Permanent seating solves the annual question of where to put the chairs by making the answer permanent. That is useful only if you like the answer in July, October, and three years from now.
Sit before you build
Try a safe mockup at the proposed seat height and depth. We once set a client's existing cushions on a trial bench beside their patio table. The seat looked generous, but the table apron pressed against knees and the cushions made the whole thing too high for comfortable dining. We revised the relationship before framing. A seat that works for a quick chat may be poor company through a long dinner.
A bench can make an edge feel intentional and keep seating available for a crowd. Loose chairs let different people choose different positions, move out of sun, and rearrange around a meal. Some decks benefit from a short bench rather than a full perimeter commitment.
Keep the edge detail separate
Where guards are required, the bench and guard arrangement needs to be assessed together. Do not assume the seat replaces fall protection or that a guard designed without seating remains suitable after a bench is added. Ask for the completed detail on the drawings.
Trex’s deck planning guidance includes seating and furniture clearance. Our recommendation is to draw seated people and the passing route, not only the furniture outline.
Use the quiet season as a test
Consider leaf removal, snow clearing, drying cushions, and access to fasteners or repairs. On that deck we kept one short bench for extra guests and left the dining chairs loose. The owners could still turn toward the garden or move into shade, and there was room to sweep behind the seating. A full perimeter bench would have supplied more seats than they needed and fewer ways to use the deck.