A deck is one of the highest-value projects a homeowner can tackle, but it is also one where structural mistakes are easy to make and expensive to fix after the fact. The decisions you make on framing, material, and fasteners before any boards go down determine how your deck looks and holds up over the next 20 years. This guide covers the core choices so you can plan with confidence and avoid the most common DIY pitfalls.
This is the first decision and it affects your budget, maintenance schedule, and fastener selection.
Pressure-treated lumber is the most affordable decking material and is what most framing (joists, beams, posts) uses regardless of what you choose for the surface. As decking boards, it requires sealing or staining every one to two years to prevent graying, cracking, and checking. Left untreated, it looks rough within a season. It is still a popular choice for surface boards on budget builds, but you have to commit to the maintenance.
Cedar and redwood are naturally rot-resistant and look significantly better than pressure-treated pine. They are softer, easier to work with, and hold stain well. They cost more than pressure-treated but less than composite. Like PT lumber, they need periodic sealing to hold their color and prevent surface cracking.
Composite boards are made from a mix of wood fiber and recycled plastic. They do not rot, splinter, or require staining. Most manufacturers offer 25-year warranties. The tradeoff is upfront cost: composite runs two to four times the price of pressure-treated for the boards alone. Installation is faster using hidden fastener systems, which also give the finished surface a cleaner look with no visible screw heads. Composite expands and contracts with temperature changes more than wood, so manufacturer spacing and fastener specs matter and should not be improvised.
Joists are the horizontal framing members that your decking boards rest on. Standard residential joist spacing is 16 inches on center for most decking orientations. If you plan to run boards at a 45-degree diagonal, drop to 12-inch joist spacing because the diagonal run spans a greater distance between joists and requires more support. Most composite manufacturers also call for 12-inch spacing, so check your specific product before framing. Joist size depends on span length. A 2x8 joist can typically span around 12 feet; a 2x10 extends that to around 14 to 15 feet. Consult your local span tables or the American Wood Council's free span calculator for your specific lumber species and load requirements. Building departments will check this if you pull a permit, and you should pull a permit for any attached deck because it protects you at resale.
Gap spacing between decking boards affects drainage, airflow, and how the deck looks. For wood decking, boards are typically installed tight together. Kiln-dried lumber will shrink slightly after installation and open up natural gaps of about a quarter inch. Wet or green lumber should be spaced at about a quarter inch at installation because it will shrink further as it dries. For composite, most manufacturers specify a quarter-inch to three-eighths-inch gap between boards at 70 degrees Fahrenheit, with adjustments for temperature at installation time. Installing composite tight in cold weather without accounting for thermal expansion leads to boards buckling in summer heat. Use a consistent spacer, like a framing nail or a manufactured composite spacer tool, and do not eyeball it.
Board ends near the house or at a fascia board need a gap too, typically a quarter inch, to allow drainage and airflow. Do not run boards tight to the house wall or a vertical surface. Water trapped in that joint is one of the primary causes of rot at the rim joist.
For wood decking, use hot-dipped galvanized or stainless steel screws or nails. Standard steel fasteners corrode quickly, especially in the presence of treated lumber's preservative chemicals, leaving rust stains on the deck surface within a year. For composite, hidden fastener clips are the preferred method and often required by the warranty. They slot into grooves on the board edges and fasten to the joist below, leaving no face screws. Face screwing composite is allowed by some manufacturers but leaves visible plugs and can cause surface cracking if not pre-drilled correctly. For any fastener in composite, always pre-drill. Composite is denser than wood and will split or bulge without it.
An attached deck connects to the house via a ledger board bolted to the rim joist or band joist of the house framing. This connection carries a significant load and is the source of many deck collapses. The ledger must be bolted, not nailed, directly to the house framing using approved structural fasteners. It needs a gap or flashing between itself and the house sheathing to allow drainage; a ledger sitting tight against the house traps water and rots both the ledger and the house framing behind it. Use metal flashing that directs water outward and down. Space ledger bolts per your local code, typically 16 inches on center in a staggered pattern. The most common structural mistakes beyond the ledger are: undersized beams for the span, missing joist hangers at connections, posts sitting on bare concrete without post bases (which traps moisture at the bottom of the post), and skipping diagonal bracing on tall decks. If your deck is more than 30 inches off the ground, a permit and inspection is required in most jurisdictions and is genuinely worth the effort.
