**5. Conclusions**

Non-contact confocal profilometry was able to quantify shelling of growth rings at the surface of flat and profiled softwood deckboards that were exposed to natural weathering. Using this technique, we have shown how the orientation of growth rings and the angle growth rings make to wood surfaces influences the severity of shelling in flat western larch deckboards exposed to natural weathering. We also show that profilometry can be used to quantify shelling in other wood species and sugges<sup>t</sup> that it can provide additional insights into how the properties of wood or treatments, such as coatings and water repellents, influence shelling. Our results confirm that shelling occurs due to inter-ring delamination in deckboards with growth rings oriented pith-side-up. We show, for the first time, that shelling occurs at the surface of profiled deckboards oriented pith-side-up. We conclude that the shelling of flat and profiled boards can be reduced by orienting deckboards bark-side-up and, in the case of profiled boards, using a wavy profile rather than a hemispherical rib profile.

**Author Contributions:** L.H.L. and P.D.E. conceived and designed the experiments; L.H.L. performed all experimental work, except for scanning electron microscopy (P.D.E.). P.D.E. analyzed all data and wrote the first draft of the paper. Both authors discussed and commented on the results and contributed to the final submitted manuscript. All authors have read and agree to the published version of the manuscript.

**Funding:** This research was funded by Natural Science and Engineering Research Council of Canada (NSERC) Collaborative Research and Development Grant (CRDPJ 485007-15).

**Acknowledgments:** We thank Steve Brown, Jarett Pereboom, Terry Cunning, Arne Flaten, Jeff Hunt, Ken Johnstone Jr. and Dan Price from Tolko for a special order of western larch lumber; Brandon Chan, Kenneth J. Cheng, Pablo Chung, Lawrence Gunther, Sina Heshmati, Joseph Doh Wook Kim and Mohammad Sadegh Mazloomi from UBC for helping to machine and characterize deckboard samples; Hua Chen and Frank Brink of the Centre for Advanced Microscopy at The Australian National University (ANU) for assistance with scanning electron microscopy; Canadian Foundation for Innovation, BC Knowledge Development Fund, FPInnovations and Tolko industries for in-kind support. P.D.E. thanks Viance, Tolko, FPInnovations, Faculty of Forestry (UBC) and the Government of British Columbia for their support of his BC Leadership Chair at the University of British Columbia, and The Australian National University (ANU) for an Honorary Professorship in the Department of Applied Mathematics, Research School of Physics at the ANU.

**Conflicts of Interest:** The authors declare no conflict of interest, and none of the individuals or organizations acknowledged above were involved in the design of our experiment, collection, and interpretation of data or the writing of this paper.
