Mass Fusion building

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The Mass Fusion building is a location in the Commonwealth in 2287. This building is one of the Commonwealth's most recognizable landmarks due to its size and unique architectural design. If Spoils of War is completed successfully, the Brotherhood of Steel will replace the Gunners and occupy the building. The Institute will occupy the building if Mass Fusion is completed similar to the Brotherhood.


The main reactor is in the lower level of the building.

Notable lootEdit

Main buildingEdit

  • Full set of possibly leveled power armor - Worn by the Gunner commander.
  • Strength bobblehead - On the head of the giant interior statue (accessible from the floor with the Gunner commander, powered elevator and exits to the Mass Fusion balcony).
  • Overdue books - On a desk on the fourth floor. You have to go up to the fifth floor and go back down to reach it. Another is on a desk on the reactor level.
  • Mini nuke - On the same floor as the bobblehead in the room to the northwest where the Gunner commander comes out from.
  • Fusion core - On a desk 3 floors from the top, accessed through a destroyed wall facing the central shaft using the techniques described for the Freefall Legs.
  • Tesla Science Magazine issue #5 - On the computer bank, southeast mezzanine room, upper offices above the glass floor (on the same floor with the elevator after power is restored). The area can be accessed by using a jetpack to jump up a hole on the floor where the Gunner commander is and unlocking a door or by waiting for a late main quest to unlock the area.
  • Freefall Legs - At the top of the interior of the building, in an area only accessible using the jetpack power armor mod, using the trash can wall climbing glitch, or during the quest Mass Fusion or Spoils of War.
  • Stealth Boy x 2 - One is on a metal shelf next to the chemistry station, three floors above the Strength bobblehead, at the same level with the glass floor. The other is in the same room as the Freefall Legs, on top of a small bookshelf.
  • Mass Fusion labs key - On the level with the glass floor in the northwest office room on a desk.
  • Executive key and ID card - in the desk on the top floor of building. Accessible during Mass Fusion or Spoils of War.
  • Jack Rockford's log - In the intern's terminal in the same room as the Freefall Legs.


  • The unique damaged hazmat suit can be found in a drawer right outside the decontamination room, that leads into the reactor room.
  • A hazmat suit can be found in the locker room behind the Attendant's terminal, sitting on a shelf of one of the lockers. And another next to the Analyst's terminal on top of a safe.
  • A legendary sentry bot spawns behind the northern security door, which can be opened through the Reactor Security Control terminal on the south side of the room before the reactor room. It has a fusion core. Alternatively, you can get the core and trip the security and the doors will open automatically.


  • The rooftop of the building is the highest point in the entire Commonwealth and offers an impressive view across the whole game world. Despite this, the Mass Fusion building is the second tallest structure in Fallout 4, after Trinity Tower.
  • Using a Brotherhood of Steel Vertibird, one can travel to the Mass Fusion building, and discover the Mass Fusion executive suite location enroute. However, the elevator ID card needed for the Mass Fusion and Spoils of War quests does not spawn until the player actually starts one of them.
  • With proper timing and careful planning, it is possible to get a Vertibird to land and drop the player off on the roof of the building, even before the associated quest.
  • With careful jumping, it is possible to reach the top of the building with a power armor equipped with a jetpack.
  • The building has multiple floors with many broken walkways. The jetpack power armor mod makes navigating the facility much easier.
  • Drinking the water in the reactor room will kill you instantly, unless you have Lead Belly at its maximum level.
  • There is a steamer trunk in the reactor room underwater on the northwest wall, below a "Danger Radioactive Materials" sign.
  • Each time you leave the reactor room, you are decontaminated and lose all rads.
  • Hacking the Reactor Security Control [Master] terminal in the southeast corner of the Main Reactor allows the player character to open the security doors: one leads to impassable rubble while the other opens the facilities room and reveals an inactive sentry bot.
  • It is possible for provisioners and their brahmin to turn up on the roof, where they will be stranded and unable to leave. The only way to get them back to ground level is by using console commands or if they are somehow lured over the edge of the building (they will survive the fall).
  • One can leap from the southwestern corner of the roof, and land safely in Goodneighbor without the use of power armor. Aim for the Old State House. You will be teleported to the main entrance upon entering the cell.
  • If the player did not support their faction in Mass Fusion or Spoils of War, the enemy faction will have taken over the building after the quest. On the other hand the player's faction will control the location if they are assisted.
  • If the player glitches into the reactor room, the Mass Fusion quest will begin.


The Mass Fusion building only appears in Fallout 4.


  • pcIcon pc ps4Icon ps4 xboxoneIcon xboxone The can chimes on the ground floor do not disappear after collecting them, however you still get XP and tin cans for doing so.[verified]
    • pcIcon pc ps4Icon ps4 xboxoneIcon xboxone Similarly the bathroom scale trap provides materials and XP upon disarming it, but the tesla trap will still go off.[verified]
  • pcIcon pc ps4Icon ps4 xboxoneIcon xboxone Taking the large circular elevator from the lobby, back up to the Mass Fusion executive suite, sometimes causes the player to arrive in the wrong location in the exterior cell - a location which was not intended to be accessible.[verified][1]



  1. Youtube video: Fallout 4 Mass Fusion Elevator Glitch

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