Tag Archives: MSR Lumber

Finger Jointed Lumber

The recent National Frame Building Association (NFBA) 2014 Frame Building Expo was a reunion event for me with several long-time friends. One of these is Ferg Evans.

In the 1990’s I was elected to the first of five terms I was to serve on the Board of Directors for the Machine Stress Rated Lumber Producers Council (www.msrlumber.org). One of my fellow board members was Ferg Evans.

The MSR Lumber Producers Council was coincidentally formed on my 30th birthday, with Ferg Evans as one of the original board members!

Ferg is now the Managing Partner of Canadian Engineered Wood Products, Ltd. (www.cewp.ca). Canadian Engineered Wood Products are the distributors for what I feel is a pretty slick product (at least from my pre-fabricated metal connector plated truss background).

finger-jointed-lumberManufactured by Pinkwood, Ltd. (www.pinkwood.ca), of Calgray, Alberta, Canada is FJLumber. FJLumber (finger jointed lumber) is quality long length lumber designed specifically for the truss industry (although I can think of many other uses for it). It is produced in one foot increments up to FORTY-EIGHT feet long!! In 2×4 and 2×6 it is available in msr grades of 2100f and 2400f, and in 2×8 1950f.

In the manufacturing process, short lengths of lumber are graded for strength first. Next, these short pieces are structurally finger jointed to each other using an ASTM (American Society for Testing and Materials) approved, heat resistant adhesive. Each newly created finger joint is in-line tension tested to 1.5 times the design specifications to insure structural integrity.

Consider this – a 2×6 #2 grade in Douglas Fir has an Fb (fiberstress in bending) value of 1170 psi (pounds per square inch); Canadian Spruce-Pine-Fir (SPF) 1137.5; U.S. Hem-Fir 1105 and Southern Yellow Pine 1000. This makes a 2×6 2400f msr graded board over TWICE as strong in bending as any of the above listed popular framing lumber!!

Now I’ve spent years look at trusses, and have a fair idea of what it is I am seeing. For a lay person, they might notice the horizontal bottom member (or bottom chord) of a truss, is not a continuous single piece of lumber (unless the span of the truss is very small). The bottom chord is typically comprised of several pieces of lumber, which have been spliced end-to-end by pressed in steel connector plates.

For a truss manufacturer, being able to get 48 foot long finger jointed lumber eliminates most instances of having to use metal connector plates for chord splicing. Besides the labor savings and cost of the plates, it also allows for greater flexibility of the truss fabricator on where webs (internal truss members) can intersect the chords (there are rules about where webs can be placed in relationship to splices).

Besides solving problems for the truss people, I’d think this could be a pretty handy way to solve some structural issues with pole building wall girts. As a builder – walls would certainly frame up quick, with the use of only a single board to do an entire girt row on a 48 foot length building!

 

Machine Graded Lumber

Lumber grades take into account natural characteristics, including knots, splits, checks, shake, and wane. Lumber design values are assigned to lumber grades to provide a means for using this material in structural applications. These values are published in Design Values for Wood Construction, a supplement to the National Design Specification® (NDS) for Wood Construction. The six design values are bending (Fb), shear parallel to grain (Fv), compression perpendicular to grain (Fc⊥), compression parallel to grain (Fc), tension parallel to grain (Ft), and modulus of elasticity (E and Emin).

Dry LumberThe current changes in design values affect visually graded lumber only. Specifically, the changes being made to southern pine lumber in 2012 are the result of laboratory testing of the strength properties of visually graded lumber. These changes resulted in a devaluation of the design values for 2×4 southern pine. Because machine graded lumber has strength properties assessed during production, Machine Evaluated Lumber (MEL) and Machine Stress Rated Lumber (MSR) grading automatically adjusts to changes in the internal quality of lumber. Changes to visual grades have no impact on the design values of MSR and MEL because of the way these products are manufactured and tested.

Produced since the 1960s, MSR lumber has documented and tested structural design values. In contrast to visual grades, machine graded lumber is produced by measuring physical properties of each piece of lumber in the production line. Manufacturers are required to test samples during each shift and the entire quality assurance process is audited by independent third parties to confirm conformance with published design values. MSR and MEL lumber consistently meet design value requirements even as timber growing practices and environmental conditions change.

Sadly, we’ve had the technology available to reliably test lumber for strength, independent of the variability of the human eye (visual grading) for half a century – and we do not universally use it. Visit the local lumber yard, and ask if they have MSR lumber for sale. Chances are the answer will be a resounding “no”. Pick up a 2×6 at a lumberyard which was “visually graded”, and you have no idea how strong it really is.  Did the lumber grader have a bad day?  Was he really paying attention on the day he was grading lumber? Does it have a huge defect hidden from the naked eye?  Can you depend on it to perform how it you think it should?

Engineers and architects are confident in the strength and performance of MSR and MEL lumber. Designers can rely on machine graded lumber properties, use full-design strength, and avoid overbuilding. MSR and MEL lumber have proven to be cost-effective, quality lumber products for component manufacturers and builders. As the tag line of the MSR Lumber Producers Council says, “We Stress Quality”.

Read more about the MSR Lumber Producers Council at: http://www.msrlumber.org/