Warped, discounted lumber would not be my 1st choice for constructing a ladder stand that I'd be entrusting my health & well-being to. While there is a certain satisfaction one gets from constructing his own stand from scratch, I would recommend that you use only 1st quality materials in your construction.
In my home state, the #1 cause of all hunting related injuries is falls from elevated treestands. A fall from a height of just 10-12 feet can cause serious permanent injury or death!
If you insist on constructing your own stand, please observe the following safety rules:
(1) always wear an approved safety harness when climbing in/out & sitting in your stand.
(2) avoid leaving your stand outdoors year-round
and
(3) be sure to do a thorough pre season safety check for any loose, damaged or missing pieces or hardware.
Good luck & good hunting!