my advice is go clear out Corvega, collect everything that isn't nailed down, return it all to the Castle, store it all in the workshop then build a few artillery if you wish
I am not sure I understand the question but let me tell you this:
Junk doesn't need to be broken down to be used for building. The Junk only needs to be either in your inventory or in the workshops inventory.
Arturo in DC sells shipments of gear if you are to lazy to search for that stuff yourself.