How to Build a Deck
Advanced · 2–4 days
A deck is a real structural build, not a weekend cosmetic project — it carries people, furniture, and snow load, so the framing underneath matters far more than the boards on top. The skill is in getting the footings deep enough, the ledger flashed and bolted right, and the frame dead level and square. Once the structure is sound, screwing down the decking is the easy, satisfying part. Pull a permit before you start; most jurisdictions require one for an attached deck, and the inspection protects you.
What you'll need
- Decking boards (use the calculator to size boards and rows including waste)
- Pressure-treated lumber for the ledger, beams, joists, and rim
- Concrete footings, post bases, and post anchors rated for your span
- Joist hangers, structural screws or hot-dip galvanized nails, and ledger bolts (lags or through-bolts)
- Ledger flashing, plus hidden fasteners or coated deck screws for the boards
- Circular saw, drill/driver, level, framing square, string line, and a post-hole digger or auger
Steps
Plan, permit, and call before you dig
Sketch the deck, confirm beam and joist spans from a span table, and pull the permit. Call 811 to mark underground utilities before any digging — it is free and required.
Attach and flash the ledger
Bolt the ledger board to the house rim joist (never just to siding) with lags or through-bolts, then flash above it so water sheds out, not behind. A poorly flashed ledger is the single most common cause of deck failure.
Dig and pour the footings
Dig footings below the frost line (varies by region) at the spacing your beam span allows. Set post bases in the wet concrete, plumb and level, so posts never sit directly on soil.
Set posts and beams
Stand the posts in their anchors, brace them plumb, and set the beam on top. Check that the frame is square by measuring the diagonals — they should match — before locking anything down.
Hang the joists
Run joists from the ledger to the beam at 16 in on center (or per your span table), seated in joist hangers and toe-screwed to the rim. Crown each joist up so the deck stays flat as it settles.
Lay the decking
Start the first board along the house, leaving a small gap, and work outward. Keep a consistent gap (about 1/8 in for kiln-dried boards; butt wet pressure-treated tight, as it shrinks) using a spacer so the lines stay even.
Trim, fasten the fascia, and add rails
Snap a line and trim the board ends flush in one pass for a clean edge, then fasten fascia over the rim. Finish with code-compliant railings — 36 in high for residential, balusters under 4 in apart.
Pro tips
- Order about 10% extra decking for cuts, pattern changes, and the occasional crooked board — the calculator builds in this waste.
- Crown every joist (bow facing up) before fastening; gravity flattens them over time and you avoid a wavy deck.
- Use only hot-dip galvanized or stainless hardware. Modern pressure-treated lumber is corrosive and eats cheap fasteners.
- Gap your boards for drainage and airflow. Decking that traps water against itself cups, rots, and grows mold fastest.
FAQ
How many deck boards do I need?
Divide the deck width by the board width plus the gap to get the number of rows, then one board per row runs the length. The deck board calculator does this and adds a waste factor for cuts.
How deep should deck footings be?
Below your local frost line so they don't heave in winter — that ranges from about 12 in in mild climates to 48 in or more up north. Check your local building code for the exact depth.
Do I need a permit to build a deck?
In most areas yes, especially for an attached deck or one above a certain height. The permit triggers an inspection that catches ledger, footing, and railing issues before they become safety problems.
Ready to estimate materials? Use the Deck Board Calculator →