Most deck failures are ledger failures. The IRC treats ledger attachment with a prescriptive fastener schedule, mandatory flashing, and a short list of surfaces you may never attach to.
1/2-in. lag screws or bolts spaced per Table R507.9.1.3(1), based on joist span — staggered in two rows with prescribed edge distances
IRC R507.9.1.3
Ledger material
Minimum 2×8 pressure-preservative-treated lumber attached to a 2-in. nominal band joist or approved engineered rim board
IRC R507.9.1.1, R507.9.1.2
Flashing
Corrosion-resistant flashing required over the ledger, preventing water intrusion into the band joist
IRC R703.4, R507.9.1.4
Prohibited attachments
Ledgers may not be supported on stone or masonry veneer, and attachment to cantilevered floor overhangs requires engineering
IRC R507.9.1.1
Lateral load connection
Deck-to-house lateral connections: either two 1,500-lb hold-down tension devices or four 750-lb connections per the prescriptive options
IRC R507.9.2
Fastener corrosion
Hot-dipped galvanized or stainless fasteners and hangers required in contact with preservative-treated lumber
IRC R317.3
Worth knowing
Nails alone are never an approved ledger attachment for the vertical load path.
Attaching through more than 1 in. of exterior sheathing/siding stack-up reduces lag screw capacity and may require engineered fasteners.
When the house band joist can’t be verified (or is I-joist without a rated rim board), build the deck free-standing.
Many jurisdictions ask for the ledger fastener layout on the permit drawing — photograph it before decking goes down.
Common questions
What does the code say about fastener schedule for Deck Ledger?
1/2-in. lag screws or bolts spaced per Table R507.9.1.3(1), based on joist span — staggered in two rows with prescribed edge distances. (IRC R507.9.1.3)
What does the code say about ledger material for Deck Ledger?
Minimum 2×8 pressure-preservative-treated lumber attached to a 2-in. nominal band joist or approved engineered rim board. (IRC R507.9.1.1, R507.9.1.2)
What does the code say about flashing for Deck Ledger?
Corrosion-resistant flashing required over the ledger, preventing water intrusion into the band joist. (IRC R703.4, R507.9.1.4)
Adopted edition by state
Base-code year from BuildSpec’s adoption records. States often amend the base code, and your city or county may differ, so confirm with your building department.
This guide is BuildSpec’s own summary, not code text. It cites the 2021 International Residential Code and the 2023 National Electrical Code as model standards. The IRC 2021 text itself is in the Code Library for signed-in members; BuildSpec publishes no NEC text, which is at nfpa.org.Neither is an adoption record: your state may be on a different edition with amendments — check your jurisdiction page or get an Address Report.