A Note on Visually-Graded Lumber 

by John A. Akande 
and Curt C. Hassler 
Akande was formerly Research Assistant 
Professor, and Hassler is Associate Professor 
and Leader, Appalachian Hardwood Center, 
West Virginia University, Morgantown, W.Va. 
Structural grades are established to allow 
orderly purchase and proper util~zation 
of specified quality of lumber in any 
desired quantity. The Northeastern Lum- 
ber Manufacturers Association (NELMA 
1986) grades-Select-Structural (SS); 
No.1; No.2; No.3 and Economy (E) are 
specified to reflect expected strength 
variations and provide technical data for 
the engineering usage of wood. Safety is 
best guaranteed when the quality of 
lumber can be accurately predicted and 
the material is utilized within its struc- 
tural potential. In the absence of Machine 
Stress Rating (MSR), design values re- 
flect the visual grade marks on surfaced 
lumber whether green or dry. Adjustment 
corrections are therefore suggested for 
moisture changes (DeBonis 1988), but 
the dry/green ratios (ASTM 1989~ gener- 
ally imply increase in strength ~Ith sea- 
soning. However, for wood species prone 
to abnormal seasoning checks like red 
oak this assumption may not always be 
valid. Furthermore, wood dressing, fol- 
lowing an initial grading, may interfere 
with some of the previously evaluated 
surface defects and change the original 
wood quality. 
The objective of this study is to assess 
the significance of seasoning and subse- 
quent dressing on visually-graded lu~~r. 
To do this, northern red oak was utilized 
because of its availability and current use 
in timber bridge construction. 
16 

Procedure 
Red oak (Quercus ruba L.) logs obtained 
from the West Virginia University Forest 
were first sawn to flitches before conver- 
sion to nominal 2 in. x 4 in. x 5 ft. test 
boards. The test materials were visually 
graded using NELMA rules at green 
conditions (M.C. range, 50% to 80%). 
After this initial grading, not many of the 
boards fell into No. 1 and "Economy" 
grades and were therefore not includ~d 
in our experiment. Actual test boards in 
the Select-Structural, No.2, and No.3 
grades totalled 900. The No.2 grad.e .was 
air-dried under laboratory conditions 
(Temp. 72°F; EMC 8%) while the SS- 
and No.3 grades were dried in a N~le 
dehumidifying kiln system to 10% mois- 
ture level by using the appropriate 
schedule. After all drying was completed, 
a WADKIN P.L.C. moulder (Model 
GB) was utilized to dress the boar~s to 
standard finished dimension of 1.5 in. x 
3.5 in. x 5 ft. after which the boards were 
regraded with the same NELMA spe~ifi- 
cations. Distribution of final grades With- 
in individual green grade class was evalu- 
ated and their proportion expressed as 
G/GT ratios where G is the final grade 
count and GT is the total green grade 
samples. 
Results and Discussion 
Defects associated with drying were 
found to be independent of whether the 
wood was air-dried or kiln-dried. This 
observation suggests that if proper dry 
kiln schedule is followed, faster drying of 
wood can be accomplished without intro- 
ducingadditional defects. The results of 
the final grade counts and proportional 
ratio based on original green grade 
samples are presented in Table 1. Appar- 
ently drying and final dressing changed 

the original lumber qualities. About 20% 
of the Select-Structural group was down- 
graded (Figure 1) while significant grade 
movements in the upward and downward 
directions occurred in the No.2 and No. 
3 categories. Evaluation of the G/~T 
ratios indicated that 19.5% up-grading 
and 16.2% down-grading resulted from 
seasoning and final dressing in the No.2 
grade category when compared to 34 ', 5% 
up-grading and 20.2% down-grading 
obtained from the original No.3 green 
	grade. 	. 
The up-grading effect recorded in the 
No.2 and No.3 grades is structurally less 
significant than the associated down- 
grading. 
Ghi-square statistical analysis was per- 
formed on the results in Table 1 to deter- 
mine if a relationship exists between the 
initial green grades and the resulting 
final grades after drying and dressing. 
Results at PSO.05 indicated that the final 
grades are not independent of the i~itial 
grades. This inference is a c~ear mam~es- 
tation of the usefulness of visual grading 
in delineating reasonably between grades. 
Nevertheless, the movements encoun- 
tered due to subsequent lumber drying 
and dressing suggest a need for caution 
when handling surfaced wood already 
graded for structural use. If graded ma- 
terials are at higher moisture levels than 
target, dimensional instability like wart:- 
age and shrinkage could re~ult. In addi- 
tion, any subsequent dressing of gr~ded 
materials can remove some of the previous 
defects and expose other defects to change 
the wood quality. 
Conclusions 
Visual grades help to delineate lu~ber 
into different groupings based on visible 
defects. Structural grades are usually 
specified for surfaced lumber whether 
WVa. Forestry Notes No. 14, 1991