I know of a perfect cabin plans that uses paracord-wrapped Estwing for All stages of it's construction(from all those pesky roots to carving that cool ceremonial ladder),it's called "barabara".
https://www.google.com/search?q=bar....69i57j0l7.14111j0j7&sourceid=chrome&ie=UTF-8
It's true that in order to do a Really nice job you'll have to violate the Stevens-Magnusson Act,and poach some marine mammals,but it'll be all Apocalypse around,and no one would pay any attention...And in any case you'll need all the meat and blubber so You won't run out of food yourself...
And for you,Sir,who seeks the Bomb-proof door,i too have a suggestion,it's an old German recipe,and works corker:
Go forth and slay all the surrounding peasantry(make sure you keep back a few well-built strong ones,you'll need them later),and pile all the burnables in a great big pile.
Then you rummage for all household goods that are made of iron,and setting that pile of fuel on fire you make those few peasants you saved forge all those household utensils flat,into plates of random size.
Then,while the fire is still hot enough,you hot-punch holes in those plates,and rivet them together into the shape of your door.
The trick is,when some rude neighbor with a bunch of his guys try to rush your castle door with their battering ram,your door will just Jangle,and Rattle,and Shake,and (magically)it'll ABSORB all the energy of the effort...
You can safely jeer from atop your walls and throw down filth on the attackers,it's a totally proven method!
(when ransacking for iron implements make sure to Especially look for paracord-wrapped Estwings,those are Particularly great for this).