Add-ons are terran auxiliary structures which are produced by and attached to a main structure capable of lifting off.

Buildings can leave behind or "acquire" add-ons through the use of lifting-off. This includes enemy add-ons. A left-behind add-on is still treated as belonging to the original player and will be attacked by enemy units. When add-ons change allegiance, their team color also changes accordingly.


The command center can be attached to two add-ons, the ComSat station and the nuclear silo. It can only be attached to one add-on at a time.

The factory can be attached to the machine shop, which is required to produce siege tanks and upgrade vultures, siege tanks and goliaths.

The starport can be attached to the control tower, needed to produced advanced ships and holds upgrades for wraiths.

The science facility can be attached to two add-ons, the physics lab and the covert ops. The former is required to produce battlecruisers and researches their upgrades, while the latter is required to produce ghosts and researches their upgrades.

If a campaign mission has a victory condition "destroy all enemy buildings", destroying the enemy add-ons are not required.


During development, terrans could salvage for resources. This was removed, and instead, they were given the ability to appropriate enemy add-ons.[1]

StarCraft IIEdit

Main articles: Reactor and Tech lab

In StarCraft II, the terrans have only two add-ons, but they can be produced from the barracks, factory, and starport. The reactor allows two units to be produced at once, while the tech lab enables the creation of certain higher-tier units. Buildings cannot be attached to more than one add-on at a time. However, the player can lift off a building, such as a barracks that was attached to a reactor, and set it down beside a tech lab, losing the double queue but enjoying the barracks' new ability to produce higher-tech units.[2]

Add-ons will be targeted just like buildings in StarCraft II. Stealing add-ons is still possible; but on earlier builds, it was more difficult, as the player used to be able to salvage them.[3]

Wings of LibertyEdit

Main article: Tech reactor

In StarCraft II: Wings of Liberty, Raynor's Raiders are given access to the tech reactor should they choose to pursue the protoss research necessary. Tech reactors allow structures to receive the benefits of both the tech lab and the reactor.[4] Tech reactors are also available to Rory Swann upon reaching level 10 in Co-op Missions.

Co-op MissionsEdit

Main article: Infested tech lab

Alexei Stukov has access to the infested tech lab as an upgrade structure that can be produced from the infested barracks, infested factory, and infested starport.


  1. Hidden Pics, Angelfire. Accessed on 2018-06-06
  2. 2007-09-13. Gameplay Video - Terran. Blizzard Entertainment. Accessed 2007-09-14.
  3. While I don't know about the 'main idea' of the add-ons being detachable is so the other side could steal them, this mechanic is still in the game. The AI does not prioritize the buildings over the the add-ons in StarCraft II. 'Stealing' is also a bit trickier to do since Terran players can salvage buildings like add-ons and bunkers to get 100% of the cost back over X period of time (in which X is subject to balance still of course). Karune. 2009-06-04. Question about Terran Add-Ons. StarCraft II General Discussion Forum. Accessed 2009-06-04.
  4. Blizzard Entertainment. StarCraft II: Wings of Liberty. (Activision Blizzard). PC. Protoss research (in English). 2010.