One of the advantages of using parallel strand lumber (PSL) products is that they can be treated and offer great resistance to the elements while also providing the advantages of composite lumbers. Weyerhaeuser provides literature on what factors to apply when considering treated products, which we’ve integrated into ClearCalcs.

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To use a treated PSL section

  1. Select any regular PSL product from our member selector:
  1. Once you’ve selected the PSL, an option will appear asking you if your member is treated or not. Set it to “Yes” if it is indeed treated
  1. If you’re specifying treated PSL, it’s quite likely that you’re not expecting it to stay dry. Weyerhaeuser’s literature considers three separate service conditions (Service levels or SL 1 to 3) as opposed to the two (wet vs dry) in the NDS. By default, we assume Service Level 2, which would be applicable to a member exposed to regular weather. If you’ll be staying dry (SL 1) or your PSL member will be in constant contact with water or the ground (SL 3), scroll down to the Design Conditions section and change as required. This’ll change the service condition factors which determine the strength.