The intended use is the largest factor for sure. Open air walk-way from one space to another will have a chance to occur both design level snow load and portion of design live load and vice versa, while I doubt the sunbathing roof terrace is getting large volume of visitors with a design level...
Canadian codes specify that the live load and the design snow load do not occur concurrently and that you would take the greater of the two to design with. Not many people on patio/roofs when a design level snow storm is occurring.
On top of the ethical conflicts jmec87 listed above having the primary beneficiary of your actions being a close friend might be the nail in the coffin for an ethics review board. I would protect the future interest of my family and not my neighbors by avoiding engaging in this activity.
Why not get involved in educational projects for the next generation? Local popsicle bridge building competitions are held in almost all areas at a variety of age ranges. You could even get in-contact with your local university for thing like the Canadian National Steel Bridge Competition.I had...
Check 4.1.8.2 of NBCC-15 for reference to seismic participating load (W). It states 60% for storage load and 100% if the contents are stored in a container.
