Simpson Strong-Tie DTT1Z Deck Tension Tie
To prevent a deck ledger and band joist from separating from a house, code requires lateral ties that connect the deck framing to the house framing. The 2015 IRC offers a promising new detail for lateral-load connections using angle brackets to tie four deck joists into a wall plate or mudsill. Simpson Strong-Tie’s new 1-1/2-in. by 7-in. DTT1Z Deck Tension Tie meets the code-required withdrawal resistance when you use four of these $2 connectors along the ledger—two within 24 in. of the deck edges and two spaced evenly in between. This is two more connectors than you’d need if you were using their DTT2 connectors, but the newer method doesn’t require access to the floor framing inside the house.
The DTT1Z can be installed using Simpson’s self-drilling Timber- Hex HDG screws, which have an integral washer head. They can also be installed with 3/8-in. galvanized lag screws and washers. If you have access to the floor framing inside the house, 3/8-in. galvanized hex-head bolts with nuts and washers are a third option.
The DTT1Z doesn’t have to be in direct contact with the wall, siding, or ledger, so you have some flexibility with the length of the fastener that connects the bracket to the house framing. The mounting screw must penetrate 3 in. into solid framing, but you can use a longer screw, driving it deep enough to go through the siding and 3 in. into the framing. With the DTT1Z pulled tight to the lag-screw head, you can fasten the L-shaped bracket to the joist without worrying about the lag screw’s extra length.
The DTT1Z is fastened to the deck joists with either 1-1/2-in. 10d galvanized metal-connector nails or Simpson’s #9 by 1-1/2-in. Strong- Drive SD Connector screws. Loads for the fastener options are indicated for both wet and dry lumber of different wood species on a table available from Simpson’s website (strongtie.com).