Crown and Plane Deck Joists Level Before You Install Them
Technique: Crowning and Planing Deck Joists
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
- Before setting them, sight down each joist to find its crown, and lay them out crown-up as usual.
- 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.
- 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.
- Release the clamps and install the joists as planned — crown still facing up, but now with matched, level tops.
Pro tip: Bar clamps long enough to span several joists at once make this fast — you don't need the most expensive brand, just something that reaches the full width of the stack so nothing shifts while you plane.