How a 16×12 deck gets built — start to finish

A 16×12 attached deck like this one takes a 2-person professional crew about 4-6 working days end-to-end: day 1 dig + pour footings (cure 24-72 hrs depending on bag), day 2 set posts + ledger, day 3 beams + joists, day 4 decking + fascia, day 5 railing + stairs, day 6 punchlist + cleanup. DIY add 60-100%. Concrete cure time is the only step you can't compress.

Strict bottom-up sequence enforced by load path: (1) layout + footings (concrete piers below frost line, IRC R403.1.4), (2) posts on J-bolts + ledger to house with flashing (R507.9), (3) beams across post tops + joists at 16″ OC perpendicular to beams (R507.5/R507.6), (4) decking on joists with 3/16″ gaps (R507.7), (5) railing posts notched/bolted to rim + balusters + top rail (R311.7.1 + R312.1.3), (6) stairs last because tread depth depends on finished deck height. Skipping order means tearing back out.

This scene shows 6 footings — the typical layout for a 16×12 attached deck. Two rows of three: one row at the house wall (ledger transfers load), one row at the outer beam. Footing count depends on beam span and joist span: tighter posts = smaller footings; wider posts = larger diameter. The Deck Footing Calculator gives the exact diameter and depth for your soil class + frost zone.

Two reasons. First, the ledger is the level reference — once it's set true to the house, the outer beam can be leveled off it instead of off a wandering string line, which compounds error. Second, the ledger sets the deck's height, which determines post length. If you cut posts before the ledger is in, you're guessing. Industry standard: ledger first, then string line to outer beam, then posts cut to fit.

In almost every US jurisdiction: yes, attached decks over 30″ above grade or over 200 sq ft (varies by jurisdiction) require a permit. A 16×12 attached deck is 192 sq ft — right at the threshold — but because it's attached to the house and likely 30″+ off the ground, a permit is virtually always required. Inspections typically cover: pre-pour (footing depth + rebar), framing (joist span, ledger flashing, hardware), and final (railing, stairs, code-compliant fasteners). Build without a permit and you face removal orders + insurance issues + sale-disclosure problems.

Skipping the flashing between the ledger and the house wall. The single most common cause of catastrophic deck collapse is water rotting the band joist behind an un-flashed ledger over 5-10 years. By the time the homeowner notices, the lag bolts are seated in spongy wet wood and the ledger pulls free under a party load. IRC R507.9.1.4 requires continuous flashing over the ledger top + behind the house siding. Other top mistakes: undersized footings (frost-heave failure), too-few joists (bouncy floor), missing post-to-beam connectors (uplift failure in wind).

Those are zoom-ins. This one is the hero condensed view of all 6 build stages in one continuous scene — same 16×12 footprint, same house wall, same posts — so you can see how each stage connects. The dedicated animations (Foundation Build, Framing Assembly, Decking Installation, Railing Construction) show each phase in 5-phase detail with components close-up. Use the hero to understand the order; click through to the individual animations to understand each step.