Parallel-strand lumber

[1] The design strength of PSL is greater than that of sawn lumber as the strands are glued together directionally and under high pressure.

Because knots and other imperfections are randomly dispersed throughout the product (and filled up and fortified with glue) strength variability from one piece of PSL to another is less than in solid-sawn wooden beams.

The invention, development, commercialisation and patent of PSL, using timber forest thinnings, dates prior to Parallam, back to the CSIRO's Division of Chemical and Wood Technology in 1976 and, since September 1977, Repco Ltd, and its subsidiary Repco Research Pty Ltd, in consultation with CSIRO.

[5][6] It is likely that the Parallam product, which uses parallel shaved veneers instead of linear crushing to form the parallel fibre structures, was developed from the technology licensed from CSIRO and commercially exploited by Scrimber International as noted in the Popular Mechanics May 1990 article pages 96–99.

[citation needed] PSL can be made from any wood species, but Douglas fir, southern pine, western hemlock, and yellow poplar are commonly chosen[9] because of their superior strength.