Deck Construction Inspection

Deck footings must extend below frost line. Posts must be pressure-treated or naturally durable wood, properly connected to footings with approved hardware.

1. Verify footings were placed below the local frost line depth (check with local building department)

2. Check that concrete footings are at least 8" in diameter for standard decks

3. Verify posts are pressure-treated lumber rated for ground contact (look for end tags)

4. Check post-to-footing connections — approved metal hardware required (no posts buried in concrete)

5. Verify posts are plumb using a level on two adjacent sides

6. Check post size — minimum 6x6 for freestanding decks, 4x4 may not be permitted in some jurisdictions

7. Inspect for post notching — notches should not exceed 50% of the post dimension

- Footings above frost line — will heave and shift with freeze-thaw cycles

- Posts set directly in concrete without hardware (traps moisture, causes rot)

- Untreated lumber used for posts (will rot in ground contact)

- Undersized footings for the deck load

- Posts not plumb

- Excessive post notching weakening the post

Ledger board must be lag-bolted or through-bolted to the house rim joist. Flashing required above the ledger. Siding must be removed where ledger contacts the house.

1. Check that the ledger is attached with 1/2" lag bolts or through-bolts (not nails or deck screws)

2. Verify bolt spacing — typically 16" on center, staggered top and bottom

3. Look for flashing above the ledger board — Z-flashing or self-adhesive membrane tucked under siding

4. Verify siding was removed where ledger contacts the house (ledger against sheathing or rim joist, not over siding)

5. Check for spacers or washers that allow water drainage behind the ledger

6. Inspect the bottom of the ledger — should not trap water or debris

- Ledger attached with nails only (major structural failure risk — #1 cause of deck collapses)

- No flashing above ledger — water enters the house wall

- Ledger bolted over siding (creates a gap, allows water entry, reduces bolt holding strength)

- Missing spacers — water trapped behind ledger causes rot

- Bolt holes not properly sealed

- Ledger not connected to rim joist (attached to sheathing only)

Deck joists must be properly sized for span, spaced per plans (typically 16" OC), and connected with approved joist hangers. All lumber must be pressure-treated.

1. Check joist spacing — typically 16" on center (12" for composite decking)

2. Verify joist hangers at ledger and beam connections — must be approved metal hangers with proper nails

3. Check that joist hanger nails are the correct type (not drywall screws or standard nails)

4. Verify all framing lumber is pressure-treated (look for end tags and stamps)

5. Check for proper bearing on beams — minimum 1.5" bearing

6. Look for blocking at beam-to-post connections and at mid-span for joists over 12 feet

7. Verify joist crown is facing up (slight bow upward)

- Joist hangers nailed with wrong fasteners (must use hanger nails, not drywall screws)

- Missing joist hangers — joists simply toe-nailed

- Untreated lumber used for framing

- Joists undersized for the span

- Missing blocking at critical points

- Joist crown facing down (will sag over time)

Guards required when deck surface is 30" or more above grade. Minimum 36" height for residential (42" for commercial). Balusters spaced so a 4" sphere cannot pass through.

1. Measure railing height — minimum 36" from deck surface to top of rail

2. Test the 4" sphere rule: try to fit a 4" ball between balusters — it should not pass through

3. Check the bottom gap — a 4" sphere should not pass between deck surface and bottom rail

4. Push firmly against the railing at multiple points — should resist 200 lbs of force without excessive flex

5. Check post connections — bolted through the rim joist or with approved post brackets (not just screwed)

6. Verify no climbable horizontal elements between 4" and 34" height (no horizontal rails children can climb)

7. Inspect all connections for proper hardware — through-bolts or structural screws, not deck screws

- Railing too short (measured from top of decking to top of rail must be 36" minimum)

- Balusters spaced too far apart (child can get head stuck)

- Posts only lag-screwed to rim joist (will loosen over time — through-bolt or use post brackets)

- Bottom gap too large — a child or pet can roll off

- Railing wobbles when pushed (inadequate connection)

- Horizontal rails that children can climb like a ladder

Decking must be properly fastened with approved screws or hidden fastener systems. Gaps between boards should allow drainage. Boards should not have excessive crown or warping.

1. Walk the entire deck surface — feel for any bouncy, loose, or raised boards

2. Check gaps between boards — should be 1/8" to 1/4" for drainage (composite boards: follow manufacturer specs)

3. Verify screw heads are set flush (not proud or too deep) and in straight lines

4. Check board ends — should have a 1/8" gap and be supported by a joist or blocking

5. Look for splits, cracks, or warped boards

6. Verify boards are bark-side up (for wood decking) to minimize cupping

7. Check that all fasteners are approved for treated lumber (stainless steel or coated)

- Boards not properly gapped — no drainage, traps debris and moisture

- Screw heads proud of surface — trip hazard and catches bare feet

- Board ends not supported (bounce when stepped on)

- Standard steel screws used with treated lumber (will corrode quickly)

- Boards cupping from being installed bark-side down

- Excessive warping or crowning