If an elevated deck moves or sways when people walk across it, the movement should not simply be ignored. A deck needs to carry gravity loads, but it also needs a reliable way to resist horizontal, or lateral, movement.
Where does the lateral movement come from?
Lateral forces can come from wind and seismic effects, but they can also be generated by people moving around on the deck. On an elevated deck, these forces can be noticeable because the deck is supported above the ground and the connections between the deck, posts and house all affect how stiff the structure feels.
A ledger that is properly connected to the house is important, but the ledger connection is not the whole story. The deck also needs a positive load path for lateral forces so that it does not pull away from the supporting structure.
A Simpson Strong-Tie solution
Simpson Strong-Tie provides deck tension ties specifically for deck-to-house lateral connections. Two examples are the DTT2 and DTT1Z. These connectors tie selected deck joists back to structurally sound framing in the house.
The DTT2 is intended for higher-capacity deck lateral-load connections. The DTT1Z provides another option and can connect a deck joist to suitable wall framing such as studs, headers or top plates, depending on the installation. This can also make it useful when improving an existing deck where access to the floor framing inside the house is difficult.
These tension ties resist horizontal forces. They do not replace the required ledger connection or other deck connections that carry vertical loads.
Is adding a tension tie always enough?
No. A moving deck can have more than one cause. Loose or deteriorated connections, inadequate post or beam connections, insufficient lateral stiffness, decay, corrosion, or problems at the foundations can all contribute to movement.
For this reason, a connector should not simply be added because a deck feels loose. The existing load path and the condition of the deck should first be understood. The appropriate connection and fastening arrangement depends on the actual framing and supporting structure.
What should you look for?
- Noticeable side-to-side movement when people walk on the deck
- A gap developing between the deck and the house
- Loose, missing or corroded connectors and fasteners
- Movement at posts, beams or post bases
- Decay or deterioration around structural connections
Have an existing elevated deck reviewed
If an elevated deck has noticeable lateral movement, a structural review can help identify where the movement is coming from and whether additional connections, bracing or other repairs are appropriate.
VBES Consulting provides structural engineering for small residential projects in North Vancouver and Metro Vancouver.
Reference: Simpson Strong-Tie, Deck Connection and Fastening Guide, and Simpson Strong-Tie deck lateral-connection guidance. Product selection and installation must follow the manufacturer’s current requirements and the requirements applicable to the specific project.
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