Most people choose a deck by its surface: the colour of the boards, the style of the railing. But the parts of a deck that decide whether it lasts are the ones you'll never see again once it's built.
Footings come first. In Ottawa, frost can push a shallow footing upward over the winter, and a deck that moves even a little starts to rack, squeak, and pull away from the house. Footings need to reach below frost depth and bear on undisturbed soil or rock.
Framing comes next. Beams and joists have to be sized and spaced for the span and the load, and a deck here has to carry snow as well as people and furniture. Hardware matters too: joist hangers and fasteners rated for treated lumber and outdoor exposure won't corrode and loosen over the years.
Height brings rules. Under the Ontario Building Code, decks more than 600 mm (about 24 inches) above the ground need guards, and stairs need proper rise, run, and handrails. Many decks also need a City of Ottawa building permit, so it's worth sorting that out before the design is final.
Once the structure is right, choose your surface. Pressure-treated wood is the budget-friendly classic; composite costs more up front but needs far less upkeep. Either way, you'll be standing on a deck that feels solid for many seasons.