Machine Stress-Rated Lumber
There is a growing interest in lumber that is graded by machine, a process
called machine stress-ratin (MSR). The MSR machine applies forces to both
sides of the lumber with deflection measured every few inches along the
length of each piece. Using the deflection measurements a computer
calculates stiffness, from which the grade of the piece is determined.
A visual grade check is also made to asses characteristics that are not
detected by the MSR machine. In the quality control process, strength
tests are performed on the MSR lumber to ensure consisten quality.
The grade stamp for MSR lumber includes the words "Machine Rated" or "MSR", and the Fb-E classification, such as 1450Fb-1.3E, which is allowable fibre stress in bending (Fb) in pounds per square inch, and the modules of elasticity (E), in million pounds per square inch.
Canadian MSR lumber has been growing rapidly and will soon reach a billion board feet per year.
MSR lumber offers a large variety of strength levels that are used to advantage by truss manufacturers, and can also be used in other applications just as joints. Supply should be checked before specifying.
Fingerjointed Lumber
Fingerjoined lumber is dimension lumber made up of short pieces whose ends
are machined in a finger profile and glued together. Canadian fingerjointed
lumber has been in productions for over twenty years and is widely
accepted throughout North America.
The fingerjointing process adds value to the lumber resource by extracting short lenghts from low quality lumber to make long lengths of higher grade lumber.
Machining of the fingers and mixing and curing of the adhesive are required to meet strict tolerances. Strength tests are preformed on fingerjoined lumber to ensure consistent quality.
Canadian fingerjoined lumber is manufactured in conformance with National Lumber Grades Authority [NLGA] Special Product Standard 1 [SPS-1] or Special Product Standard 3 [SPS-3]. Fingerjoined lumber conforming to SPS-1 may be used interchangeably with regular lumber as a joist, stud or rafter.
Fingerjoined lumber conforming to SPS-3 is intended for use only as studs. The Stud frade design values for the species group are applicable to SPS-3 lumber that is marked 'stud'. However, bending and tension stresses apply only to short-term loading, such as wind or earthquake events.
The grade stamp resembles a regular grade stamp but also includes one of two designations: CERT FGR JNT [conforming to SPS-1 for use as joists, rafters, and studs] or CERT FGR JNT VERTICAL USE ONLY [conforming to SPS-3 for use as studs only].