What Deck Inspectors Actually Check — And How to Pass the First Time

The Three Deck Inspection Stages

Most deck permits require three separate inspections: footing, framing, and final. Each must be scheduled at the right construction stage — too early or too late, and the inspector either can't evaluate the work or must ask you to uncover completed work for re-inspection.

Understanding the correct timing for each inspection is as important as passing them. Schedule inspections too late (after the next stage of work covers what the inspector needs to see), and you'll be excavating concrete or removing decking boards — both costly and time-consuming.

Inspection 1: Footing Inspection

When to schedule: After footing holes are dug but before any concrete is poured. The inspector must be able to see the hole dimensions and soil conditions.

What the Inspector Evaluates

Footing dimensions: Diameter and depth must match your approved drawings. The inspector will physically measure the diameter of the hole and check that the depth extends below the local frost depth into undisturbed soil. Undisturbed soil has a different color and texture than the excavated material — inspectors are trained to recognize the transition.

Setback confirmation: The inspector will verify that the footing locations match the site plan you submitted. This is where errors in the site plan or measurement errors in layout get caught. If a footing is outside the approved location by more than a few inches, you may need to relocate it before getting approval.

Soil bearing capacity (in some jurisdictions): In areas with soft, expansive, or problematic soils — clay-heavy areas of the Midwest, certain mountain soils, coastal areas — the inspector may probe the bottom of the hole to assess soil bearing capacity. If the soil seems insufficient, they may require deeper footings, wider footings, or drilled piers.

Pre-Footing Inspection Checklist

• All footing holes dug to the depth shown on approved drawings
• Footing diameter matches approved drawings at every location
• Bottom of holes is into undisturbed native soil (not disturbed fill)
• Footing locations match the site plan layout
• Permitted plans and permit card are on-site and accessible
• No debris in hole bottoms (leaves, loose soil, water)

Inspection 2: Framing Inspection

When to schedule: After all structural framing is complete — posts, beams, joists, ledger (if attached), stair framing — but before any decking boards are installed. The inspector must be able to see all connections and hardware.

What the Inspector Evaluates

Ledger attachment (highest-scrutiny item): The ledger board connection to the house is the most carefully reviewed element at the framing inspection, and the most common source of deck failures. Inspectors verify:

• Lag screw size (typically ½" diameter minimum) and spacing per IRC Table R507.9.1.3(1)
• Lag screws penetrate into the house's rim joist or structural framing (not just sheathing)
• Flashing is installed behind the ledger to prevent water intrusion — missing or improper ledger flashing is the #1 cause of ledger rot and eventual deck collapse
• Ledger is not attached through stucco, EIFS, or other drainage-critical cladding without proper standoff hardware

Post-to-beam connections: The connection between posts and beams must use approved hardware — typically a post cap (Simpson BC series or equivalent). Posts sitting loose on a beam with no hardware will fail the inspection. Toenailed connections are not sufficient for this connection.

Joist hangers: All joist-to-beam and joist-to-ledger connections must use joist hangers appropriate for the joist size. The hangers must be fully nailed with the correct nail size and count — missing nails in hanger flanges is a common failure point. Using wrong-size nails (drywall nails, roofing nails) in structural hangers is also a failure.

Beam connections: Beams must be properly supported at each post. The inspector verifies that the beam doesn't cantilever beyond code limits and that the connection hardware is correct for the beam size and load.

Lumber species and grade: Pressure-treated lumber in contact with concrete or soil must be rated for ground contact (UC4A or UC4B) — not above-ground treatment (UC3B). The lumber markings must be visible. Inspectors often check the end-tags on PT lumber to verify treatment level.

Blocking: Blocking between joists is required at the beam location and at the ledger to prevent joist rotation. Missing blocking is a common framing inspection failure.

Pre-Framing Inspection Checklist

• All post bases and footing hardware properly installed and fastened
• Beam size and span match approved plans
• All joist hangers installed with correct nails, fully populated
• Ledger lag bolt pattern matches approved drawings
• Ledger flashing properly lapped and sealed
• Joist spacing matches approved plans (typically 12" or 16" o.c.)
• Blocking installed between joists at beam and at ledger
• All PT lumber is rated for its application (ground contact where required)
• Stair framing is in place (stringers, blocking, handrail blocking)
• No decking boards installed yet
• Permit plans on-site and accessible

Inspection 3: Final Inspection

When to schedule: After all work is fully complete — decking, railings, stairs, balusters, handrails, and any electrical or lighting connections. The project must be finished before the final inspection, not "mostly done."

