How to design a custom deck shape

Give every extra corner a job

A recess can preserve access to a door or an existing obstruction. A clipped corner can open a walking route, and a wider bay can make room for a table without widening the entire deck. These are useful reasons to depart from a rectangle.

Each change also creates edges to support, finish and sometimes guard. An attractive outline may leave narrow board pieces, awkward railing bays or a footing in the wrong place. Start with the simplest shape that serves the activities, then add corners only where they earn their material and labour. The deck outline and the support layout must be considered together.

Start with the outside decking dimensions

Open Shape in the Deck Designer. Rectangle and L shape provide measured starting layouts. Trapezoid, Clipped corners and Angled wraparound open an editable outline before changing the deck.

The outline is the finished outside boundary of the decking. Picture-frame boards occupy part of that boundary area; the field boards are fitted inside them. A railing, stair or beam location is a separate part of the design.

Draw or edit the corners

Choose Draw new outline to place corners in order around the perimeter. Tap the first corner or use Close outline to close the shape. Choose Edit corners to reshape the existing deck.

Select a corner and enter From left (X) and From top (Y) for precise coordinates. Edge length and direction move the next corner. Use Add corner to edge to split an edge, or Remove corner to simplify it. Apply outline commits the result; Cancel leaves the deck as it was.

• Use 3–24 corners, with each edge at least 12 in (304.8 mm).
• Keep the overall length and depth between 2 and 50 ft (609.6–15,240 mm).
• Edges cannot cross or touch another non-adjacent edge.
• The model has one closed perimeter. True curves, interior holes and separate deck levels are not represented.

Add a recess or extension from an edge

For a measured notch or bump-out, select the lettered edge in the plan and open Add a recess or extension under Edges. Measure its position from the edge start dot toward the arrow, then enter its width and depth. The result becomes a custom footprint.

Changing Overall length or Overall depth scales a custom footprint. For a local change that should leave the other corners in place, use Edit corners instead.

Review the details after reshaping

The designer retains house sides, border choices and railing settings on edges it can match. A stair opening that no longer fits a changed edge may be removed; the notice tells you to place it again.

Beams linked to an edge follow that edge as the deck changes. If an edge is split or removed and its identity is ambiguous, its beam can become a fixed custom path. Review the beam paths and support messages after applying the outline.

• Mark every house side, including returns; choose the ledger arrangement separately in Framing.
• Use Exposed edges for a border that follows the house selection, or Full perimeter to include the house sides.
• Recalculate framing after changing the decking support requirements.
• Use Generate beams from joists when the support layout needs to be rebuilt for the new outline.

Lay out the framing for the new footprint

Keep the drawing and order together

Inspect the Decking plan, Framing plan and 3D view before downloading the project. Numbered cuts & stock comparisons opens the board calculator in a separate tab with the current footprint, pattern, stock and pricing inputs.

Changes made in that board-calculator tab do not update the saved designer project. Return to the designer to revise the shape and send a fresh layout when necessary.