Planning a deck: boards, fasteners, and finish
A good deck starts on paper, not at the lumber yard. This guide walks through the planning decisions a homeowner actually controls — size, shape, board layout, and finish — and points clearly to where local code and span tables take over.
Start with size and shape
Before you count a single board, decide how big the deck needs to be and what shape fits the space. A rough rule for furniture-friendly seating is about 20 square feet per person you expect to host at once, plus room for a grill, a table, or a path to the door. Sketch the footprint against the house and mark where the ledger board will attach.
Keep the shape as simple as the yard allows. A plain rectangle is the cheapest and easiest deck to build — every angle, notch, and multi-level transition adds cuts, framing, and labor. If you want visual interest, get it from the railing, the decking pattern, or a built-in bench rather than a complicated outline.
Which way to run the boards
Decking boards should run perpendicular to the joists — that's what lets each board span and stay supported. Within that constraint you still have a choice of look: boards running the long way make a narrow deck feel longer, while running them parallel to the house is the most common and forgiving layout. A diagonal or herringbone pattern looks great but uses more material and demands tighter framing, so plan it deliberately, not as an afterthought.
Leave a gap between boards
Wood decking needs a gap so water drains and air moves underneath. A common starting point is 1/8" to 1/4" between boards. Wet, freshly milled pressure-treated lumber will shrink as it dries, so it's usually installed with a smaller gap (it widens on its own); drier or kiln-dried boards are spaced wider from the start. Use a consistent spacer — a nail or a deck spacing tool — so every gap matches.
Estimating boards and fasteners
To estimate decking, divide the deck area by the coverage of one board, including the
gap. A nominal 5/4 × 6 board is about 5½ in wide; add your
gap and each board covers a bit under 6 in of width. Count how many board-rows you
need across the deck, multiply by the deck length, and then add about 10% for
cuts, waste, and the occasional bad board — more for diagonal layouts.
Fasteners depend on how you attach the boards, and the two common methods change both the look and the count:
- Face screws — driven down through the top of the board into each joist. Plan on roughly two screws per board at every joist. Cheapest and strongest hold, but the screw heads are visible.
- Hidden clips — clips that sit in a groove on the board's edge and fasten to the joist, leaving a clean top surface. You'll need about one clip per board at each joist, plus the screws that come with them. More expensive and slower, common with composite and premium decking.
Either way, your fastener count scales with the number of joists, so you can't finalize it until the joist spacing is set — which is exactly where code comes in.
Finishing a new deck
A finish protects the wood from UV and moisture and slows graying — but timing matters. Brand-new pressure-treated lumber is often too wet to seal right away; finish won't soak in and will bead or peel. The common advice is to wait until the wood is dry enough, which can be a few weeks to several months depending on the lumber and weather. A simple test: sprinkle water on the boards — if it soaks in rather than beading, the wood is ready to take a finish.
When it's ready, clean the deck, let it dry, and apply a stain or sealer on a mild, dry day — not in direct hot sun, which flashes the product before it penetrates. A semi-transparent or solid stain adds color and UV protection; a clear sealer mainly handles water. Follow the can for coverage and recoat timing, and expect to reapply every one to three years depending on sun and traffic.
Turn your plan into a material list
Once your size and layout are set, plug the numbers into the matching calculator and it will handle the board counts, fasteners, and stain coverage for you: