What is the minimum size of the lag screws used to attach a deck ledger to a house?

The minimum size of lag screws used to attach a deck ledger to a house is 1/2 inch. This specification is critical for ensuring that the deck is securely anchored to the structure to prevent failure under load, as the ledger board is a key component that supports the weight of the deck and provides stability.

Using 1/2 inch lag screws provides sufficient strength and structural integrity to handle the vertical and lateral loads applied to the deck, particularly when considering factors such as potential live loads (people, furniture) and environmental loads (wind, snow). Additionally, the diameter of the screws needs to be compatible with the depth and spacing of the structural framing of the house to ensure that they have adequate anchoring into the wood members.

While smaller screw sizes might seem sufficient at first glance, they could lead to potential issues with pull-out strength or shear strength. Thus, the use of a minimum of 1/2 inch lag screws is not just a matter of code adherence but a best practice for safety and durability in deck construction.