Set Deck Joists Flush on Top Before the Hangers Go On

The Problem

Two joists from the same lift are rarely the same height — a 2x10 can run an eighth over or under its neighbor, and pressure-treated stock is worse. If you pre-set all the joist hangers to a common line and drop the joists in, every one of those height differences ends up on top, where the decking goes. The walking surface comes out wavy, and no amount of screwing it down fixes lumber that's sitting at different heights.

The Technique

Make the top of the frame the reference instead of the hanger.

1. Screw a scrap 2x4 along the top of the beam or header as a temporary fence, and pre-set screws in it at each joist location.
2. Set each joist crown up — always — and line it up with your layout line.
3. Pull the joist up until its top is dead flush with the top of the beam, then drive one of the pre-set screws to pin it there.
4. With the joist held flush, install the hanger underneath it. The hanger lands wherever that particular joist needs it to.
5. Toe-screw the bottom of the joist to the layout line so it can't twist while the hanger gets nailed off.

Slower than dropping joists into pre-set hangers — and the top of the deck comes out flat, which is the only side anyone walks on.