How a joist hanger gets installed — every nail counted

For a Simpson LUS210 (the most common hanger for a 2×10 joist), the full schedule is 18 nails: 10 × 10d common into the ledger flanges (5 per side) + 8 × 10d through the hanger side walls into the joist (4 per side). Under-nailing is the #1 deck-failure mode at the hanger; many DIYers stop after the ledger-side nails and skip the joist-side nails entirely, which drops the rated capacity by roughly half.

10d common nails — specifically 0.148″ diameter × 1-1/2″ length (sometimes labeled 10d × 1-1/2″ N10 in the Simpson catalog). NOT 16d sinkers (too long, will split the ledger band), NOT roofing nails (under-diameter), NOT deck screws unless they're rated structural screws like SD Connector screws from Simpson. The hanger's published load rating assumes the exact nail spec — substituting voids the rating.

Only if they're explicitly rated for joist hanger use. Simpson SD9 or SD10 Connector screws (0.135″–0.162″ shank) are approved replacements for 10d common nails in their hangers. Standard deck screws (#9 or #10) are NOT approved — they have a brittle shank that snaps under shear and they're not rated for the joist hanger load tables. The cost difference is negligible (~$0.20/screw); use the structural ones or use nails.

Hangers are required by IRC R507.6 + R507.10 for any joist supported by a ledger or beam where the joist top is flush with the ledger top. Toenailing alone (driving nails at an angle through the joist into the ledger) is NOT code-compliant for deck construction — toenails can't carry the live + uplift load and the connection fails catastrophically under a party load. Hangers are required. Toenails optionally supplement them.

Flanges OUT — meaning the two L-shaped tabs fold AWAY from the joist pocket and lie flat against the face of the ledger. The pocket itself faces toward where the joist will land. If you install it backwards (flanges pointing into the pocket), there's no surface to nail into the ledger. Look at the nail holes: they should be visible on the flat outer flanges before installation, not inside the cup.

All three are 2×10 face-mount joist hangers but they differ in load rating and nailing schedule. LUS (Light gauge, Universal, Skewed-capable) is the most common at ~1,065 lb download. LU is heavier-gauge at ~1,425 lb. U (no L prefix) is the heavy-duty version at ~1,800+ lb for engineered applications. For a typical residential deck, LUS210 is what your big-box lumber yard stocks and what the IRC default tables assume.

Use a skewed hanger (Simpson LSU or SUR/SUL) — not a straight hanger bent in the field. Bending a straight hanger work-hardens the galvanized steel at the fold line and cracks the zinc coating, leading to corrosion failure within 5-7 years. The Skewed Hanger Calculator on DeckMath tells you which Simpson SKU matches your joist angle (15°, 22.5°, 45°). For diagonal-pattern decks, expect to use skewed hangers for the perimeter joists.