An essential and simple facility to have in Fallout 4 is to build a small shack with a decontamination arch inside it, 1 small generator, 1 lightbulb for light, a container for food and water with a radio to listen to it(Decorations, Misc.) on top of a small end table(Furniture) and a chair to sit in in the middle of the decontamination arch with a sleeping bag in front of the chair while wearing a gas mask to reduce rads and any rad storm damage. You'll be able to eat radioactive food with rad damage removal and rad storm damage, drink radioactive water then sit to remove its damage and then sleep to restore all hit points. With one or two machine gun defenses on top of the shack all you have to de is have a water source nearby while hunting and scavenging for a food stockpile to be in god mod in survival mode because immunity to radiation is normally a god mode console command only.
https://fallout.fandom.com/wiki/Decontamination_arch
You'll need medicine for disease in survival mode so building a chemist lab to craft meds and explosives is useful in that shack and matches the decontamination chemist lab theme. A build that uses Chemist, Demolition Expert for stronger explosives and mines, Sneak to not set off mines after third rank and easily pick them up to use them as well as Rifleman to hunt while sneaking for extra sneak damage and local leader with two ranks to build a chemistry lab is in god mode with that shack, a sniper rifle and a gas mask which many raiders drop as loot. Dabble in armorer perks for leaded armor upgrades to further reduce radiation damage and apply to combat armor dropped as loot, you'll need to scavenge or buy junk from merchants that has lead in it and duct tape or wonderglue for adhesive needed to mod the combat armor. Then dabble in Gun Nut to improve your rifle followed by raising your Perception to get the Sniper perks going for headshots.
Edit:// Also, make the shack with no roof over the center so the decontamination arch fits inside it.
Musical bonus and bed to heal damage.
Build a small table with a cooler on top of it for your food, water and medicine. Next to the decontamination station chair.
Last but not least the best spot for it in a settlement is nearest to water, to animals to hunt or wild food to forage. A cooking station outside the shack is useful and optional. Use the chair when rad storm is rolling in to wait and avoid being damaged.