Examine the wood you choose for floor joists. These boards should be free of large knots or blemishes as that could affect the strength of the boards.
Pick lumber that is 2 inches by 6 inches, 8 inches, or 10 inches.
Lay out your joists so that they will be spaced 16 inches on center.
Decide whether you wish to set the joists so that they run over a beam, butt together over the beam, or fit them into hangers attached to the sides of the beams.
Fit the joists into the joists hangers if you choose that method of installing floor joists.
Install hangers onto the beams carefully, making sure that they are not crooked. After you install the floor joists, check them with a level to make sure they're level.
Put the floor joists in so that they curve upward evenly of the lumber you are using us crowned. Over time, the crown will disappear. Make sure that the floor joists butt into a bearing wall.