Residential Building Inspector B1Building Planning and Life SafetyHard
An inspector is reviewing a proposed residential deck that will be attached to a dwelling. The deck ledger board will be attached to the band joist of the dwelling. What is the minimum diameter of lag screws or bolts required for attaching the ledger board where the joist depth is 2x10?
- A3/8 inch
- B1/4 inch
- C1/2 inch
- D5/8 inch
Show answer & explanationAnswer & explanation
Correct answer: C. 1/2 inch
According to the 2021 IRC, Table R507.2.1(1) Fastener Spacing for a Deck Ledger, for a 2x10 joist depth, the minimum diameter for lag screws or bolts is 1/2 inch (12.7 mm). The table also specifies spacing based on ground snow load and joist span.
Why the other options are wrong
- A. 3/8 inch is too small for ledger board attachment to a 2x10 joist.
- B. 1/4 inch is too small for ledger board attachment to a 2x10 joist.
- D. 5/8 inch is larger than required but would be acceptable, though potentially overkill.
Deck Ledger Fastener Diameter
The minimum diameter of lag screws or bolts used to securely attach a deck ledger board to a dwelling's band joist.
- Critical for structural integrity and safety of the deck.
- Varies based on joist depth, ground snow load, and joist span.
- Specified in IRC Table R507.2.1(1).
Memory trick: Deck ledgers need strong bolts, half-inch or more, to bear the weight.