The Southern Pine Inspection Bureau (SPIB) has submitted proposed design values for all grades and sizes of visually graded Southern Pine dimension lumber to the American Lumber Standard Committee (ALSC). The ALSC Board of Review will meet on October 18, 2012 to hear testimony from interested parties and will consider all input before making a final decision. SFPA and key customer groups continue to support an orderly transition to new design values and will encourage the ALSC Board of Review to once again recommend an approximate six-month transition period after certification of new design values for all grades and sizes.
As a rules-writing agency, SPIB must follow a rigorous, approval process to establish design values for Southern Pine lumber. SPIB and Timber Products Inspection worked cooperatively to complete a full In-Grade testing matrix as required by consensus standard ASTM D1990. More than 7,400 full-size samples of commercially produced Southern Pine were destructively tested in a two-step process. The data analysis combined all data from steps one and two to provide the best estimates of design values.
The analysis of the full In-Grade test data resulted in smaller reductions for the wider widths and higher grades as compared to the No.2 2x4s, and even some small increases as compared to current design values. The analysis also resulted in upward revisions to some of the new design values that became effective June 1, 2012 based only on No.2 2x4 data. For No.2 2x4s for example, the bending design value will increase from 1050 to 1100 psi (pounds per square inch) and the modulus of elasticity will increase from 1.4 to 1.5 million psi.
There is no change in Southern Pine’s specific gravity value of 0.55. Design values for shear and compression perpendicular-to-grain also will not change.
“The results are encouraging, better-than-expected news for Southern Pine lumber producers and users,” says Cathy Kaake, vice president of technical marketing for the Southern Forest Products Association (SFPA). “For example, the impact on joists, rafters and headers is smaller than originally projected due to smaller reductions for the wider widths commonly used for those applications,” she adds.
Southern Pine’s strength and stiffness remain comparable to other softwood species used in residential and commercial construction. Southern Pine users have many available product options including visually graded dimension lumber and an increasing supply of mechanically graded lumber. From framing a house to building a deck, Southern Pine continues to be a dependable product with superior treatability against decay and termites.
BACKGROUND: The last major change for visually graded dimension lumber occurred in 1991 when design values for Southern Pine and other North American species were published based on In-Grade testing of full-size samples of commercially produced lumber. Since 1994, SPIB has conducted an annual resource monitoring program developed in collaboration with the U.S. Forest Products Laboratory (FPL).
SFPA does not test lumber or establish design values. SFPA’s primary function is to market lumber products and to help users understand Southern Pine grading rules and design values.
Complete information about Southern Pine design values is available at www.southernpine.com.
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