Crown and Plane Deck Joists Level Before You Install Them

The Problem

Deck and floor joists rarely come out of the lumber stack perfectly straight — nearly every board has some crown, a slight bow along its length. Standard practice is to install each joist crown-up, but crown alone doesn't guarantee the tops line up with each other. Small differences between boards show up later as a bouncy deck surface or high and low spots once decking goes down.

The Technique

1. Before setting them, sight down each joist to find its crown, and lay them out crown-up as usual.
2. Line several joists up side by side on sawhorses or the deck framing, and clamp them together at both ends so the top edges are held in the same plane.
3. Run a hand or power planer along the clamped-together top edges, taking down any high spots until every joist top is level with its neighbors.
4. Release the clamps and install the joists as planned — crown still facing up, but now with matched, level tops.