Are built-in benches and planters on a deck worth it?

When a built-in beats furniture

Furniture is flexible and a built-in is not, so the built-in has to earn its place. It does when space is tight and a bench against the edge seats four people in the footprint two chairs would take. It does when a low deck has no railing and needs an edge people can feel. It does when you want the deck and the garden to meet at a planted edge rather than a fascia board. And it does when you simply want the deck to look finished and designed from the moment you step out.

It does not earn its place in the middle of a traffic path, in a spot nobody will sit because of the sun, or along an edge you will later want open for a view. We mock up bench locations with a couple of sawhorses and a plank before committing.

The bench as the edge of a low deck

On a deck less than 30 inches above grade, the building code does not require a guard, which frees the edge for a bench. A comfortable bench seat sits around 17 to 18 inches above the deck and 16 to 20 inches deep; a backrest, if you add one, leans back a few degrees and doubles as a low screen. Built from the same decking as the floor with a picture-frame border carried up the face, the bench reads as part of the structure.

On a deck that does need a guard, a bench is not a substitute. A bench against a guard actually raises the point people stand on, so the guard height is measured from the seat, and most deck guards would then be too short. In that case the bench moves inboard or the guard gets taller.

Planters: the rot problem and how to avoid it

A planter is a box of wet soil sitting on wood, and that is exactly the condition we spend most of our repair work undoing. A built-in planter needs a rigid or heavy-gauge liner that keeps soil and water off the wood entirely, a drain fitting that carries water through the deck to the ground below rather than onto the boards, and an air gap between the liner and the wood so the wood can dry. Drip irrigation inside the planter should be on its own zone and checked for leaks.

The simplest robust version is a wood surround with a removable insert, such as a galvanized or fiberglass trough, sitting on cleats with a gap. When the insert eventually fails, it lifts out. A planter where soil touches wood is a repair waiting to happen, no matter the species.

Materials that hold up

Bench seats take sun, bodies and spilled drinks, so capped composite or a dense hardwood such as ipe is the practical choice; softwood seats finished with penetrating oil work too but ask for recoating. Frames inside benches and planters should be pressure-treated or rot-resistant, kept off the deck surface on spacers so water can run under them, and fastened with stainless or coated hardware. Any storage inside a bench lid needs drainage and ventilation or it becomes a mildew box.

Details we plan before framing

• Blocking in the deck frame under bench legs and planter corners so they are fastened to structure, not just to decking.
• A drain path from every planter to the ground below, checked with a hose before the planter is filled.
• Conduit for low-voltage lighting under bench lips or in planter faces, with the connections left to a licensed electrician.
• Lift-off lids or removable panels so the inside can be inspected and dried.
• Cushion dimensions decided first, so the seat is built to the cushions and not the other way around.

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