40 37 34 32
12 48 44 40 38 35
13 48 44 41 38
14 48 45 42
15 48 45
16 48
the scale deduction (Table 6). The scale
deduction is then added to the sweep de-
duction to give the total scale and sweep
deduction.
Example: The log in previous example has
a 6” diameter round hole in the butt end
that extends 4’ (30%) up the log. The defect
length factor is 0.5 and the defect cross-
section factor is 8 (Table 6). The total scale
deduction is 0.5 x 8 = 4. The total scale and
sweep deduction is 4 + 30 (from the previ-
ous example) = 34%.
Grading a Log Using the
Forest Service System
The process for grading a log is relatively
simple. The biggest challenge is identifying the
location and extent of defects.
● Step 1. Measure diameter and length. This
is also required for scaling the log. Note if
the log is a butt or upper section.
● Step 2. Find the grade face. Faces should
be arranged to produce the highest grade
log possible. Ignore the worst face and
grade the next worst (or third best) face.
Seams that can be positioned between two
faces can be ignored.
● Step 3. Determine the size, number and
yield of clear cuttings on the grade face.
● Step 4. Check that sweep and scale de-
ductions are within the allowed limits.
The requirements listed Table 3 are the
minimum requirements for logs for each
grade. Each log must meet all of the require-
18
Table 6. Scaling deduction factors. To determine the scale deduction, multiply the length factor by the cross-section factor.
Adapted from McKenna, 1981.
Length factors
Log diameter (inches)
Length of log that has defect (percent)
10 20 30 40 50 60 70 80 90 100
8 1.2 2.4 3.5 4.7 5.9 7.1 8.2 9.4 10.6 11.8
9 .9 1.8 2.7 3.6 4.5 5.4 6.3 7.2 8.1 9.0
10 .7 1.4 2.1 2.8 3.6 4.3 5.0 5.7 6.4 7.1
11 .6 1.1 1.7 2.3 2.9 3.4 4.0 4.6 5.2 5.8
12 .5 1.0 1.4 1.9 2.4 2.9 3.3 3.8 4.3 4.8
13 .4 .8 1.2 1.6 2.0 2.4 2.8 3.2 3.6 4.0
14 .3 .7 1.0 1.4 1.7 2.0 2.4 2.7 3.1 3.4
15 .3 .6 .9 1.2 1.5 1.8 2.1 2.4 2.6 2.9
16 .3 .5 .8 1.0 1.3 1.5 1.8 2.0 2.3 2.6
17 .3 .4 .7 .9 1.1 1.4 1.6 1.8 2.0 2.3
18 .2 .4 .6 .8 1.0 1.2 1.4 1.5 1.8 2.0
19 .2 .4 .5 .7 .9 1.1 1.2 1.4 1.6 1.8
20 .2 .3 .5 .6 .8 1.0 1.1 1.3 1.4 1.6
21 .2 .3 .4 .6 .7 .9 1.0 1.2 1.3 1.4
22 .1 .3 .4 .5 .7 .8 .9 1.0 1.2 1.3
23 .1 .2 .4 .5 .6 .7 .8 1.0 1.1 1.2
24 .1 .2 .3 .4 .5 .6 .8 .9 1.0 1.1
25 .1 .2 .3 .4 .5 .6 .7 .8 .9 1.0
Cross-section factors
Width (short axis) of defect (inches) Height (long axis) of defect (inches)
2 3 4 5 6 7 8 9 10 11 12 13 14 15
2 2 2 3 3 4 4 5 5 6 6 7 7 8 8
3 3 3 4 5 5 6 7 8 8 9 10 10 11
4 4 5 6 7 8 9 10 10 11 12 13 14
5 6 7 8 9 10 11 12 14 15 16 17
6 8 10 11 12 13 15 16 17 18 19
7 11 12 14 15 17 18 19 21 22
8 14 16 17 19 20 22 23 25
9 17 19 21 23 24 26 28
10 21 23 25 27 29 31
11 25 27 29 31 33
12 29 32 34 36
13 34 36 39
14 39 42
15 44
19
ments for each grade. Logs that do not meet
Grade 3 are “cull” or below grade.
