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How Grading Agencies Establish Lumber Design Values

How Grading Agencies Establish Lumber Design Values

Originally published in SBCA Magazine January 16, 2024

Nearly all roof trusses and floor trusses are created using cutting-edge software. Embedded in that software are engineering principles outlined in the National Design Specification, Design Values for Wood Construction (NDS), as well as published design values for the sizes and grades of softwood lumber used in North America. Consequently, it’s important to know where those published design values come from and how they are established.

The NDS Supplement provides a succinct answer in the introduction:

“Reference design values for most species and grades of visually graded dimension lumber are based on provisions of ASTM Standard D 1990-16 (Establishing Allowable Properties for Visually Graded Dimension Lumber from In-Grade Tests of Full-Size Specimens)…Reference design values for machine stress rated (MSR) lumber and machine evaluated lumber (MEL) are based on nondestructive testing of individual pieces…The stress rating systems used for MSR and MEL lumber is regularly checked by the responsible grading agency for conformance to established certification and quality control procedures.”

In other words, softwood lumber species groups are regularly subjected to established testing protocols to ensure they retain their published design values over time. In North America, there are seven grading agencies that have jurisdiction over establishing softwood lumber design values and are responsible for conducting ongoing testing to verify them. Those grading agencies are:

· National Lumber Grades Authority (NLGA)
· Northeastern Lumber Manufacturers Association (NELMA)
· Northern Lumber Manufacturers Association (NLMA)
· Redwood Inspection Services (RIS)
· Southern Pine Inspection Bureau (SPIB)
· West Coast Lumber Inspection Bureau (WCLIB)
· Western Wood Products Association (WWPA)

Each of these grading agencies follow grading rules approved by the American Lumber Standard Committee’s (ALSC) Board of Review (BOR) and are certified for conformance with the U.S. Department of Commerce Voluntary Product Standard (VPS) process. For softwood lumber used in the U.S., the VPS is maintained by the ALSC and is referred to as American Softwood Lumber Standard PS 20 (PS 20). The current edition is PS 20-20.

Once each grading agency completes its regular testing protocols, it’s required to report to the ALSC BOR the resulting data, along with any recommendations it has regarding to changes to current published design values. Fortunately, changes are rare. The most significant in recent years was with SPIB and their recommended changes to the design values of Southern Pine (SP) in 2012.

Again, these published design values are integrated into component design software. The parameters of each truss assumes that the lumber species, grade, and size used in the manufacturing process matches what was input into the design. This assumption emphasizes the importance of the lumber grade stamp placed on each stick of dimensional lumber that help users identify key structural properties. The next article in this series will look at how lumber manufacturers grade each stick of lumber and how to read its corresponding grade stamp.

This entry was posted in Barndominium, purlins, Lumber, Pole Barn Design, Pole Barn Planning, Pole Barn Structure, Budget, Columns and tagged machine stress rated lumber, Design Values for Wood Construction (NDS), machine evaluated lumber, lumber design values, ASTM Standards on March 7, 2024 by admin.

All-in-One Door Seal Kit

The following article was originally produced and published at www.Builderonline.com, who is solely responsible for its content. This story is being republished to raise awareness of information publicly available online and the accuracy of author’s claims has not been verified. As such, we cannot vouch for the validity of any facts, claims or opinions made in this article.

DAP has bundled a number of its sealant and flashing products with an assortment of third-party door hardware to create the DAP QuickKit, an all-in-one kit that contains all the materials and parts necessary to install and weatherproof one exterior door.

According to Tom Rapps, Director of Marketing and Business Development for DAP, this kit serves to simplify the purchasing process for door installers, as these components can be hard for contractors to find in one place, or in the right quantities.

“As materials and techniques for exterior door installation have evolved over the past decade, finding the right materials in the right quantities has become a challenge, resulting in the loss of valuable time and money,” says Rapps. “The DAP QuickKit alleviates these issues by providing exactly what the installer needs to complete the job all in one box, without concern for missing materials, excess waste, or quality. No guesswork required.”

The kits are available in single entry-door, double entry door, and sliding patio door configurations. The single-door kit, available in a green box, accommodates rough openings up to 40 inches wide, while the double-door kit, packaged in a black box, accommodates rough openings up to 80 inches wide. Both are available in 4 and 9/16th inch and 6 and 9/16th inch jamb sizes. The sliding-door kit, also in a black box, accommodates rough openings up to 72 inches wide, and is available in 3 and 1/4th inch and 3 and 5/8th inch jamb sizes.

