Deck planning guide (layout, gaps, stairs, and materials list)

Board direction and borders change waste

Deck board direction affects both board count and waste. Straight installs on simple rectangles usually waste less than diagonal layouts. Picture-frame borders, stairs, and landings add complexity and often increase waste.

Stairs and fascia are separate line items

Stairs, landings, and fascia often use different board lengths and can consume more material than expected. Estimate them separately.

• Count stair treads and risers before you order boards.
• Plan fascia boards and trim from the same product line.

Gaps and actual board width affect coverage

Coverage depends on actual board width (not nominal) and the gap you leave. Composite and wood often have different recommended gapping rules—follow the product guidance.

If you are comparing materials, use the same assumptions (board width and gap) or the estimates won’t be comparable.

Diagonal and borders: quick waste ranges

• Posts, stairs, borders, and lots of cut interruptions push waste higher.
• If color matching matters (some composite products), buying enough up front is safer than topping up later.

Stairs: estimate as a separate line item

Stairs can add board count quickly. Treat steps and landings separately rather than hoping the main deck waste covers them. If you are planning a border or diagonal pattern, expect more waste on stairs.

Footings and posts (do not guess depth)

Footing depth and post size are driven by load, span, and local frost depth. If you under-plan footings, the whole deck can move. Confirm footing depth before you buy concrete or posts.

• Local frost depth often drives minimum footing depth.
• Heavier railings or hot tubs increase loads and may require larger footings.

Framing checklist (joists, beams, posts, and hardware)

A deck board estimate covers surface boards. Framing includes joists, beams, posts, connectors, and fasteners. Framing needs depend on span, spacing, and local requirements, so estimate framing as a separate list.

• Joist spacing (often 12/16/24" on center depending on decking and code)
• Beam layout and spans (affects beam size and post count)
• Ledger vs freestanding design (changes hardware and flashing needs)
• Railing and stair loads (adds blocking and connectors)
• Joist hangers and hanger nails/screws
• Post bases, brackets, and anchor hardware
• Ledger flashing and waterproofing details

Railing and code considerations

• Guard rail height and spacing requirements can affect post layout.
• Stair rails often require different hardware than deck rails.
• If your deck is elevated, plan railing posts before you set the framing layout.

Materials list (beyond deck boards)

• Fasteners/clips (product-specific)
• Flashing and waterproofing details (where needed)
• Joists/beams/posts and hardware (separate framing estimate)
• Railing materials and hardware
• Stair stringers and connectors (if applicable)

Drainage and water management

• Plan deck slope or gaps so water can drain away from the house.
• Keep soil or mulch from burying deck framing and posts.
• If attaching to a house, prioritize ledger flashing and waterproofing details.

Composite vs wood planning (what changes)

• Gapping rules differ: composites can expand/contract differently than wood—follow the specific product instructions.
• Fastening systems differ: hidden clip systems can change board-to-board spacing and waste.
• Blocking needs can change for diagonal installs and for composite to meet deflection limits (project dependent).

Ledger and waterproofing (a common long-term failure point)

If your deck is attached to a house, ledger flashing and water management are critical. Water trapped behind a ledger can cause structural rot. This is more important to long-term safety than saving a few boards of decking.

• Plan ledger flashing, fastener type, and waterproofing details per code and manufacturer guidance (project dependent).
• If you’re unsure, consider a freestanding design or professional review for attachment details.

Layout sanity checks (before ordering)

• Confirm board run lengths and where seams will land (avoid tiny end pieces where possible).
• Confirm stair/landing geometry and the number of steps needed (it often drives extra boards).
• Confirm railing line and post locations early so you can plan blocking and avoid surprise cutouts.

• Deck calculator
• Deck guide
• Board feet explained
• Baseboard waste tips