- Seat height. 17–18 inches is the normal chair height. Lower feels like a lounge and is harder to stand up from.
- Span. If the seat is over 4 feet, the plan needs a center support. No support means it bounces.
- Wood. Cedar or treated lumber outside. Indoor pine, left raw, will rot.
One bench plan is enough if this is your only outdoor project. A library makes sense if you also want a shed or a table. That comparison is on the Ted’s Woodworking review.