When sizing lumber for your deck frame, the same guide-line apply as when doing so for you home. We will consider all key factors including but not limited to; wood species, joist span, post spacing, built-up ply count, and supported/unsupported lengths. With all of these factors in mind we will then refer to our National Construction code to check the charts for sizing. In Quebec our reference for this information is the CMHC Wood frame Construction manual. And our most commonly referenced charts are table 43 and table 44 of appendix A.
However there guidelines are a matter of safety. And even a deck structure that is bouncy may still be considered safe. At Espace Unik our guidelines for lumber sizing well exceed those of our National standard. Where they allow a 2x6 to span 9'-2", we will not exceed 6'. And where they allow for a 2 ply 2x8 beam, we will always opt for 2 ply 2x10 beam.
Unlike other builders, we distinguish ourselves by not using minimum sized lumber. We size for maximum strength and maximum safety.