Subscribe to Forest2Market's email updates, right in your email, North America - Charlotte Headquarters+1.704.540.1440. On January 31, the American Lumber Standards Committee (ALSC) Board of Review unanimously approved the new southern pine design values previously submitted by the Southern Pine Inspection Bureau (SPIB). Not all Southern Pine lumber has gotten weaker. Forest Products Laboratory, 2008. Note: Forestry experts saw this coming a long time ago. That's a judgment call. Forest Products Laboratory, 2001. Should I adjust my framing practices to reflect this change? Influence of Juvenile Wood Content on Shear Parallel, Compression, and Tension Transverse to Grain Strength and Mode I Fracture Toughness for Loblolly Pine. SPIB didnt investigate the reason for the reduction in wood strength, only speculating that a change in the timber resource mix may be responsible. NIST, 2010. Forest Products Laboratory, 2008. Southern pine lumber is covered by the Southern Pine Inspection Bureau. What about wood trusses made with Southern Pine? Copyright 2022 Zonda Media, a Delaware corporation. On May 10, Tom Frost, Senior Vice President for Technical Services at the ICC, responded: "The ICC has made no determination regarding the lumber design value reductions, the Board having denied the American Wood Council's (AWC) request for an emergency amendment at this time." How Do Lumber Producers Determine Log Value. These younger trees have a higher proportion of juvenile wood, which has reduced strength. SFPA, 2013. Fill in your details below or click an icon to log in: You are commenting using your WordPress.com account. National Design Specification for Wood Construction. Are other species of wood also getting weaker? National Design Specification for Wood Construction. Why is Southern Pine wood getting weaker? (LogOut/ There have been no failures reported of wood in service related to this issue, as far as we are aware. Create a free website or blog at WordPress.com. In addition, sawmill technology has changed in recent decades to allow production of lumber from logs as small as 6 inches in diameter. Southern Pine Reference Design Values. Softwood Lumber Prices Tumble 40%; Is Another Rally on the Horizon? The kick in the teeth is that the new values show a sizable decrease in capacity for compression, bending, and tension, with reductions ranging from 10-30%. During the meeting, Kirk Grundahl of the Structural Building Components Association expressed concern over a portion of the proposed language found in Appendix A, which provided information on the derivation of design values. Southern Pine is mostly produced in plantations, rather than sawn from trees in naturally occurring forests. The changes are the result of the large-scale destructive testing of thousands of pieces of southern pine lumber. Nobody is predicting any kind of structural failures as a result of this issue. Coastal Connection has been following this story closely, keeping in touch with the agencies involved, as well as with industry organizations and academic researchers who are studying the issue. AWC, 2008. SPIB, 2011. These results are based on full-scale testing of various lumber sizes, and supersede the interim results that went into effect last year, which only affected 2-4 sized lumber. Roof and floor framing may be affected more significantly. Plantation growing practices have resulted in a high proportion of young trees which were grown rapidly for frequent harvest, with more weak "juvenile wood" and fewer annual growth rings per inch. This is merely speculation, though the strength reduction of juvenile wood does seem to match that observed in the new design values. What are design values? Contributing editor Ted Cushman reports on the construction industry from Hartland, Vt. Remodeling provides the indispensable business tools, product information, design ideas, cost-estimating tools, and management advice that enable full-service remodeling businesses to thrive. If the building is designed using the prescriptive code and the current span tables based on the old Southern Pine design values, your building still complies with code until such time as your local jurisdiction changes its code. Other dimensions and grades are currently undergoing sampling and testing; it appears likely that when this testing is complete, the design values for larger dimensions and higher grades of Southern Pine will likewise be decreased by how much, is yet unknown. For now, here is a quick Q&A on the important questions raised by this event. However, even truss systems benefit from the redundancy of using multiple trusses to share a roof or floor load. In particular, the weakest 5th percentile of Southern Pine lumber in the marketplace has become weaker. For a 1991 report from USDA Forest Products Laboratory's David Kretschmann about weakness of Southern Pine sawn from 16-inch-diameter, 28-year-old trees, see: "Ultimate Tensile Strength and Modulus of Elasticity of Fast-Grown Plantation Loblolly Pine Lumber," by David E. Kretschmann and B. Alan Bendtsen. The volatile North American softwood lumber market continues to keep us all guessing as we enter mid-2Q2022. The American Wood Council has published addenda to its 2012 Wood Frame Construction Manual, as well as its recommended amendments to the building code span tables, at this link: "Codes and Standards Addenda and Amendments Related to Design Value Changes.". In those situations, using larger dimension lumber, doubling up members, and carefully selecting lumber with close grain spacing, straight grain, and no knots, would all be good practice. Wall framing is extremely conservative, and will likely not be affected greatly by this change. The reductions