Cedar shims for joists
 

Anyone have experience, good or bad, using cedar shims for uneven deck joists?

Most of the time the difference in height of the joist is dew to moisture content. Shimming them all to level may not give you the results you want.

If that's the case, I can't be 100 percent level due to change in moisture levels. What should my tolerance be? 1/8 inch? I'm installing PVC decking.

Evan if you get it level, it will be moving over time as some parts of the deck dry out and other parts are subject to more water.
Shimming it to get level will be fine and easyer to install the decking for sure.