Clear Face Grading
Clear face log grading rules are used by
many log buyers. Many variations on clear face
grading rules exist but, like the Forest Service sys-
tem, these rules require minimum diameters and
lengths for logs. Clear-face log grading rules
also divide the log into four equally-sized faces;
however, instead of examining the clear cuttings
on the grade face, the number of completely
clear (defect free) faces are counted. Higher
grades require more clear faces. Although no
standard clear-face log grading rule exists, figure
5 gives an example of a clear face grading rule.
Grade Diameter Length
Clear
Faces
Super Prime 18” 14’ 4
Prime 1 18” 12’ 4
Prime 2 15” 10’ 4
Select 1 16” 10’ 3
Select 2 15” 10’ 3
#1 14” 8’ 2
#2 12” 8’ 1
#3 10” 8’ 0
Notes:
•Poplarminimum20”diameterforPrime
•Whiteoak,HickoryandBeech-minimumlengthof10’
Figure 5. An example of a clear face grading rule. Note that this
rule is specific to this mill – other log buyers will have different
requirements.
20
The Log Grading Rules Compared
The US Forest Service Log Grading Rule
The Forest Service system for grading logs
has a number of advantages. As a published
standard it can be widely used and under-
stood. It is also independent of tree species, so
any log can be graded using the same meth-
od. However, the biggest advantage is that it
can be used to predict the amount of high-
grade lumber that will be produced from a log.
The Forest Service system was developed over
many years by measuring over 20,000 logs
and grading the lumber that was produced
from those logs. Based on those measure-
ments, the following predictions are possible:
Grade 1 (F1)
…logs will
produce…
60%+
…1Common
or
better
lumber
Grade 2 (F2) 40-60%
Grade 3 (F3) Less
than
40%
Clear Face Rules
Some people prefer clear face grading
rules because they can be simple to apply;
there is no need to calculate clear cutting
yield. Clear face rules usually have more than
three grades, which allows for more price lev-
els for logs of different quality.
Weight Scaling
When buying logs by weight, an average
grade (and scale) of the logs in the load is as-
sumed. Weight scaling has the advantage of
being easy and fast; however, it provides very
21
little information about the quality and quan-
tity of lumber that will be produced.
Tree Grading
The principles of log grading can be ap-
plied to standing trees to estimate the value
of the log contained within the bole. Table 7
shows a summary of a tree grading system
developed by the United States Forest Service.
This tree grading system is very similar in many
ways to the log grading system.
Because the logs have not yet been cut
from the tree, the grading section can be lo-
cated anywhere in the bottom 16’ of the tree.
Once the grading section has been located,
Table 7. Summary of US Forest Service Rule for Tree
Grading. Adapted from Hanks, 1976.
Grade 1 Grade 2 Grade 3
Grading section Best 12’ in 16’ butt section
Diameter at
breast height
(DBH – inches)
16 13 10
Diameter at
top of grading
section (inside
bark – inches)
13 16 20 11 12 8
Clear cuttings (on three best faces)
Min. length (feet) 7 5 3 3 3 2
Max. number on
each face
2 2 3 No limit
Min. yield per
face
5/6 2/3 1/2
Cull deduction
(percent)
9 9 50
22
the diameter of the tree is measured at breast
height and the scaling diameter at the top of
the grading section is estimated. Then, the size
and number of clear cuttings on the grade
face are determined. Of course, because
the tree has not yet been cut, possible end
defects are not a factor; only defect indica-
tors on the surface of the tree are considered.
Tree grading also can be used to predict the
proportion of high-grade lumber that can be
sawn from the tree (see Hanks, 1976).
