| SOUTHERN PINE SEASONING
REQUIREMENTS* |
Based on 1994 SPIB Grading Rules |
Southern Pine grading rules restrict moisture content
of lumber 2" and less in thickness to a maximum of 19%. If specified as
"KD," "KD19," "dry" or "air-dried" the maximum is
19%. If specified as "KD15" (kiln-dried) or "MC15" the maximum is 15%.
Material identified by a certified grade mark is evidence that Southern Pine has been
properly seasoned.
Moisture content restrictions apply at time of shipment and
delivery to buyer, as well as time of dressing, if dressed lumber is involved.
Moisture
Content Limit |
Items
(Nominal thickness) |
Kiln-Dried |
Dry |
D and
Better Grades |
|
|
1" and
1-1/4" |
Max. 12% on 90%
of pieces |
15% |
| |
15% on
remainder |
|
1-1/2",
1-3/4" and 2" |
15% |
18% |
Over 2",
but not over 4" |
15% |
19% |
Over 4" |
18% |
20% |
Paneling |
12% |
12% |
Boards 1 |
19% |
19% |
Dimension 1,2 |
19% |
19% |
Decking 3 |
19% |
19% |
Timbers 2 |
20% |
23% |
*Lumber dressed at a moisture content
within the limits of these rules is sufficiently stabilized for most uses, but limited
size changes will occur from shrinkage or expansion if the moisture content is further
reduced or increased after dressing. The normal shrinkage allowance is 1% reduction in
size for each 4-point reduction in percentage of moisture content and same tolerance for
any expansion.
(1) KD15 or MC15 may be specified if
desired.
(2) Moisture content provisions must be
specified for material 2-1/2" and thicker because seasoning is not mandatory for
these sizes.
(3) All thicknesses of roof decking should
be specified at 15% maximum moisture content.
*NGR applies to dimension lumber and
excludes items such as cross-arms, factory and shop lumber, finish (select), foundation
lumber, industrial clears, ladder stock, laminating stock, railroad stock, rough lumber,
scaffold planks, ship decking and plank stock, and special product rules for items such as
radius edge decking, and prime & merchantable dimension.
AMERICAN SOFTWOOD
LUMBER STANDARD
The American Softwood Lumber Standard,
PS 20-94, of the U.S. Department of Commerce relates lumber size to moisture content.
Separate size schedules for green and dry lumber assure that both products will
approximate the same size in service. All bills and invoices are required to show actual
net sizes of lumber. Strength and stiffness values for Southern Pine products in current
SPIB rules have been approved by the Board of Review of the American Lumber Standard
Committee. PS 20-94 provides for a National Grading Rule (NGR)* with simplified
grade names and sizes to assure uniformity, efficiency and economy in the use of dimension
lumber. The NGR was incorporated in the SPIB Standard Grading Rules for Southern Pine
Lumber, 1994 Edition, published by the Southern Pine Inspection Bureau. Dimension
lumber sizes and grades are:
Structural Light Framing: 2"
to 4" thick, 2" to 4" wide Select Structural, No. 1, No. 2, No. 3
Light Framing: 2" to
4" thick, 2" to 4" wide Construction, Standard, Utility
Studs: 2" to 4"
thick, 2" and wider Stud
Structural Joists & Planks: 2"
to 4" thick, 5" and wider Select Structural, No. 1, No. 2, No. 3 Select
Structural, No. 1 and No. 2 grades also include Dense and NonDense options. |
