CSLB General Building (B)Framing and CarpentryMedium
A contractor is attaching a deck ledger board to the rim joist of an existing house using 1/2-inch lag screws. Per standard deck construction practice, what is the typical maximum on-center spacing for these lag screws in a staggered pattern?
- A16 inches on center
- B24 inches on center
- C8 inches on center
- D32 inches on center
Show answer & explanationAnswer & explanation
Correct answer: A. 16 inches on center
Standard deck ledger attachment tables (based on IRC prescriptive tables for deck ledgers) typically require 1/2-inch lag screws or bolts spaced at approximately 16 inches on center in a staggered two-row pattern to adequately transfer deck loads to the house structure.
Why the other options are wrong
- B. 24 inches on center is generally too widely spaced for adequate load transfer in prescriptive tables.
- C. 8 inches is closer spacing than standard tables require and would be excessive for typical loads.
- D. 32 inches on center is far too sparse and would not meet minimum ledger attachment requirements.
Deck Ledger Fastening
Deck ledgers are typically attached with staggered rows of 1/2-inch lag screws or through-bolts spaced about 16 inches on center per prescriptive deck-building tables.
- Staggered two-row pattern typical
- 1/2-inch diameter lag screws or bolts common
- Spacing and edge distance vary with joist span and species
Memory trick: Sixteen inches, staggered rows, keeps your deck from falling off the house.