[header] How to build bunk bed stairs [title] Use 2 x 4 dimensional lumber for the side rails. [step] A pair of 8 feet (2.4 m) long pieces of good-quality 2 x 4 dimensional lumber will work well for this job. Pick through the pile at the lumber yard to avoid pieces that are warped, bowed, or cracked. 
[substeps] Check that lumber is straight and " true " by holding one end up to your eyes and looking down the length of the wood. [title] Grab 1 x 3 dimensional lumber for the stair treads (ladder rungs).