Log Bucking Optimization
After a tree is felled and limbed, it is
“bucked” into logs. The location of the bucking
cuts on the tree stem can greatly influence
the grade, and thus the value, of the resulting
logs. Studies have shown that improved buck-
ing practices can increase the average value
of logs by 15 to 35%. Loggers should keep the
following rules-of-thumb in mind when making
bucking decisions:
● Know the market. Different log buyers use
different log grading methods and small
differences in the grading system can result
in large differences in log values. By being
familiar with what the buyer wants, a logger
can make bucking decisions that improve
the value of the logs cut from trees.
● Find the best log. In general, it is best to
locate the top grade log from a stem first
and then arrange the other bucking cuts
around it. Often this highest-value log will
be the butt log but in many cases the best-
23
grade log will be located further up the
stem. In some cases, this process will involve
discarding cull sections at the butt end.
Because of the relatively high value of top-
grade logs, it is usually advantageous to
lose some scale (volume) if it will result in a
higher grade (quality) log.
It is also important to remember that
longer lengths of logs do not necessarily
have higher value. Although the minimum
length requirements for various grades and
products must be met, the length of a log
should be adjusted (if possible) to yield the
highest grade logs from the tree.
Example: In the white oak log pictured be-
low, the grade can be improved from #2
(log A) to #1 (log B) by cutting off the butt
2’. Even though the scale is reduced, the
overall value of the log is higher because #1
logs sell for $800/thousand board feet and
#2 sell for $500/thousand.
14”
14’2’
Scale = 88’
Grade = 1 ($800/thousand)
Value = $70
(Cull)
A
16’
14”
Scale = 100’ (Doyle scale)
Grade = 2 ($500/thousand)
Value = $50
24
● Keep logs straight. As described above,
sweep can lower log grade. For this reason,
it is often best to buck stems where they
curve. The resulting logs will be straighter
and could be a higher grade.
● Put the defects on the end. Many log buy-
ers will consider the location of defects in
a log, especially if they are using the Forest
Service’s grading system. Defects that are
close to the ends of a log are easier for the
sawyer to cut around (to produce clear
lumber). For this reason, defects near the
ends of a log often won’t reduce the grade
as much as defects that are in the middle.
More information on hardwood log buck-
ing is available on the internet at http://www.
hardwoodvip.org/
Summary
A knowledge of how hardwood log values
are determined can help buyers and sellers
decide on a fair price for timber sales. Mea-
suring incoming log quality can also help
sawmills to evaluate the efficiency of their mills.
Log values are a function of the grade (qual-
ity), scale (size) and wood species. Log grade
affects the quality mix of lumber that will be
sawn from a log; high quality logs produce a
larger proportion of high quality lumber. Log
grading rules vary by region and individual
buyer but the principles remain the same ev-
erywhere: High grade logs have few defects
(especially knots), are large in diameter, and
are of a minimum length. Small differences in
25
grade can mean large differences in price,
so it is important to understand how grade is
determined. Loggers in particular should be
familiar with the log market and applicable
grading rules so that they can make buck-
ing decisions that maximize the value of logs
coming from a tree.
References
Hanks, Leland F. 1976. Hardwood Tree Grades
for Factory Lumber. USDA Forest Service
Research Paper NE-333.
Hardwood Value Improvement Program
(HVIP). 2006. Increase Log Quality Through
Improved Bucking. Internet website at
http://www.hardwoodvip.org/. Accessed
November 20, 2006.
Kenna, Karen M. 1981. Grading Hardwood
Logs for Standard Lumber: Forest Service
Standard Grades for Hardwood Factory
Lumber Logs. Formerly Publication No.
D1737-A, Forest Products Laboratory, USDA
Forest Service. Revised 1981.
Rast, Everette D., David L. Sonderman and
Glenn L. Gammon. 1973. A guide to
hardwood log grading. USDA Forest Service
General Technical Report NE-1
National Hardwood Lumber Association
(NHLA). 2003. Rules for the Measurement &
Inspection of Hardwood & Cypress. PO Box
34518, Memphis TN 38184. www.nhla.com
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