Solutions for deck ledger connections to floor trusses using several blocking details that provide a wood-to-wood-bearing load path for deck design loads to a wall or sill plate can be found in the Structural Building Components Association research report SRR-1408-01, “Attachment of Residential Deck Ledger to Metal Plate Connected Wood Truss Systems”. Included in this report are details for fastening the deck ledger when the floor trusses are both parallel to and perpendicular to the deck joists, as shown in the drawings below.
Important additions to the report (but not included here) are tables based on different loads and ledger-to-truss connection details that provide the required spacing of 1/2-inch-diameter lag screws or bolts based on deck span. The fastener schedules given in SRR-1408-01 are based on the essential assumption that the floor trusses are supported by “wood-to-wood bearing” at the location of deck ledger attachment.
A free-standing deck design—which eliminates the need for a deck ledger—is always a viable option that can be used with all types of floor systems. Free-standing decks must also be able to resist lateral loads, either by diagonal bracing provided between the support posts and the deck frame both side to side and front to back, or by specially engineered hardware used at the post-to-beam connections (or both). Another option is to anchor the deck frame to the primary structure with lateral load connectors; SRR-1408-01 includes lateral load connection details for deck ledgers fastened to open-web truss floor systems.
Note that these are not prescriptive details approved by any building code. When a builder uses the SBCA deck connection document, the construction comes under the code as an IRC R301.1.3 “Alternative materials, design, and methods of construction provisions” subject to the approval of the building official, who could say, “Yes, the detail looks like it’s OK, but you still need a P.E. to sign off on it.”
