It is too bad that we don't have a good forest of Bamboo in mainland USA. The video below from youtube shows a young woman using on a few simple hand tools for harvesting and then using the wood for making sturdy furniture. In this case a bench, daybed and table. It would certainly be adaptable for building out a van bed. Bamboo is incredibly strong and also light weight. The building systems for it don't require any hardware to hold the structures together. Of course you would might some hardware to secure it to the walls or floor of a van. On the round tubular area pipe straps would work nicely for that.
https://www.youtube.com/watch?v=mRm_V9p-UfU
But even if you don't build furniture with it you can use it for the horizontal and the post for an awning type of shelter outside of the van doorway. That smaller diameter of bamboo is easy to purchase and also to harvest from gardens. You can also find bamboo furniture in thrift stores including shelves, dressers, desk, garden tables, etc. Very eco friendly and non toxic too.
https://www.youtube.com/watch?v=mRm_V9p-UfU
But even if you don't build furniture with it you can use it for the horizontal and the post for an awning type of shelter outside of the van doorway. That smaller diameter of bamboo is easy to purchase and also to harvest from gardens. You can also find bamboo furniture in thrift stores including shelves, dressers, desk, garden tables, etc. Very eco friendly and non toxic too.