A modular sectional is the right answer when your deck is not a rectangle, when you are not sure how much seating you need yet, or when you want the option to expand later. You buy individual pieces, arrange them to your space, and add to the set whenever the budget or the layout changes.
Sketch your deck and plan in module counts rather than total inches, then leave a deliberate gap where people walk through. The most common configuration is an L formed from two or three middles, one corner and two arm pieces. Do not push the whole set against a wall, pulling it forward even 12 inches makes the area feel considerably larger.
Seating modules include base and cushion. Endcaps ship as base only. Cushions are replaceable on their own, so the frames outlast several fabric cycles.