: Polyurethane sounds like a good idea.

: I thought I was taking the smart approach. I bought what I thought were good
: straight boards two months ago. I bought my boards ahead of time because I
: was concerned about using green lumber. Much of the twisting occured as
: the boards continued to dry in my garage.

Your idea was valid. What you have to look for in that case would be a fairly straight grain, either flat or verticle. You want to avoid the pith or center of the tree, which is what most of the deminsion lumber ( for building ) is. If you DO end up with the boards with the center in them, then on each side of the ladder beam, put the curved grain in opposite directions. That way, as they dry, they will pull against each other and cancel most or all of the movement. Don't know how you were putting them together, but instead of nails, you might use lag screws with fairly big washers. They will pull it together and hold about as tight as can be expected. FWIW

Rehd