The numerous buildings you can build on a planet in Stellaris allow you to acquire resources and puts your citizens to work. The citizens are normally quite happy to have some form of employment, giving them purpose in your empire and giving your grand machine additional expansion opportunities. With patch 3.0, building slots are locked, and you will not be able to unlock them unless you meet certain requirements. Previously, your planet’s population had to increase, and at a specific number, a building slot would unlock. That is no longer the case.
There are two ways you can unlock the building slots on a planet.
Build a city district
The more common method will be to construct a city district. These are just like the industrial, generator, mining, and agricultural districts you choose to build. Each planet has a certain number of districts you can build. If you want to expand the number of districts available, you’ll have to visit the ‘features’ option to the districts page’s right and clear the blockers on your planet.
Not all of the blockers in the planetary features provide you more districts for your planet. When removed, some may add a population to your planet, it might increase the maximum number of a type of district you can build or give your empire the chance to discover an artifact. You want to make sure to read the description of any of the blockers on the planetary features page before committing resources to it.
Upgrade your Planetary Administration building
The next choice is to upgrade the planetary administration building. This option is typically available when your empire has colonized a new planet, and the citizens there are slowly growing their small colony into a new city. Once the city becomes large enough, the planetary administration building will not have any other upgrades.
Here is all of the upgrades you can give to your planetary administration building.
- Reassembled ship shelter (starting colony building)
- Planetary Administration building (requires planetary government technology)
- Planetary Capital (requires colonial centralization technology)
- System Capital-Complex (requires galactic administration technology)
Once you’ve reached the system capital-complex upgrade, you have to rely on removing blockers and adding city districts to a planet to unlock more building slots.