The second level looks modest on a plan. A little step, a little lounge area, a little dining area. The trouble starts when the actual dining set is not little.
Size the rooms before separating them
Draw each furniture group in use, with chairs pulled back and space to move around it. On a sloping-yard project, the first two-level sketch put the dining table neatly on the upper platform. The owner's actual chairs crossed the proposed step when pulled out. We enlarged the upper dining area and reduced the lower lounge area before the framing layout went for review. Counting empty chairs would have missed the problem.
A single broad platform can change from family meal to party without negotiating an internal stair. Split levels can make sense where the ground changes and each platform gets a distinct, well-sized purpose. The level change should answer something the site or routine actually asks.
Think about the frequent journeys
Follow the trip with a serving tray, a laundry basket, and a guest who finds stairs tiring. On that layout we kept the regular kitchen-to-table journey on the upper level; the lower space became an occasional sitting area with its own clear approach. That still left stairs to the garden. Have the transition, lighting, landing, guards, and structure designed for the site, and decide whether the extra level earns the daily effort.
Trex’s design considerations discuss multi-level planning alongside circulation. They are useful design prompts, not Ontario permit drawings.
Keep one level if the second has no job
Keep one generous platform if splitting it would leave the dining chairs squeezed against a step. Add a second level when the site and a separate activity give it a clear job. Either way, settle where the deck stairs meet the yard while the furniture is still on the drawing. That's the route you'll use with dinner in your hands.