A substantial home can make an average-sized deck appear undersized. Expanding the footprint without a clear purpose creates a different problem, leaving large areas that require furniture simply to keep the surface from feeling empty.
The dimensions should come from the way you expect to use the deck. A dining table needs enough clearance for occupied chairs, and a grill requires room to work that does not interfere with the doorway. Lounge seating may call for additional depth, though it does not automatically need to share the same portion of the surface.
We also study the space that will remain between the deck and the farther reaches of the property. That distance influences where the stairs should lead and how strongly the deck needs to define its outer boundary. On a broad lot, a pronounced fascia or carefully selected railing can help the structure hold its place against the larger landscape. A lower deck may call for a softer transition that allows the nearby planting to come closer.
The rear architecture provides another reference point. Window spacing, existing
pergolas, masonry and rooflines can guide the width of the deck without forcing it to mirror the house exactly. The finished structure should carry enough presence to look deliberate while preserving the visual calm expected from a well-kept property.