What the Inspector Evaluates

Railing height: The inspector will physically measure railing height from the deck surface to the top of the rail. The IRC requires a minimum of 36 inches for decks 30–72 inches above grade, and 42 inches for decks over 72 inches above grade (some states have adopted the 42" minimum at lower heights). The measurement is taken from the deck surface to the top of the rail cap — not the bottom of the cap or the top of the top rail.

Baluster spacing: The inspector will attempt to pass a 4-inch sphere through baluster gaps. Any gap that allows a 4-inch sphere to pass through fails — this is based on child safety standards. Common failure: balusters installed with too much spacing at the corners or near post connections where the layout gets irregular.

Stair dimensions: Each riser (vertical face) must be within ⅜ inch of all other risers — inconsistent riser heights are a tripping hazard and a code violation. The run (horizontal tread depth) must be at least 10 inches. The maximum riser height is 7¾ inches. The inspector measures multiple steps, not just one.

Graspable handrail: Any stair with 4 or more risers requires a graspable handrail — one you can wrap your hand around (1¼" to 2" in diameter). A flat 2×4 top rail does not qualify as a graspable handrail. A separate graspable rail element must be provided if the top rail isn't graspable in profile.

Deck-to-house connection completed: The inspector verifies that all connections to the house are final, flashed, and properly sealed. Any gaps where water could enter behind the ledger are a failure.

Overall completion: The finished deck must match the approved drawings in all material respects. If you made changes during construction (moved stairs, changed deck shape, added square footage), those changes need to have been submitted as revision drawings and approved before the final. Unauthorized changes can delay final approval significantly.

Pre-Final Inspection Checklist

• Railing height ≥ 36" measured from deck surface to top of rail cap
• Baluster spacing: 4" sphere cannot pass through any gap
• All balusters secure — no loose or missing balusters
• Stair risers consistent within ⅜" of each other
• Stair treads minimum 10" deep
• Maximum riser height 7¾"
• Graspable handrail on any stair with 4+ risers
• All railing post connections secure (post-to-framing, not post-to-decking)
• Ledger and house connection fully sealed and flashed
• Decking boards properly gapped for drainage (typically ⅛"–3/16")
• No construction debris on or under deck
• Site matches approved plans — no unauthorized changes

The Most Common Inspection Failures (And How to Avoid Them)

Based on patterns from building departments across the country, these are the most common deck inspection failures:

1. Ledger Flashing Defects (Framing Inspection)

Missing, improperly installed, or incomplete ledger flashing. The flashing must extend behind the house's water-resistive barrier (house wrap or felt) and lap over the ledger to create a continuous water barrier. Many DIY installers apply flashing tape on the face of the ledger without going behind the siding — this fails.

2. Wrong Joist Hanger Nails (Framing Inspection)

Joist hangers must be nailed with the specific nail size called out in the hanger manufacturer's specifications — typically 10d × 1½" joist hanger nails (not common 10d nails, which are longer and may split the joist). Using the wrong nail size, even if the hanger looks fully nailed, fails the inspection.

3. Railing Posts Connected to Decking, Not Framing (Final Inspection)

Railing posts bolted through the decking boards only, without connection to the deck's structural framing, fail in virtually every jurisdiction. Posts must be through-bolted to the rim joist or band joist of the deck frame, or connected using an approved post base that attaches to the framing.

4. Inconsistent Stair Risers (Final Inspection)

When DIY builders cut their own stair stringers, the riser heights are often slightly inconsistent. A variation of more than ⅜" between any two risers on the same stair run is a code violation. Use a consistent layout tool and measure every riser before installing treads.

5. Footing Depth Insufficient (Footing Inspection)

In frost-prone areas, footings that don't extend below the frost line will be rejected. This is especially common when homeowners estimate rather than measure frost depth, or when the soil transitions to a harder layer (like caliche or clay hardpan) before reaching the required depth.