All QuickKit components are tested to meet the highest ASTM standards. Each kit includes:

DAP Dynaflex 800 Sealant: 3-4 10 oz. cartons. The mold-resistant sealant is watertight, weatherproof, and equipped to seal dissimilar substrates. It is tested to meet AAMA 800 specificaitons.

DAP Draftstop 812 Window and Door Foam: one 9 oz. can. The foam is AAMA 812-tested to seal out water, air, and sound. Its closed-cell structure resists water absorption.

DAP LT Poly Flash 711: one 4 by 30-inch roll. Available at a smaller roll size than standard, providing just enough flashing for one installation. Includes a split-release liner and may be installed in temperatures as low as 0 degrees F.

One bundle of 12 pre-scored composite shims.

Jamsill Guard Sill Pan: one center extrusion for single doors and two center extrusions for double and patio doors, supplied in partnership with Jamsill, Inc. The ASTM 2112-compliant sill includes sloped weep areas.

Aluminum head flashing: 1-2 42” drip caps.

Twelve galvanized screws.

This entry was posted in Uncategorized, Pole Building Doors and tagged DAP QuickKit, Dynaflex Sealant, mold-resistant sealant, AAMA 800 specifications, ASTM Standards on November 15, 2018 by admin.

PEX Tubing

I’ve espoused previously on the joys of hydronic radiant floor heating (https://www.hansenpolebuildings.com/2012/08/radiant-floor-heating/) and would encourage anyone who is going to install a concrete slab on grade in their new (or existing) post frame (pole) building to consider at least making a provision for it in the future.

As we all realize, once a concrete floor is poured, it is literally “cast in stone”. Without huge expenses, there really is no going back for a do over.

The key to being prepared for the future, is to have PEX tubing installed in the concrete slab at time of pour.

PEX (or crosslinked polyethylene) is part of a water supply piping system which has several advantages over metal pipe (copper, iron, lead) or rigid plastic pipe (PVC, CPVC, ABS) systems. It is flexible, resistant to scale and chlorine, doesn’t corrode or develop pinholes, is faster to install than metal or rigid plastic, and has fewer connections and fittings.

PEX tubing is made from crosslinked HDPE (high density polyethylene) polymer. The HDPE is melted and continuously extruded into tube. The crosslinking of the HDPE is accomplished in one of three different methods.

Crosslinking is a chemical reaction which occurs between polyethylene polymer chains. Crosslinking causes the HDPE to become stronger and resistant to cold temperature cracking or brittleness on impact while retaining its flexibility. The three methods of crosslinking HDPE are the Engels method (PEX-a), the Silane Method (PEX-b), and the Radiation method (PEX-c). Several industry participants claim the PEX-a method yields more flexible tubing than the other methods. All three types of PEX tubing meet the ASTM, NSF and CSA standards.

Some applications require PEX with added oxygen barrier properties. Radiant floor heating (or hydronic heating systems) may include some ferrous (iron-containing) components which will corrode over time if exposed to oxygen. Since standard PEX tubing allows some oxygen to penetrate through the tube walls, various “Oxygen Barrier PEX” tubing has been designed to prevent diffusion of oxygen into these systems. Two types of specialty PEX pipe are offered:

Oxygen barrier PEX has a layer of polymer laminated to the outside surface (or sandwiched internally between PEX layers) which prevents oxygen from penetrating. The polymer film is usually EVOH (ethyl vinyl alcohol copolymer), used in the food industry as an oxygen barrier.

PEX-Al-PEX (or PEX-Aluminum-PEX or “PAP”) is a specialty PEX tubing manufactured by several suppliers. This tubing has a layer of aluminum embedded between layers of PEX to provide an oxygen barrier. PEX-Al-PEX may also be called multilayer pipe or composite plastic aluminum pipe. PEX-Al-PEX will also retain shape when bent, and may also exhibit less expansion and shrinkage during temperature fluctuations, but may be less flexible than PEX tubing. PEX-AL-PEX costs about 30% more than standard PEX.

As with so many things construction, there is one opportunity to do something right or wrong, personally I would recommend making the extra investment in PEX-Al-PEX. The few extra dollars can lead to a lifetime of happy heating for your new pole building.