Residential Building Inspector B1Building Planning and Life SafetyMedium
An inspector is reviewing a proposed residential deck that will be attached to a dwelling. The deck ledger board is to be attached to the band joist of the existing dwelling. What is the minimum diameter of lag screws required for attaching the ledger board to the dwelling's band joist?
- A1/2 inch
- B3/8 inch
- C1/4 inch
- D5/8 inch
Show answer & explanationAnswer & explanation
Correct answer: A. 1/2 inch
For proper structural integrity and safety, the IRC specifies minimum fastener sizes for critical connections like deck ledger boards. Lag screws used to attach a ledger board to a dwelling's band joist must be at least 1/2 inch in diameter.
Why the other options are wrong
- B. While larger than 1/4 inch, 3/8 inch lag screws are typically not sufficient for ledger board attachment.
- C. This diameter is generally too small for ledger board attachment and would not provide adequate structural support.
- D. This diameter exceeds the minimum required, but 1/2 inch is the specified minimum.
Deck Ledger Fastener Diameter
The minimum required diameter for lag screws or bolts used to connect a deck ledger board to the existing dwelling's band joist, ensuring structural stability.
- Crucial for deck safety.
- Diameter specified by building codes (IRC).
- Ensures adequate shear and withdrawal resistance.
Memory trick: Ledger's 'L' for Lag, 'L' for Large (1/2 inch).