How to Design a Deck (Step by Step)
Designing a deck means more than an outline: you set the height, the framing, and the footings, then verify the material list — because free deck tools usually under-count.
Measure and set the height
Measure the space and the height of the door threshold off the ground; your deck surface sits about an inch below it. Draw the deck outline to scale against the house.
Frame it: joists, beams, footings
Set joist spacing (16 inches on-center is typical), beam sizes, and footing locations. Good tools let you adjust these; if yours can’t change framing sizes, treat the plan as conceptual and confirm spans with local code or the ICC DCA 6 deck guide.
Pick a railing and check code
Most decks over 30 inches need a guardrail, commonly 36 inches tall, and any raised or attached deck usually needs a permit. The software flags standards but can’t know your local rules — confirm with your building department.
Verify the material list
Export the plan and material list, then re-check the lumber yourself. Free brand tools (Trex, TimberTech, Lowe’s) commonly skip waste, blocking, hangers, and stair framing — add 10 to 15 percent before you buy.
Tools that help
Questions, answered
Do I need a permit to build a deck?
Usually yes for any raised or attached deck. Requirements vary by locality, so confirm with your building department before you build — design software can’t determine local code for you.
Part of the WebHomeTools guides. See all guides.