Keep Ceiling Joists Level when Installing

Q:  I'm building a room in the top of my garage and need to hang the ceiling joists. In this case, the joists will hang off the rafters. What is the best way to make sure the joists stay level across the room?

A: Set up some tightly pulled string lines to guide the installation, using a laser level or string level. Install the joists across the shortest distance. Keep in kind that all 2-by lumber has a small crown, so install the joists so they all crown in the same direction—probably up.