digest
Short Summary
Main recommendation: Use the correct engineered joist hanger fasteners, meaning the matched screws or nails designed for that hanger (not generic screws or framing nails), install the hanger so it sits fully flush, and get the work permitted and inspected. The speaker says mismatched fasteners and loose or uneven installation cut the joist's load capacity and can lead to deck failure.
Key Points
- Joist hangers attach joists to a ledger board, and the bottom saddle carries the weight, so a gap between hanger and ledger means only part of the bracket is working.
- Generic ACQ screws can lose shear strength once the coating is scratched and rust starts, and framing nails can stick out nearly two inches, which is why the speaker says both fail.
- Building inspectors look for the manufacturer's stamp on the fastener head, and the speaker says the wrong nail will fail inspection even if the hanger itself is correct.
- Varying lumber thickness (the speaker found about a quarter inch difference across six boards) means hangers mounted at the same height will leave joist tops uneven.
- Screws resist pull-out forces that nails do not, which the speaker demonstrates as the main reason screws are necessary on decks people walk and gather on.
Details Worth Noting
- Concrete instructions:
- Use the matching engineered nails (1-1/2 inch, same manufacturer and stamp) in every hole, or the matched screws; do not use generic framing nails or ordinary screws.
- For the standard SD-style hanger holes, use number 9, 1-1/2 inch screws; for the angled holes, use number 9, 2-1/2 inch screws, with two on each side, and angle the first screw slightly upward to pull the hanger tight.
- Attach a 2x4 block to the joist, set the joist on the block, and temporarily drive a screw into the ledger to hold it.
- Squeeze the hanger together so it holds its shape, press it flush to the ledger, push up on the bottom with a thumb, drive the first screw, check the bottom is still flush, then add the remaining screws.
- Measure from the hanger head to the desired location to get the correct joist length, since the hidden hanger raises it almost a quarter inch.
- Remove the 2x4 block after the joist is secured and save it for reuse.
- For a 45-degree wall angle, use the angled hanger so joists keep the same direction; the speaker says a nail may leave a gap there, and a screw can pull the hanger tight.
- Use a double hanger for doubled joists, and a hurricane tie to connect joists to the beam for uplift protection; the speaker says over-the-top hangers are a poor choice for deck boards.
- Use straps to connect each level down to the post and helical pile so the whole structure is tied together.
- The speaker says to get a permit, and asks viewers to share any unique local building code situations in the comments.
Bottom Line
Joist hanger failures on decks usually come from the wrong fastener or a hanger that is not seated flush, so match the hardware to the hanger and install every joist to carry its full load.