in lumber strength obviously mean that more, larger members will be required to carry a given load. As reported in a previous update to this story, the new design values call for lower values for all lumber 2x 4 thick and 5-12 wide, with the exceptions of No. Its interesting to see that wood, which we might think of as natural and thus unchanging, isnt immune to this. SFPA, 2012. The new values were rescheduled for review in January after the SPIB withdrew its initial proposal in light of Forest Products Laboratorys report of discrepancies back in October. However, some Southern Pine, such as wood harvested from naturally reproducing stands in the National Forest, is still as strong as ever. Interactive Business Intelligence Platform. The design values are extremely conservative: they are based on the tested value of the weakest 5th percentile of the wood. (LogOut/ If the grading agencies see a change in strength for any type of lumber, design values for that lumber will eventually be changed. Will the change in Southern Pine design values affect the building codes? Eventually, but not right away. The biggest concern would be with rare cases where a single member is relied on to handle some sort of critical load for example, in the case of a knee brace on a deck frame. Design values also determine the allowable spans for floor joists and rafters, developed by the American Wood Council (AWC), which are published in span tables and referenced by the prescriptive code to guide the construction of buildings where case-by-case design engineering is not required. SPIB Proposed Design Values and Analysis. Testing of randomly sampled 2x4s from sawmills across the Southern Pine-producing region has shown that the strength of the lumber has declined significantly since the official design values were published several decades ago. 1 Dense and higher grades in Select Structural categories, compression parallel to grain, tension parallel to grain and bending, which received lower pounds per square inch (psi) values. Southern Pine Design Value Forum: Findings and Recommendations. In any case, manufacturers have had at least six months to adjust their designs to reflect the new values for Southern Pine. 1 Dense and higher grades. ASTM D1990 Design values describe the key characteristics of wood as an engineering material: strength in bending, density, and tensile strength. The Structural Building Components Association (SBCA), an organization of wood truss manufacturers, wrote a formal letter to the International Code Council asking if the design value change would result in an immediate change in building code requirements in the field. Southern Pine Design Value Forum: Findings and Recommendations. On June 1st, new design values for southern pine lumber came into effect. Does this mean the buildings I've already framed with Southern Pine are unsafe? Higher psi values for tension parallel to grain were applied to the No. Conventional wall, floor, and roof framing is very conservative, with multiple members sharing the loads and with many factors of safety built into the span and load tables. The Development of Pine PlantationSilviculture in the SouthernUnited States. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); Formation andProperties ofJuvenile Wood in Southern Pines:A Synopsis. Anyone can design a building that stands up. Change). The published design values for all grades and species of lumber are the numbers that engineers use to design wood structures. It's official: effective June 1, Southern Pine #2 2x4 lumber has been downgraded. Change), You are commenting using your Twitter account. More information can be found at the SPIB site.
But the average strength of Southern Pine lumber has gone down. As a result, a greater proportion of 2x4 lumber on the market now shows lower values for bending strength and tensile strength than in decades past. If youre already in construction on a project framed with Southern Pine, with an engineered design that used the old design values, you may want to have your engineer re-evaluate those designs.
After testing of Southern Pine #2 2x4 lumber showed a surprising decline in strength, the American Lumber Standards Council (ALSC) Board of Review instructed grading agencies for all other species of lumber in the U.S. market to conduct comprehensive testing of all sizes, grades, and species of lumber. Design values are published by official lumber grading agencies based on randomized statistical sampling and testing of lumber produced for market. In the coming year or two, updated values for all species, sizes, and grades will be reported. Fox et al, 2006. The red-hot softwood lumber market has garnered a lot of attention over the last two years. Looking through any old building code or textbook, and its obvious how much stronger modern steels and cements are. Incorporation of the emergency amendment into the adopted Code shall be subjected to the process established by the adopting authority.'" If you want to make allowances now for the changing design values, there are updated, more conservative span tables available, but they have not yet been incorporated into the building code. Trusses are an example of value-engineered design, where the strength of a single truss chord or web member could affect the performance of the entire truss or the entire roof. (For more, see: "ICC Indicates Hands-Off Approach Regarding SP Design Value Changes," SBC Magazine.). NIST, 2010. One likely explanation is the average age of modern pines at harvest. As Lumber Prices Plummet, Manufacturers are Asking 2 Important Questions. Southern Pine Reference Design Values. The Development of Pine PlantationSilviculture in the SouthernUnited States.
