Do you know that one of our worst nightmares —– deck collapses is mostly caused by a ledger pulling away from rim joists?

To adhere a ledger to a rim joist from the house, we usually choose lag screws or through-bolts. Namely, the usage of through-bolts demands accesses to rim joist back-side. This means occasionally we need to remove a significant amount of drywall within the structure.


During a home inspection, when we are unable to verify the positive connections to the primary building structure, we can assume the decks should be free-standing (self-supporting), stated in most building codes.


Since the determination of the precise spacing for the ledger fastener is based on a lot of factors, instead of the length of the joints primarily determined the spacing and here we apply InterNACHI’s ledger fastener spacing formula where:


The on-center spacing of ledger fasteners in inches = 100 ÷ joist length in feet.


Given that it means when we have much fewer ledger fasteners than our calculated result based on the above formula might have safety issues.


Three ways of attaching a joist to a ledger:

  1. notching over a ledger strip
  2. resting it on a ledger strip
  3. hanging them with joist hangers.


Possible ways of Ledger Board and Band Joist connections:

  • Kept separated by a stack of washers to enable water flow
  • Insulated
  • The unlucky situation is when the siding or exterior finish system was not cleared before the launch of the ledger board. If the ledger board and band joist are not sandwiching structural sheathing, this kind of indirect contact between the two members greatly decreases the strength of the ledger connection.