Wood is a highly variable material, and so requires a large number of samples to reliably establish safe design values. The SPIB has published the new design values in Supplement 13 to the Standard Grading Rules for Southern Pine Lumber, 2002 Edition, as well as the new span tables. Results of that testing for S-P-F #2 2x4 (Spruce-Pine-Fir), a lumber produced in Northern and Western regions, have been reported and the testing indicates no decline in strength for S-P-F wood. It will take years for the full implications of the Southern Pine strength downgrade to play out across the construction industry. But it takes a structural engineer to design one that BARELY stands up. Ultimate Tensile Strength and Modulus of Elasticity of Fast-Grown Plantation Loblolly Pine Lumber, Structural Building Components Association, ICC Indicates Hands-Off Approach Regarding SP Design Value Changes, Codes and Standards Addenda and Amendments Related to Design Value Changes, Deck Design Improves Under the 2021 Building Code, Lumber Lowdown: Understanding the Roots of Lumber Volatility and Future Market Expectations, Panel Discussion: Safe and Durable Deck Stairs, Training the Next Generation of Building Professionals, A Radical Approach to Protecting Finished Floors, A Builder's Guide to Breathable Indoor Air, NAHB: Building Construction Time Slows in 2021, AIA: Demand for Nonresidential Services Remains Strong in June Billings, Survey Reveals Top Frustrations and Confrontations Among Neighbors, New Home Pending Sales Index Decreases 7.5% on Year-Over-Year Basis in June, Wan Bridge Secures Site for Newest Build-to-Rent Community in Greater Houston, NKBAs Residential Kitchen and Bath Market Outlook Update Forecasts Double-Digit Increase Over 2021, A Deck Builder's Guide to 'Google My Business', JLC Rolls Out Deck and Railing Skills Workbook, Webinar: What You Need to Know About Decking. The SPIB agreed to remove the sentence, Designers of wood structures.and grade grouping from Appendix A. Because wood is a highly variable material, design values are based on average strength measured in testing of many individual samples. It speaks to the integrity of those involved that the SPIB, not an unbiased organization, would so willingly promulgate a change that will harm its interests. 2022 Forest2Market, INC. All Rights Reserved. The June 1 effective date should allow time for an orderly transition to the new design values. (LogOut/ If your building includes any design engineering, your engineers should always use the latest published design values. Apparently not, but the jury is still out. As a result of the new testing, official "design values" for Southern Pine #2 2x4 wood have dropped by about 30%.
Pine is an immensely popular building material, but theres been speculation as to how much the inevitable cost increase will result in a switch to Douglas Fir, or other woods. MSR lumber's performance is much more predictable and more uniform, making it ideal for engineered applications or critical uses. Testing organizations must be certified by the American Lumber Standards Committee. This appears to be the result of changes in the way Southern Pine is grown, harvested, and sawn. Why Mexico City Gets Such StrongEarthquakes. The Board approved the SPIB proposal with the amended language in place. These are available online at Southern Pine, which is provided by the Southern Forest Products Association. This sort of testing first began in the late 1800s, and is conducted every so often by lumber testing organizations. Change), You are commenting using your Facebook account. Truss makers now should be using the new design values in all their engineering calculations.
Part of this efficiency comes from a reduction in the rotation age, the time it takes for a tree to be harvested after planting. Wrote Frost: "Please note that section 2.4.3 of CP #28 states, in part, that Emergency amendments to any Code shall not be considered as a retro-active requirement to the Code. Inquiring minds from Main We provide detailed transactional data, cost benchmarks and in-depth analytics for participants in the wood raw materials supply chain. MSR lumber is mechanically tested piece by piece at the mill, rather than visually graded. And remember: if you're framing a structure or building a component where it's important to have full assurance of the lumber's actual strength, you can always use machine stress rated (MSR) lumber. Forest Products Laboratory, 2001. Influence of Juvenile Wood Content on Shear Parallel, Compression, and Tension Transverse to Grain Strength and Mode I Fracture Toughness for Loblolly Pine. Building materials, of course, have never had static, unchanging properties.